In his 1905 paper Einstein effectively states that the simultaneity of events in the "stationary" frame must be assumedI don't think Einstein would have referred to any frame as 'the stationary' frame in his 1905 paper. If your posts here are going to misrepresent the ideas of others, then your reasoning is fallacious.
If we consider the clock synchronisation thought experiment:Cutting in here. It is not specified, but it seems that you are envisioning the first two clocks not moving relative to the first observer, and these are two different clocks that are not moving relative to the second observer. The situation then is entirely symmetrical. Two pairs of clocks, each pair synchronized in the frame in which the pair is stationary. If this is not the case, you need to say so.
the observer in the "stationary" frame is located at the mid-point between 2 clocks. A co-located emitter sends a light pulse to each clock (to start them ticking). The light pulses are reflected to the observer at the mid-point and arrive simultaneously. The observer concludes that their clocks are synchronised because they know the speed of light and the distance to the clocks, and because the light pulses returned simultaneously.
While the observer in the "stationary" frame is performing this clock synchronisation, they observe a relatively moving observer perform the exact same synchronisation process. They are also located midway between 2 clocks.
The "moving" observer concludes that their clocks are synchronised. The "stationary" has observed that the clocks are not synchronised.More to the point, each observer concludes that the pair of clocks stationary relative to themselves are synchronized, and each observer concludes that the other pair of moving clocks are not. Again, entirely symmetrical.
Here, in the original thought experiment, we are provided with a clear case of why the assumption of synchronisation/simultaneity is unjustified.The symmetry says it is entirely justified.
The oberver in the "stationary" frame observes the "moving" observer perform the exact same synchronisation procedure, with the light pulses simultaneously returning to the mid=point, yet, the clocks are not synchronised. This should, at the very least, cause the 'stationary" observer to question whether their clocks are in fact synchronised.They're not in his frame, and his clocks are not synchronized in the other observer's frame. There is no 'the stationary' frame. There's just this frame and that one.
Imagine, on top of this, both observers are wearing body cameras and record footage of their counterparts synchronisation attempts. They then send the footage to each other - by light signal. Each observer will be presented with observational evidence that their clocks are not synchronised.That's fine since neither expects their own clocks to be synchronized in a different frame. This additional footage evidence is not required.
The reasonable conclusion in this scenario would be to accept that each was mistaken in their assumption about the simultaneity of the clock synchronisation events, give the observational evidence to the contrary.The simultaneity of all those events is frame dependent. That's what relativity of simultaneity means.
Light Clock Thought ExperimentThat it does. The theory again predicts this, so the neither observer needs bodycam evidence from the other to show what he already knows.
For this, we need only consider the thought experiment involving each observer carrying a single light clock - a photon bouncing between mirrors. The "stationary" assumes thata their clock is ticking normally, while they observe the "moving" clock as ticking slowly, as the photon travels a longer, diagonal path between the 2 mirrors.
Again, imagine each exchanging bodycam footage and being presented with evidence that their own clock is also ticking slowly. It makes sense to both observers.
What about the speed of light? If they measure the speed of light in the light clock, will they not measure it as having a slower speed, if they can only detect the vertical velocity component?The vertical component is easily deduced with simple trigonometry. Light moving horizontal for instance has zero vertical velocity component.
Any attempt to measure the speed of light will always yield the same value because their clock will be biased by the same factor.Another absolutist joins the ranks. You have plenty of company here.
Absolute time is indistinguishable from a timeless universe. Clocks provide units of comparison - they don't measure a background phenomenon called "time".OK, so maybe you don't like absolute time either. Clocks indeed provide units of comparison, as do meter sticks. That doesn't means I get no information from a clock. The timeless conclusion doesn't follow any more than a conclusion that my meter stick is dimensionless because its length is frame dependent.
ConclusionStrawman fallacy. Einstein assumes no special 'the stationary' frame in special relativity.
The above highlights the circular reasoning in the Einsteinian interpretation. It is the assumption of the simultaneity of events in the "stationary" frame which leads to the conclusion of the Reativity of Simultaneity.
I don't think Einstein would have referred to any frame as 'the stationary' frame in his 1905 paper. If your posts here are going to misrepresent the ideas of others, then your reasoning is fallacious.In order to render our presentation more precise and to distinguish this system of co-ordinates verbally from others which will be introduced hereafter, we call it the “stationary system.” (Einstein, 1905).
Cutting in here. It is not specified, but it seems that you are envisioning the first two clocks not moving relative to the first observer, and these are two different clocks that are not moving relative to the second observer. The situation then is entirely symmetrical.
Two pairs of clocks, each pair synchronized in the frame in which the pair is stationary. If this is not the case, you need to say so.This is the crux of the issue. The idea that they are synchronised is purely an assumption and, as is being argued, an unjustified/unjustifiable assumption.
More to the point, each observer concludes that the pair of clocks stationary relative to themselves are synchronized, and each observer concludes that the other pair of moving clocks are not. Again, entirely symmetrical.Again, this is the crux of the issue! They conclude that the "stationary clocks" are synchronised. What is it that leads to this conclusion? There is no experiment that can determine the simultaneity of the clock synchronisation events, so they assume that the clocks are synchronised. Why? Because they know the speed of light, the distance to each clock, and [crucially] the light reflected from the "stationary clocks" returns to them simultaneously.
The symmetry says it is entirely justified.It is the assumption of simultaneity in their own frame, which is not justified.
OK, so you are a relativity denier. That also wasn't clear at first. Maybe you just don't understand, but you are writing a paper somewhere, so you presumably think that you know this stuff.Not a denier, just advocating for a different, more parsimmonious interpretation. It is similar to the Lorentz-Poincare interpretation except that it is a timeless interpretation.
They're not in his frame, and his clocks are not synchronized in the other observer's frame. There is no 'the stationary' frame. There's just this frame and that one.The point is that the observer in the "stationary system" sees the relatively moving observer perform the exact same syncronisation procedure, with the exact same observational results but the moving clocks fail to synchronise. How does the "stationary" observer know that the exat same issue isn't afflicting their own synchronisation procedure? They don't because, in keeping with the Galilean Priniciple of Relativity, there is no experiment they can conduct to determine that their clocks are actually synchronised or that events are simultaneous, in their frame.
That's fine since neither expects their own clocks to be synchronized in a different frame. This additional footage evidence is not required.The bodycam footage represents observationl evidence that their clocks are not synchronised versus their assumption that their clocks are synchronised. The reasonable conclusion is that each observer is mistaken in their assumption of the simultaneity/synchronisation of their clocks, given the observational evidence to the contrary.
The simultaneity of all those events is frame dependent. That's what relativity of simultaneity means.The notion of relativity of simultaneity follows from the unjustified assumption that the simultaneity of events can be determined in any frame. That is, it starts by assuming that events are simultaneous in a given frame, when no such determination can be made. Without this assumption of simultaneity, RoS doesn't get off the ground.
That it does. The theory again predicts this, so the neither observer needs bodycam evidence from the other to show what he already knows.The bodycam footage shows that the assumption, by the observer in the "stationary system", that the photon in their clock travels a perpendicular distance between the mirrors, is unjustified.
The vertical component is easily deduced with simple trigonometry. Light moving horizontal for instance has zero vertical velocity component.The point is that, as per the Galilean Principle of Relativity, the observer in the "stationary system" will always observe only the vertical velocity component of the photon and has no way off knowing if it has a horizontal component. This would be the case if they were "stationary" or "moving"; if the photon traced the perpendicular distancce between mirrors, or the longer diagonal distance.
If you think clocks are biased, how biased are they? For instance, how long does it really take for Earth to make one sidereal rotation (on average)? The biased clock in Greenwich says ~23:56:04. What is it really? If you can't answer it, then your bias argument falls apart.Perhaps I don't see the relevance. The point I was making is that the 2nd postulate can be interpreted to mean that it is the measurement of the speed of light that is constant. Einstein's own thought experiment shows us how nature would "conspire" against us to ensure that we always measure the same speed of light.
OK, so maybe you don't like absolute time either. Clocks indeed provide units of comparison, as do meter sticks. That doesn't means I get no information from a clock. The timeless conclusion doesn't follow any more than a conclusion that my meter stick is dimensionless because its length is frame dependent.Without the assumpion of relativity of simultaneity we are left with absolute simultaneity and absolute time. To quote Lee Smolin, "were it not for the external clock, one could already say that time has disappeared".
Strawman fallacy. Einstein assumes no special 'the stationary' frame in special relativity.His actual phrasing was "stationary system" but it''s the same difference.
I stand corrected then. He is labeling the frames, for convenience, as 'stationary' and 'moving' then. So long as there is no assertion about the stationary one being in some way special (which would violate the first principle), this is acceptable.I don't think Einstein would have referred to any frame as 'the stationary' frame in his 1905 paper. If your posts here are going to misrepresent the ideas of others, then your reasoning is fallacious.In order to render our presentation more precise and to distinguish this system of co-ordinates verbally from others which will be introduced hereafter, we call it the “stationary system.” (Einstein, 1905).
Apologies, I am assuming familiarity with the clock synchronisation thought experiment hereI'm not familiar actually, but I think I worked it out. Your description of how the clocks are synced describe a valid method to perform the task.
There is also a relatively moving observer with 2 clocks in the "moving system" - we are considering things only from one perspective, for the time being.Fine.
Agree, and I didn't say that they were synchronized. I said each pair was synchronized in a specific frame, and not in the other. If you consider that an assumption, well, I suppose it could be, especially if we have a different interpretation of what it means for clocks to be synchronized.Quote from: HalcTwo pairs of clocks, each pair synchronized in the frame in which the pair is stationary. If this is not the case, you need to say so.This is the crux of the issue. The idea that they are synchronised is purely an assumption and, as is being argued, an unjustified/unjustifiable assumption.
We establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A.(Einstein, 1905).That's pretty out of context. The definition of what? From reading the quote, it seems to be the definition of points in space (A and B), and points in space require a frame for their definition.
Yes, but different pairs of clocks are stationary relative to the frames of each observer.Quote from: HalcMore to the point, each observer concludes that the pair of clocks stationary relative to themselves are synchronized, and each observer concludes that the other pair of moving clocks are not. Again, entirely symmetrical.Again, this is the crux of the issue! They conclude that the "stationary clocks" are synchronised.
What is it that leads to this conclusion? There is no experiment that can determine the simultaneity of the clock synchronisation events, so they assume that the clocks are synchronised.You described in your OP a simple experiment to do just that. Light from stationary equidistant clocks emitted at the two synchronization events are observed simultaniously. That's an empirical verification if I ever saw one.
Why? Because they know the speed of light, the distance to each clock, and [crucially] the light reflected from the "stationary clocks" returns to them simultaneously.Sorry, but it seems you contradict yourself. They know all these things, yet you say it cannot be known.
Indeed, it is the symmetry of the situation which means that their assumption about the simultaneity of the clock events is unjustified. They observe their counterpart conduct the exact same synchronisation procedure, with the exact same observational evidence - distance to each clock, speed of light, and light pulses returning simultaneously. Yet, the "moving" clocks are not synchronised.Nobody ever said they were.
The symmetry of the situation should lead the "stationary" observer to at least question the assumption of simultaneity/synchronisation of their clocks.They do question it, but all observers are right. Their clocks are synchronized in their frames, as they empirically verified.
Not a denier, just advocating for a different, more parsimmonious interpretation. It is similar to the Lorentz-Poincare interpretation except that it is a timeless interpretation.OK, that's valid. If it makes no different predictions, what's the advantage of the interpretation? Does it simplify anything that's more complicated in the relative interpretation? You call it parsimonious, like it perhaps requires less effort in some way.
The point is that the observer in the "stationary system" sees the relatively moving observer perform the exact same syncronisation procedure, with the exact same observational results but the moving clocks fail to synchronise.Again, the intentional drop of the frame reference. The moving clocks do very much synchronize in the second frame. He did not fail at all.
How does the "stationary" observer know that the exat same issue isn't afflicting their own synchronisation procedure?He is afflicted. Symmetry demands it. His clocks are similarly not synchronized in the other frame.
They don't because, in keeping with the Galilean Priniciple of Relativity, there is no experiment they can conduct to determine that their clocks are actually synchronised or that events are simultaneous, in their frame.Galilean PoR doesn't say that. It says what can be done in one frame can be done in another, and since there is very much an empirical verification that can be performed (which you describe in your OP), both observers can verify that their clocks are actually synchronised or that events are simultaneous, in their frame.
The notion of relativity of simultaneity follows from the unjustified assumption that the simultaneity of events can be determined in any frame. That is, it starts by assuming that events are simultaneous in a given frame, when no such determination can be made.But you show how to determine it. It isn't hard. I totally don't understand this assertion that given a frame, ordering of events cannot be determined. The assumption you speak of isn't made ever. It is a conclusion at best.
The point is that, as per the Galilean Principle of Relativity, the observer in the "stationary system" will always observe only the vertical velocity component of the photon and has no way off knowing if it has a horizontal component.He does have a way. If it had a horizontal component, the light wouldn't come back to the detector that is stationary in that frame.
As per the thought experiment, if the oberver tries to measure the speed of light in their light clock they will have to use another light clock - the circularity should be apparent. This circularity is the "conspiracy"They're up front about that. A light clock by definition cannot be used to measure light speed, yes. It would take some other sort of clock. Light speed was initially measured using another reliable clock that could be moved closer and further away. It was an inertial clock (a steadily rotating thing like Earth), not based on light at all.
Or maybe I got that wrong....Quote from: HalcOK, so maybe you don't like absolute time either.Without the assumpion of relativity of simultaneity we are left with absolute simultaneity and absolute time.
We can make time "disappear" simply by chllenging the assumption that "a clock measures [a background phenomenon called] time".No, relativity has no background standard. That was my point about building a device that cancels out its own bias. Relativity cares not about that background and doesn't assume it at all. It just cares that this duration is somehow comparable to that other duration over there, but never to a base rate.
If we examine the processes of a clock, nowhere is this background phenomenon actually measured.Exactly, yes.
Strawman fallacy. Einstein assumes no special 'the stationary' frame in special relativity.His actual phrasing was "stationary system" but it''s the same difference.[/quote]
I stand corrected then. He is labeling the frames, for convenience, as 'stationary' and 'moving' then. So long as there is no assertion about the stationary one being in some way special (which would violate the first principle), this is acceptable.I make a separate point about this in the paper, but it is more of an aside, so there's no need to go into it here.
Agree, and I didn't say that they were synchronized. I said each pair was synchronized in a specific frame, and not in the other. If you consider that an assumption, well, I suppose it could be, especially if we have a different interpretation of what it means for clocks to be synchronized.This is the crux of the issue. The Simultaneity/synchronisation in the stationary frame i.e. in his frame is assumed. I will clarify below. And we have the same definition.
that's pretty out of context. The definition of what? From reading the quote, it seems to be the definition of points in space (A and B), and points in space require a frame for their definition.The definition is [to paraphrase] that the journey time from A to B equals the journey time from B to A. It has to be assumed bcos to actually measure it would require synchronised clocks - see the issue. It is the reason that the 1-way speed of light cannot be measured.
You described in your OP a simple experiment to do just that. Light from stationary equidistant clocks emitted at the two synchronization events are observed simultaniously. That's an empirical verification if I ever saw one.The returning light pulses are observed simultaneously. But the observer in the "stationary system" observes the light return simultaneously to the "moving" observer also, this is despite the fact that the "moving" clocks are not synchronised, from the perspective of the "stationary" observer.
Sorry, but it seems you contradict yourself. They know all these things, yet you say it cannot be known.If it is known, then it must be known that light pulses will return simultaneously whether clocks are synchronised or not. This highlights the fact that Simultaneity of the Synchronisation events - in the stationary frame - is assumed.
Nobody ever said they were.Given the symmetry, we only need to talk about the perspective from the "stationary" frame - so the frame can be assumed. Apologies, if that wasn't clear.
You confuse 'sychronized' with 'synchronized in frame X'. I notice you drop the frame references whenever it's convenient to your point. The only way two clocks can be synchronized (no frame reference) is if they follow the same worldline, essentially being the same clock.
They do question it, but all observers are right. Their clocks are synchronized in their frames, as they empirically verified.All observers are right and by extension all observers are also wrong. If it weren't for the circularity of the reasoning ensuring that the interpretation is self consistent, this woul be a paradox in anyone's language- but not for relativity!
OK, that's valid. If it makes no different predictions, what's the advantage of the interpretation? Does it simplify anything that's more complicated in the relative interpretation? You call it parsimonious, like it perhaps requires less effort in some way.It's more parsimonious bcos it makes fewer assumptions and it is simpler bcos it doesn't involve paradoxical scenarios where observers are both right and wrong, and it eliminates the Relativity of Simultaneity.
Again, the intentional drop of the frame reference. The moving clocks do very much synchronize in the second frame. He did not fail at all.In case the point still hasn't been clearly made:
He is afflicted. Symmetry demands it. His clocks are similarly not synchronized in the other frame.His clocks reside in his own frame. He assumes that they are synchronised. The relatively moving observer provides observational evidence that the clocks, in his localised region of space, are not synchronised.
Galilean PoR doesn't say that. It says what can be done in one frame can be done in another, and since there is very much an empirical verification that can be performed (which you describe in your OP), both observers can verify that their clocks are actually synchronised or that events are simultaneous, in their frame.The idea is that we can extend principle to Simultaneity and synchronization - there is no experiment that can determine the Simultaneity of events.
But you show how to determine it. It isn't hard. I totally don't understand this assertion that given a frame, ordering of events cannot be determined. The assumption you speak of isn't made ever. It is a conclusion at best.Hopefully I have now shown that it is the simultaneous return of light pulses that leads them to assume (not determine) the Simultaneity of synchronization events. The light pulses return simultaneously whether the clocks are synchronised or not.
He does have a way. If it had a horizontal component, the light wouldn't come back to the detector that is stationary in that frame.Talking about the single light clock with the photon bouncing between mirrors.
They're up front about that. A light clock by definition cannot be used to measure light speed, yes. It would take some other sort of clock. Light speed was initially measured using another reliable clock that could be moved closer and further away. It was an inertial clock (a steadily rotating thing like Earth), not based on light at all.An observer moving relative to the Earth cannot use the Earth. Of course, if they did their motion relative to the earth would cancel out the effect, by way of biasing their clock.
]No, relativity has no background standard. That was my point about building a device that cancels out its own bias. Relativity cares not about that background and doesn't assume it at all. It just cares that this duration is somehow comparable to that other duration over there, but never to a base rate.Special Relativity is a background dependent theory, General Relativity is not. If a clock doesn't measure some background phenomenon called "time" then clocks simply count units of measurement, like a tape measure counts metres. This makes "time" nothing more than a system of measurement just like the metric system. Therefore, time is neither fundamental nor emergent, just as the metric system isn't.
As a notational convenience, yes he said that. It was not to make that frame in any way special/preferred.As mentioned, there is a separate argument in the paper on this point, which references Leibniz's identity of indiscernibles in relation to the absolute rest frame of Newtonian Mechanics.
The definition is [to paraphrase] that the journey time from A to B equals the journey time from B to A.That is a statement, and not one that defines anything. The statement is not true in general. A and B can be objects and have differing times for the light journeys due to the fact that objects are not obliged to stay put.
It has to be assumed bcos to actually measure it would require synchronised clocks - see the issue. It is the reason that the 1-way speed of light cannot be measured.Wrong. Again, the earliest light speed measurement was done one way, and while it employed multiple clocks, they were not particularly synchronized.
The returning light pulses are observed simultaneously. But the observer in the "stationary system" observes the light return simultaneously to the "moving" observer also, this is despite the fact that the "moving" clocks are not synchronised, from the perspective of the "stationary" observer.The first observer sees that the moving clocks are not the same distance from the other observer when they're zeroed. That's why they're not synced in that frame.
This demonstrates to the "stationary" observer that the light would return [to him] simultaneously even if his clocks are not synchronised. He is simply assuming that they are synchronised in his frame.They are verified in sync because he can measure that his clocks are equidistant from him, while the two moving-clock synchronization events are not equidistant from the moving observer, thus they must not be in sync.
If it is known, then it must be known that light pulses will return simultaneously whether clocks are synchronised or notThis statement is nonsense. If two sources emit light simultaneously from different distances, the near one will be observed first. Ditto if I do it with mirrors at different distances and the light source originates by me.
Given the symmetry, we only need to talk about the perspective from the "stationary" frame - so the frame can be assumed. Apologies, if that wasn't clear.Fine then. The moving clocks are not synchronized in that frame, and the all observers agree with that fact. There's no conflict.
It's more parsimonious bcos it makes fewer assumptionsFewer than two? What one assumption does your interpretation make?
and it is simpler bcos it doesn't involve paradoxical scenarios where observers are both right and wrong,There's no paradox to remove.
and it eliminates the Relativity of Simultaneity.That it does. Seems to make everything more complicated to do so, but it does indeed eliminate that.
In case the point still hasn't been clearly made:In this particular case yes. Not always, as I point out above.
The "stationary" observer witnesses an alternative explanation for the simultaneous return of the light pulses. They see that the light pulses return simultaneously whether clocks are synchronised or not.
The bodycam footage offers empirical evidence that their clocks, in their localised region of space, are not synchronised.What do you mean 'localized'? The clocks are separated, not local to each other. If they were local, they'd be synced in any frame.
This contradicts their assumption that the clocks are synchronised in their own frame.How? You didn't say that they were shown to be not synchronized in that frame. No footage demonstrated that. I see no contradiction.
His clocks reside in his own frame. He assumes that they are synchronised.No he doesn't. Nobody assumes clocks are synchronized. They demonstrate (not assume) that they're synchronized in their own frame, but not that they're synchronized. Again, the distinction between those wordings escapes you, or you're being deliberate about it. Ignorance or troll? You interpret relativistic statements as absolute ones, and then find conflict. Indeed, the interpretations don't mix.
Simply ask the question: is it possible that the observer in the stationary frame is mistaken about the simultaneity of the clock synchronisation events? Given that they see a scenario where light returns simultaneously from non-synchronised clocks.The question lacks frame references, so is largely meaningless.
Both assume their clocks are synchronisedNo they don't. They're not absolutists, so they make no absolute assumptions like that. In all probability, none of the 4 clocks is synchronized in an absolute way since none of them attempted an absolute procedure to do it. Why should they? It serves no purpose.
The observer was on Earth. There was little choice in the matter at the time.Quote from: HalcLight speed was initially measured using another reliable clock that could be moved closer and further away. It was an inertial clock (a steadily rotating thing like Earth), not based on light at all.An observer moving relative to the Earth cannot use the Earth.
The point is, if every clock is biased by the same factor, then it will all cancel out, as though the universe is "conspiring" to ensure the speed of light is always measured to have the same value.They're not all biased out by the same factor. They're all dilated to some extent for multiple reasons.
clocks simply count units of measurement, like a tape measure counts metres.Agree, the units are arbitrary. No alien is going to come up with a meter or a second. That doesn't mean spacetime isn't fundamental. Just that the units into which we choose to slice it up are not.
That is a statement, and not one that defines anything. The statement is not true in general. A and B can be objects and have differing times for the light journeys due to the fact that objects are not obliged to stay put.We have not defined a common “time” for A and B, for the latter cannot be defined at all unless we establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A. (Einstein, 1905).
That's why I had to look up the quote to see what definition was being referenced.
Wrong. Again, the earliest light speed measurement was done one way, and while it employed multiple clocks, they were not particularly synchronizedThe "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to the detector and back again. Albert Einstein chose a synchronization convention (see Einstein synchronization) that made the one-way speed equal to the two-way speed... Experiments that attempted to directly probe the one-way speed of light independent of synchronization have been proposed, but none has succeeded in doing so.
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The first observer sees that the moving clocks are not the same distance from the other observer when they're zeroed. That's why they're not synced in that frame.Again, this is the heart of the problem. The first observer, Alice, has no way of determining that the very same is not true for her own clocks - in her own reference frame. Indeed, the observational evidence, in the form of the bodycam footage, suggests that the same is true for her clocks also, on the platform.
They are verified in sync because he can measure that his clocks are equidistant from him, while the two moving-clock synchronization events are not equidistant from the moving observer, thus they must not be in sync.You're conflating two different things here, the distance from the observer to each clock and the distance from the two "moving-clock synchronization events" to the moving observer. You are somewhat mistaken though, bcos the moving observer, Bob, is equidistant from the clocks and therefore from the "moving-clock synchronization events".
Fine then. The moving clocks are not synchronized in that frame, and the all observers agree with that fact. There's no conflict.The point that "all observers agree with that fact" is a bit misleading. One of the ways in which the Einsteinian interpretation resolves the obvious disagreement is by allowing there to be disagreements between observers.
There's no paradox to remove.I know it might seem that because the Einsteinian interpretation is self consistent, that there are no paradoxes, but in anyone's language, where an observer can be both right and wrong about events in the physical world, where a ladder can both be too big to fit in a garage and small enough to fit completely, and where "time" on board a train can tick at an infinite number of different rates and when one clock can tick both slower and faster than another clock, those are paradoxes in anyone's language.Quoteand it eliminates the Relativity of Simultaneity.That it does. Seems to make everything more complicated to do so, but it does indeed eliminate that.
In this particular case yes. Not always, as I point out above.OK, maybe we can progress from here.
What do you mean 'localized'? The clocks are separated, not local to each other. If they were local, they'd be synced in any frame.My aplogies if I have caused confusion with my use of the term "localized". It might instead be more clear to talk in terms of two locations. We have the clocks "onboard the train" and the clocks "on the platform". In this sense relativity says, the clocks onboard the train are synchronised, in the frame of the train, but not from the perspective of an observer at rest on the platform.
How? You didn't say that they were shown to be not synchronized in that frame. No footage demonstrated that. I see no contradiction.Alice looks at bodycam footage of her clocks located on the platform. The bodycam footage shows that the clocks did not synchronise. This is observational evidence that the clocks did not synchronise.
I have clarified that we can assume "in the frame of the 'stationary system" given the symmetry.QuoteSimply ask the question: is it possible that the observer in the stationary frame is mistaken about the simultaneity of the clock synchronisation events? Given that they see a scenario where light returns simultaneously from non-synchronised clocks.The question lacks frame references, so is largely meaningless
No they don't. They're not absolutists, so they make no absolute assumptions like that. In all probability, none of the 4 clocks is synchronized in an absolute way since none of them attempted an absolute procedure to do it. Why should they? It serves no purpose.Again, we can imply "in the frame of the "stationary system". The point being contested is that simultaneity is frame dependent. An unavoiable requirement of frame dependent simultaneity is that there must be one reference frame in which events are simultaneous (otherwise there is no basis for the relativity of simultaneity). To delare that events are simultaneous in any frame simply isn't justified. To say that events are simultaneous in one frame requires us to assume that they are simultaneous in that frame.
Maybe I've misunderstood your point. We were talking about the use of clocks to measure the speed of light, in the context of the thought experiment. What clock are you suggesting that Bob use to measure the speed of light, where the effect of relative motion won't result in his clock offsettiing any discrepancy in the speed of light?QuoteThe observer was on Earth. There was little choice in the matter at the time.Quote from: HalcLight speed was initially measured using another reliable clock that could be moved closer and further away. It was an inertial clock (a steadily rotating thing like Earth), not based on light at all.An observer moving relative to the Earth cannot use the Earth.
They're not all biased out by the same factor. They're all dilated to some extent for multiple reasons.Yes, the clocks are dilated, not "time" and this dilation will always result in Alice and Bob getting the same result when they measure the speed of light. And, in such a way that it doesn't result in the relativity of simultaneity
Agree, the units are arbitrary. No alien is going to come up with a meter or a second. That doesn't mean spacetime isn't fundamental. Just that the units into which we choose to slice it up are not....BTW, I don't think they're fundamental either. I just disagree with the validity of the argument you use to conclude that.The metric system is neither fundamental nor emergent. "Time" is system of measurement like the metric system and so, it is neither fundamental nor emergent either. The metric system attempts to express distances in common units, time attempts to express duration in commin units.
1) We can assume the reference frame to be that of "the stationary system". This is because, given the symmetry of the situation, both observers consider themselves to be in "the stationary system".If you do that, then the words 'the stationary system' do not identify a frame since each observer names a different frame with those words. You'd have to say 'Observer A's stationary system' and 'Observer B's stationary system', which seems a lot more complicated than just saying Frame A and Frame B.
2) The contention here isn't that the Einsteinian interpretation isn't self-consistent. I [finally*] accept that it is self-consistent. You have made a few statements to the effect that there is no "conflict" or that "all observers agree**". The intention isn't to demonstrate a conflict or contradiction in the Einsteinian interpretation.Can we drop the whole bodycam thing then? The purpose of that seemed to be to prove a case to the other observer over some point about which they disagreed, but they agree on all points. There is no conflict as you say.
3) The point that is being attempted, is to demonstrate that there is an [unjustified] assumption being made in the Einsteinian interpretation. That assumption is that observers in "the stationary frame" assume that their clocks are synchronised (in their own frame of reference).In whose stationary frame? See? Those words are no longer meaningful without identification of which observers stationary frame. You've not identified an observer here.
4) You have made repeated references to the frame dependence of simultaneity. The point being made is that, without the assumption of #3 above, one cannot arrive at a conclusion of frame dependent simultaneity.Point 3 is valid, even given its ambiguous wording. It isn't an assumption. It is a deduction given the two premises of SR.
5) Simultaneity of events in the "stationary system" is an assumption, while the bodycam footage represents observational evidence to the contrary.No frame identified (per point 1). This statement is meaningless.
I want to try and clarify the point by means of the inner monologue of one of the observers. I think it will also be heplful to name our observers - good ol' Alice and Bob - because it will make it easier to keep track of reference frames.On loan from the QM department, eh? Good. I like them. This corresponds nicely to frame A and B BTW. 'Frame A' or 'Alice's frame' seems a lot easier to say than 'Alice's stationary system', never mind the improved clarity of the former.
Alice:The silly goose! His clocks are not synchronised,There is no meaning to 'synchronized' without a frame reference. Alice does not say that, and Bob does not consider his clocks to be objectively synchronized as you imply. I repeat this point in all my prior posts, and you continue to use this invalid wording. There is no conflict between what Alice claims and what Bob claims, remember? Yet you persist.
Oh look, the light pulses returned to me simultaneously, that means my clocks must be synchronized.Again, no, for the same reasons.
We have not defined a common “time” for A and B, for the latter cannot be defined at all unless we establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A. (Einstein, 1905).Einstein had defined A and B to be points in space in that quote, which is a frame dependent concept. Thus Alice and Bob do not share common points in space.
It can't be any more explicit that what is being defined is the time required by light to travel from A to B equals the “time” it requires to travel from B to A, this is required to establish a "common time for A and B" i.e. to synchronise A and B.Yes, but remember that A and B are frame dependent, so the above is a frame dependent statement.
They did just that, so your statement is obviously incorrect. It was one way, and lacked any synchronization. The fact that they got a pretty good figure for the speed (when before they had no clue) shows that the method is valid. Try reading up on it.Quote from: HalcAgain, the earliest light speed measurement was done one way, and while it employed multiple clocks, they were not particularly synchronized.The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector.
What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to the detector and back again.That can be measured, yes, but a light speed determination need not necessarily use this method.
Experiments that attempted to directly probe the one-way speed of light independent of synchronization have been proposed, but none has succeeded in doing so.Obviously not, since the very first measurement was done exactly in that manner. Remember this is way before atomic clocks and such.
Nonsense. She has a tape measure. That's how its done. She can't use it for Bob's clocks since they're moving, but both Alice and Bob know that Bob's clocks are not synced in Alice's frame.Quote from: HalcThe first observer sees that the moving clocks are not the same distance from the other observer when they're zeroed. That's why they're not synced in that frame.Again, this is the heart of the problem. The first observer, Alice, has no way of determining that the very same is not true for her own clocks - in her own reference frame.
You're conflating two different things here, the distance from the observer to each clock and the distance from the two "moving-clock synchronization events" to the moving observer.All frame dependent things, and all these things are meaningless without those references. Your whole problem (which I suspect is deliberate) is trying to interpret frame dependent statements as frame independent statements. I've pointed it out in every post, yet you persist in statements like the above one, and a great deal of the others. Few of the statements are absolute (frame independent), and there is only conflict when you incorrectly treat them as such.
You are somewhat mistaken though, bcos the moving observer, Bob, is equidistant from the clocks and therefore from the "moving-clock synchronization events".See what I mean? You did it again there.
I think what you mean is that the light pulse travels a shorter distance to one clock than the other.And again. No, I don't mean this. You repeat the same mistake with almost every statement. You'll do it in the next post. You'd get a poor grade if you took the course because you won't see your mistake when it is repeatedly pointed out.
The experimental support for relativity has lead us to accept such "spooky action"Spooky action is more of a QM thing, but until a message can be sent via such a mechanism, I see no action. I personally stand by the principle of locality. Others choose different principles. You can't have them all.
My aplogies if I have caused confusion with my use of the term "localized". It might instead be more clear to talk in terms of two locations. We have the clocks "onboard the train" and the clocks "on the platform". In this sense relativity says, the clocks onboard the train are synchronised, in the frame of the train, but not from the perspective of an observer at rest on the platform.Wow, you kept the references that time. Very good.
Because reltivity says that this is more than just the case that the clocks appear unsynchronised from the platformIt says they're not synced in the platform frame. We've not made any statement about appearances. It could appear to the platform observer that one train clock runs at twice the rate of the other. We'd need a lot more information to determine appearances.
it says that both statementss are equally true. Therefore, the clocks onboard the train are both synchronised with each other and not-synchronised with each other, in their physical locations onboard the train.It says none of these statements at all actually. Both statements are meaningless, hence not even wrong.
By point 1 above, even those words no longer identify a frame.Quote from: HalcThe question lacks frame references, so is largely meaninglessI have clarified that we can assume "in the frame of the 'stationary system" given the symmetry.
To rephrase: Simply ask the question: is it possible that the observer in the stationary frame is mistaken about the simultaneity of the clock synchronisation events, in the stationary frame?No. They are correct about it.
Given that they see a scenario where light returns simultaneously from non-synchronised clocks.In a given frame, light can arrive at an event simultaneously from non-simultaneous sources if those sources are not equidistant from the point of measurement.
Again, we can imply "in the frame of the "stationary system".Ambiguous, per point 1. You mean Alice's frame?
The point being contested is that simultaneity is frame dependent.OK. If it isn't, there are some interesting empirical falsifications I can suggest.
An unavoiable requirement of frame dependent simultaneity is that there must be one reference frame in which events are simultaneous (otherwise there is no basis for the relativity of simultaneity).All events? No. Random events X and Y? No. The Titanic makes contact with iceberg. The Titanic make contact with the ocean floor. The is no reference frame in which those two events are simultaneous. Only with pairs of events separated in a space-like manner is there a set of reference frames in which the pair is simultaneous.
To delare that events are simultaneous in any frame simply isn't justified.But I can demonstrate it using the methods you describe, so the declaration is totally unnecessary.
You were trying to show that light clocks could not be used to measure light speed, and I agreed. So they used a non-light clock. I think LIGO uses a light clock of sorts, not to measure time, but to measure a difference in time.Quote from: HalcMaybe I've misunderstood your point. We were talking about the use of clocks to measure the speed of light, in the context of the thought experiment.QuoteThe observer was on Earth. There was little choice in the matter at the time.Quote from: HalcLight speed was initially measured using another reliable clock that could be moved closer and further away. It was an inertial clock (a steadily rotating thing like Earth), not based on light at all.An observer moving relative to the Earth cannot use the Earth.
What clock are you suggesting that Bob use to measure the speed of light, where the effect of relative motion won't result in his clock offsettiing any discrepancy in the speed of light?Any clock will do. You need to devise an experiment where the effect of relative motion cancels out. So maybe in a different frame the distance is 10% shorter, but the simple clock also runs 10% slower, so the same light speed measurement is obtained. So we know that the speed can be determined without a requirement for the test being performed in a special frame.
The metric system is neither fundamental nor emergent. "Time" is system of measurement like the metric system and so,No. The metric system is about grams and meters and such, not mass and length. Likewise the system of time measurement is seconds and years and such, not time. You're making an invalid comparison between a thing and the units of measuring the thing.
time attempts to express duration in commin units.That's like saying that length attempts to express distance in common units. No, it is the metric system that slices up distance like that, just like the arbitrary units of seconds and such is the standard Earth system that slices up time. Time is not the units. With that I agree.
3D space is self-evident (not to say the holographic principle isn't correct). The "dimension of time" however, is not self-evident. We only ever observe things in the present instant i.e. the "now". Therefore, we cannot - not even in principle - oberve a temporal dimension; that is, we can never observe things extended in time.Agree, but a corollary of that is that you can't observe space either. If you can only observe things in the present, then you only have access to input here and now. The cup in front of me cannot be observed even in principle since it takes time for light to get to me from there. I can only suspect it is there now due to the current image I have that shows a state in the past that no longer exists if there is no time dimension.
I have to keep repeating them bcos they clearly haven't been understood. And your reply to this point shows precisely where your misunderstanding lies.QuoteNonsense. She has a tape measure. That's how its done. She can't use it for Bob's clocks since they're moving, but both Alice and Bob know that Bob's clocks are not synced in Alice's frame.Quote from: HalcThe first observer sees that the moving clocks are not the same distance from the other observer when they're zeroed. That's why they're not synced in that frame.Again, this is the heart of the problem. The first observer, Alice, has no way of determining that the very same is not true for her own clocks - in her own reference frame.
I tire of this endless repeating of the same points. Are you going to say anything new?
Can we drop the whole bodycam thing then? The purpose of that seemed to be to prove a case to the other observer over some point about which they disagreed, but they agree on all points. There is no conflict as you say.They do not agree on all points!
I'm not sure why you're having such difficulty with the idea of "the stationary system" aka "the stationary frame". In his 1905 paper, Einstein starts by talking about an observer in "the stationary system" and builds up from there.He clearly designates one arbitrary frame as such for notational convenience. I notice you didn't include that part of the quote despite its importance.
I'm simply following the convention used by Einstein in that paper.Then your point 1 contradicted that convention. Why can't we say Alices's frame instead? Alice is designated the stationary one if we're to go by Einstein's convention. The first observer is arbitrarily designated the stationary one.
We're looking at things solely from Alice's perspective, in Alice's frame, on the platform and making deductions based on her observations.Then don't quote statements made about different frames.
You keep retorting with "frame dependence" but that is simply using the conclusion to justify the assumption - I'm challenging the assumption, so "frame dependence" isn't a given.OK.
=========Yes, I do.
Conflation
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Here is the issue, here is the assumption I have been trying to demonstrate. You are conflating the distance that Alice measures, [with her measuring tape] from the emitter to each clock, in her frame of reference, with the distance that the light pulses travel from the emitter to each clock, in her frame of reference.
Herein lies the assumption.Why is it a bad assumption to make? All clocks, observer, tape measures, etc are all stationary in this frame and remain so for the duration between the relevant events.
Remember that [from her reference frame] Alice sees Bob measure the distance from his emitter to each of his clocks, on the train, with his measuring tape.Bob is moving, so she doesn't see this happen in her reference frame. He's measuring things that are not standing still in Alice's frame, so his measurements are invalid in that frame. How can Bob know where the clocks will be (in Alice's frame) when they emit their sync pulse? They haven't gone off yet, or they did a while ago, and either way, they're not at that spot when he takes his distance measurement.
She sees that he measures the distance from emitter to each clock as being equidistant on the train, with his measuring tape.She sees no such thing. Bob is using completely invalid methods for making that measurement in Alice's frame, like trying to measure the height of a hyperactive child that won't stop jumping up and down.
What she then sees is the light pulse from Bob's emitter, travel a shorter distance to the clock at the rear of the train - because that clock is moving towards the light pulse - and travel a longer distance to the clock at the front of the train - because that clock is moving away from the light pulse. She sees all of this from her vantage point, in her frame on the platform.I agree that the one pulse goes the longer distance in that frame, and thus takes longer to get between the clocks than does the other pulse. This is easily worked out from the premise of constant light speed. The gif Janus showed you (does he make those?) makes that pretty clear.
The opposite is true for each light pulse on the return leg, so the effects cancel out and the light pulses return simultaneously to Bob.I think you mean that light going from Bob to the front and back to Bob travels the same net distance as the one going from Bob to rear and back. Yes, that's obviously true since the departure and arrival of both signals is simultaneous (one event 1 and 3). But since in Alice's frame the one going forward takes so much longer on the first leg, the rear mirror reflection event (that starts the clock there) obviously occurs first in that frame, so the clocks are very obviously not in frame as far as Alice is concerned. This is exactly what she expected and Bob agrees with that assessment.
He clearly designates one arbitrary frame as such for notational convenience. I notice you didn't include that part of the quote despite its importance.My apologies, I presumed that everyone who would be replying this would already be familiar with Einstein's paper and his use of the convention. I presumed they would recognise that I was folllowing that convention. I take your point though, it's always better to be explicit about these things.
In post 6 (point 1) you redefined the words to mean one's own frame, which makes the term ambiguous in absence of identification of whose frame we're talking about. I like that much better since it emphasizes the symmetry.
Anyway, I framed all my replies for post 6 with this new definition of 'the stationary frame' which you give in the first point of that post.
Then your point 1 contradicted that convention. Why can't we say Alices's frame instead? Alice is designated the stationary one if we're to go by Einstein's convention. The first observer is arbitrarily designated the stationary one.We're not in disagreement here. We can (and do) use Alice's frame. We could just as easily start with Bob, the symmetry of the scenario means that the reasoning applies eqally well to either. We are choosing one of them and examining things solely from their perspective.
Any statements made are based on observations made by Alice, until we introduce the bodycam footage. This is perfectly valid if you don't a priori assume the validity of the Einsteinian interpretation i.e. if you don't assume your conclusion of frame dependence. It's valid regardless, but jumping to the conclusion before the validity of the foundational assumption has been established just serves to obfuscate the issue.QuoteWe're looking at things solely from Alice's perspective, in Alice's frame, on the platform and making deductions based on her observations.Then don't quote statements made about different frames.
Why is it a bad assumption to make? All clocks, observer, tape measures, etc are all stationary in this frame and remain so for the duration between the relevant events.Be careful here with your frame dependent terminology. They all remain stationary, with respect to what? Bare in mind that one cannot be stationary with respect to a set of imaginary, mathematical co-ordinates. To describe the physical scenario we should more accurtely say that Alice is at rest relative to the emitter, and both are at rest relative to the clocks. This is her synchronisation set up.
Be careful with your use of the term "moving" here because your confusing two different things. At this point in the discussion, we're not talking about Bob's observations of Alice, we're talking about Bob setting up his synchronisation procedure, on the train.QuoteRemember that [from her reference frame] Alice sees Bob measure the distance from his emitter to each of his clocks, on the train, with his measuring tape.Bob is moving, so she doesn't see this happen in her reference frame. He's measuring things that are not standing still in Alice's frame, so his measurements are invalid in that frame. How can Bob know where the clocks will be (in Alice's frame) when they emit their sync pulse? They haven't gone off yet, or they did a while ago, and either way, they're not at that spot when he takes his distance measurement.
You do realise that this is contradictory to what Einsteinian relativity actually says, right? The whole point is that Bob's measurements of Alice's experiments are just as valid as Alice's measurements of her own experiments. This where the Relativity of Simultaneity comes from. Bob measures events to be non-simultaneous in Alice's frame (that she assumes are simultaneous in her frame).QuoteShe sees that he measures the distance from emitter to each clock as being equidistant on the train, with his measuring tape.She sees no such thing. Bob is using completely invalid methods for making that measurement in Alice's frame, like trying to measure the height of a hyperactive child that won't stop jumping up and down.
I agree that the one pulse goes the longer distance in that frame, and thus takes longer to get between the clocks than does the other pulse. This is easily worked out from the premise of constant light speed. The gif Janus showed you (does he make those?) makes that pretty clear.Alice makes the above observation of Bob's light pulses. She assumes that the same is not true for her because she employs the Einsteinian convention that the time from A to B equals the time from B to A. Her observations of Bob's synchronisation procedure offer an alternative explanation for her own, which would result in the exact same observations being made. Add to this Bob's empirical observation [of Alice's synchronisation procedure] and Alice is left with her assumption that the clocks are synchronised versus the observtional evidence that they are not.
I think you mean that light going from Bob to the front and back to Bob travels the same net distance as the one going from Bob to rear and back. Yes, that's obviously true since the departure and arrival of both signals is simultaneous (one event 1 and 3). But since in Alice's frame the one going forward takes so much longer on the first leg, the rear mirror reflection event (that starts the clock there) obviously occurs first in that frame, so the clocks are very obviously not in frame as far as Alice is concerned. This is exactly what she expected and Bob agrees with that assessment.Agreed. The point being that Alice has no way of knowing that the same has not happened in her own synchronisation procedure. She assumes that the distance the signals travel to each clock is the same - as per the Einsteinian convention - however, it is just that, an assumption. If she was mistaken in her assumption, she would have no way off knowing bcos the signals would travel the same net distance and arrive back simultaneously.
With respect to the frame referenced. That's what 'stationary in this frame' means.Quote from: HalcAll clocks, observer, tape measures, etc are all stationary in this frame and remain so for the duration between the relevant events.Be careful here with your frame dependent terminology. They all remain stationary, with respect to what?
Bare in mind that one cannot be stationary with respect to a set of imaginary, mathematical co-ordinates.The frame is not imaginary (except it is since this is a thought experiment). The frame was defined using real references, in this case Alice or either of her clocks. One doesn't even need a stationary object to define a frame.
To describe the physical scenario we should more accurtely say that Alice is at rest relative to the emitter, and both are at rest relative to the clocks. This is her synchronisation set up.That was all described in the OP, yes, except we hadn't named that observer Alice at that point.
But, Alice can say the exact same thing about Bob's set up. He is at rest relative to the emitter, and both are at rest relative to the clocks. This is his synchronisation set up, as observed by Alice. Both are in motion relative to each other.All of Alice's components are stationary in her frame. Bob and his clocks and tape measure are obviously not stationary in Alice's frame.
You say that "all clocks, observer, tape measures, etc are all stationary in this frame and remain so
" but you are leaving out the central actor in the whole synchronisation process, the light pulses. They do not remain "stationary". So, how is the distance they travel in Alice's frame determined. She assumes that the distance traveled by the light pulse to clock A is the same as the distance traveled by the light pulse to clock B and that both these distances are the same as the distance she measured from the emitter to each clock.Yes, she can validly determine that since the clocks are stationary. Neither emitter nor Alice need be stationary. We just need to know the location in space where the emit event takes place and the observation of the return (if there is one) takes place. Since both are stationary, we know where these events take place.
She observes Bob making similar measurements on the train (from her perspective). He too assumes that the distance traveled by the light pulse to clock A is the same as the distance traveled by the light pulse to clock BHe does not. We're assuming everything in Alice's frame, remember? Bob knows he and his clocks are moving in that frame and is not using a valid procedure for syncing them in that frame. At no point is Bob mistaken about anything. We assume he's educated.
Observing - what she considers to be - Bob's failed synchronisation attempt, offers an alternative explanation for her own synchronisation procedure. It is possible that, in her frame, clock A was moving towards the light pulse while clock B was moving away from it.Not possible. The clocks are nailed to the floor on which the tape measure is glued. She's not moving across that floor. Are you suggesting she's faking the evidence, or that somebody is moving her clocks when she blinks?
Everything would still appear the same to her, everything would appear stationary in her frame and the light pulses would return simultaneosuly just the same. As per the Galilean Principle of Relativity, there is no experiment she can do to verify or dismiss this.Yes there is. This whole paragraph is wrong. She would see the clocks moving away or closer, tough to do when they're nailed down. So she'd see the nails breaking or the floor ripping up. It isn't difficult to detect motion relative to ones self. If you doubt it, sit in the street.
I reference only Alice's frame in all that, repeatedly even. The statements are not ambiguous. If you think they are, I'll repeat: All that is described from Alice's frame.Quote from: HalcBob is moving, so she doesn't see this happen in her reference frame. He's measuring things that are not standing still in Alice's frame, so his measurements are invalid in that frame. How can Bob know where the clocks will be (in Alice's frame) when they emit their sync pulse? They haven't gone off yet, or they did a while ago, and either way, they're not at that spot when he takes his distance measurement.Be careful with your use of the term "moving" here because your confusing two different things.
At this point in the discussion, we're not talking about Bob's observations of Alice, we're talking about Bob setting up his synchronisation procedure, on the train.I never described Bob watching Alice. Perhaps Alice is watching Bob since you think that's important, but she already knows that Bob isn't trying to sync his clocks in her frame.
No. Bob knows very much that he's moving in Alice's frame, and (Galilean) relativity doesn't say otherwise.Quote from: HalcBob is using completely invalid methods for making that measurement in Alice's frame, like trying to measure the height of a hyperactive child that won't stop jumping up and down.You do realise that this is contradictory to what Einsteinian relativity actually says, right?
The whole point is that Bob's measurements of Alice's experiments are just as valid as Alice's measurements of her own experiments.Bob doesn't measure any of Alice's experiments. He just watches Alice do it, and Alice does a valid measurement of her stuff in her frame. But Bob does not do valid measurement of his own stuff in Alice's frame. It isn't symmetrical because we're considering only Alice's frame. You want symmetry, consider what Bob is doing in Bob's frame.
This where the Relativity of Simultaneity comes from. Bob measures events to be non-simultaneous in Alice's frame (that she assumes are simultaneous in her frame).We're talking about Alice's events, right? Bob hasn't measured them, having only watched Alice do it, but if he did, they would be measured simultaneous in Alice's frame. Those events are only non-simultaneous in Bob's frame. So I disagree with your statement. You seem not to know your relativity at all. We haven't even touched on the mathematics yet. You don't understand the base concepts at all.
Alice makes the above observation of Bob's light pulses. She assumes that the same is not true for her because she employs the Einsteinian convention that the time from A to B equals the time from B to A.In Alice's frame, there is not A to B and B to A. If light is emitted at point A, B is a mirror, then there is nothing at A when the light gets back because Bob there has moved elsewhere. How can you not see that?
Her observations of Bob's synchronisation procedure offer an alternative explanation for her ownNo they don't. She's not moving in her frame. Bob is very much moving in her frame.
The point being that Alice has no way of knowing that the same has not happened in her own synchronisation procedure.You keep insisting on this, but it is wrong. She has every way of knowing, which is why nobody disagrees on anything. Everybody is doing precise measurements and nobody is guessing about anything. There is no alternative explanation about anything since there is no conflicting assessment of what happened. Everybody is right.
She assumes that the distance the signals travel to each clock is the same - as per the Einsteinian conventionEinstein says that distance is frame dependent. Nobody assumes anything. I tire of saying that. Relativity isn't about anybody assuming anything. Go to an absolute interpretation if you want assumptions being necessary.
- however, it is just that, an assumption.Not sure which clocks you're talking about. No asumptions either way. Her own clocks are not moving in her frame, so she knows (not assumes) the distance to them is the distance that light travels to get to them in her frame.
If she was mistaken in her assumption, she would have no way off knowing bcos the signals would travel the same net distance and arrive back simultaneously.
All of Alice's components are stationary in her frame. Bob and his clocks and tape measure are obviously not stationary in Alice's frame.OK, let's try to break things right down. Let's take a common formulation of the thought experiment. Let's say Alice and Bob are in spaceships.
Let's clear all components out of the spaceship, including Alice, so we are left with just the spaceship. Is the spaceship stationary?Relative to what?
Relative to what?Indeed, relative to what? It's a simple question. So, again is the spaceship stationary?
It certainly is relative to the spaceship! However, Bob might disagree.
ou can also set up a frame which moves with the spaceship and the spaceship is at rest relative to that.We don't need to add anything more, it's a simple foundational question from which we can expand. So, is the spaceship at rest - you can add any qualifiers you wish.
ou seem to have problems with the different viewpoints here, but there is no surprise that Alice and Bob see different things and that these differences are symmetrical, but this does not affect whether they can say their own clocks in their own frames are synchronised. The same sort differences of viewpoint occur in Galilean relativity. Also, if you follow through the differences of measurements performed in their respective coordinates (coordinate transforms) you will see that these differences are to be expected and easily understood.I'm familiar with what the Einsteinian interpretation says and with the fact that it is internally consistent. I'm proposing an alternative interpretation.
It makes no difference that Alice is intelligent and can work out what’s happening, she takes measurements from her frame.
In Galilean relativity we can see that Bob on a railway carriage sees a ball bouncing up and down, in order to shoot it down his gun need only track up and down, Alice however sees the ball following a sine wave, a very different prediction.
We are also used to everyday experiences of frame dependant views, we all know that the passenger in a car following a curve continues in a straight line, but that doesn’t make the centrifugal force any less real to the passenger.
I would recommend you look at the coordinate transforms for Alice’s viewpoint in order to understand this situation as you are getting lost in misunderstanding what the bodycam footage really shows - the view from one frame only, which is not relevant to what the other frame views.
Alice doesn’t need to question whether her clocks are synchronised, she’s a bright girl and can work out that they are, but that synchronisation only applies to her frame.
it's a simple foundational question from which we can expand. So, is the spaceship at rest - you can add any qualifiers you wish.The simple answer is that we don’t know.
Are you familiar with the empirically equivalent Lorentz-Poincare interpretation, which is based on absolute simultaneity?Yes I am. Again, we don’t care, because we have all we need to work out the relative viewpoints and measurements.
The simple answer is that we don’t know.Precisely! Which is why it can't be assumed that the distance the light pulses travel is equal to the distance from emitter to clock. The clocks in Alice's reference frame could be moving relative to the light pulses - well, we know they are - they could be moving in such a way that one clock moves towards the light pulse, while the other is moving away. Alice has no way of knowing which situation is the true situation - as per the Galilean Principle of Relativity.
The qualifier is that we don’t care, because it is at rest relative to it’s own reference frame and that’s all we need to know.Objects in the physical world can only be in motion or at rest relative to other physical objects. We have 2 spaceships, where are you getting this 3rd physical entity, which you are calling the spaceships "own rest frame", relative to which you are saying it is at rest?
Yes I am. Again, we don’t care, because we have all we need to work out the relative viewpoints and measurements.Interesting that "we" don't care. Both interpretations make different ontological claims about the underlying physical structure of the universe. You might think that this would be of concern to a field of research that concerns itself with the nature and functioning of the physical world.
Bob's ship and his components are not, unless the scenario has changed. The fact that they're in ships makes no difference.Quote from: HalcAll of Alice's components are stationary in her frame. Bob and his clocks and tape measure are obviously not stationary in Alice's frame.OK, let's try to break things right down. Let's take a common formulation of the thought experiment. Let's say Alice and Bob are in spaceships.
All components are stationary, in her frame.
Let's clear all components out of the spaceship, including Alice, so we are left with just the spaceship. Is the spaceship stationary?It is stationary in the ship's frame, by definition. Sans that frame reference, the question has no meaning under the relativistic interpretation.
It certainly is [stationary] relative to the spaceship! However, Bob might disagree.To clarify, Bob might says the ship is not stationary relative to his ship, but he does not disagree that Alice's ship (without Alice even) is stationary relative to itself, and yes, saying this is a meaningless tautology, as is "the ship is at rest in the frame in which it is stationary".
Colin is open to the question having meaning without a reference, such as "what is the distance to my elbow?". I'm being precise in saying the question has no meaning, and is thus not a thing we don't know, but rather a thing whose answer is not even wrong.Quote from: Colin2BPrecisely!QuoteSo, is the spaceship at rest?The simple answer is that we don’t know.
Alice has no way of knowing which situation is the true situation - as per the Galilean Principle of Relativity.She very much knows this, per that principle. The principle says there is no true situation. Only the absolute interpretation denies the principle, giving meaning to the question and allowing an answer, even if it is still "I don't know". But Alice knows because she's a relativist.
Objects in the physical world can only be in motion or at rest relative to other physical objects.Which is why motion is undefined in a universe with a sole existant. In an absolute universe, motion is defined but unknown even with multiple existants.
I know you are committing the fallacy of reification with respect to the mathematical co-ordinates and saying that the spaceship is at rest relative to them;Nobody claims a reference frame is a physical object. It not being physical does not make it a valid reference. It just needs definition.
Interesting that "we" don't care. Both interpretations make different ontological claims about the underlying physical structure of the universe. You might think that this would be of concern to a field of research that concerns itself with the nature and functioning of the physical world.Yes, the interpretations do indeed make different ontological claims. We don't care because it makes no empirical distinction. Research is for empirical differences. The different interpretations is just philosophy. The relativistic interpretation is consistent with itself, and I'm only defending that stance against your misrepresentation of it. I'm not claiming another interpretation is wrong, especially if it makes no different empirical predictions.
That is beside the point tho. The point is that there is an alternative interpretation of Relativity which doesn't involve the Relativity of Simultaneity.Agree, there is. I'm well aware of it.
I'm probably making things a bit difficult for myself here, so to try and simplify:This whole post is obfuscated by a lack of definition of what A and B are, per Einstein's quote. That's what definition is being referenced (not made) in that quote. The quote is being taken completely out of context.
Einstein's clock synchronization convention unequivocally states that the synchrony of clocks must be assumed. This is done by establishing - as a matter of definition - that the time for light to travel from A to B equals the time from B to A.
This applies in the Set-up with Alice and Bob where the time from emitter to A is established by definition to be equal to the time from emitter to B.Einstein talked about A to B equaling B to A, not E to A equaling E to B. So this statement has zero to do with your chosen Einstein quote.
Bob's observational evidence demonstrates that Alice's assumption is incorrect.Bob fully agrees with Alice's deductions. You repeat this assertion over and over. It is wrong. It is mostly wrong because you misrepresent what Alice has demonstrated.
To try and refer to frame dependence - to disqualify Bob's observational evidence of Alice's synchronization procedure - is simply to assume the conclusion of frame dependence.We tried to assume frame independence, and it ran into contradictions. So again, the conclusion is deduced, not assumed. Bob's observational evidence is never disqualified. Both are in agreement, so disqualification is not necessary. If you think Bob concludes something else, be explicit about where there is disagreement, because I assert there is none.
or you are populating the universe with clocks at rest relative to the spaceship and referring to those. In the latter case, we said not to introduce anything more and just talk about the spaceship.you said that, not me, not @Halc.
Alice has no way of knowing which situation is the true situation - as per the Galilean Principle of Relativity.OK you raise Galilean relativity, let's update his famous thought experiment.
Bob's bodycam footage provides observational evidence to the contrary.No it doesn't, it only shows movement relative to Bob's ship.
The point is that there is an alternative interpretation of Relativity which doesn't involve the Relativity of Simultaneity. This just further demonstrates the point that the Einsteinian interpretation makes the assumption of Simultaneity in "the stationary system"If your intention was to discuss LET or Poincaré-Lorentz, it would have been better to start there rather than this route which has made things difficult for yourself.
Einstein talked about A to B equaling B to A, not E to A equaling E to B. So this statement has zero to do with your chosen Einstein quote.Do you genuinely not see how it's the exact same thing? If you can't grasp this point, there is little hope that the rest will be understood:
Coordinate systems and references are for essential understanding measurements, be those coordinates latitude/longitude etc, so it is reasonable to introduce them.The ship analogy and measuring relative distances is fine because at the relative velocities involved, relativistic effectss will be negligible.
OK you raise Galilean relativity, let's update his famous thought experiment.
We are on board a modern warship. Deep in the bowels of the ship, with no direct outside view is the fire control centre. The officer in charge has a radar screen, he and the ship are at the centre, distance lines are set out on the screen which correspond to actual distances outside. This is not reification, as no one believes there are actual lines on the sea anymore than Alice believes there are real lines outside her ship. The Officer can measure the relative positions of other ships in the vicinity and make predictions about thier future positions. All this without knowing any absolute position or velocity of his own ship, and assuming only that he is at rest relative to himself - not a meaningless tautology, but an important reference point. As @Halc says we need to reiterate this as if you don't recognise the importance of 'at rest relative to a reference frame' then we have to find a concrete anchor.
By the way, I would also answer “don't know” to @Halc question "what is the distance to my elbow?", bcause there is insuficient information to form an answer.All observers willl measure the same value, won't they? They will just disagree on the simultaneity of clocks involved in the measuring procedure and the "length" of the units of measurement.
Hopefully this gets addressed by the point below.Bob's bodycam footage provides observational evidence to the contrary.No it doesn't, it only shows movement relative to Bob's ship.
If your intention was to discuss LET or Poincaré-Lorentz, it would have been better to start there rather than this route which has made things difficult for yourself.
I have a great deal of respect for Poincaré and there is no doubt that he almost developed the theory of relativity. In 1905 he said “It seems that this impossibility to disclose experimentally the absolute motion of the earth is a general law of nature ; we are led naturally to admit this law, which we shall call the Postulate of Relativity, and to admit it unrestrictedly”, if he had only taken the step of fully accepting the implications of this we would now be referring to Poincaré’s theory of relativity.
The ship analogy and measuring relative distances is fine because at the relative velocities involved, relativistic effectss will be negligible.Depends on how fast our respective observers go, which wasn't specified in the thought experiment. But it has nothing to do with one observer being on a ship or a planet.
His reference frame being at rest "relative to itself" doesn't give him any information about how his reference frame is in motion relative to the light signals he uses to synchronise his clocks.An object is not in motion relative to light. Light does not constitute a valid reference frame. If it was, light would be stationary in it, which would violate the constant speed of light premise.
How might one attempt the measurement? Keep it simple. The question wasn't related to a reference frame.Quote from: Colin2BBy the way, I would also answer “don't know” to @Halc question "what is the distance to my elbow?", bcause there is insuficient information to form an answer.All observers willl measure the same value, won't they?
They will just disagree on the simultaneity of clocks involved in the measuring procedure and the "length" of the units of measurement.You're going to use a clock to measure the distance to my elbow?
1) I'm not arguing that the Einsteinian interpretation is inconsistent, I'm arguing that its self-consistency stems from its assuming its conclusion, an assumption which I am arguing is contradicted by [implied] obervational evidence - implied by the thought experiment used to explain it.You've not demonstrated that. You just assert it, not demonstrate it. The conclusion was deduced from just the two premises. From there, that deduced conclusion can be used to demonstrate that the view is entirely consistent, despite your assertions otherwise.
They assume that it must rely on an Ether and that it can only be formulated as a dynamical theory.Well you did say "Objects in the physical world can only be in motion or at rest relative to other physical objects.", and yet you talk all the time about the speed of an object without specifying the other object relative to which that speed is meaningful. You're very self inconsistent.
Essentially, we don't need an absolute reference frame, we need a privileged referece frame that defines "true time".You'll have to explain the difference to me. If there is a privileged frame defining true time, how does it possibly not correspond to an absolute frame giving meaning to location and speed of all objects?
the rest frame of the Earth plays this role because that is how we have defined our units of measurement, for use in real world experiments.That just means that all speeds and locations are relative to Earth. It doesn't make it absolute at all. It is just an arbitrary selection for a standard frame. I can frame the Alice and Bob thing in that frame and they'll again find no inconsistency.
3) ... then we are left with an alternative kinematical interpretation that has been derived without reference to any form of dynamics, luminiferous ether, or absolute reference frame.You're still left with your reference to the arbitrarily selected standard frame, which makes it relative. I don't think this is what Poincaré-Lorentz had in mind.
As per the the Synchronisation Convention, the journey time for a light signal from clock A to clock B is assumed to be the same as the journey time from B to A.Depends on what A and B are. The statement above is trivially not true for any A and B, but you drive it to inconsistency by taking it out of the context where A and B are defined in such a way that the statement is always true.
Einstein talked about A to B equaling B to A, not E to A equaling E to B. So this statement has zero to do with your chosen Einstein quote.Do you genuinely not see how it's the exact same thing? If you can't grasp this point, there is little hope that the rest will be understood:
@Halc: this point needs addressing before we can proceed.I genuinely do not.Einstein talked about A to B equaling B to A, not E to A equaling E to B. So this statement has zero to do with your chosen Einstein quote.Do you genuinely not see how it's the exact same thing?
It might dawn on you if we label the emitter as A and the clock on the left as B1 and the clock on the right as B2.Unclear what you're talking about. I see one setup. Two if we count Bob's.
Can you see that what we effectively have, is 3 examples of Einstein's clock synchronization convention in the one Synchronisation set-up?
If you can't then I'll break it down.Do that please. Einstein wasn't referring to objects with A or B. You are. You're thus misinterpreting his statement. Be very clear about what those things are when you drag one of Einstein's quotes out of context into your argument.
I genuinely do not.The light clock set-up is based on two clocks equidistant from the emitter, so this analogy is a misrepresentation of it.
London (E) is closer to Paris (A) than to Tokyo (B). E to A does not equal E to B. But the distance from Paris to Tokyo (as measured along the Earth surface) is equal to the distance from Tokyo to Paris.
Einstein wasn't talking about distance, he was talking about the time it takes light to cover that distance.So are we, but it is worth noting that the distance from clock A to clock B is, by necessity, equal to the distance from clock B to clock A.
That time is not necessarily the same if either London or Paris is moving, so in general (ignoring the referenced definition of A and B), Einstein's statement that the time it takes light to go from A to B being the same as the time it takes going from B to A is not true.We're not concerned with this just yet. We are simply examining how the clock synchronisation set-up in the "stationary system" is [effetively] the same as in the thought experiment, and how the thought experiment represents a 3-in-one.
Do that please. Einstein wasn't referring to objects with A or B. You are. You're thus misinterpreting his statement. Be very clear about what those things are when you drag one of Einstein's quotes out of context into your argument.Einstein was talking about establishing a "common time" for two clocks A and B i.e. synchronising clocks A and B. We are talking about synchronising two clocks B1 and B2, only in a manner that is immaterially different.
I know, but Einstein's statement that you quoted doesn't say at all what A and B are. It was important. It was there in the paper, but you didn't include it.I genuinely do not.The light clock set-up is based on two clocks equidistant from the emitter, so this analogy is a misrepresentation of it.
London (E) is closer to Paris (A) than to Tokyo (B). E to A does not equal E to B. But the distance from Paris to Tokyo (as measured along the Earth surface) is equal to the distance from Tokyo to Paris.
It would be more accurate to say London to Paris and London to-some-other-location-that-is-the-same-distance-from-London-as-Paris.That lacks a verb. I might agree that the distance from E to A is the same as E to B, but I would not agree (for the same reason as the A->B, B->A thing) that light takes the same time to traverse those two distances, without further clarification of the statement at least. As I said, Einstein wasn't talking about objects like London and Paris.
Agree.Quote from: HalcEinstein wasn't talking about distance, he was talking about the time it takes light to cover that distance.So are we, but it is worth noting that the distance from clock A to clock B is, by necessity, equal to the distance from clock B to clock A.
Einstein did not define either A or B as a clock, but rather points in space where the clocks are located. You seem to be using them as the clocks themselves, but you've haven't actually explicitly said so.Quote from: HalcThat time is not necessarily the same if either London or Paris is moving, so in general (ignoring the referenced definition of A and B), Einstein's statement that the time it takes light to go from A to B being the same as the time it takes going from B to A is not true.We're not concerned with this just yet. We are simply examining how the clock synchronisation set-up in the "stationary system" is [effetively] the same as in the thought experiment, and how the thought experiment represents a 3-in-one.
One must take the comment in the context in which A and B were defined as Einstein defined them.
Einstein was talking about establishing a "common time" for two clocks A and B i.e. synchronising clocks A and B.He never references "clock A" or "clock B". Yes, he was talking about establishing a "common time" for two clocks at those locations, but A and B do not refer to the clocks. I cannot emphasize that distinction enough, because you're drawing false conclusions from interpreting his quotes otherwise.
Einstein was talking about 2 spatially separated clocks A and B.No, he was not. Read the text and what I said just above. Say it the way Einstein does if you're going to quote him.
So, for the sake of clarity lets say that the distance from emitter (A) to clock B1 equals the distance from A to B2 - and both are equal to the distance between clock A and B from Einsteins 1905 paper.It can easily be demonstrated otherwise, so your statement is false. If you word it the way Einstein does, the statement becomes true. This is an excellent illustration of why it is important to get all the definitions and wordings correct.
So, Einstein's synchronisation convention talked about two trips for the single llight signal" from
1) clock A to clock B
2) clock B to clock A
the time for both journeys is assumed to be the same i.e. it is established by definition that the time for both trips are the same - the distance is the same by matter off necessity.
Einstein did not define either A or B as a clock, but rather points in space where the clocks are located. You seem to be using them as the clocks themselves, but you've haven't actually explicitly said so.My apologies, I was working on a "steelman" assumption and an assumption that reasonable inferences would be made.
He never references "clock A" or "clock B". Yes, he was talking about establishing a "common time" for two clocks at those locations, but A and B do not refer to the clocks. I cannot emphasize that distinction enough, because you're drawing false conclusions from interpreting his quotes otherwise.The conclusions being drawn aren't based on this distinction. I have clarified this above.
No, he was not. Read the text and what I said just above. Say it the way Einstein does if you're going to quote him.For "clocks A and B" read clocks at A and at B.
What can be demonstrated otherwise; which statement is false?QuoteSo, for the sake of clarity lets say that the distance from emitter (A) to clock B1 equals the distance from A to B2 - and both are equal to the distance between clock A and B from Einsteins 1905 paper.It can easily be demonstrated otherwise, so your statement is false. If you word it the way Einstein does, the statement becomes true. This is an excellent illustration of why it is important to get all the definitions and wordings correct.
So, Einstein's synchronisation convention talked about two trips for the single llight signal" from
1) clock A to clock B
2) clock B to clock A
the time for both journeys is assumed to be the same i.e. it is established by definition that the time for both trips are the same - the distance is the same by matter off necessity.
I assumed that one could reasonably infer that we were talking about clocks located at A and at B in "the stationary frame" on the basis that we were talking about Eintein's clock synchronisation in "the stationary frame"Per the premises, it works in any frame. Said "stationary frame" is not special in that regard.
I also assumed that the chosen nomenclature of "Clock A" to refer to the clock at A and "Clock B" to refer to the clock at B would be intelligible to most.You are drawing false conclusions from the alternate wording, so that wording is wrong, not just a difference of nomenclature.
That Einstein doesn't label the clocks A and B doesn't prevent us from doing so. The logic of the argument is unaffected by thisIt very much is, and you very much rely on that change of meaning in your argument. You can deny it, so I must simply insist that you say Clock at A else we will waste countless posts in disagreement of the terms. You can say 'clock A' of course, but you cannot put that wording in Einstein's statement since the term doesn't mean "clock at A".
What can be demonstrated otherwise; which statement is false?This one:
So, Einstein's synchronisation convention talked about two trips for the single llight signal" fromThere is no definition of anything that asserts that time for light to travel from one object to another equals the time to travel between them the other way. It is pretty easy to come up with a counterexample showing this, as I've done in prior posts.
1) clock A to clock B
2) clock B to clock A
the time for both journeys is assumed to be the same i.e. it is established by definition that the time for both trips are the same
Bear in mind, "in the 'stationary system'" is implied - because I have repeatedly stated that it is implied.If the clocks are moving in that stationary system, then Einstein's statement (A and B being locations) would be true but your statement (A and B being clocks) would be false.
OK.I assumed that one could reasonably infer that we were talking about clocks located at A and at B in "the stationary frame" on the basis that we were talking about Eintein's clock synchronisation in "the stationary frame"Per the premises, it works in any frame. Said "stationary frame" is not special in that regard.
If you mean clock at A, say clock at A, not clock A. I wouldn't insist if it wasn't important.QuoteI also assumed that the chosen nomenclature of "Clock A" to refer to the clock at A and "Clock B" to refer to the clock at B would be intelligible to most.You are drawing false conclusions from the alternate wording, so that wording is wrong, not just a difference of nomenclature.QuoteThat Einstein doesn't label the clocks A and B doesn't prevent us from doing so. The logic of the argument is unaffected by thisIt very much is, and you very much rely on that change of meaning in your argument. You can deny it, so I must simply insist that you say Clock at A else we will waste countless posts in disagreement of the terms. You can say 'clock A' of course, but you cannot put that wording in Einstein's statement since the term doesn't mean "clock at A".QuoteWhat can be demonstrated otherwise; which statement is false?This one:QuoteSo, Einstein's synchronisation convention talked about two trips for the single llight signal" fromThere is no definition of anything that asserts that time for light to travel from one object to another equals the time to travel between them the other way. It is pretty easy to come up with a counterexample showing this, as I've done in prior posts.
1) clock A to clock B
2) clock B to clock A
the time for both journeys is assumed to be the same i.e. it is established by definition that the time for both trips are the sameQuoteBear in mind, "in the 'stationary system'" is implied - because I have repeatedly stated that it is implied.If the clocks are moving in that stationary system, then Einstein's statement (A and B being locations) would be true but your statement (A and B being clocks) would be false.
I say all this because you very much try to apply Einstein's statement to Bob's moving clocks and assert that there is some sort of contradiction going on. The contradiction goes away if A and B are locations instead of clocks.
I suspect you are in danger of committing the reification fallacy by implying that Alice's spaceship is at rest relative to a set of imaginary, mathematical coordinates, but that remains to be seen.It's a thought experiment, so the frame is as imaginary as Alice. If you're going to declare that fallacious, then all such thought experiments are fallacious.
Does this clarification suffice:That works, sure.
In the "stationary system" i.e. Alice's spaceship, Alice marks out (with chalk/spraypaint/whatever) three points A, B1 and B2.
At point A she puts an emitter with a clock that has the letter A painted on it. At points B1 and B2 she positions one clock [at each point] painted with B1 and B2 respectively. All of these components are secured to the spaceship at the points marked on the floor of the spaceship.Bolted to the floor is the way I put it I think in a prior post.
Alice, and all the components for her, synchronization procedure - including the points ( A and B) marked on the floor - are co-moving with the spaceship in a state of inertial motion?None. We've added a ship to which the object are attached and the marks made. Is the purpose of it to have something more concrete to represent the frame?
Any objections to this so far?
It's a thought experiment, so the frame is as imaginary as Alice. If you're going to declare that fallacious, then all such thought experiments are fallacious.The thought experiment represents a [plausible] real-world experimental set-up i.e. one which could manifest itself in the physical world. The same canot be said of invisible mathematical coorinates.
Secondly, frames do not provide coordinates, only relative ones. One needs to specify an origin to make it into a coordinate system.Duly noted.
Yep and a spaceship just to free us from any psychological baggage associated with the idea of "stationary"QuoteDoes this clarification suffice:That works, sure.
In the "stationary system" i.e. Alice's spaceship, Alice marks out (with chalk/spraypaint/whatever) three points A, B1 and B2.QuoteAt point A she puts an emitter with a clock that has the letter A painted on it. At points B1 and B2 she positions one clock [at each point] painted with B1 and B2 respectively. All of these components are secured to the spaceship at the points marked on the floor of the spaceship.Bolted to the floor is the way I put it I think in a prior post.None. We've added a ship to which the object are attached and the marks made. Is the purpose of it to have something more concrete to represent the frame?
I recall Einstein also using physical frames like this on which marks were made and such.Cool. We're good to go so.
The thought experiment represents a [plausible] real-world experimental set-up i.e. one which could manifest itself in the physical world. The same canot be said of invisible mathematical coorinates.Good. The mathematical coordinates are anything but invisible. There's numbers printed on the ship if that makes a difference to you. It doesn't to me. All that is needed is the clocks actually to anchor the frame, the ones we're trying to sync. Those are quite real, not abstract.
Glad you want to do that.Quote from: HalcNone. We've added a ship to which the object are attached and the marks made. Is the purpose of it to have something more concrete to represent the frame?Yep and a spaceship just to free us from any psychological baggage associated with the idea of "stationary"
A couple of things. "Event B1" refers to the light signal making physical contact with clock at B1 while "Event B2" refers to the same thing for clock at B2.Agree. B1 for the spatial location, and event B1 or EB1 for the event that occurs there at that specific moment.
At t_0 - on her co-located clock (A), Alice sets the light pulses off towards clocks B1 and B2 (which are still bolted to the floor); clock A is ticking uniformly - at any rate it is the same for both signals; how does Alice determine what reading on clock A co-incides with event B1 and the reading on clock A that co-incides with event B2?First of all, the clocks should be named something like C1, C2, and C0 say, which happen to be located at B1, B2, and A respectively. C0 wasn't there before and serves little purpose.
A point of note: I'm not asking for you to tell me what the reading is, rather how does she determines what it is? Bearing in mind that light must travel from the clocks to her so that she can actually make an observation.Alice computes d/c. Looking at the clock serves no purpose in any of that, but we have to know that the clock reads zero at the emit event E0, so perhaps the clock triggers the emission event when it reaches 0, or the emission event zeroes the clock that is right there. The sole purpose of Alice seems to be that of a detector of the light signals coming back from events B1 and B2, plus she also performs computations. She needs to be at location A when she does the detection thing just like the emitter needs to be there when it does the emit thingy. It really doesn't matter where these things are at different times. The clock at A needs to stay put else the computation of what it reads will be off. I see little point in anybody actually looking at any of the clocks. We're syncing them (a write operation), not reading them (a read op).
The distance from A to B1 and B2 is known, so one can simply compute the time it takes for light to cover that distance, which makes an assumption of frame independent light speed. This is valid to do since that's one of the two premises of SR, and we're doing an SR procedure here.Yes, we are doing an SR procedure here and the point being made is that the [clock synchronization] events, in the stationary frame, are assumed to be simultaneous, under the SR interpretation.
If B1 is distance d away from A, then C0 reads d/c at a time simultaneous with events B1 and B2.This is a [mathematical] prediction, which says that the reading d/c on the physical clock C0 coincides with the EB1 and EB2. Where is the observational verification of this calculation/prediction?
Alice computes d/c. Looking at the clock serves no purpose in any of that
Looking at the clock serves no purpose in any of that but we have to know that the clock reads zero at the emit event E0, so perhaps the clock triggers the emission event when it reaches 0, or the emission event zeroes the clock that is right there. The sole purpose of Alice seems to be that of a detector of the light signals coming back from events B1 and B2, plus she also performs computations.C0 provides the timestamp by which we determine whether EB1 and EB2 are simultaneous. As you said above: If B1 is distance d away from A, then C0 reads d/c at a time simultaneous with events B1 and B2. That is a prediction. So looking at the clock serves the very important purpose of verifying that prediction. Afterall, Alice doesn't just assume her mathematical predictions are correct without verifying them against real world observations, does she??
Yes, we are doing an SR procedure here and the point being made is that the [clock synchronization] events, in the stationary frame, are assumed to be simultaneous, under the SR interpretation.Their synchronization is known, not assumed, under the SR interpretation. The only thing assumed is the SR interpretation itself, which is a pair of premises. There is not a third premise that these two clocks are synchronized.
Indeed, an assumption of frame independent light speed is made in the form of the assumption that the journey time from A to the clock B1 (located at point B1) is equal to the journey from A to the clock B2 (located at point B2).Disagree. In an alternate interpretation (say one where location and speed are properties of things instead of relations between them), speed of light might be constant, but that fact isn't frame independent. In that alternate interpretation, the rule of light taking the same time to travel from a given location to another is also the same as the time to travel from the latter to the former. So that rule isn't an SR specific assumption. It is an assumption that light going one way goes the same speed as light going another way. I am unaware of a valid interpretation that would not make that assumption, but I suppose it could exist.
Alice's computation represents a mathematical prediction that needs to be verified against observations in the physical world.Not sure which computation you mean. The fact of the sync? That wasn't computed. It was just set up so it would happen. Alice computing or verifying isn't what made those clocks be in sync. She's an entirely optional presence. She may be, for some reason, unaware of the facts as have been described in these posts, but if she was, there is no assumptions going on. If she's coming late to the party, as it were, then perhaps she needs to take additional steps to verify the sync of the clocks.
Which says that event where C0 reads d/c coincides with the zeroing event of the other two clocks, in the frame in question, yes.Quote from: HalcIf B1 is distance d away from A, then C0 reads d/c at a time simultaneous with events B1 and B2.This is a [mathematical] prediction, which says that the reading d/c on the physical clock C0 coincides with the EB1 and EB2.
Where is the observational verification of this calculation/prediction?I just suggested one. Without it, as I said, your statement above isn't a prediction, just an assertion. SR asserts that c0 says d/c at that event. It predicts, on the other hand, that if you run some sort of verification procedure, that it will be consistent with this value. There are several ways to go about it.
She, being an abstract entity, can't do that. All we can have here do is a verification procedure, but it takes a real person to actually take the measurement and verify a prediction. All we can do with Alice is compute what will happen based on our premises. If the theory is wrong, Alice lives in a different universe and her verifications will yield different results than would be had by a real observer.Quote from: HalcAlice computes d/c. Looking at the clock serves no purpose in any of that
It serves the very important role of checking to see if Alice's computation is confirmed by empirical observations.
C0 provides the timestamp by which we determine whether EB1 and EB2 are simultaneous.I didn't use C0. I wasn't even aware that the clock was there in the original description. It seemed to serve a purpose in neither the sync effort nor the verification (the reflected signal) step. So I disagree with your comment. C0 is baggage.
As you said above: If B1 is distance d away from A, then C0 reads d/c at a time simultaneous with events B1 and B2. That is a prediction. So looking at the clock serves the very important purpose of verifying that prediction.Sure, but verification of the sync of C1 and C2 doesn't need C0 at all, especially since no signal reaches C0 when it reads d/c. All we're doing with C0 is computing what it says at various points. I can do that with any clock anywhere, which doesn't directly verify the sync of two unrelated clocks.
Afterall, Alice doesn't just assume her mathematical predictions are correct without verifying them against real world observations, does she??Alice does exact that. She lives in the SR world, be it valid description of our universe or not. The predictions are to be verified by us, so show that we live in the same sort of universe as does Alice.
So, how does Alice empirically confirm that the EB1 and EB2 coincide with the reading d/c on C0?? She simply cannot. She must assume that it is true.She knows it's true. Mathematics demands it. It's the nature of what Alice is, an observer put explicitly in a universe run by SR rules.
Their synchronization is known, not assumed, under the SR interpretation. The only thing assumed is the SR interpretation itself, which is a pair of premises. There is not a third premise that these two clocks are synchronized.You are conflating the mathematical description of the theory with the [plausible] real-world experiments used to verify that description. The thought experiment represents one such [plausible] experimental set-up from which we can draw inferences and make deductions about the Einsteinian/Minkowskian interpretation of the mathematics.
Disagree. In an alternate interpretation (say one where location and speed are properties of things instead of relations between them), speed of light might be constant, but that fact isn't frame independent. In that alternate interpretation, the rule of light taking the same time to travel from a given location to another is also the same as the time to travel from the latter to the former. So that rule isn't an SR specific assumption. It is an assumption that light going one way goes the same speed as light going another way. I am unaware of a valid interpretation that would not make that assumption, but I suppose it could exist.Consider the thought experiment and drop the assumption that Alice's (or anyone else's) clocks are synchronised - more pointedly, that this can be determined. Here it is the two-way speed of light that is constant. This essentially just extends the Galilean principle of relativity to the determination of simultaneity/synchronization.
]Not sure which computation you mean. The fact of the sync? That wasn't computed. It was just set up so it would happen. Alice computing or verifying isn't what made those clocks be in sync.Precisely, clocks in the real-world aren't synchronised by the mathematical formulations of a theory. Just because Alice calculates that the events B1 and B2 are simultaneous, that doesn't necessarily make it so. Her calculation represents a prediction - in this case an untestable/unfalsifiable one.
She's an entirely optional presence. She may be, for some reason, unaware of the facts as have been described in these posts, but if she was, there is no assumptions going on. If she's coming late to the party, as it were, then perhaps she needs to take additional steps to verify the sync of the clocks.Alice is required to make observations to test the predictions of the theory. What additional steps can she take to verify that the clocks are synced?
Einstein of course is demonstrating his methods, so he's less likely to rely on the conclusions of SR to make this assessment. He needs to derive that these methods will indeed result in the clocks being in sync in this frame. I on other hand am begging the conclusions. If you want to challenge that, you need to demonstrate which conclusions of SR are contradictory with its premises, and therefore are invalid for me to wield in making my statements.I'm not saying it's contradictory, I'm saying it's circular. The point being, how can it be demonstrated - by way of observation - that the clocks are indeed in sync in the given frame?
Which says that event where C0 reads d/c coincides with the zeroing event of the other two clocks, in the frame in question, yes.The thought experiment represents a [plausible] real world experiment. As such, it allows us to make certain inferences and deductions.
Calling it a prediction is incorrect, since there is no measurement proposed. A prediction needs that. I had proposed such a way to do a verification procedure (Alice going off to the side and taking a picture). Even that is not a prediction. Predictions are not made in thought experiments since Alice cannot in fact perform any verification. Predictions must be verified in real experiments.
I just suggested one. Without it, as I said, your statement above isn't a prediction, just an assertion. SR asserts that c0 says d/c at that event. It predicts, on the other hand, that if you run some sort of verification procedure, that it will be consistent with this value. There are several ways to go about it.The issue is that there will remain an alternative interpretation of those results, one which doesn't assume the Simultaneity of events.
She, being an abstract entity, can't do that. All we can have here do is a verification procedure, but it takes a real person to actually take the measurement and verify a prediction. All we can do with Alice is compute what will happen based on our premises. If the theory is wrong, Alice lives in a different universe and her verifications will yield different results than would be had by a real observer.Alice represents a plausible real-world observer. As such, we can make inferences and deductions about her verification procedure i.e. what she can and can't observe.
There is in fact a 3rd premise actually to SR: That of flat spacetime. So it works fine for Alice and Bob in their Special case of reasonably massless ships, but in reality, spacetime isn't flat so there are very much empirical differences between SR and reality. This is why SR is considered a local theory. Space is locally flat, but on larger scales it is not.I am aware of that. It's fine though, the issues of determining the Simultaneity of events in the stationary frame still apply.
I didn't use C0. I wasn't even aware that the clock was there in the original description. It seemed to serve a purpose in neither the sync effort nor the verification (the reflected signal) step. So I disagree with your comment. C0 is baggage.You used it to show the clock reading (d/c) which coincides with events B1 and B2 - how else does one determine that the events were simultaneous?
Sure, but verification of the sync of C1 and C2 doesn't need C0 at all, especially since no signal reaches C0 when it reads d/c.Precisely the point! How can the simultaneity of the events be determined then?
All we're doing with C0 is computing what it says at various points. I can do that with any clock anywhere, which doesn't directly verify the sync of two unrelated clocks.Computing what the reading on a physical clock will be at the time of two given events is a prediction about the physical world. How do we verify that the calculation is in fact correct and that our mathematical model accurately represents the physical world, in this specific case - given that there is an alternative, mathematically and empirically equivalent interpretation. How do we verify that the time coordinate that we have ascribed to events B1 and B2 is actually the correct time coordinate for those events? What observation can we make to verify this.
Alice does exact that. She lives in the SR world, be it valid description of our universe or not. The predictions are to be verified by us, so show that we live in the same sort of universe as does Alice.Alice assumes that she lives in an SR world, but only bcos she assumes her conclusions. Alice represents a real-world experimental set-up from which we can make deductions about the Einsteinian interpretation of the mathematical formulation and predictions.
She knows it's true. Mathematics demands it. It's the nature of what Alice is, an observer put explicitly in a universe run by SR rules.How does she know it's true? It's certainly not on the basis of empirical evidence.
I am not. I was quite thorough in pointing out that Alice lives in the SR universe, and the mathematical description is the territory, not the map, since it is a pure abstract mathematical universe with known rules. The prediction/verification business is for real people to do. If it matches what Alice sees, then the SR model is a valid description of our universe, not only hers. If the predicted things don't match measurements, then the model isn't valid, not entirely anyway. That's the interpretation I have of this thought experiment. I am assuming SR interpretation, but Alice knows it because that's how I set up her environment.Their synchronization is known, not assumed, under the SR interpretation. The only thing assumed is the SR interpretation itself, which is a pair of premises. There is not a third premise that these two clocks are synchronized.You are conflating the mathematical description of the theory with the [plausible] real-world experiments used to verify that description.
The predictions of the theory can be extracted from the mathematical formulation.Yes, and Alice's observations become predictions for us. She cannot test that my universe corresponds to her own. Real people must verify or falsify those predictions.
One such prediction made by the theory pertains to the reading on the physical clock (Alice's C0) that coincides with the two events B1 and B2 - the prediction being that the clock reading [equal to] d/c will coincide with the two events i.e that the two events will be simultaneous. This is an untestable prediction, under the foundational assumptions of the theory, meaning that this prediction is unfalsifiable.Given an SR interpretation of physics, there are multiple ways to test that assertion, and those methods are very much falsifiable. Given a different interpretation, I don't think the simultaneity of two clocks can be set up nor verified.
It is a crucial prediction because the conclusion that simultaneity is relativity rests entirely upon it.If you say so. I found the reading on clock C0 to be fairly irrelevant. But if you find it important, do you suggest that any empirical test of C0 in Alice's frame would not yield a difference of d/c with either of the other two clocks?
Given that it is an untestable prediction it can only be assumed to be true.I posted one way to test it. There are others. If it is actually untestable, then it makes no empirical difference, and the fact of it becomes irrelevant. But it is quite testable given an SR interpretation. If you mean to say that it is untestable without assuming an SR interpretation, then I agree.
Assuming that it is true leads, by way of necessity, to the conclusion of RoS but that is only because the first, emboldened part of the conclusion - "events which are simultaneous in one frame are not simultaneous in a relatively moving frame" - is assumed.Very hard to parse that, but if you're saying that one needs to assume RoS is true to demonstrate that C0 coincides with C1 in Alice's frame, then I agree. Any verification procedure relies on the interpretation. We're demonstrating only that SR is valid, not falsifying any other interpretations.
Without this assumption we are left with the underlined part of the conclusion above, whic is derived from the totality of empirical evidence.Your underlined statement assumes a relative interpretation. It is not always true in that interpretation (two events might still be simultaneous in two different frames so long as motion component along the axis connecting the events is not different). In an absolute interpretation, two simultaneous events are just that. There is no frame dependency about it. Alice has not performed a valid sync procedure for such an interpretation.
If Alice's assumption is dropped - in the face of this overwhelming evidence - the RoS simply disappears.I agree that if Alice's assumptions of the SR premises are dropped (the premises from which RoS is derived), then the RoS disappears. I'm not sure what the 'overwhelming evidence' of which you speak is. The statement seems to stand without mention of that.
Consider the thought experiment and drop the assumption that Alice's (or anyone else's) clocks are synchronised - more pointedly, that this can be determined.I would have to drop other assumptions to do that.
Here it is the two-way speed of light that is constant. This essentially just extends the Galilean principle of relativity to the determination of simultaneity/synchronization.I don't know what you mean when saying "the two-way speed of light that is constant".
Her calculation represents a prediction - in this case an untestable/unfalsifiable one.Then it isn't a prediction.
Alice is required to make observations to test the predictions of the theory.Sorry, no. That's our job, not hers. Alice would still see exactly what we say she does, but we would observer something else if the theory corresponds only to her universe but not ours.
I'm not saying it's contradictory, I'm saying it's circular. The point being, how can it be demonstrated - by way of observation - that the clocks are indeed in sync in the given frame?It is indeed circular. SR shows a method to sync clocks, and also to verify the same. If one assumes an SR interpretation, only only need follow the described procedures, and the clocks will be in sync as defined by that interpretation. If one assumes a different interpretation, 'simultaneous' is defined differently and those clocks are probably not in sync. The fact of their being in sync is interpretation dependent then. It is a philosophical distinction.
The thought experiment represents a [plausible] real world experiment. As such, it allows us to make certain inferences and deductions.Not if there is no description of when to take the reading on the C0 clock. Of course the reading of d/c is going to go by, so observing that doesn't in any way demonstrate its simultaneity with the zeroing events somewhere else. A prediction needs a distinct observation. Seeing d/c on the clock isn't it, since that time would go by whether or not that event happened at the same time as the other events or not.
We can extract the prediction from the mathematics. The event where C0 reads d/c coincides with the zeroing event of the other two clocks, in the frame in question, is the prediction because d/c corresponds to an observable reading on C0.
Standing off to the side and taking a photo is best by the same problems, you're still dealing with the issuesof two-way light signals.Taking a photo involves one way light. No light need travel from the camera to anything. It records what is seen from that event off to the side. The picture need not be taken at any particular time. Tomorrow is fine.
The issue is that there will remain an alternative interpretation of those results, one which doesn't assume the Simultaneity of events.Agree, except I don't see how that is the issue. Yes, I am assuming one interpretation when performing the procedure. The procedure is entirely wrong for a different interpretation. My goal is to demonstrate the validity of the one interpretation, not that it is the only valid one.
Your OP described it:Quote from: HalcC0 is baggage.You used it to show the clock reading (d/c) which coincides with events B1 and B2 - how else does one determine that the events were simultaneous?
The light pulses are reflected to the observer at the mid-point and arrive simultaneously. The observer concludes that their clocks are synchronised because they know the speed of light and the distance to the clocks, and because the light pulses returned simultaneously.That is the verification procedure, and it didn't involve a clock C0 at all. No mention is made of it. If you want to introduce a 3rd clock that is not in sync, a similar procedure can be used to verify how far out of sync (d/c) it is. But the original story didn't have this clock at all. Not sure why you introduced it. I think I named it, but I didn't propose its existence.
How do we verify that the calculation is in fact correct and that our mathematical model accurately represents the physical world, in this specific case - given that there is an alternative, mathematically and empirically equivalent interpretation.If there was such a test, they would not be interpretations, but competing theories. There is no such test. I've laid no claim that the relative interpretation is the correct one.
Alice assumes that she lives in an SR world, but only bcos she assumes her conclusions.More like the other way around, but yes, it is sort of circular.
How does she know it's true? It's certainly not on the basis of empirical evidence.Alice is doing things the relative way because we're testing that interpretation via this thought experiment.
One such demand that the mathematics makes is that a real-world, physical clock must show a reading [corresponding to] d/c to coincide with two events B1 and B2. This demand that mathematics seeks to impose upon the physical world constitutes a prediction.No it doesn't, because in a different interpretation, C0 reading d/c doesn't coincide with events B1 or B2, yet no empirical test would distinguish the two cases. That lack of distinction makes it not a prediction. A prediction needs an empirical distinction.
To summarise: SR makes an untestable/unfalsifiable prediction about the simultaneity of events in a stationary frame. This prediction is critical to the conclusion that simultaneity is relative.That's not the conclusion I'm going for. I'm concluding that simultaneity could be relative. What made you think I'm asserting otherwise? You're the one suggesting that it can not be, and that suggestion is why I'm here challenging it.
It therefore assumes its conclusion that simultaneity is relative.I actually can think of no scientific theory that does this: asserting itself. No theory claims to be the correct one. They only claim to be self-consistent.
I am not. I was quite thorough in pointing out that Alice lives in the SR universe, and the mathematical description is the territory, not the map, since it is a pure abstract mathematical universe with known rules. The prediction/verification business is for real people to do. If it matches what Alice sees, then the SR model is a valid description of our universe, not only hers. If the predicted things don't match measurements, then the model isn't valid, not entirely anyway. That's the interpretation I have of this thought experiment. I am assuming SR interpretation, but Alice knows it because that's how I set up her environment.It seems that allowing the assumption that Alice lives in an SR universe is hindering your ability draw the necessary conclusions. It is more accurate to say that Alice is trying to determine what kind of universe she lives in.
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Yes, and Alice's observations become predictions for us. She cannot test that my universe corresponds to her own. Real people must verify or falsify those predictions.
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[Taken from below]
Sorry, no. That's our job, not hers. Alice would still see exactly what we say she does, but we would observer something else if the theory corresponds only to her universe but not ours.
Given an SR interpretation of physics, there are multiple ways to test that assertion, and those methods are very much falsifiable. Given a different interpretation, I don't think the simultaneity of two clocks can be set up nor verified.It is not a given. I see from the points you make below that you seem to have made a presupposition that I am claiming that the Einsteinian interpretation of relativity isn't self-consistent. I'm fairly certain that I was extremely explicit earlier in the thread that this was not the contention. The contention has been that it's self-consistency derives from it's circularity.
If you say so. I found the reading on clock C0 to be fairly irrelevant. But if you find it important, do you suggest that any empirical test of C0 in Alice's frame would not yield a difference of d/c with either of the other two clocks?You found it relevant enough to ascribe a reading to it to coincide with the events B1 and B2. A resding that is predicted by the Einsteinian interpretation of the mathematics - what else could provide the "common time" necessary for determining the Simultaneity of the events?
I posted one way to test it. There are others.The journey for the signals from the events to the camera is effectively the same idea as returning to the mid-point, it just moves the location. As long as the camera is equidistant from B1 and B2, the same issue applies.
If it is actually untestable, then it makes no empirical difference, and the fact of it becomes irrelevant.The conclusion that Simultaneity is relative rests entirely upon it. So, it has more than a little relevance.
But it is quite testable given an SR interpretation. If you mean to say that it is untestable without assuming an SR interpretation, then I agree.It's not testable given any interpretation, especially that of SR - under the foundational assumptions of the theory itself, it is untestable/unfalsifiable.
Very hard to parse that, but if you're saying that one needs to assume RoS is true to demonstrate that C0 coincides with C1 in Alice's frame, then I agree. Any verification procedure relies on the interpretation. We're demonstrating only that SR is valid, not falsifying any other interpretations.I can't speak for you, but I have been trying to demonstrate that the Relativity of Simultaneity is based on circular reasoning. That is, that SR assumes its conclusion.
If you think I'm trying to prove the relative interpretation, I'm not. I lay no claim that your interpretation is wrong. I am merely reacting to your suggestion that the relative interpretation is wrong. If it is wrong, then a contradiction must result from assuming it. There would be a falsification test. You've identified no such self-contradiction.As I have been at pains to point out, I was not trying to demonstrate that SR is self-contradictory. I have been trying to demonstrate that its self-consistency derives from its circularity.
Your underlined statement assumes a relative interpretation. It is not always true in that interpretation (two events might still be simultaneous in two different frames so long as motion component along the axis connecting the events is not different). In an absolute interpretation, two simultaneous events are just that. There is no frame dependency about it. Alice has not performed a valid sync procedure for such an interpretation.
I agree that if Alice's assumptions of the SR premises are dropped (the premises from which RoS is derived), then the RoS disappears. I'm not sure what the 'overwhelming evidence' of which you speak is. The statement seems to stand without mention of that.Alice only needs to modify the premises from which the mathematical predictions of SR is derived. If she says that the speed of light is always measured to be the same, she frees herself from the assumption of Simultaneity of events in her stationary system and she no longer needs to employ circular reasoning to arrive at one of the most fundamental conclusions of SR - that Simultaneity is relative.
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I would have to drop other assumptions to do that.
I don't know what you mean when saying "the two-way speed of light that is constant".
The one-way speed of light has been shown to be constant. If you disagree with that empirical fact, then demonstrate how it is wrong, and how light speed (previously totally unknown) was fairly accurately measured via a one-way test, long before they had super-accurate clocks. The fact that they got a valid number at all means it works. With more accurate equipment, the same test could be (and is) done today to get far more accurate results.
The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to the detector and back again. Albert Einstein chose a synchronization convention (see Einstein synchronization) that made the one-way speed equal to the two-way speed
Then it isn't a prediction.It makes a truth claim about the configuration of a physical system, it is therefore a prediction. That it is untestable/unfalsifiable under the foundational assumptions of the theory itself doesn't change this, it simply represents an undesirable aspect of the theory.
It is indeed circular.Precisely the point being made. Hence, the conclusion that Simultaneity is relative is circular and therefore untestable/unfalsifiable.
SR shows a method to sync clocks, and also to verify the same. If one assumes an SR interpretation, only only need follow the described procedures, and the clocks will be in sync as defined by that interpretation.No such [empirical] verification is described. The foundational assumptions of the theory explicitly state that it must be assumed.
If one assumes an SR interpretation...You have made repeated statements to this effect. Let me put it in context:
If one assumes a different interpretation, 'simultaneous' is defined differently and those clocks are probably not in sync. The fact of their being in sync is interpretation dependent then. It is a philosophical distinction.One can simply drop the assumption of Simultaneity altogether - effectively extending the Galilean Principle of Relativity to the notions of Simultaneity/Synchronization.
Not if there is no description of when to take the reading on the C0 clock. Of course the reading of d/c is going to go by, so observing that doesn't in any way demonstrate its simultaneity with the zeroing events somewhere else. A prediction needs a distinct observation. Seeing d/c on the clock isn't it, since that time would go by whether or not that event happened at the same time as the other events or not.SR predicts that the signals will make contact with B1 and B2 at a time d/c. This time d/c corresponds to the reading on a real-world, physical clock. In this sense SR makes a truth claim about the configuration of a physical system i.e. it makes a prediction.
Taking a photo involves one way light. No light need travel from the camera to anything. It records what is seen from that event off to the side. The picture need not be taken at any particular time. Tomorrow is fine.Light from the events B1 and B2 must travel to the camera. This is equivalent to traveling back to the mid-point, just that the location for receiving the reflected signals is moved.
Agree, except I don't see how that is the issue. Yes, I am assuming one interpretation when performing the procedure. The procedure is entirely wrong for a different interpretation. My goal is to demonstrate the validity of the one interpretation, not that it is the only valid one.The validity of the interpretation is very questionable. The preponderance of evidence is against the assumption of Simultaneity of events in the stationary system.
That is the verification procedure, and it didn't involve a clock C0 at all. No mention is made of it. If you want to introduce a 3rd clock that is not in sync, a similar procedure can be used to verify how far out of sync (d/c) it is. But the original story didn't have this clock at all. Not sure why you introduced it. I think I named it, but I didn't propose its existence.The signals returning simultaneously to the emitter does not verify that the signals made physical contact with B1 and B2 at a time corresponding to a reading of d/2 on C0 i.e. it doesn't confirm that the zeroing events were simultaneously - you have unequivocally stated that this must be assumed, not verified.
If there was such a test, they would not be interpretations, but competing theories. There is no such test. I've laid no claim that the relative interpretation is the correct one.We are in total agreement then. The conclusion that Simultaneity is relative i.e. that it is frame dependent is based on circular reasoning. As such, it is an untestable/unfalsifiable prediction/conclusion/hypothesis however you want to frame it.
More like the other way around, but yes, it is sort of circular.Hahaha forgive me, I read this to mean SR assumes its conclusions, so Alice assumes she lives in an SR universe.
Alice is doing things the relative way because we're testing that interpretation via this thought experiment.Alice is simply performing an experiment to try and help her determine what kind of universe she/we lives in. From her plausibly actualised observations we can draw conclusions about the universe thst we live in.
One is also quite capable of considering the exact same scenario through a different interpretation, in which case Alice's clocks are not synced at all.
No it doesn't, because in a different interpretation, C0 reading d/c doesn't coincide with events B1 or B2, yet no empirical test would distinguish the two cases. That lack of distinction makes it not a prediction. A prediction needs an empirical distinction.SR makes a statement about the configuration of the physical system, it is therfore a prediction. That it is untestable/unfalsifiable under the foundational assumptions of the theory represents an issue with the theory itself.
That's not the conclusion I'm going for. I'm concluding that simultaneity could be relative. What made you think I'm asserting otherwise? You're the one suggesting that it can not be, and that suggestion is why I'm here challenging it.Either simultaneity is relative or it isn't.
Circular logic is the most self-consistent logic there can be. That doesn't mean that the circle cannot be broken howeverQuoteIt therefore assumes its conclusion that simultaneity is relative.I actually can think of no scientific theory that does this: asserting itself. No theory claims to be the correct one. They only claim to be self-consistent.
It seems that allowing the assumption that Alice lives in an SR universe is hindering your ability draw the necessary conclusions. It is more accurate to say that Alice is trying to determine what kind of universe she lives in.She going about that task all wrong then. She's doing this funny procedure with some clocks and light equipment. At no point is she instructed to perform some kind of test that would distinguish between one kind of universe and another. She's in the wrong thought experiment.
As the thought experiment is a plausible, real-world one, we can speak of it as though it has actually been conducted because it is an accurate representation of what the different interpretations say will occur. If the experiment weren't to unfold in the way the thought experiment does then the theory would be invalidated, which is why we can assume that the thought experiment maps to the real world.If the experiment weren't to unfold in the way the thought experiment does then both interpretations would be wrong, since both interpretations predict the same observations for Alice.
It allows to consider the observations that would be made as a matter of necessity. From this, we can draw inferences and deductions about those real world observations and thereby glean more information to help us (and Alice) determine if we actually do live in an SR universe.What observation are you talking about? You didn't describe any such observation.
The mathematical description is open to interpretation;Yes. That means the exact opposite of what you say next:
it makes predictions which can be used to determine if the description represents an accurate map of the territory and by which we may be able to distinguish between the interpretations.If it made such a prediction, the description would not be open to interpretation. So this is nonsense. There have been attempts at doing just that, whenever the test comes up positive for the relative interpretation, the test is declared invalid rather than being declared actual falsification of said alternate interpretation. Translation: the testers commit selection bias.
I see from the points you make below that you seem to have made a presupposition that I am claiming that the Einsteinian interpretation of relativity isn't self-consistent. I'm fairly certain that I was extremely explicit earlier in the thread that this was not the contention. The contention has been that it's self-consistency derives from it's circularity.It does, but so does yours. That's the nature of any interpretation of something. The circularity is necessary. Self consistency means there are no contradictions along the circle.
You found it relevant enough to ascribe a reading to it to coincide with the events B1 and B2. A resding that is predicted by the Einsteinian interpretation of the mathematics - what else could provide the "common time" necessary for determining the Simultaneity of the events?An actual measurement, as described, also predicted by (and assuming) that interpretation.
There is no such test, which can make such a determination, which is why the assumption should be dropped - especially given the preponderance of evidence of non-simultaneity.No claim of simultaneity was made. Alice tested that the clocks are simultaneous in this one frame (the ship in the latest description). That test relied on the interpretation of choice, yes. She performed no test to attempt a falsification of one interpretation or the other. Nobody in the thought experiment attempted to do an absolute sync of the two clocks. If they desired to do so, the procedure they're using is completely wrong.
Well Alice didn't conclude that. She performed a frame dependent test that makes syntactic sense only in the one interpretation. If it makes you feel better, she demonstrated (in the absence of interpretation assumptions) that C1 and C2 appear simultaneous in that frame and wrote off the issue of their being actually simultaneous or not as having no practical significance, only philosophical significance. She'd be right about that.Quote from: HalcIf it is actually untestable, then it makes no empirical difference, and the fact of it becomes irrelevant.The conclusion that Simultaneity is relative rests entirely upon it. So, it has more than a little relevance.
It is assumed under SR, not tested. Meaning the conclusion of RoS (in SR) is assumed.It does not assume its conclusions (RoS for instance). The conclusions are all derived. You repeat this claim without evidence. Show where in Einstein's paper a conclusion is assumed before it is derived.
I can't speak for you, but I have been trying to demonstrate that the Relativity of Simultaneity is based on circular reasoning. That is, that SR assumes its conclusion.
The Relativity of Simultaneity says that "events which are simultaneous in one frame are not simultaneous in another, relatively moving frame". As you are in agreement with, SR assumes the simultaneity of events in one frame.There are no specific events which are being assumed simultaneous. It (the whole thing, not the bolded part) is a statement of RoS which can be applied to events already found to be (not assumed to be) simultaneous in a frame.
That is, the first part of the conclusion is assumed (in bold above).The bolded part makes no assertions. It is effectively a conditional phrase: "If two events are simultaneous in some frame". It is not assuming any specific events are in fact simultaneous since no events are identified. The meaning of 'simultaneous in a frame' is already established at the time such a statement would be made.
Without this assumption there is no conclusion of RoS - hence, it is circular, hence SR assumes its conclusion.The statement above is not one concluding RoS. It is stating (not concluding) that two such events meeting the qualification in bold part might also meet the qualification in the underlined part. It uses the already established (not assumed) RoS to do this.
As you have pretty explicitly agreed that RoS is based on circular reasoning i.e. that the conclusion is assumed.I never said any conclusion was assumed. All were derived. It is circular in that it assumes (never proves) its own premises. It results in a relative definition of 'simultaneous', but that again is derived, not assumed.
Alice only needs to modify the premises from which the mathematical predictions of SR is derived. If she says that the speed of light is always measured to be the same, she frees herself from the assumption of Simultaneity of events in her stationary system and she no longer needs to employ circular reasoning to arrive at one of the most fundamental conclusions of SR - that Simultaneity is relative.For the record, SR theory proper does not assert constant light speed. It only presumes the frame independent appearance of it. It is the relative interpretation of SR theory that makes the metaphysical assumption that said light speed actually is constant. This metaphysical interpretation is probably the most mainstream interpretation, but being metaphysics, lacks any kind of evidence to support it. Einstein himself very much used the relative interpretation.
The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector.They had a convention. This is pre-relativity, so they used Earth frame without knowing that it mattered. They were (in hindsight) measuring the speed of light as it appeared in that frame. It wasn't until considerably later that measurements became accurate enough to conclude the frame independence of that appearance.
Albert Einstein chose a synchronization convention (see Einstein synchronization) that made the one-way speed equal to the two-way speedThe people back then used a different convention, but one just as valid. In particular, it didn't rely on two-way light trips. There were no mirrors involved.
You and I have quite a different definition of what a prediction is. I have an empirical definition, not a metaphysical one.Quote from: HalcThen it isn't a prediction.It makes a truth claim about the configuration of a physical system, it is therefore a prediction.
How is the premise a conclusion? It's just a tautology. Assuming that I have 5 apples, then I have 5 apples. Yes, that's circular, but not invalid. I don't consider my having 5 apples to be a conclusion, but rather the premise. RoS on the other hand is not a premise.Quote from: HalcIf one assumes an SR interpretation...You have made repeated statements to this effect. Let me put it in context:
If one assumes that the Flying Spaghetti Monster created the initial conditions of the universe, then one will conclude that the FSM is responsible for the current state of the Universe.
One can simply drop the assumption of Simultaneity altogether - effectively extending the Galilean Principle of Relativity to the notions of Simultaneity/Synchronization.Don't know what you mean by this. The first part seems to suggest that simultaneity is meaningless. The second part seems to suggest a different metaphysical assumption, and you seem to balk at such assumptions, labeling any conclusions drawn from them to be circular and thus somehow fallacious.
We were talking about testing C0, so it would be light from A and B1 that must travel to the camera. We've already done the procedure for B1 and B2. You introduced this 3rd clock and asked how to verify how much it is out of sync with the other two.Quote from: HalcTaking a photo involves one way light. No light need travel from the camera to anything. It records what is seen from that event off to the side. The picture need not be taken at any particular time. Tomorrow is fine.Light from the events B1 and B2 must travel to the camera.
You said you accepted the interpretation as valid. Now you say otherwise.Quote from: HalcYes, I am assuming one interpretation when performing the procedure. The procedure is entirely wrong for a different interpretation. My goal is to demonstrate the validity of the one interpretation, not that it is the only valid one.The validity of the interpretation is very questionable.
The preponderance of evidence is against the assumption of Simultaneity of events in the stationary system.So you assert, but this evidence is never presented. So this is an empty assertion. Please don't make statements like this without referencing at least one piece of evidence that contradicts what the interpretation says should be observed. I don't make this statement about your pet interpretation despite my thinking that it has metaphysical issues.
Remember, as you have repeatedly stated, the Simultaneity of those events must be assumed not observered empirically.Where did I say that? I assumed an actual constant relative speed of light. I cannot prove that it doesn't just appear to be that way. I made no more assumptions than that. I did not conclude from that assumption that those events were simultaneous.
All other observers provide empirical evidence that the events weren't simultaneous.Nobody provided any evidence that the events were simultaneous or not simultaneous. I was waiting for you to introduce Bob and make such a statement. Took you a while...
The signals returning simultaneously to the emitter does not verify that the signals made physical contact with B1 and B2 at a time corresponding to a reading of d/2 on C0 i.e. it doesn't confirm that the zeroing events were simultaneouslyI didn't claim that. You are putting a lot of words in my mouth. How many times must I point out claims that I didn't make? The signals returning simultaneously to the detector verify that C1 and C2 are in sync in that frame, and do not constitute any sort of verification concerning C0.
The 3rd clock was introduced to try and make the set-up more similar to Einstein's formulation. You kindly named the third clock "C0" and told us the prediction that SR makes about the reading on that clock that should coincide with events B1 and B2 - that is, you pointed out the claim that SR makes about the configuration of the physical system.Yes to all that, but none of that describes a verification procedure for it.
We are in total agreement then. The conclusion that Simultaneity is relative i.e. that it is frame dependent is based on circular reasoning.I will not agree to that. I've said repeatedly that SoR does not assume SoR. It follows from different premises. I agreed that those different premises cannot be proved.
As such, it is an untestable/unfalsifiable prediction/conclusion/hypothesis however you want to frame it.With that I agree.
I've clarified this above. Alice represents us trying to determine what kind of Universe she/we live in.She's going about it all wrong then.
Alice is simply performing an experiment to try and help her determine what kind of universe she/we lives in. From her plausibly actualised observations we can draw conclusions about the universe thst we live in.How so? What has Alice ever done that might make you conclude one way or the other?
One can simply drop any assumptions about the Simultaneity of events in a stationary system.Good start, yes. You suggested this above, where I replied "Now what?".
The conclusion that simultaneity is relative requires the conclusion to be assumed.No, it requires the premises leading to that conclusion to be assumed. Nobody ever assumed RoS. They assumed something else. That something else is what we need to drop if we wish to determine what sort of universe we live in (A or R). To not drop that assumption would indeed be begging a conclusion, even if RoS isn't the assumption being dropped.
The conclusion that it isn't relative simply require us to not make the assumption that it is.Wrong. That conclusion also requires you to assume that it isn't relative, not just drop the assumption that it is relative. You've made a different assumption if you don't do that.
It simply requires us to consider the totality of empirical evidence only and not append any assumptions to that evidence; assumptions that are contradicted by the evidence.I agree you need to do that, but it is not enough. It requires more than that. It in fact requires a falsificaton test, and lacking that, the two views remain just interpretations.
An actual measurement, as described, also predicted by (and assuming) that interpretation.So you agree that it is predicted by the interpretation?
She going about that task all wrong then. She's doing this funny procedure with some clocks and light equipment. At no point is she instructed to perform some kind of test that would distinguish between one kind of universe and another. She's in the wrong thought experiment.My apologies, I may have overstated the case.
If that's her task, why do we have her doing this unrelated procedure?
If the experiment weren't to unfold in the way the thought experiment does then both interpretations would be wrong, since both interpretations predict the same observations for Alice.Agreed, which is why we can treat it as though it has actually happened and draw inferences and deductions from it.
What observation are you talking about? You didn't describe any such observation.I'm talking about the observations Alice must make and the observations she cannot make. We can deduce this from the thought experiment and apply it to a real-world experimental set-up.
If it made such a prediction, the description would not be open to interpretation. So this is nonsense. There have been attempts at doing just that, whenever the test comes up positive for the relative interpretation, the test is declared invalid rather than being declared actual falsification of said alternate interpretation. Translation: the testers commit selection bias.The mathematics are the same for the different interpretations. As such, they make truth claims about the configuration of a system. That is, predictions about the configuration of the system can be extracted from the different interpretations.
It does, but so does yours. That's the nature of any interpretation of something. The circularity is necessary. Self consistency means there are no contradictions along the circle.The position being advanced is that the Simultaneity of events in the stationary system cannot be determined – this fact is derived from the observational evidence, not from an assumption, so it is not circular.
The two interpretations have differing definitions of simultaneity, so each must assume its own definition when describing simultaneous events. That's the circular conclusion that must be employed. But the differing definitions are not premises, but rather necessities that follow from the premises. So in that sense, neither interpretation is circular.
No claim of simultaneity was made. Alice tested that the clocks are simultaneous in this one frame (the ship in the latest description). That test relied on the interpretation of choice, yes. She performed no test to attempt a falsification of one interpretation or the other. Nobody in the thought experiment attempted to do an absolute sync of the two clocks. If they desired to do so, the procedure they're using is completely wrong.The Einsteinian interpretation makes a prediction about the configuration of the physical system – the reading on C0 that coincides with B1 and B2 (note, this a claim of simultaneity in the stationary system). Alice's attempt at the synchronization procedure can be seen as a test of this prediction.
Well Alice didn't conclude that. She performed a frame dependent test that makes syntactic sense only in the one interpretation. If it makes you feel better, she demonstrated (in the absence of interpretation assumptions) that C1 and C2 appear simultaneous in that frame and wrote off the issue of their being actually simultaneous or not as having no practical significance, only philosophical significance. She'd be right about that.On what basis are you saying that they appear to be simultaneous? On the basis that light signals from both return to Alice/C0 simultaneously? As has been outlined, they would return simultaneously in the case when the clocks are not synchronised either, so this cannot be taken to indicate one or the other.
There are no specific events which are being assumed simultaneous. It (the whole thing, not the bolded part) is a statement of RoS which can be applied to events already found to be (not assumed to be) simultaneous in a frame.This is the crux of the issue! How are the events “found to be (not assumed)” simultaneous in the frame i.e. what observation does Alice make that confirms that events B1 an B2 are simultaneous meaning that the clocks are sychronised. What observation does she make that confirms that the demands of the mathematics are fulfilled?
The bolded part makes no assertions. It is effectively a conditional phrase: "If two events are simultaneous in some frame". It is not assuming any specific events are in fact simultaneous since no events are identified. The meaning of 'simultaneous in a frame' is already established at the time such a statement would be made.The Einsteinian interpretation says simultaneity is relative. Either way, to satisfy the first part of the conditional – that leads to the conclusion that simultaneity is relative – the simultaneity of events in the stationary frame have to be assumed. IF events are not assumed to be simultaneous, the conclusion that simultaneity is relative cannot be reached.
The statement above is not one concluding RoS. It is stating (not concluding) that two such events meeting the qualification in bold part might also meet the qualification in the underlined part. It uses the already established (not assumed) RoS to do this.The question as to what empirical observation can be made to determine that two such events are simultaneous in the physical configuration of the system remains. The answer is that no such observation can be made as a matter of practicality of the real world, but also as a matter of principle according to the foundational assumptions of the Einsteinian interpretation.
I never said any conclusion was assumed. All were derived. It is circular in that it assumes (never proves) its own premises. It results in a relative definition of 'simultaneous', but that again is derived, not assumed.You are confusing the idea of deriving something mathematically and deriving something rom observation. The simultaneity of the events that is derived from the mathematics is a prediction. Just as the statement about the configuration of the system - where events B1 and B2 coincide with the reading d/c on C0 - derived from the Einsteinian interpretation, is a prediction (as you’ve stated above). It certainly isn’t derived from observation. The accuracy of the statement – about the physical configuration of the system – made derived from the Einsteinian interpretation must be assumed because it certainly is not observed, in any empirical manner.
Alice is performing a relative procedure (assuming a relative interpretation) and concluding that two events are simultaneous in a way meaningful only to that interpretation. That's the circularity of it that I'm talking about.It is also the circularity I am talking about. Alice is performing a valid variation on the prescribed synchronisation procedure. As such, inferences and conclusions can be drawn from it.
We can simply say that the average [of the two-way] speed of light is c. Or just not make any assumptions about the simultaneity of events.
For the record, SR theory proper does not assert constant light speed. It only presumes the frame independent appearance of it. It is the relative interpretation of SR theory that makes the metaphysical assumption that said light speed actually is constant. This metaphysical interpretation is probably the most mainstream interpretation, but being metaphysics, lacks any kind of evidence to support it. Einstein himself very much used the relative interpretation.
That said, in making that statement above, you burden yourself with an assumption that there is a stationary system. If we're going to drop the metaphysical assumption that light speed is (not just appears) constant in any frame, we also need to drop the stationary frame concept. Not doing so would be 'circular reasoning' the way you seem to use the term.
So we drop all these assumptions. Now what? In the absence of such assumptions, where do we go?
Sounds very interesting. Can you recommend a source that shows the peer review of this confirming that it measures the one-way speed of light. I and many others would be very interested in reading it. Until then, I’ll go with the peer reviewed stuff that says it hasn’t been successfully measured.
They had a convention. This is pre-relativity, so they used Earth frame without knowing that it mattered. They were (in hindsight) measuring the speed of light as it appeared in that frame. It wasn't until considerably later that measurements became accurate enough to conclude the frame independence of that appearance.
You put a clock far away and observe it from a distance. When it appears to read zero, you zero the local clock. That's the sync convention that was used. The two clocks, unchanged, should always locally appear to read the same value.
I’m presuming you can see how this means that the two clocks aren’t actually synced.
If light speed was infinite, then the local clock would always be in sync with the observed value on the distant clock (and in fact would be the actual value). If light speed is some finite number, then changing the distance between the observer and the distant clock should (and did) change the sync between the two clocks. The distant one would appear to log less time (run slower) as it moved further away and more time was needed for light to get from there one-way to the observer. It would appear to get ahead as the distant clock grew closer.
By observing this change in the sync between the two clocks, a remarkably accurate measurement of one-way light speed was taken.
....
The people back then used a different convention, but one just as valid. In particular, it didn't rely on two-way light trips. There were no mirrors involved.
A statement about the configuration of the physical system can be derived from the Einsteinian interpretation. This represents a prediction. It is a statement upon which one of its core conclusions rests entirely. It is a statement whose accuracy must be assumed; therefore one of its core conclusions must be assumed.
You and I have quite a different definition of what a prediction is. I have an empirical definition, not a metaphysical one.
A more accurate analogy:
How is the premise a conclusion? It's just a tautology. Assuming that I have 5 apples, then I have 5 apples. Yes, that's circular, but not invalid. I don't consider my having 5 apples to be a conclusion, but rather the premise. RoS on the other hand is not a premise.
Not that it is meaningless, just that the simultaneity of two events, in a stationary system, cannot be determined by a comoving observer. So no circular conclusions need be drawn.
Don't know what you mean by this. The first part seems to suggest that simultaneity is meaningless. The second part seems to suggest a different metaphysical assumption, and you seem to balk at such assumptions, labeling any conclusions drawn from them to be circular and thus somehow fallacious.
We’re checking to see if the reading d/c on C0 coincides with events B1 and B2 i.e. testing to see if B1 and B2 are acctually synchronised in the stationary system – as the conclusion of RoS necessitates. Play around with it and you’ll see why its just the same issue in a different location.
We were talking about testing C0, so it would be light from A and B1 that must travel to the camera. We've already done the procedure for B1 and B2. You introduced this 3rd clock and asked how to verify how much it is out of sync with the other two.
My apologies, I probably intended to say that it was self-consistent. It’s validity is dependent on whether an interpretation that assumes its conclusions is more valid than one that doesn’t.
You said you accepted the interpretation as valid. Now you say otherwise.
The empirical evidence is that which can be deduced from the thought experiment – which represents a plausible real world experimental set-up, from which we can draw inferences and conclusions – the empirical observations of all other observers.
So you assert, but this evidence is never presented. So this is an empty assertion. Please don't make statements like this without referencing at least one piece of evidence that contradicts what the interpretation says should be observed. I don't make this statement about your pet interpretation despite my thinking that it has metaphysical issues.
Precisely. There is no observation that can be made to “prove” the simulltaneity of the events. That is, there is no empirical observation [that can be made] to verify the prediction/statement of the physical system than can be derived from the Einsteinian interpretation. There is no empirical observation which supports the contention that the clocks on Alice’s spaceship are synchronised, all empirical evidence shows the clocks on the spaceship are not synchronised. The contention that the clocks on board the spaceship are synchronised (from anyone’s perspective) is not supported by empirical observation so it can only be assumed. This contention is the string by which RoS dubiously hangs.
Where did I say that? I assumed an actual constant relative speed of light. I cannot prove that it doesn't just appear to be that way. I made no more assumptions than that. I did not conclude from that assumption that those events were simultaneous.
By “putting words in your mouth” I think you will find that I am simply making inferences an deductions about what follows by way of necessity from what you do say.
I didn't claim that. You are putting a lot of words in my mouth. How many times must I point out claims that I didn't make? The signals returning simultaneously to the detector verify that C1 and C2 are in sync in that frame, and do not constitute any sort of verification concerning C0.
I also said that the reading on the C0 clock at the time did not play any role in the verification of what Alice is attempting to do with C1 and C2.
It wouldn’t be like you [to be picky]! :P
To be picky: B1 and B2 are locations, and one cannot make physical contact with a location.
That was probably a typo. You mean physical contact with the clocks C1 and C2 bolted there.
It would represent a verification procedure; indeed, it represents the only way in which the simultaneity of synchronisation events could actually be verified. That this cannot be verified is the point being made.
Yes to all that, but none of that describes a verification procedure for it.
See what I mean about having difficulty with seeing how the thought experiment represents a valid variation on Einstein’s synchronisation procedure. That is why C0 – the name you gave it – was introduced. In Einstein’s convention he has light going from [the clocks at]:
Did Einstein put a 3rd clock between the two in his description of the convention to sync the first two? Don't remember that.
If there is no empirical observation that the clocks in Alice’s spaceship are synchronised with each other, in her frame of reference, then it can only be assumed to be a valid prediction. Assuming this assumes the conclusion.
I will not agree to that. I've said repeatedly that SoR does not assume SoR. It follows from different premises. I agreed that those different premises cannot be proved.
As such, it is an untestable/unfalsifiable prediction/conclusion/hypothesis however you want to frame it.With that I agree.[/quote]
Alice has demonstrated that the idea, that her clocks are synchronised in her frame, is not supported by any empirical evidence so it must therefore be assumed. Indeed, the totality off observational evidence contradicts her assumption by showing that her clocks are not synchroniseed. It therefore shows us that the conclusion that simultaneity is frame dependent i.e. that simultaneity is relative i.e. the conclusion of RoS is propped up solely by circular reasoning i.e. the conclusion is assumed.QuoteAlice is simply performing an experiment to try and help her determine what kind of universe she/we lives in. From her plausibly actualised observations we can draw conclusions about the universe thst we live in.How so? What has Alice ever done that might make you conclude one way or the other?
It requires that the truth of the statement: clocks in the stationary system are synchronised, in that frame, be assumed – because it cannot be verified experimentally. Assuming the validity of this statement means the conclusion of RoS is assumed.
No, it requires the premises leading to that conclusion to be assumed. Nobody ever assumed RoS. They assumed something else. That something else is what we need to drop if we wish to determine what sort of universe we live in (A or R). To not drop that assumption would indeed be begging a conclusion, even if RoS isn't the assumption being dropped.
The alternative doesn’t rely on circular reasoning because it makes no statement about the simultaneity of events in the stationary system. It simply says that this cannot be determined – a statement which can be derived from the observational evidence. That is, it starts with “We don’t know if the clocks are synchronised”. No conclusions assumed there.
Wrong. That conclusion also requires you to assume that it isn't relative, not just drop the assumption that it is relative. You've made a different assumption if you don't do that.
It is the difference between "I don't know" and "I know R is wrong". Only under the latter assumption allows the conclusion you make above. You are otherwise assuming the conclusion.
If you want to make a determination between the two, start with "I don't know".
If we consider Alice’s assumption:
QuoteIt simply requires us to consider the totality of empirical evidence only and not append any assumptions to that evidence; assumptions that are contradicted by the evidence.I agree you need to do that, but it is not enough. It requires more than that. It in fact requires a falsificaton test, and lacking that, the two views remain just interpretations.
My apologies, I may have overstated the case.None of her deductions and inferences can be applied to other interpretations since she assumed an interpretation in making those deductions and inferences.
She is performing a procedure from which deductions and inferences can be drawn and applied to the different interpretations.
You can treat it as though it has actually happened. But yes, you cannot draw interpretation independent inferences from it IF those inferences where made from one interpretation or another. That's been your problem all along. You made an interpretational assumption and you're repeatedly trying to apply your inferences to what Alice has been doing under a different interpretation. All your conflicts come from doing this.Quote from: HalcIf the experiment weren't to unfold in the way the thought experiment does then both interpretations would be wrong, since both interpretations predict the same observations for Alice.Agreed, which is why we can treat it as though it has actually happened and draw inferences and deductions from it.
The mathematics are the same for the different interpretations.The mathematics is very much not, but I don't see how this is relevant to the comment above.
As such, they make truth claims about the configuration of a system.Does Alice make a truth claim? She says that if she draws a line through the two sync events B1 and B2, that the coordinates of those two events along any second line drawn perpendicular to this first line will be the same. That includes all three of the remaining axes. I suppose that is a truth claim, and since it is an entirely abstract geometric one, it seems hard to contest the truth of it. Perhaps you think she's making a different truth claim than this one, but doing so risks the committing of the strawman fallacy.
That is, predictions about the configuration of the system can be extracted from the different interpretations.
Truth claims are not predictions since there is no way to directly verify them.I think there are ways to verify the truth claim stated just above. Provide a counterexample if you disagree with it.
From the Einsteinian interpretation we can extract a prediction about the configuration of the physical system which says the reading on clock A will be d/c for events B1 and B2 i.e. events B1 and B2 will be simultaneous with the reading d/c on C0 – this statement about the physical system can be extracted from the interpretation.This is not a prediction, merely a truth claim, and a meaningless one without a frame reference. If we're talking about her frame, then this would be a meaningful truth claim, but still not a prediction.
The position being advanced is that the Simultaneity of events in the stationary system cannot be determined – this fact is derived from the observational evidence, not from an assumption, so it is not circular.Do you mean that the simultaneity of events relative to the arbitrarily designated system with Alice stationary in it? If so, I disagree since Alice has shown exactly that.
This is the crux of the issue! How are the events “found to be (not assumed)” simultaneous in the frame i.e. what observation does Alice make that confirms that events B1 an B2 are simultaneous meaning that the clocks are sychronised.The setup assures the sync in frame A, even without observation. An observation of the simultaneous return signal serves as a redundant confirmation of this. Come on, you know these answers. Why must I endlessly repeat them?
What observation does she make that confirms that the demands of the mathematics are fulfilled?All the setup observations need to be made as well: that the clocks are indeed placed equidistant from the middle point for instance. That observation of the setup is only needed for Alice to know the clocks are synced. The clocks are synced in that frame whether or not those observations are made. The setup is enough.
The Einsteinian interpretation says simultaneity is relative.It demonstrates that, not just assumes it. Using 'says' doesn't make that very clear. It is an interpretational statement, yes. It isn't true in an absolute interpretation of relativity theory, not because the physics is different, but the language is different. Since the physics is the same, there can be no predictions to help Alice with her task of determining the correct interpretation.
IF events are not assumed to be simultaneous, the conclusion that simultaneity is relative cannot be reached.Trying to parse this one, and failed. Are you claiming that RoS implies that all events are simultaneous? Probably not, but that's how this reads.
The question as to what empirical observation can be made to determine that two such events are simultaneous in the physical configuration of the system remains.Nope. Those words have no interpretation-independent meaning. If you're going to use those words, you need to choose (assume if you will) an interpretation. Only then can some empirical observation be made to make such a determination.
You are confusing the idea of deriving something mathematically and deriving something from observation.No I'm not. It's all quite mathematical since we're discussing synchronization, something that only has abstract meaning. Synchronization of separated clocks cannot be observed. What can be observed is perhaps the time displayed on a clock or several. If 'synced' was defined as two clocks reading the same value at some observation event, then synchronization would be an observable (and event dependent) thing. Well, it isn't defined that way by either interpretation. Both interpretations have an abstract definition of it, which is necessary for any non-local definition of something.
The simultaneity of the events that is derived from the mathematics is a prediction. Just as the statement about the configuration of the system - where events B1 and B2 coincide with the reading d/c on C0 - derived from the Einsteinian interpretation, is a prediction (as you’ve stated above).I've stated no such thing. I said quite clearly that none of these things constitute predictions. A prediction is a much stronger claim than any of that.
It certainly isn’t derived from observation. The accuracy of the statement – about the physical configuration of the system – made derived from the Einsteinian interpretation must be assumed because it certainly is not observed, in any empirical manner.Which is why it isn't a prediction, yes.
Just to be clear, the alternative interpretation says that the simultaneity of events cannot be determined in the stationary system and so does not rely on circular logic.The alternative interpretation assumes an interpretation, so it is circular in the same way as you use the term. If an interpretation cannot assume itself, then your statement above carries no meaning.
That statement isn't meaningful under the interpretation. In fact, all other observers completely agree with Alice's statement: The two events are simultaneous relative to her frame.Quote from: HalcAlice is performing a relative procedure (assuming a relative interpretation) and concluding that two events are simultaneous in a way meaningful only to that interpretation. That's the circularity of it that I'm talking about.It is also the circularity I am talking about. Alice is performing a valid variation on the prescribed synchronisation procedure. As such, inferences and conclusions can be drawn from it.
She “[concludes] that [the events] are simultaneous in a way meaningful only to that interpretation. Let’s think about that statement. How is it meaningful to that interpretation? All other observers say the events weren’t simultaneous.
Alice must conclude that events in her frame are simultaneous for this interpretation to be valid.That said events are simultaneous in her frame. Very different meaning. I'm being entirely precise lest you quote me on agreeing with a statement that is misleading.
How does she conclude that the events are simultaneous? Not by way of empirical observation – the theory itself precludes it.It does not. You're begging a different interpretation with that statement.
Empiricism requires that mathematical predictions/calculations be verified by empirical observations (hence the name empiricism). How then does she conclude that the events were simultaneous in such a way that it is meaningful to the interpretation?I never claimed empiricism. She needs not do any verification at all for the clocks to be synced in her frame, so I guess she's not an empiricist. If the setup is done correctly, that's all that is needed. If Alice doesn't trust the setup, then she can't really trust the verification either. Maybe somebody put mirrors and such in places that changed the path lengths and the setup isn't really as you described it in the OP. In that case, Alice has been fooled.
[An assumption must be made that] events are simultaneous in her frame – bcos we already have the observational evidence to the contraryYou never identify this 'contrary evidence', so pony up or shut up about it already. Bob has no such evidence, nor does anybody's bodycam, so does it come from some other source?
I think people in the 19th century attempted to test that and it was falsified. Remember my example with the canoe on the creek? It has an average speed of 1, despite the current in the creek, but the round trip time for the canoe is empirically dependent on the current of the water, and the round trip time for light is not empirically dependent on the reference frame represented by the creek.Quote from: HalcSo we drop all these assumptions. Now what? In the absence of such assumptions, where do we go?We can simply say that the average [of the two-way] speed of light is c.
Or just not make any assumptions about the simultaneity of events.Since such statements are interpretation dependent, we have to of course. One defines it as a 2-way relation and the other as a 3-way relation.
Either way, we can draw inferences and deductions from the thought experiment, as is.Can we? We've left little language in common to discuss what Alice is doing.
Sounds very interesting. Can you recommend a source that shows the peer review of this confirming that it measures the one-way speed of light.I can find no such review. Olaus Roemer, 1676. A fairly accurate measurement was first taken, long before any 2-way method was attempted. Do you contest that it was a 1-way experiment? Do you suggest that since it wasn't two way, that the measurement was a guess?
I and many others would be very interested in reading it. Until then, I’ll go with the peer reviewed stuff that says it hasn’t been successfully measured.Ah, I see. The measurement for some reason threatens your claim, thus it needs to be discarded.
It is interesting though that you are offering something which measures a different value for the speed off light (close though it may be) and asserting that this different value demonstrates that the one way speed of light is constant.I don't thing the initial measurement of any value (say distance to the sun as a random example) was initially measured to the same precision as in subsequent refinements.
That's the metaphysical definition, yes.A statement about the configuration of the physical system can be derived from the Einsteinian interpretation. This represents a prediction.
You and I have quite a different definition of what a prediction is. I have an empirical definition, not a metaphysical one.
It is a statement upon which one of its core conclusions rests entirely. It is a statement whose accuracy must be assumed; therefore one of its core conclusions must be assumed.Agree, but none of this makes it an empirical prediction.
A more accurate analogy:OK, the fruit is frame dependent. If that's the foundational assumption, nobody has any empirical evidence to contradict it. The observer assumes the interpretation, but given that, he knows the fruit is apples because he's in the frame where it's apples. That part is not an additional assumption.
If 5 pieces of fruit are apples in one frame, then they are oranges in a relatively moving frame. The observer in the stationary frame cannot see the pieces of fruit – under the foundational assumptions of the interpretation (a glass box with a non-transparent lid, where they can only look down on the box. All relatively moving observers make empirical observations (seeing into the box from the side) that the pieces of fruit in the box are oranges. The observer assumes that the 5 pieces of fruit are apples, therefore fruit is frame dependent.
We’re checking to see if the reading d/c on C0 coincides with events B1 and B2 i.e. testing to see if B1 and B2 are acctually synchronised in the stationary systemThe i.e. makes no sense. C0 plays no role in the verification that C1 and C2 are synced. It is just a 3rd clock that you brought for Alice to make additional observations.
How can it be self consistent but not valid? What do the two mean to youterms ?Quote from: HalcYou said you accepted the interpretation as valid. Now you say otherwise.My apologies, I probably intended to say that it was self-consistent.
It’s validity is dependent on whether an interpretation that assumes its conclusions is more valid than one that doesn’t.Ah, I see. Relativity doesn't assume RoS. At no point is it listed as a premise or is any conclusion based on it before it is demonstrated (and it is demonstrated with a simple example, so like, a couple pages if Einstein is wordy in his examples).
Hmm... Neither the specific observation nor the contradiction is identified. You just keep asserting that there is one. Thought so.Quote from: HalcPlease don't make statements like this without referencing at least one piece of evidence that contradicts what the interpretation says should be observed.The empirical evidence is that which can be deduced from the thought experiment – which represents a plausible real world experimental set-up, from which we can draw inferences and conclusions – the empirical observations of all other observers.
While it doesn’t contradict the interpretation, it contradicts the assumption upon which the interpretation hangs.
The interpretation represents a map. The plausible real world set-up [as represented by the thought experiment] represents the territory. On the map there is a lake called Loch Ness. “In” the lake there is a picture of a partially submerged creature labelled “the Loch Ness Monster”. The key on the side of the map says that the Locch Ness Monsters presence in the lake must be “established by definition” i.e. it must be assumed that Nessy be in them there waters. The territory might look a lot like the map, but the underwater footage of the lake with no sign of Nessy certainly contradicts the assumption.Two mistakes. 1) The monster is an assumption, not a conclusion. If it was demonstrated given different assumptions, then the interpretation doesn't assume that conclusion. 2) Absence of evidence is not evidence of absence. No actual contradiction was demonstrated Oh yea, 3) you personal feeling of implausibility is a good reason to prefer a different interpretation, but it isn't evidence of anything.
There is no empirical observation [that can be made] to verify the prediction/statement of the physical system than can be derived from the Einsteinian interpretation.True of any interpretation, by definition of the word 'interpretation'. You didn't answer the question I asked.
There is no empirical observation which supports the contention that the clocks on Alice’s spaceship are synchronised, all empirical evidence shows the clocks on the spaceship are not synchronised.You have a test for the latter claim? Alice could use it to falsifiy one or the other interpretation. If you don't, then it's just another empty assertion. You have to stop doing those. BTW, I agree with the first statement (the part before the comma that should have been a semicolen).
The contention that the clocks on board the spaceship are synchronised (from anyone’s perspective) is not supported by empirical observation so it can only be assumed.They're synced relative to a frame. They're synced relative to Alice's frame even from Bob's perspective, so it isn't specific to a perspective, despite the usage of that wording by some people to mean a frame reference.
The signals returning simultaneously to the detector verify that C1 and C2 are in sync in that frame. No they don’t! They verify that the signals return simultaneously to the detector. As has been pointed out, the signals would return simultaneously if the time to C1 and C2 were not the same, as this would be evened out on the return leg.And as has been pointed out (by you), if the time to B1 and B2 from A were not the same, then the signals would not arrive back at A at the same time. Since the emitter and detector are at A and the clocks at the B locations in that frame, and since the time from A to B is the same as B to A by definition, the verification is valid.
As you quite rightly state it does not “constitute any sort of verification concerning C0”, as such verification is impossible.It's entirely possible to verify some things concerning C0. I just said the two reflected signals are not involved in that verification.
Ask yourself, how then can Alice be sure that her calculations (which rest on her assumption) are actually correct, in her frame?We'd have to assume she's capable of mathematics, and that stuff like 2+2=4 is not a frame dependent fact. Are we casting doubt on these things now?
How does Alice determine that the clocks are synchronised if it isn’t by way of observation that both events happen “at the same time”. How does she determine that the “demands” made by her mathematics are met by the physical system?See prior answers to this endlessly repeated question.
It might be worth pointing out now, too, that her conclusion of length contraction also rests on the assumption that her clocks are synchronised.Does your interpretation not include length contraction? For that matter, how does a conclusion of length contraction follow from a determination of two clocks being synchronized? What exactly is assumed to contracted in this example?
Given that both clocks remain bolted to their respective spots means that for the purposes of what we are discussing – Alice’s synchronisation procedure in her spaceship – the distinction between points and clocks are immaterial because they remain co-located.Only in the frame of the ship. So in Bob's frame, C1 is not at any one location.
See what I mean about having difficulty with seeing how the thought experiment represents a valid variation on Einstein’s synchronisation procedure. That is why C0 – the name you gave it – was introduced. In Einstein’s convention he has light going from [the clocks at]:Yes, and he is giving a definition of simultaneity between clocks at A and B, using a different method than putting anything equidistant between them.
A > B > A
In our thought experiment we have light going from the clocks at:From/To A, yes, but the clock there was not referenced. It's from emitter at A, and to observer at A.
A > B1 > A
A > B2 > A
Can you now see how it is a valid variation on Einstein’s convention?Clocks at A and B1 (or B2) are not claimed to be in sync. It is a valid variation to get clocks at B1 and B2 in sync, yes. Did I say otherwise? Notice that I say clock at B (as does Einstein), not clock C. It needs to be established that it is at location B1 and B2 (or Einstein's A and B) for the statement to be true. The definition of simultaneous you quote requires this.
Incidentally, I don’t remember Einstein mentioning anything about flying 2 atomic clocks around the world on commercial airliners, but this represents a test of his theory because the prediction can be derived/extracted from the interpretation. Just as the statement/prediction pertaining to the reading on C0 can be derived/extracted.Agree. I derived what it says. That clock is by definition not in sync with the other two. If you subtracted d/c from what it says (fall behind, not spring ahead), Alice could verify that it is now in sync with the other two, and do so without moving. I had her moving to a midpoint and taking a photo from there. That was a needlessly complicated way to go about it. Just use the definition.
There is an empirical observation. Alice can use the definition and have light go between the two clocks if you like. So glad you agree that Alice has determined this.Quote from: HalcIf there is no empirical observation that the clocks in Alice’s spaceship are synchronised with each other, in her frame of reference
I've said repeatedly that SoR does not assume SoR. It follows from different premises.
Given that the conclusion of RoS hangs by a string on the idea that the clocks are synchronisedBut I don't give that at all. It hangs on constant light speed. No mention of clocks is necessary to show it. You're making up strawman arguments. Are you finding these arguments on your denial sites (that you call 'peer review'). Peer review means the peers of the person (like Roemer for instance) putting out new science, not your peers.
She can follow the very definition of synchronized, so this is wrong. Again, you have no response of your own to this, so you just repeat this statement. I doubt your peers actually said that since they would not have worded it that way. Alice very much has empirical evidence of the way you word it there.Quote from: HalcWhat has Alice ever done that might make you conclude one way or the other?Alice has demonstrated that the idea, that her clocks are synchronised in her frame, is not supported by any empirical evidence so it must therefore be assumed.
It assumes there is such a concept as a stationary system. Drop that if you want to distinguish between interpretations.Quote from: HalcIf you want to make a determination between the two, start with "I don't know".The alternative doesn’t rely on circular reasoning because it makes no statement about the simultaneity of events in the stationary system.
It simply says that this cannot be determinedThat's an interpretation specific conclusion. If you assert that, you are assuming your conclusions. Drop that as well.
If we consider Alice’s assumption:If her goal is to find the correct interpretation, then she has not assumed one. She's done a procedure that does not meet Einstein's definition of simultaneous, so such a determination has not been made.
The clocks on Alice’s spaceship are synchronised with each other.
What empirical evidence is there to support that assumption? There is no actual evidence to support it.You're the one making assumptions. Alice has no idea if her clocks are synced. She doesn't care actually. She's there to determine which interpretation is correct, and here she is doing this procedure that doesn't help. She has no plan actually.
Synchronization of separated clocks cannot be observed.This is exactly the point!
The synchronisation procedure is a real-world, physical process. It is not "all quite mathematical", it is not simply a mathematical procedure. Yes, mathematics are abstract and the definition of synchronisation under a mathematical co-ordinate frame is an abstraction, but there's a reason why empirical tests are required to verify mathematical predictions. To check the validity of the abstract mathematics.QuoteYou are confusing the idea of deriving something mathematically and deriving something from observation.No I'm not. It's all quite mathematical since we're discussing synchronization, something that only has abstract meaning.
Again, we have to bring things right back to basics before we can proceed any further, and I believe this is the sticking point.I didn't say 'in her inertial frame'. Given an abstract selection of a coordinate system, the synchronization of two clocks can very much be measured/observed, per Einstein's definition of synchronized clocks. That procedure even works in your interpretation.Quote from: HalcSynchronization of separated clocks cannot be observed.This is exactly the point!
If Alice cannot observe that the clocks in her inertial frame are synchronised
It requires a selection of a coordinate system, which makes the result of the real world procedure only as physical as that selection, which is to say it isn't.Quote from: HalcThe synchronisation procedure is a real-world, physical process. It is not simply a mathematical procedure.QuoteYou are confusing the idea of deriving something mathematically and deriving something from observation.No I'm not. It's all quite mathematical since we're discussing synchronization, something that only has abstract meaning.
Yes, mathematics are abstract and the definition of synchronisation under a mathematical co-ordinate frame is an abstractionBut that abstraction is all that Alice is claiming.
but there's a reason why empirical tests are required to verify mathematical predictions. To check the validity of the abstract mathematics.Disagree. I can think of no physical procedure that is used to verify a purely mathematical concept. One can verify the prediction that a sync procedure (done from the midpoint say) indeed produces a valid sync by doing the verification by definition (which is not done at the midpoint), but that is a test that the physical behavior matches the mathematical model, not a verification of the mathematical definition.
The abstract mathematics doesn't necessarily imply that the clocks are synchronised.No frame reference, so I don't disagree with this.
The Lorentz-Poincare interpretation also employs the Lorentz transformation between the relatively moving reference frames, but the clocks in those reference frames are not synchronised, under that interpretation.By definition, yes. Still not disagreeing.
So, from the abstract, mathematical, stationary, co-ordinate reference frame that Alice chooses to employIt isn't stationary. It is an arbitrary frame. The fact that you found one mention of the word 'stationary' as a simple designation in Einstein's work is not an assertion that the frame is a preferred one. I continue to harp on this because you're using the concept to give metaphysical meaning to something that isn't a metaphysical statement.
we can derive a prediction about the [real-world, physical, not-mathematical] clock synchrnoisation procedure that Alice carries out onboard her physical, not mathematical spaceship, which constitutes her "stationary system". This mathematical description says that the reading on the [real-world, physical, not-mathematical] clock, which we have labelled as "A", that the reading on this clock that corresponds to the [real-world, physical, not-mathematical] photon making physical - not mathematical - contact with the [real-world, physical, not-mathematical] clocks [which we have labelled] B1 and B2 (because they are nailed to the floor at points B1 and B2, in her "stationary system"/in her reference frame), that the reading on this clock will correspond to a value of d/c and will be the same for both [real-world, physical, not-mathematical] events.I didn't get the last bit: "will be the same for both events". What events? I assume the zeroing events of the clocks at B1 and B2, in which case I agree that the reading of d/c on clock at A would be simultaneous with those two zeroing events in the frame where all the clocks involved remain at their respective locations. I would not agree to the ambiguously worded statement of something being the same for both events.
If she cannot observe it then she can only assume it, she can only establish it by definition.Establishing it by definition is not assuming it. She's quite capable of applying the definition and verifying it. She has not done so in the procedure you describe above. The definition doesn't involve a 3rd location.
Hey roosh, how was the trip?It was good, thanks :D. Just left the monastery today and am heading to Malaysia in the next couple of days for another 2 week retreat. I had time to flesh out a different part off the argument I'm making, which we'll hopefully get to :D
I didn't say 'in her inertial frame'.This is probably a big part of the issue. I am trying to clarify my thinking but I am using terms imprecisely/interchangably, which is probably leading to us talking past each other in some cases. I'm having a similar discussion on another forum with people who I'e debated against before, who are probably used to me doing this, so haven't been pulling me up on it, because they understand the point I am trying to make. So, I haven't learned to be more precise. So apologies if that is the case.
Given an abstract selection of a coordinate system, the synchronization of two clocks can very much be measured/observed, per Einstein's definition of synchronized clocks. That procedure even works in your interpretation.Apologies, can we walk thru this bcos I'm not fully clear on your reasoning here. I'll outline my understanding, sticking as closely to the Einsteinian synchronisation procedure as I can, and you can highlight where I'm going wrong - if that suits?
You send a pulse at time T1a from a clock at one location and measure the time T1b on the clock at the distant location when that pulse is received. Subtracting the two gives duration D1. You do the same in the reverse direction to get D2. Iff D1 and D2 are equal, the clocks at those two locations are in sync in the selected frame by definition.
Since the frame selection is an arbitrary selection of abstract coordinate systems, the statement that two clocks are in sync in that frame is a purely abstract statement. Perhaps your disconnect is along those lines, like Alice is making some sort of metaphysical claim when she runs her verification procedure. She's not.This is where the disconnect is, I think. We don't need to assume that she is making a metaphysical claim - even though such a claim has pretty drastic metaphysical implications pertaining the the physical structure of the universe, stemming from that claim.
And what we're doing is seeing how well Alice's abstraction maps onto the physical world. We're checking to see if her abstraction can be verified empirically.QuoteYes, mathematics are abstract and the definition of synchronisation under a mathematical co-ordinate frame is an abstractionBut that abstraction is all that Alice is claiming.
Disagree. I can think of no physical procedure that is used to verify a purely mathematical concept. One can verify the preduction that a sync procedure (done from the midpoint say) indeed produces a valid sync by doing the verification by definition (which is not done at the midpoint), but that i8 a test that the physical behavior matches the mathematical model, not a verification of the mathematical definition.As has been stated, we can derive a statement from Alice's abstraction about the physical configuration of her inertial frame i.e. her physical, "stationary system". This claim pertains to the reading on the clock at the midpoint. It is a logically necessary statement about the physical system, derived from her abstraction. As a statement about the configuration of a physical sysyem, it is subject to the rules of empiricism. Empirically speaking it is untestable. So, from a purely empiricial standpoint, it is an assumption.
The Lorentz transformation does not necessitate that simultaneity is relative because there are [at least] 2 difffering interpretations of the evidence which employ the LT. One interpretation concludes the relativity of simultaneity, the other doesn't, so RoS is not a necessity of the Lorentz Transformation.QuoteThe abstract mathematics doesn't necessarily imply that the clocks are synchronised.No frame reference, so I don't disagree with this.QuoteThe Lorentz-Poincare interpretation also employs the Lorentz transformation between the relatively moving reference frames, but the clocks in those reference frames are not synchronised, under that interpretation.By definition, yes. Still not disagreeing.
It isn't stationary. It is an arbitrary frame. The fact that you found one mention of the word 'stationary' as a simple designation in Einstein's work is not an assertion that the frame is a preferred one. I continue to harp on this because you're using the concept to give metaphysical meaning to something that isn't a metaphysical statement.Apologie, I threw that in there in a state of exasperation in attempt to cover all bases. I am not imbuing the term "stationary" with any metaphysical qualities. My imprecise usage is causing some difficulty in some cases.
I didn't get the last bit: "will be the same for both events". What events? I assume the zeroing events of the clocks at B1 and B2, in which case I agree that the reading of d/c on clock at A would be simultaneous with those two zeroing events in the frame where all the clocks involved remain at their respective locations.This is precisely what I meant. This is the statement about the configuration of the physical system that can be derived from Alice's abstraction. It is this that cannot be observed and which must be assumed. If either of the zeroing events is not simultaneous with this reading, then the two clocks are not synchronised. Alice has no way of verifying, empirically, that the zeroing events are simultaneous with this clock reading . Therefore, from an empirical standdpoint, she can only assume that this is the case.
Establishing it by definition is not assuming it.Maybe not. However, it is the not being able to verify it empirically that makes it an assumption.
She's quite capable of applying the definition and verifying it. She has not done so in the procedure you describe above. The definition doesn't involve a 3rd location.She cannot verify it. As you have said yourself, the synchronisation of spatially separated clocks cannot be observed. If it cannot be observed, then it cannot be verified - at least not empirically.
Let me correct my statement then. One can empirically observe the simultaneity of clocks given an abstract coordinate system, using the empirical method described by Einstein's definition. That definition is meaningless sans said coordinate system, hence my statement that one 'cannot observe synchronization of clocks' without specification of that choice of coordinate system. Einstein's definition is entirely empirical, which means the state can indeed be observed, given a frame.Quote from: HalcI didn't say 'in her inertial frame'.This is probably a big part of the issue. I am trying to clarify my thinking but I am using terms imprecisely/interchangably, which is probably leading to us talking past each other in some cases. I'm having a similar discussion on another forum with people who I'e debated against before, who are probably used to me doing this, so haven't been pulling me up on it, because they understand the point I am trying to make. So, I haven't learned to be more precise. So apologies if that is the case.
Apologies, can we walk thru this bcos I'm not fully clear on your reasoning here. I'll outline my understanding, sticking as closely to the Einsteinian synchronisation procedure as I can, and you can highlight where I'm going wrong - if that suits?OK. The synchronization procedure is not the same as the verification-by-definition procedure... just so you know. The former is how one goes about syncing the clocks in a frame, and the latter is one way to verify that they're indeed in sync in that frame.
You have the 2 clocks as you outline there. Let's call the clocks C1 and C2 for convenience. At time T0 on C1, you send the pulse to C2, which zeros C2. How do you measure the duration of the journey from C1 to C2?The verification procedure (the 'by definition' one) doesn't zero anything. When clock at C1 reads T1, it sends the pulse, which is received at C2 at T2 say. The duration is T2-T1 as measured by those respective clocks. That's the number we're after. It might be negative, but the clocks are not in sync if it is negative.
or, do you mean:This sounds better. Yes, it doesn't matter what time the pulse is sent, so long as it is known.
that both clocks are started independently, not synchronously and at the random time T1a [on C1], a pulse is sent from one clock to the other clock [C2] which registers the time of T1b. Subtract the 2 values to get D1. This would give us a random value not necessarily the duration of the journey from C1 to C2 - because we don't know if the clocks were started simultaneously. Lets, for arguments sake, say that the value it gives us is 2 units of time.
Then, at a random time T2b a pulse is sent from C2 to C1. The 2 values are subtracted to give D2. Let's imagine for a second though, that C2 was started 1 unit of time before C1. Subtracting the two values will give us 0 (assuming the same journey time).Yes, except worded as 'clock at location C1, C2, not clocks C1 and C2'. It's really important to distinguish between the two. I see you got a duration of 2 one way and 0 the other way. They're not in sync in that frame, by definition.
This is where the disconnect is, I think. We don't need to assume that she is making a metaphysical claim - even though such a claim has pretty drastic metaphysical implications pertaining the the physical structure of the universe, stemming from that claim.How is this a disconnect? We seem to agree that Alice is not making any metaphysical assumptions. She's doing physics, not metaphysics. The latter doesn't involve all the toy's she's playing with.
We need only talk about the physical system in which Alice finds herself, and the physical synchronisation procedure that she carries out. We're talking about empirical verification of Alice's claims. In this sense, her statement that the two clocks are in sync is not a purely abstract statement. It's a statement about the physical configuration of a real-world inertial system.Again, she claims they're in sync in the one frame. Different claim. Agree with the rest.
All OKQuote from: HalcBut that abstraction is all that Alice is claiming.And what we're doing is seeing how well Alice's abstraction maps onto the physical world. We're checking to see if her abstraction can be verified empirically.
Given Alice's abstraction we are free to derive/deduce other claims about the configuration of her physical system that follow as a necessity from her abstraction. Alice may not have expreessly stated these from the outset, as she may have been unaware of them, but as with any physicl theory/interpretation, we can see what it logically necessitates and go about testing that, empirically. In doing so, we can see that her abstraction includes a logically necessary statement about the simultaneity of clock synchronisation events and their coincidence with the reading on a clock located midway between them. This is simply a statement about the configuration of the physical system that we can deduce from Alice's abstraction and which gives us further insight into her interpretation.
As we have agreed, this part of Alice's abstraction cannot be verified empirically, that is, we cannot determine, by way of observation, that Alice's abstraction is an accurate representatation of the physical world.We just agreed that there are all these verification tests that can be done and all the bit you just got finished typing. Now you say that it cannot be done. Pick a story please. Alice is going to make all these additional observervations and every one of them will be a frame dependent observation, but that doesn't make them non-empirical tests. She has a test for clocks being in sync, and given that plus a little trivial mathematical work, she can verify that the clock at the midpoint is indeed fast by d/c compared to either of the other two clocks. Not compute it, but empirically verify it.
For Alice to maintain her belief in this abstraction she does so, not on the basis of empirical observation, she does so only by way of assumption.And here you go with this assertion of assumptions again. There is an empirical way to verify these things. None of it is assumed. Your comment doesn't follow at all.
In this sense, Alice's abstraction (co-ordinate reference frame) is the "map" and her physical, inertial frame is the territory.The inertial frame is the abstraction. The territory is all the toys. You are making a metaphysical assumption in declaring an inertial frame to be a physical thing. I'm not doing that, and neither is Alice.
As has been stated, we can derive a statement from Alice's abstraction about the physical configuration of her inertial frame i.e. her physical, "stationary system".You stated that wrong. The coordinate system is an abstraction, not a physical system. I cannot go over and lean on the X axis.
This claim pertains to the reading on the clock at the midpoint. It is a logically necessary statement about the physical system, derived from her abstraction. As a statement about the configuration of a physical sysyem, it is subject to the rules of empiricism. Empirically speaking it is untestable. So, from a purely empiricial standpoint, it is an assumption.It is quite testable, so not an assumption at all. We had Alice doing just such a test. You're just making up false assertions without backing them.
The Lorentz transformation does not necessitate that simultaneity is relative because there are [at least] 2 difffering interpretations of the evidence which employ the LT.Agree. I said the sync verification procedure works with either interpretation.
One interpretation concludes the relativity of simultaneity, the other doesn't, so RoS is not a necessity of the Lorentz Transformation.Agree. Are you claiming I said otherwise?
No, it is an abstract claim based on the abstract selection of coordinate system. Claims of simultaneity are abstract claims. They can be physically verified only given a choice of abstract coordinate systems.Quote from: HalcI didn't get the last bit: "will be the same for both events". What events? I assume the zeroing events of the clocks at B1 and B2, in which case I agree that the reading of d/c on clock at A would be simultaneous with those two zeroing events in the frame where all the clocks involved remain at their respective locations.This is precisely what I meant. This is the statement about the configuration of the physical system that can be derived from Alice's abstraction.
It is this that cannot be observed and which must be assumed. If either of the zeroing events is not simultaneous with this reading, then the two clocks are not synchronised. Alice has no way of verifying, empirically, that the zeroing events are simultaneous with this clock reading . Therefore, from an empirical standdpoint, she can only assume that this is the case.Frame reference missing, so all this is meaningless. If you mean to imply 'in her selected frame', then the statement is merely wrong, as per my comments above.
Maybe not. However, it is the not being able to verify it empirically that makes it an assumption.I suppose it would be. Good thing we have an empirical verification that can be performed.
OK. The synchronization procedure is not the same as the verification-by-definition procedure... just so you know. The former is how one goes about syncing the clocks in a frame, and the latter is one way to verify that they're indeed in sync in that frame.OK, hopefully we can make some progress by focusing on this.
The verification procedure (the 'by definition' one) doesn't zero anything. When clock at C1 reads T1, it sends the pulse, which is received at C2 at T2 say. The duration is T2-T1 as measured by those respective clocks. That's the number we're after. It might be negative, but the clocks are not in sync if it is negative.There is a critical issue with the statement "the duration is T2-T1 as measured by those respective clocks". The issue lies in the fact that we have not established a "common time" for both clocks.
There is a critical issue with the statement "the duration is T2-T1 as measured by those respective clocks". The issue lies in the fact that we have not established a "common time" for both clocks.Maybe we shouldn't call it a duration then. T1 is what the one clock at the first location reads when the pulse is sent from there. T2 is what the seconds clock reads when the pulse is received from there. Subtracting them gives a figure, and it seems to offend you to call it a duration, which seems fine since indeed, no common time has been established. So we simply have a number that is the difference between the two readings. The clocks literally can say anything, so this value can be any figure at all, positive or negative. So let's just not call it a duration.
If the clock at C2 started one unit of time before the clock at C1 such that when the clock at C1 reads T=0 the clock at C2 reads T=1You don't know this. You can't make this assumption about something not yet measured.
then the value T2-T1 will not accurately reflect the journey time for the pulse. If the pulse takes 1 unit of time to reach the clock at C2 then the reading on the clock at C2 will be T=2. Subtracting the two values will give a journey time of 2 units of time.Quite right. Shouldn't call it a journey time then either. Just a difference of 2 units between the pair of readings.
Now, if the pulse is reflected from the clock at C2No reflection is part of the procedure. The pulse can be sent at any time. Yes, it can be done exactly at the moment the signal was received from location C1, but it doesn't have to be. We just need to know what the clock there said when the pulse is sent.
from the clock at C2 but takes 3 units of time in the opposite direction. but takes 3 units of time in the opposite direction, it will arrive at the clock at C1 when that clock reads T=4. Subtracting the two values will give a journey time of 2 units of time. Concluding that the clocks are synced is clearly erroneous given the starting configuration of the system.Both differences are empirically measured to be 2, so by Einstein's definition, the clocks are empirically in sync. Only the empirical readings of the clocks were used to determine this.
Maybe we shouldn't call it a duration then. T1 is what the one clock at the first location reads when the pulse is sent from there. T2 is what the seconds clock reads when the pulse is received from there. Subtracting them gives a figure, and it seems to offend you to call it a duration, which seems fine since indeed, no common time has been established. So we simply have a number that is the difference between the two readings. The clocks literally can say anything, so this value can be any figure at all, positive or negative. So let's just not call it a duration.I'm not offended at all by calling it duration. I was just pointing out the error in your reasoning. If you don't want to call it a duration that's fine, we can call it a figure or a reading or a value, whatever. The issues still remain.
You don't know this. You can't make this assumption about something not yet measured.It's called specifying the intial conditions of the experimental set-up.
No reflection is part of the procedure. The pulse can be sent at any time. Yes, it can be done exactly at the moment the signal was received from location C1, but it doesn't have to be. We just need to know what the clock there said when the pulse is sent.Let a ray of light start at the “A time” tA from A towards B, let it at the “B time” tB be reflected at B in the direction of A (Einstein, 1905).
Both differences are empirically measured to be 2, so by Einstein's definition, the clocks are empirically in sync. Only the empirical readings of the clocks were used to determine this.I have outlined a case where both differences are empirically measured to be 2, using only the empirical readings of the clocks to determine this. The initial conditions of the set-up were specified such that the clocks were not in sync but still both differences are empirically measured to be 2.
I noticed that you needed to posit light speed in one direction (something you've asserted cannot be measured, and thus a metaphysical assumption) being thrice that of light going the other direction. You're free to add this strange complication, but it doesn't change the empirical facts.
In the frame in which they stay at their locations, the clocks are still in sync by definition.The clocks stay in their locations in her inertial frame, bolted to the floor of her spaceship. As for the motion of her spaceship, Galileo taught us that that we cannot determine the nature of the inertial motion of her spaceship. So, whether or not one of the clocks advances towards the light pulse while the other moves away from it, Alice simply cannot determine this by way of experiment.
I think you need to respond to post 46 which covers the earliest measurement of the speed of light, and which used a one-way method. It would be a long time before a two-way method could be employed. Your argument here seems to hinge on a metaphysical assumption of direction-dependent light speed.I'll take a look at it again. Did you provide the provide the peer reviewed papers? From what I read you were trying to assert that attempts to measure the one-way speed of light came oh so, very nearly close to providing an exact measurement for the speed of light. This can be translated as, they demonstrated a variable speeed of light because it wasn't the defined value c.
The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to the detector and back again.
Experiments that attempted to directly probe the one-way speed of light independent of synchronization have been proposed, but none has succeeded in doing so.[3] Those experiments directly establish that synchronization with slow clock-transport is equivalent to Einstein synchronization, which is an important feature of special relativity. Though those experiments don't directly establish the isotropy of the one-way speed of light, because it was shown that slow clock-transport, the laws of motion, and the way inertial reference frames are defined, already involve the assumption of isotropic one-way speeds and thus are conventional as well.[4] In general, it was shown that these experiments are consistent with anisotropic one-way light speed as long as the two-way light speed is isotropic.[1][5]
an assumption that is made by standard formulations of the Special Theory of Relativity, but which has no experimental support, and which may even be untestable in principle—the assumption,namely,that the measured one-way speed of light is a constant in all directions in all inertial frames.
The natural place to begin is with Einstein,and his original, 1905 formulation of the Special Theory. There, Einstein explicitly assumed that the one-way speed of light is a constant in all inertial frames. He did not,however, view that postulate as one for which there was experimental evidence. His position was rather that,while there is evidence for the assumption that the round-trip speed of light in a vacuum is a universal constant,the further postulate that the time taken for light to travel between two locations is the same in both directions is instead something which one establishes as true ‘by deﬁnition’.194 On Einstein's own approach,therefore,it is simply a matter of convention that the one-way speed of light in a vacuum is a constant.195. This idea that one can view it as true by deﬁnition that the oneway speed of light is a constant is a rather jarring one, and has given rise to a controversy that is still not yet fully resolved.
Thus,on the one hand,a number of philosophers, starting with Hans Reichenbach,have strongly defended the view that the non- conventional content of the Special Theory of Relativity precludes any experiment that could be used to determine whether the oneway speed of light is in fact a constant.196 But,on the other hand, a number of proposals have been advanced, and continue to be advanced,by physicists and others,concerning experiments that could be carried out to determine the one-way speed of light. The experiments proposed so far,however, all seem to be ﬂawed,for, upon close scrutiny,all of the experiments appear to involve some principle or other that is true only if the one-way speed of light is a constant,and, if this is right, then none of the experiments proposed so far can possibly result in a value for the one-way speed of light which differs from that of the average round-trip speed.197
You're making an assumption that gets contradicted by the empirical measurement taken. The empirical test (the numbers you provided in your example) trumps the assumption, proving it incorrect. You can't presume the peg to be square and measure it to be round and expect the presumption to still hold.Quote from: HalcIt's called specifying the intial conditions of the experimental set-up.QuoteIf the clock at C2 started one unit of time before the clock at C1 such that when the clock at C1 reads T=0 the clock at C2 reads T=1You don't know this. You can't make this assumption about something not yet measured.
The pulse can be sent at any time. Yes, it can be done exactly at the moment the signal was received from location C1, but it doesn't have to be.
Let a ray of light start at the “A time” tA from A towards B, let it at the “B time” tB be reflected at B in the direction of A (Einstein, 1905).I'm just saying that it isn't a requirement. It didn't say it wasn't allowed.
Your assumption of the initial conditions (peg is square) was shown to be incorrect by an empirical measurement of a round peg. The premise (of not-in-sync) was proven incorrect. The empirical test passed. The clocks are in sync in that frame by definition.Quote from: HalcBoth differences are empirically measured to be 2, so by Einstein's definition, the clocks are empirically in sync. Only the empirical readings of the clocks were used to determine this.I have outlined a case where both differences are empirically measured to be 2, using only the empirical readings of the clocks to determine this. The initial conditions of the set-up were specified such that the clocks were not in sync but still both differences are empirically measured to be 2.
As Alice cannot distinguish between the two scenarios on the basis of empirical observation, this set of empirical observations does not empirically verify the synchrony of the clocks.She can very much tell. She sees that 2 = 2. That's the only measured fact. The premise that they're not in sync is demonstrably wrong.
But, here's the kicker: there are other empirical observations of the process, all of which show that the clocks aren't synchronised and that the light does take longer to travel in one direction than the other.I don't recall Alice or anybody else measuring any such thing. Wouldn't matter if they did, since the definition was satisfied.
You're correct, we are free to add this complication and it doesn't change the empirical facts. It is precisely that the empirical facts are not changed which allows us to draw the conclusion that Alice cannot distinguish between the two empirically and so, she can only rely on assumption to make the statement that her clocks are synced - in a frame dependent manner or an absolute manner.No assumptions are made. Light can be faster one way than the other if that interpretation makes you happy. I know of no alternate interpretation that suggests this, but there's nothing invalid about it. It doesn't change the fact that the clocks are synced in that frame by definition, and the premise about them not being synced is shown to be wrong.
Alice simply cannot determine this by way of experiment.She doesn't have to. She's chosen a coordinate system in which her stuff is stationary, a requirement of the test. Her (purely abstract) conclusion then only applies to her choice of abstract coordinate systems.
I'll take a look at it again. Did you provide the provide the peer reviewed papers?The guy is in the history books as the first to measure light speed. If his peers found his methods invalid, he would not hold that honor. It gained support by Newton and others and was confirmed 50 years later by different methods.
From what I read you were trying to assert that attempts to measure the one-way speed of light came oh so, very nearly close to providing an exact measurement for the speed of light.Didn't say oh-so-close. He was off by about a quarter, which isn't bad considering they didn't have any idea how many zeros the figure would have before then.
This can be translated as, they demonstrated a variable speeed of light because it wasn't the defined value c.Not sure what you're talking about. There was no defined 'c' back then. They didn't know it to have a finite speed or a constant one. The test can be (and was) repeated in different directions, and yields the same figure in any of them.
Until you provide some sort of reference or link, I'm going to go with wikipedia and its referencesOK:
Following one of the references led me to a book called Time, Tense, and Causation by Michael Tooley:Newton assumed a direction-independent light speed, despite not assuming a frame independent one. Yes, all interpretations of relativity (including absolute ones) assume a direction independent constant light speed. You are allowed to posit an interpretation that does otherwise, but I don't see the point in such a needless complication. If you do make such a premise, the definition of synced clocks needs to change accordingly. You cannot discredit the relative interpretation by making contradictory premises like that.Quotean assumption that is made by standard formulations of the Special Theory of Relativity, but which has no experimental support, and which may even be untestable in principle—the assumption,namely,that the measured one-way speed of light is a constant in all directions in all inertial frames.
Now, you can continue to try and frame the discussion however you like, but you there is no escaping the very simple fact that there is no experiment which can empirically determine that two spatially separated events are simultaneous (in any way, frame dependent or otherwise).Lacking a premise of direction-independent light speed, I agree that the defined test for simultaneity doesn't work.
Therefore, any conclusion that states that two [specific] events are simultaneous (in any way, frame dependent or otherwise) assumes that conclusion.Relativity makes a constant light speed premise, but the rest is derived from that premise, never assumed as you continue to assert. The derivations are in the paper. There is no conclusion made that light speed is constant, thus there is no circularity about it.
It doesn't change the fact that the clocks are synced in that frame by definition, and the premise about them not being synced is shown to be wrong.You've mistakenly assumed that I am trying to demonstrate an inconsistency or contradiction in the Einsteinian interpretation and it is against this contention that you are arguing. You might be drawing inferences from other threads that I have started and incorrectly applying them in the context of this disucssion.
I think your problem is that you're running with a different definition of being in sync than what Einstein describes. If you want to show an inconsistency with Einstein's interpretation, you need to use his definitions.
we establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A.This is the part that cannot be determined by way of empirical observation. It is an assumption, plain and simple. This is the expressed assumption.
Let a ray of light start at the “A time” tA from A towards B, let it at the “B time” tB be reflected at B in the direction of A, and arrive again at A at the “A time” t0 A.If tease this abstract convention apart, we can see that it simply boils down to:
In accordance with definition the two clocks synchronize if tB - tA = t' A - tB
You're making an assumption that gets contradicted by the empirical measurement taken. The empirical test (the numbers you provided in your example) trumps the assumption, proving it incorrect. You can't presume the peg to be square and measure it to be round and expect the presumption to still hold.OK, maybe I'm being too presumptuous in assuming that you understand the concept of "the initial conditions of an experimental set-up". There are questions after this so we can try to diagnose where your lack of undderstanding lies.
The guy is in the history books as the first to measure light speed. If his peers found his methods invalid, he would not hold that honor. It gained support by Newton and others and was confirmed 50 years later by different methods.Well, I wouldn't be so presumptuous to assume that I am a peer of those scientists who peer review papers for inclusion in journals, or those scientists who have peer reviewed papers that now represent accepted scientific fact. That is who you are talking about when you talk about "[my] peers" right? Bcos, that's what I mean when I talk about peer reviewed evidence.
I also mentioned that you're probably looking for review from your peers, not his. Do some thinking for yourself for once and tell me what's wrong with his methods.
[moved up] But I assert that the test can be run today with under 1% error. Why can't a similar experiment be run today with our far more accurate clocks and such?You tell me! It would seem that for all of the experimental verification of
If we compare the one-way experiments of [48] in Fig. 7 with the two-way experiments in Fig. 6, the results are about 4 to 6 orders of magnitude smaller in the one-way experiments than those of two-way experiments. Also the most recent one-way experiment performed by Krisher et al [79] in 1988 in NASA- Jet Propulsion Laboratory Deep Space Network (DSN) presents 2 orders of magnitude smaller values than that of NASA‟s previous experiment by Vessot et al [77, 78] in 1976. This is contradictory to our expectation based on STR [the Special Theory of Relativity] where we expect lower order of magnitude values with greater improvements.
The results of the one-way experiments are increasing in magnitude with time, whereas, the two-way experiments are decreasing in magnitude with greater precision and improvements with time. However, the results from the limits of the one-way experiments of [11] at the GRAAL facility are consistent with STR. But the regularity in the variations of the reported results of the GRAAL measurements reported in [11] in different timeperiods remains unclear and needs further experimental investigations.
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you'll like this part
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We have presented a comparison of experiments in Fig. 8 that shows the one-way speed of light measurement is approximately 2000 times more sensitive than that of round-trip test. Will [48] showed that experiments which test the isotropy in one-way or two-way (round-trip) have observables that depend on test functions but not on the particular
synchronization procedure. He noted that “the synchronization of clocks played no role in the interpretation of experiments provided that one is careful to express the results in terms of physically measurable quantities”. Hence the synchronization is largely irrelevant and one-way speed of light is measurable.
Results of the experimental tests spanning at least 24 hours periods in different seasons of the year should be recorded. Any hypothetical diurnal variations that might be observed should follow the figures presented in the
section 2.2 in Fig. 3 and Fig. 4.
Some authors such as Mansouri and Sexl (1977)[9][10] as well as Will (1992)[11] argued that this problem doesn't affect measurements of the isotropy of the one-way speed of light, for instance, due to direction dependent changes relative to a "preferred" (aether) frame Σ. They based their analysis on a specific interpretation of the RMS test theory in relation to experiments in which light follows a unidirectional path and to slow clock-transport experiments. Will agreed that it is impossible to measure the one-way speed between two clocks using a time-of-flight method without synchronization scheme, though he argued: "...a test of the isotropy of the speed between the same two clocks as the orientation of the propagation path varies relative to Σ should not depend on how they were synchronized...". He added that aether theories can only be made consistent with relativity by introducing ad-hoc hypotheses.[11] In more recent papers (2005, 2006) Will referred to those experiments as measuring the "isotropy of light speed using one-way propagation".[6][12]
However, others such as Zhang (1995, 1997)[1][13] and Anderson et al. (1998)[2] showed this interpretation to be incorrect. For instance, Anderson et al. pointed out that the conventionality of simultaneity must already be considered in the preferred frame, so all assumptions concerning the isotropy of the one-way speed of light and other velocities in this frame are conventional as well. Therefore, RMS remains a useful test theory to analyze tests of Lorentz invariance and the two-way speed of light, though not of the one-way speed of light. They concluded :"...one cannot hope even to test the isotropy of the speed of light without, in the course of the same experiment, deriving a one-way numerical value at least in principle, which then would contradict the conventionality of synchrony."[2] Using generalizations of Lorentz transformations with anisotropic one-way speeds, Zhang and Anderson pointed out that all events and experimental results compatible with the Lorentz transformation and the isotropic one-way speed of light must also be compatible with transformations preserving two-way light speed constancy and isotropy, while allowing anisotropic one-way speeds.
You've mistakenly assumed that I am trying to demonstrate an inconsistency or contradiction in the Einsteinian interpretation and it is against this contention that you are arguing. You might be drawing inferences from other threads that I have started and incorrectly applying them in the context of this disucssion.You state, in this thread, that Alice makes one claim that is contradicted by some alternate claim by Bob. You seem to leverage this assessment of contradiction in order to push whatever alternate position (this atemporal universe as the title calls it) that you hold.
What I'm not doingLet me quote the OP then:
Let me state it once again: I am not trying to show an inconsistency with Einstein's interpretation - at least not in this line of discussion.
While the observer in the "stationary" frame is performing this clock synchronisation, they observe a relatively moving observer perform the exact same synchronisation process. They are also located midway between 2 clocks. The light pulses are sent to each clock and reflected; crucially, the "stationary" observer sees the light pulses hit each clock not-simultaneously, get reflected, and arrive at the "moving" observer simultaneously. The "moving" observer concludes that their clocks are synchronised. The "stationary" has observed that the clocks are not synchronised.My bold. You misrepresent the claims of the two observers (later to be named Alice and Bob) and also lay claim that assumptions were made (none were other than assumptions of the premises of SR, neither of which mention simultaneity). It is that statement that prompted me to jump into this thread. The entire thread since then seems to have been about this, despite your claim here that it is not what you are doing. If you're not intending to show inconsistency with the interpretation, then don't claim said inconsistency in your OP like that.
Here, in the original thought experiment, we are provided with a clear case of why the assumption of synchronisation/simultaneity is unjustified.
What I am doingYou need to be far more explicit that this empty statement here. The conclusion you seem to claim to be assume is the simultaneity of a pair of clocks in a given frame, but since a statement concerning simultaneity is not part of either of the premises of the interpretation, this doesn't hold water. Maybe you mean something else. Say it clearly instead of vacuously like that. There are exactly two assumptions made, and neither of them is listed as a conclusion.
What I am saying, however, is that the conclusions of the Einsteinian interpretation are assumed i.e. the conclusions are arrived at through circular reasoning.
What is requiredThere are valid alternative interpretations. In what possible way would that be evidence of the circularity of the first interpretation?
In order to demonstrate this circular logic we need only present an alternative interpretation of the evidence
In order to do this we need only demonstrate that there is no way to distinguish between the two cases by way of empirical observation.Of course there is no way. They wouldn't be interpretations if there was an empirical way to distinguish them. You don't need to demonstrate this since nobody asserts otherwise.
It directly follows from the 2nd premise of SR. Even an absolute interpretation assumes that premise. Perhaps your interpretation does not. Anyway, it isn't a 3rd premise. It follows from the 2nd. No additional assumptions have been made.Quotewe establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A.This is the part that cannot be determined by way of empirical observation. It is an assumption, plain and simple. This is the expressed assumption.
Let a ray of light start at the “A time” tA from A towards B, let it at the “B time” tB be reflected at B in the direction of A, and arrive again at A at the “A time” t0 A.If tease this abstract convention apart, we can see that it simply boils down to:
In accordance with definition the two clocks synchronize if tB - tA = t' A - tB
then bouncing a light signal from A to B and back to A IF" tB - tA = t' A - tB then in accordance with definition the two clocks synchronize.They are synchronized. The action doesn't synchronize the clocks if they were not before we did this. The wording here makes it sound like the latter.
This is all fine, there is absolutely no problem with any of that. Incidentally, you might not recognise it bcos it isn't expressly stated, but the initial conditions that are implied include synchronised clocks.Not so. It was a conditional. Iff they are synchronized, the condition tB - tA = t' A - tB will be met, and if they are not, that condition will not be met. Alice need not assume the clocks are in sync in order to run the test.
We can start with different initial conditions however and say:No you cannot. This violates the 2nd premise. Work out your own sync convention if you want to go with a different set of premises. I stated above that the convention doesn't work if that premise is dropped. Even most absolute interpretations keep that premise, thus making this sync convention valid under them.
IF we start with two clocks that aren't syncronised, with one having started 1 unit of time before the other and IF we assume that the time from A to B is 1 unit of time while the time from B to A is 3 units of time
Here we have two different scenarios - one with clocks synchronised, one with clocks not synced - with the exact same empirical evidence. There is therefore, no way to distunguish between the two by way of empirical observation.That why your alternate interpretation might be valid. It's why they're called interpretations.
Now, it might be tempting to jump to the conclusion that choosing one over the other represents an equal assumptionIt represents an assumption of the two premises. No more. Your interpretation apparently doesn't assume either of them.
but you'd be wrong, because the two scenarios - despite the empirical equivalence - are not equal.I never concluded that assuming those two premises is equal to assuming different premises. Where are you going with any of this?
Relativity of SimultaneityNot necessarily at least. Pairs of events can definitely be simultaneous in more than one frame. Anyway, I know what you mean, and yes, this is a conclusion drawn from the two premises.
As has been mentioned, there are two parts to the relativity of simultaneity:
1) Events which are simultaneous in one frame (the "stationary system")
2) are not simultaneous in relatively moving inertial frames
It is number 1 above that is in contention because there is no experiment which can be carried out to reliably determine the simultaneity of spatially separated events.Number 1 is a sentence fragment identifying a pair of events, and your statement here is worded in a way that has no meaning under the interpretation. So it is like saying there is no experiment which can locate the invisible pink unicorn.
This is a direct consequence of the Galilean Principle of Relativity. When light signals arrive at an observer simultaneously from two equidistant locations (in the physical world), they cannot rule out the possibility that they were advancing towards one light signal, while retreating from the other.Meaningless statement under the relative interpretation. You are using language from a different interpretation. That makes you the one making additional assumptions.
We are free to choose any initial conditions for the experiment that we chooseIf they're in violation of the premises of a given interpretation, they are initial conditions for a different interpretation, and in no way invalidates the first interpretation.
I said your peers, not Roemer's peers. I presume you're not submitting papers to journals. Many of your arguments seem to come from your peers, and not from you.Quote from: HalcI also mentioned that you're probably looking for review from your peers, not his. Do some thinking for yourself for once and tell me what's wrong with his methods.Well, I wouldn't be so presumptuous to assume that I am a peer of those scientists who peer review papers for inclusion in journals
He's in the history books because he demonstrated that the speed of light is finite, when the thinking at the time was that it was infinite/instantaneous. He isn't in the history books bcos his measurement in any way verifies that the one-way speed of light is constant, in all directions, in all inertial frames and is equal to the value represented by c.His experiment can be reproduced today with modern measuring devices. I am looking to you for a reason why his non-round-trip method is an invalid method to measure light speed. Don't quote other sites which you interpret as asserting that it cannot be done. Tell me why it can't be done. Suppose light moved at thrice the speed in one direction as the other. Wouldn't Roemer see triple the time if he did the experiment in one direction as the other? You evade this question because it is an apparent inconsistency in your 'initial condition' that not even the absolutist interpretation will take. Resolve the inconsistency or conisder that interpretation to be falsified.
His measurement was off by about 25%, as you mentioned. So, if you're holding this up as evidence for Einstein's interpretation of relativity, I'm arfraid you are achieving the opposite. If it were to be taken as a serious experimental test of Einstein's relativity it would invalidate it.Are you asserting that modern measurements would still be off by 25%? That would indeed quickly falsify all modern interpretations, including LET, which still presumes direction independent light speed. Here's your chance to be famous. The experiment is pretty trivial. Surely somebody would have noticed by now.
Is that the answer that "[my] peers" give? You seem to know better than me who these "peers" are.No, I've not known anybody to suggest direction-dependent light speed before. That's a new one.
You tell me! It would seem that for all of the experimental verification ofI'm talking about experimental verification of your interpretation with direction dependent light speed. Not even Lorentz-Poincare suggests that.Lorentz-PoincareEinsteinian relativity
You state, in this thread, that Alice makes one claim that is contradicted by some alternate claim by Bob. You seem to leverage this assessment of contradiction in order to push whatever alternate position (this atemporal universe as the title calls it) that you hold.A couple of important points:
It would be a contradiction in the interpretation if they actually made contradictory claims as you state. I've been taking the position that all their claims are entirely consistent.
My bold. You misrepresent the claims of the two observers (later to be named Alice and Bob) and also lay claim that assumptions were made (none were other than assumptions of the premises of SR, neither of which mention simultaneity). It is that statement that prompted me to jump into this thread. The entire thread since then seems to have been about this, despite your claim here that it is not what you are doing. If you're not intending to show inconsistency with the interpretation, then don't claim said inconsistency in your OP like that.
Say it is fine, but here is some alternate interpretation. I notice that nobody is discussing that since you've taken the hostile route and declared the mainstream interpretation to be wrong.
You need to be far more explicit that this empty statement here. The conclusion you seem to claim to be assume is the simultaneity of a pair of clocks in a given frame, but since a statement concerning simultaneity is not part of either of the premises of the interpretation, this doesn't hold water. Maybe you mean something else. Say it clearly instead of vacuously like that. There are exactly two assumptions made, and neither of them is listed as a conclusion.The "important points" 1 & 2 above address this. But in brief again:
So if your purpose here is to do that, you need to name the assumption that is the same as the conclusion. Without that, there is no circularity, only A that leads to B without any additional assumptions. B doesn't lead back to A. Show me a circle, or your claims of this circularity are empty.
There are valid alternative interpretations. In what possible way would that be evidence of the circularity of the first interpretation?The alternative interpretations are based on the exact same empirical obervations but they have Alice's clocks not being synced in her own frame. This demonstrates that the empirical evidence cannot be used to verify that the clocks are synced in the relevant frame.
...
Of course there is no way. They wouldn't be interpretations if there was an empirical way to distinguish them. You don't need to demonstrate this since nobody asserts otherwise.
But none of this supports a claim that any interpretation assumes its conclusions.
The mainstream alternative interpretation keeps constant light speed but replaces Galilean relativity with one where position become a property instead of a relation. The sync definition outlined by Einstein still works perfectly in this interpretation.Not necessarily discarding it, rather replacing or reinterpreting it:
You're suggested discarding the constant light speed premise as well. Then the sync definition doesn't work anymore. It is a strange interpretation, but not invalid if that's what you want to go with. Not sure if it is actually valid. Have to think about it.
It directly follows from the 2nd premise of SR. Even an absolute interpretation assumes that premise. Perhaps your interpretation does not. Anyway, it isn't a 3rd premise. It follows from the 2nd. No additional assumptions have been made.Again, points 1 & 2 above, address this in the difference between explicit and tacit assumptions.
Not an assumption. That is necessary given constant light speed.The isotropic one-way speed of light is an assumption bcos it has not been - and possibly cannot ever be - measured.
They are synchronized. The action doesn't synchronize the clocks if they were not before we did this.Precisey my point about the implicit initial conditions.
The wording here makes it sound like the latter.I noticed that too. You might want to take it up with the translator of the 1905 paper bcos I've quoted directly from that.
Alice doesn't need to assume it bcos the initial conditions are tacitly (there's that word again) prescribed.QuoteThis is all fine, there is absolutely no problem with any of that. Incidentally, you might not recognise it bcos it isn't expressly stated, but the initial conditions that are implied include synchronised clocks.Not so. It was a conditional. Iff they are synchronized, the condition tB - tA = t' A - tB will be met, and if they are not, that condition will not be met. Alice need not assume the clocks are in sync in order to run the test.
No you cannot. This violates the 2nd premise. Work out your own sync convention if you want to go with a different set of premises. I stated above that the convention doesn't work if that premise is dropped. Even most absolute interpretations keep that premise, thus making this sync convention valid under them.Again, I'm not trying to demonstrate an inconsistency in the Einsteinian interpretation, I'm demonstrating a tacit assumption that is implicit within that interpretation.
That why your alternate interpretation might be valid. It's why they're called interpretations.It is this which demonstrates - not an inconsistency within Einstein relativity - but the tacit assumption wiith regard to clock synchronisation/simultaneity of events.
Meaningless statement under the relative interpretation. You are using language from a different interpretation. That makes you the one making additional assumptions.Again, not trying to show an inconsistency in the Einsteinian interpretation.
If they're in violation of the premises of a given interpretation, they are initial conditions for a different interpretation, and in no way invalidates the first interpretation.Indeed, they are initial conditions for a different interpretation. An interpretation which is empirically equivalent. That means that the evidence does not distinguish between the two. Given that they are contradictory interpretations, this demonstrates that - at least one of them - must be assuming its conclusions bcos both cannot be correct.
His experiment can be reproduced today with modern measuring devices.What are the results of these modern day measurements and can you provide peer** reviewed papers that demonstrate that these measurements represent empirical verification of STR? I'm sure you realise that such a paper would be pretty big news, so if such exists you shouldn't have much trouble finding it. Obviously, "my peers" would like to keep this sort of thing suppressed which is probably why I haven't been able to find anything on it, but I'm sure you should have no trouble coming up with the goods.
I am looking to you for a reason why his non-round-trip method is an invalid method to measure light speed. Don't quote other sites which you interpret as asserting that it cannot be done. Tell me why it can't be done.I don't need to know all of the reasons why it can't be done. The onus is on you to demonstrate how it has been done. I have referenced peer** reviewed literature that outlines reasons why all attempts thus far have failed. If you wish to adopt the position that those peer** reviewed papers are incorrect, go right ahead. You might have to base it on a litle more than your own "say-so" though.
Suppose light moved at thrice the speed in one direction as the other. Wouldn't Roemer see triple the time if he did the experiment in one direction as the other?Unlikely given that the sensitivity of such a one-wway measurement is "2000 times" more sensitive than that of a two-way measurement, and I don't think his equipment was up to it. I'm not sure modern equipment is up to it yet.
You evade this question because it is an apparent inconsistency in your 'initial condition' that not even the absolutist interpretation will take. Resolve the inconsistency or conisder that interpretation to be falsified.Nope, I haven't evaded it. I just know that the 75%-accurate measurement of the speed of light made in the 1600s isn't an empirical verification of Einstein's interpretation of relativity. I chose to address it in a different manner by referencing peer** reiewed literature from this aeon. I even referenced literature that attempts to make your case, so as not to be biased.
Are you asserting that modern measurements would still be off by 25%? That would indeed quickly falsify all modern interpretations, including LET, which still presumes direction independent light speed. Here's your chance to be famous. The experiment is pretty trivial. Surely somebody would have noticed by now.Are you asserting that modern day measurements have been conducted such that they conclusively distinguish between the competing interpretations?
I see you continue to quote wiki pages unrelated to what Roemer was doing.We are discussing Einsteinian relativity, so therefore we are discusssing the one-way, isotropic speed of light - because that is what is pertinent to Einstein's relativity. If you think the information I posted is not relevant to the case of Rřmer, then ipso facto, Rřmer isn't relevant to this discussion - because the stuff I referenced is relevant Einsteinian relativity.
He wasn't testing isotropy. He was measuring light speed using a one-directional method.
1) There is a difference between the explicit assumptions that Einstein starts with and the tacit assumptions required for the interpretation to be considered valid.Show me such a tacit assumption then. There are plenty, like thermodynamic laws and such, but to illustrate your objection, you need to show an example that doesn't make the tacit assumption. The one you gave wasn't such an example since it violated one of the explicit premises. If you can't do that, then your claim here is empty.
2) If something cannot be verifiied empirically but it forms part of your conclusion, then it is assumed to be true.A premise is not an assumption of truth. It is merely a foundation for the subsequent conclusions. The conclusions are only as strong as the premises, and thus the conclusions are not true. Even mathematical proofs need at some point rest on some fundamental axioms which are not provably true, and thus are only true given those axioms.
Creationists employ this sort of reasoning to support their claims about God.As do those that claim no God. Both claims are only as strong as their premises, which in both cases are usually pretty weak. The SR premises on the other hand (Laws of physics not empirically behaving in a frame dependent manner, and that empirical frame independence being extended to electromagnetism) are both empirical claims. They seem to be quite sound premises, unlike the ones typically chosen to prove or disprove God.
It is Alice's assumption that her clocks, in her own frame, are in sync - add all the qualifications in the world you like - which is rendered unjustified by the totaity of empirical observations.This is what I mean. This statement is totally wrong. Alice has demonstrated the fact, not assumed it. Nobody's observation anywhere has contradicted that. If you feel otherwise, name the observation that contradicts what Alice has demonstrated. Everybody has assumed the premises of SR and nothing else. Sure, somebody else making different assumptions might assume that her clocks are not in sync, but even that person could not not deny her demonstration that they're in sync in her frame, which is what Alice is actually demonstrating.
The evidence presented by Bob contradicts this assumption because the evidence presented by Bob shows that the clocks didn't sync.
the empirical observations that he has made show him that the clocks are not in sync.Those observations show no such thing. This statement is in complete contradiction with your statement that you find the relative interpretation to be self consistent. You don't understand the theory at all if you make this statement.
Does Bob agree that Alice's clocks are in sync "in her own co-ordinate system"? Well, if he quotes the Book ofOh he saw. He's got a bodycam and verified everything. He's taking nobody's word for it. He's using his own observations, not Alice's. The nice thing about the verification definition is that it doesn't require the observer to be at a location, or remain at one. The procedure can be done by a moving observer.RevelationRelativity and the Gospel according to Einstein: "Blessed are those who believe without seeing", then yes, he agrees with Alice's claims. But he doesn't do so on the basis of any empirical observations that he has made.
Alice devises a method of verification for her claim that the LNM is in the lake. Her verification method says:Alice has made no claim of evidence supporting her premises. They remain premises. It would be circular reasoning if she had. Your example is not applicable.
IF the LNM is in the lake then, IF it breathes, we will see bubbles on the lake. Alice sees Bubbles on the lake and concludes that the LNM is there, even if she hasn't observed the LNM.
The empirical verification that you point to only works IF we assume the clocks are already in sync and IF we assume the one-way speed of light is isotropic.That's actually right. I though you incapable of making a sane statement there for a while. You seem to be losing it. Anyway, that (constant light speed) is indeed one of the premises, an assumption as you put it. She performs no experiment that concludes that.
This is further illustrated by presence of alternative interpretations which return the same empirical values from different starting conditions - conitions under which the clocks are not in sync and the one-way speed of light is not isotropic.I bet a non isotropic SoL interpretation could be driven into self contradiction. Even Lorentz-Poincare interpretation assumes isotropy. I don't think your skillset is up to a total rewrite of everything that would be required. What prevents something from traveling faster than light if light in a certain direction can be arbitrarily slow? One could send messages ahead of light in one direction, and faster than c (using light) in the other.
Agreed.Quote from: HalcYou need to name the assumption that is the same as the conclusion. Without that, there is no circularity, only A that leads to B without any additional assumptions. B doesn't lead back to A. Show me a circle, or your claims of this circularity are empty.Einstein's conclusion is that simultaneity is relative. That is, that events which are simultaneous in one frame are not simultaneous in relatively moving reference frames
The simultaneity of spatially separated events (in any frame) cannot be determined empirically.Blatantly wrong. Einstein outlined a 100% empirical procedure to do it. You argument rests on this?? It just fell apart.
The alternative interpretations are based on the exact same empirical obervations but they have Alice's clocks not being synced in her own frame.Your non-isotropic interpretation maybe (one whose validity hasn't been tested). The mainstream ones like Lorentz-Poincare still have Alice being correct about it. L-P still holds to light speed being isotropic, but as you point out, that is an assumption.
That has been empirically demonstrated, and is a subset of SR theory's 2nd premise. You'd have to deny something fundamental like the concept of proper distance if you were to suggest a different premise than that one.Quote from: HalcYou're suggested discarding the constant light speed premise as well.Not necessarily discarding it, rather replacing or reinterpreting it:
not that the round-trip speed of light is a constant relative to all inertial frames,but rather that the round-trip speed of light is a constant as measured within all inertial frames
I said "given constant light speed". Can you not read? How could light speed in any direction be constant and still not isotropic?Quote from: HalcNot an assumption. That is necessary given constant light speed.The isotropic one-way speed of light is an assumption bcos it has not been - and possibly cannot ever be - measured.
Given that we can specify different intial conditions and derive a contradictory - yet empirically equivalent - condition (tB - tA = t' A - tB = non-synced clocks), this demonstrates that the "empirical verification procedure" cannot distinguish between synced clocks (with an isoptropic one-way speed of light) and unsynced clocks (with an isotropic round-trip speed of light).You had to violate the premises of SR to do it, rendering the example irrelevant to SR definitions. Alice is assuming those premises, not the conclusion that she demonstrates.
That means that the evidence does not distinguish between the two. Given that they are contradictory interpretations, this demonstrates that - at least one of them - must be assuming its conclusions bcos both cannot be correct.I actually disagree with this. The two interpretations (the main ones, not yours) seem not to be contradictory since neither makes a claim denied by the other. OK, one has a teapot and makes claims relative to that teapot such as its location maybe, which are meaningless in an interpretation without the teapot, but it isn't contradictory. Alice isn't denying that one clock isn't closer to the teapot than the other. She just says I know of no teapot.
What are you talking about? SR was not on the radar when the experiment was first done. SR did not invalidate what he did. It isn't an SR test. It is a method of measuring light speed. I didn't say it was the one typically used today. I just said it could be done. It very likely has been done, and the absolutists would be all over the results if it produced a result that deviated from c more than the error bar of the experiment. Roemer's least accurate device was the sundial he used as a clock. His 2nd clock was far more accurate, but his local clock was the weakest link his chain. Today it could be done with a couple atomic clocks that could be put in view of each other.Quote from: HalcHis experiment can be reproduced today with modern measuring devices.What are the results of these modern day measurements and can you provide peer** reviewed papers that demonstrate that these measurements represent empirical verification of STR?
I'm sure you realise that such a paper would be pretty big news, so if such exists you shouldn't have much trouble finding it.It's old news. It was done 350 years ago. It would be big news if doing it today yielded a value other than c, but it doesn't, so it isn't news.
I don't need to know all of the reasons why it can't be done.It was done. Did something happen in 350 years that it cannot be done anymore? More funding to science back then? It's a pretty simple test.
The onus is on you to demonstrate how it has been done.Read the wiki page I quote. That's how it was done. Your mistake is thinking that your site is measuring the same thing. They're after the metaphysical one way speed of light, rather than the physical speed of light using a one-way method. The former cannot be done, I agree. The latter has been done, as outlined by my initial post about it. The test is pretty trivial.
If you wish to adopt the position that those peer** reviewed papers are incorrect, go right ahead.The papers are not wrong. I'm saying they don't apply. The test has to yield a number, and if it wasn't c, that would be amazing news. But it yields c, which is exactly what Roemer was after, but not what your peer reviewed web sites are after. They already know the value of c. It's been published to a lot of digits today.
But, just for your benefit, one of the reasons why it would appear that it cannot be measured accurately is because a "common time" would need to be defined at two spatially separated locations.Why? Roemer didn't do that. The two clocks were never synced in any manner like Alice does. The test had no requirement for his clocks to be synced.
This reply makes no sense. There was no 2-way measurement at the time. There was no equipment that was 2000 times more sensitive than some other piece of equipment. He had two clocks, and the least accurate of the two was the sundial. There was a telescope involved, with which the distant clock could be observed. There was no more equipment than that.Quote from: HalcSuppose light moved at thrice the speed in one direction as the other. Wouldn't Roemer see triple the time if he did the experiment in one direction as the other?Unlikely given that the sensitivity of such a one-wway measurement is "2000 times" more sensitive than that of a two-way measurement, and I don't think his equipment was up to it. I'm not sure modern equipment is up to it yet.
The other paper I quoted - which supports your position - also makes reference to other issues that need to be accounted for like measurements taken over a longer period of time, seasonal efects, etc.That was a lot of the source of the 25% error. The two measurement were taken 5-6 months apart, and the sundial held its time better over those months than did any timepiece of the day. His measurement was off by about 5 minutes. Not bad for a sundial.
I just know that the 75%-accurate measurement of the speed of light made in the 1600s isn't an empirical verification of Einstein's interpretation of relativity.When did I ever claim that anything was empirical evidence of some interpretation? My claim is that light speed can be measured using a one-way method. That is an empirical claim, not a claim about any interpretation.
I chose to address it in a different manner by referencing peer** reiewed literature from this aeon. I even referenced literature that attempts to make your case, so as not to be biased.You're referencing literature that is discussing a different thing. Roemer is apples. Your literature is oranges. I said that repeatedly but you know better apparently.
If you wish to adopt the position that Rřmer's measurement is an empirical verification of Einstein's theoryRoemer was over 2 centuries before Einstein. I never suggested his work as verification or falsification of any modern theory or interpretation.
or if you want to adopt the position that the one-way speed of light has been measured in such a way as to conclusively distinguish between the competing interpretations of the evidencePlease tell me where I suggested any such thing.
She lives in the SR world, be it valid description of our universe or not.
Everybody has assumed the premises of SR and nothing else. Sure, somebody else making different assumptions might assume that her clocks are not in sync
I bet a non isotropic SoL interpretation could be driven into self contradiction.
You had to violate the premises of SR to do it, rendering the example irrelevant to SR definitions. Alice is assuming those premises, not the conclusion that she demonstrates.You keep harping back to the idea that Alice is an SR girl, in an SR wo-orld....wrapped in plastic, life's fantastic (you're better off if you don't get the reference!). You keep saying that she and "everybody" has assumed the premises of SR. The problem with that is, NO THEY HAVEN'T!
Here's the problem. You're stuck arguing against the same strawman.Strong words from the guy that regularly has Alice and Bob making claims that they don't.
I own a copy of that song. I get it the reference.Quote from: HalcShe lives in the SR world, be it valid description of our universe or not.You keep harping back to the idea that Alice is an SR girl, in an SR wo-orld....wrapped in plastic, life's fantastic (you're better off if you don't get the reference!).
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Everybody has assumed the premises of SR and nothing else. Sure, somebody else making different assumptions might assume that her clocks are not in sync
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You had to violate the premises of SR to do it, rendering the example irrelevant to SR definitions. Alice is assuming those premises, not the conclusion that she demonstrates.
You keep saying that she and "everybody" has assumed the premises of SR. The problem with that is, NO THEY HAVEN'T!My quotes you selected just above contradict your assertion. I said somebody else is quite capable of making different assumptions, thus drawing different conclusions. All my conclusions are contingent on the premises of SR. I am not asserting that those premises must be true.
I will repeat again:Then stop claiming that Alice and Bob make claims contradictory to each other, because you continue to do that (a strawman fallacy). They don't even make claims that contradict a (mainstream) absolute interpretation. Your own posts are stronger evidence than a statement made in caps.
I AM NOT ATTEMPTING TO DEMONSTRATE AN INCONSISTENCY WITHIN SR!!*
Given the similarities to the "usual" arguments (of "my peers")I mention the usual arguments because all your ideas seem to come from such sites, and none from yourself. You've given me almost no evidence that you're capable of your own thought. The one-way measurement of the speed of light thing is something I've harped on because it showed that fact to me clearly. You run from it because despite it being a really simple case that doesn't threaten any alternate interpretation, you lack the ability to express the scenario in the interpretation of your choice. You cannot find discussion about the scenario on the denial sites from which your arguments are provided.
given that SR has now become pretty much intuitive for you, your intuitive response is to deploy the same arguments in the assumption that they address the issue. In this case, however, they don't.This statement seems to contradict the thing you did in all caps up there. If you mean the thing in caps, stop implying that SR does not address certain issues.
The fact is, neither Alice nor Bob know if they live in an SR worldI didn't say they did. I said they assumed it. Everybody is entitled to their interpretation, and Alice/Bob chose that one. Charlie and Dave can be the absolutists in the same scenario if you like, and you're free to express their conclusions as well. Best off if you are explicit about their premises. I gave my absolutist premises, but I'm not sure if they're the official ones.
What I am doing is playing the competing theories off against each other, holding them up against each other and seeing what we can deduce.What sort of things do you expect to deduce if there are no empirical differences between them? All you can deduce is that the interpretations are valid, and I'm not contesting that.
Now, given that there are key elements between the interpretations which are mutually exclusive,Not disagreeing, but I actually find very little of that. So name a couple.
but based on the same empirical evidence, it tells us that:I question this one. If you add a 4th premise of a preferred moment, which would be ontologically incompatible with a 4th premise asserting the lack of one, but AFAIK, neither interpretation necessitates the preferred moment premise. A lot of the 'denial' sites have members that make exactly that assertion, so it isn't uncommon.
a) the interpretations cannot both be true
b) therefore, the empirical evidence cannot verify both interpretationsHow does that follow from (a) even if I accept (a)? Theories don't get verified by evidence. They get verified by not being falsified by evidence. So you should instead say that b) Empirical evidence cannot falsify either interpretation. This is true by definition. If there was an empirical difference between the two, they would be alternate interpretations. They'd be alternate theories.
c) therefore, the same empirical evidence cannot verify the mutually contradictory conclusionsNonsense. Each interpretation must assume its own premises, but not the validity of them. The validity must be put to the test. If it fails the test, then the interpretation cannot correspond to reality.
d) therefore, one (or both) of the interpretations must be assuming the validity of their conclusions.
e) One of the mutually exclusive elements pertains to the synchrony of Alice's clocks.I have claimed otherwise.
f) therefore, one (or both) of the interpretations must be assuming the conclusion as it pertains to clock synchronisation.Neither interpretation assumes its conclusions. They all assume only their premises. You continue to make this mistake over and over.
*forgive the all caps sentence. I read in Daniel Kahneman's Thinking fast and slow that statements tend to be remembered better when they are in clear fontI remember best your statement a bit later on that contradicts the all caps sentence.
This is the problem. You're saying that Alice and Bob assume the premises of SR. From that starting point you are defending the self-consistency of SR. With regard to the absolutists, we don't need to change to Charlie and Dave, we can stick with Alice and Bob and say that they start from absolutist premises, and from there demonstrate the self-consistency of such an interpretation.Here's the problem. You're stuck arguing against the same strawman.Strong words from the guy that regularly has Alice and Bob making claims that they don't.
My quotes you selected just above contradict your assertion. I said somebody else is quite capable of making different assumptions, thus drawing different conclusions. All my conclusions are contingent on the premises of SR. I am not asserting that those premises must be true.
Your accusation of strawman fallacy fall flat. At no point do I make a claim about some interpretation or fact that is inconsistent with that interpretation or fact. You on the other hand do this regularly when you have Alice making claims that do not follow from the SR premises.
I didn't say they did. I said they assumed it. Everybody is entitled to their interpretation, and Alice/Bob chose that one. Charlie and Dave can be the absolutists in the same scenario if you like, and you're free to express their conclusions as well. Best off if you are explicit about their premises. I gave my absolutist premises, but I'm not sure if they're the official ones.
I am rubber and you are glue. Get that reference?I'd heard it before but had forgotten what it meant. Turns out it shares the same frame dependent symmetry of SR :P
I mention the usual arguments because all your ideas seem to come from such sites, and none from yourself. You've given me almost no evidence that you're capable of your own thought. The one-way measurement of the speed of light thing is something I've harped on because it showed that fact to me clearly. You run from it because despite it being a really simple case that doesn't threaten any alternate interpretation, you lack the ability to express the scenario in the interpretation of your choice. You cannot find discussion about the scenario on the denial sites from which your arguments are provided.I get that you think that I'm simply parrotting ideas that I've heard elsewhere, but I'm only familiar wiith one such site you mention, which is now closed down (the forum section anyway). If you like, I can link you to the sites where I have been discussing similar topics on and off for almost a decade, and you can see that I have chosen to discuss them with "your peers" because:
This statement seems to contradict the thing you did in all caps up there. If you mean the thing in caps, stop implying that SR does not address certain issues.You're argument that SR is self-consistent doesn't address the issue being raised because the issue being raised isn't SRs self-consistency.
Not disagreeing, but I actually find very little of that. So name a couple.Oh, I don't know, the idea that simultaneity is reltive maybe. The interpretations of length contraction and time dilation are also mutually exclusive.
I question this one. If you add a 4th premise of a preferred moment, which would be ontologically incompatible with a 4th premise asserting the lack of one, but AFAIK, neither interpretation necessitates the preferred moment premise. A lot of the 'denial' sites have members that make exactly that assertion, so it isn't uncommon.Simultaneity cannot be both relative and absolute.
To parrotphrase Daniel Kahneman in Thinking, fast and slow a statement that can explain two contradictory outcomes explains nothing at all; evidence that verifies (by way of not falsifying) two contradictory propositions verfies neither.Quoteb) therefore, the empirical evidence cannot verify both interpretationsHow does that follow from (a) even if I accept (a)? Theories don't get verified by evidence. They get verified by not being falsified by evidence. So you should instead say that b) Empirical evidence cannot falsify either interpretation. This is true by definition. If there was an empirical difference between the two, they would be alternate interpretations. They'd be alternate theories.
When two contradictory propositions pass the same test, then the test has verified neither bcos it has not falsified one over the other.Quotec) therefore, the same empirical evidence cannot verify the mutually contradictory conclusionsNonsense. Each interpretation must assume its own premises, but not the validity of them. The validity must be put to the test. If it fails the test, then the interpretation cannot correspond to reality.
d) therefore, one (or both) of the interpretations must be assuming the validity of their conclusions.
Neither interpretation assumes its conclusions. They all assume only their premises. You continue to make this mistake over and over.Maybe I haven't been totally clear on this point, although I have repeatedly tried to be explicit about it.
Einstein,as I noted earlier, was happy to treat that proposition as true by deﬁnition. But the principle of the constancy of the one-way speed of light is not a very plausible candidate for an analytic truth,and it is not surprising that many later physicists and philosophers have sought for ways to put that principle to the test of experiment. As noted earlier, however, no one as yet appears to have described an experiment which could be used to determine the one-way speed of light,and which is such that different results would be compatible with the part of the Special Theory of Relativity that is independent of the one-way velocity principle. So one can say,at the very least, that standard formulations of the Special Theory of Relativity involve an assumption for which,more than ninety years after Einstein's formulation of the theory,there is absolutely no experimental support. The fact that the modiﬁed theory* does not entail the One-Way Light Principle would seem to be a reason,therefore, for preferring it to standard formulations of the Special Theory of Relativity—though not,of course, to formulations of the ∈-Lorentz variety.Bold is mine. Now, I know that you're just itching to isolate the emboldened part and tell me how you don't disagree with this and that it is the premise upon which the theory is based and the conclusions are derived from this, but we can extrapolate from there to show the further tacit, empirical assumptions that the interpretation entails.
This is the problem. You're saying that Alice and Bob assume the premises of SR. From that starting point you are defending the self-consistency of SR.My defense of SR rests on its lack of being falsified. What Alice and Bob are doing is irrelevant to that unless what they actually conclude (not your strawman conclusions) is found to be in contradiction with the premises of SR.
With regard to the absolutists, we don't need to change to Charlie and Dave, we can stick with Alice and Bob and say that they start from absolutist premisesShall we do that? It might be instructive. Alice is in the stationary system, but it hasn't been specified if she knows that. If she doesn't know, then her clocks are synced but she has no no way to determine that. Bob once again agrees with everything and makes no contradictory conclusions.
and from there demonstrate the self-consistency of such an interpretation.What's the point? I never said it wasn't. Einstein's sync convention still works even. It doesn't with your non-isotropic interpretation, but that's a third (unverified) interpretation.
As I said, Alice and Bob do not know which type of world they live in, and so they assume neither.Fine. Alice still shows that her clocks are synced in her frame, even if that statement is not one of being actually synced in an absolute interpretation. She never claimed the clocks were actually synced. OK, she did assume isotropy to make her claim. If she can't assume that, there's really nothing that can meaningfully be known about the relative state of a pair of clocks, so there's no point in doing a procedure involving them.
They simply carry out the experiments and then employ an Edward de Bono-like method of analysis of the empirical observations. They see that there are a number o different possible interpretations of the empirical results and so they carry out a cross-comparison to see if they can make any further deductions.And they can't get further, can they?
They see that, according to one interpretation their clocks are syncedIn no known interpretation do they see that. Not even in your funny one.
while according to another [interpretation] their clocks are not synced.That also has not been determined. In any interpretation, they don't know if the pair of clocks is synced. If the results were different, then not-in-sync could be known in some interpretations, but not the results you describe in the experiments they ran.
The same empirical evidence fits both interpretations so, the empirical evidence doesn't falsify either - but both cannot be true bcos they are mutually exclusive.I don't know is mutually exclusive with I don't know? I don't think so. I maintain that the isotropic interpretations might both be true.
b) I find the best way to test your ideas is against the strongest possiblle oppositionYou don't seem to have expressed any ideas. The whole thread has been what I take to be false statements being made about the relative interpretation, such as it assuming its conclusions. All such statements have been refuted.
You might find it hard to believe that people can independently arrive at the same conclusions about relativity, but if you bear in mind that, for the vast majority of people, Special Relativity is counter-intuitive, then you would realise that everyone starts from a position where SR is not accepted.Most people also don't start out from a stance that a view that they don't understand is wrong. They just don't worry about it. This site is for people that want to go a little further than that. Laypeople don't come here. Let em believe in Santa and all that.
And that is the problem. You are deploying the usual arguments because you are arguing against a strawman, as you have repeatedly demonstrated by presupposing that I am attempting to demonstrate an inconsistency within SR.I am pointing out the statements that I feel are doing just that. You making those statements makes my claims actual, not strawman. Similarly, the circularity claim you repeat, when SR is not circular. It does not assume its conclusions nor does it conclude any of its premises. Either of those would be an example of circularity, yes, but it doesn't do either of them. Your argument commits the strawman fallacy when you assert that RoS is assumed for instance. It isn't. Read the paper. It is derived. It follows from the premises.
With regard to the Romer point. I genuinely don't know what your intention is with that point.It's a really simple case that came up due to the usage of a different sync convention than the one Einstein uses. But your reaction to it made it into a little test to see if you can think through a simple scenario on your own. So far I've not seen you do it.
Not bcos it isn't in the manual for how to respond to the arguments of Einsteinian Relativists that "my peers" have clearly given me - the manual is part of the starter pack when you join the mailing list (the t-shirt and hat have to be paid for).You joke, but its real. There's quite an industry set up to separate this crowd from their money, same as it done for any fanatic group. The religions don't have a monopoly on doing that. OK, they do if you consider it a religion, which it probably is since the sites are often religion based. Apparently Einstein and God have become mutually exclusive, despite my school teaching the exact opposite.
I've got an idea. Why don't we jump on over to Physics Forums and you can start a thread there with the point you are trying to make and we can see what "your peers" have to say about it.What would I say? They did this thing, and I agree that they did it. How is that possible?
Maybe they will put it in such a way that its relevancy to this discussion becomes clear.What is relevant to this thread? You're certainly not going about pushing your new interpretation. Haven't heard a word of it. Just pages of asserting that the one interpretation is not the only valid one, and nobody has disagreed with that. Why the continued discussion if nobody has disagreed with this 2nd point you're supposedly trying to make?
Just a different definition, an abstract, not physical difference. They're not mutually exclusive. Points A being closer to one arbitrarily chosen line than point B, but B being the same distance as A to another such line, does contradict a statement that point B is in fact the closer to some actual real line. That's what I mean by saying the two statements are not mutually exclusive.Quote from: HalcNot disagreeing [that there are key elements between the interpretations which are mutually exclusive], but I actually find very little of that. So name a couple.Oh, I don't know, the idea that simultaneity is reltive maybe.
The interpretations of length contraction and time dilation are also mutually exclusive.That's an empirical claim. So the Hafele–Keating experiment is predicted to have different results in a different interpretation. Sure you want to go with that?
Simultaneity cannot be both relative and absolute.Of course they can. I gave a nice example just above with A,B and the lines. You're asserting that if there is a physical line that is closer to B, then there cannot be a 2nd abstract line parallel to one connecting both points. That is pretty obviously incorrect. If you think the example is inappropriate, then you don't understand relativity, because that's the exactly what Alice is doing: Selecting a line so A and B are equidistant from it. The points have an absolute relationship with the real line (which cannot be oriented a different way), and a relative relationship with the chosen one.
To parrotphrase Daniel Kahneman in Thinking, fast and slow a statement that can explain two contradictory outcomes explains nothing at all; evidence that verifies (by way of not falsifying) two contradictory propositions verfies neither.This is a rule for theories, yes. No so for interpretations. This is a lot of the reason why physics courses in college don't dwell on interpretations. Take a QM class if you don't believe this. They might touch on the interpretations, but debating them explains nothing at all. The class focuses on empirical facts.
When two contradictory propositions pass the same test, then the test has verified neither bcos it has not falsified one over the other.Again, verification consists of inability to falsify. Passing all tests is part of that. If two both pass the test, then neither is falsified by that test, but might be falsified by some other test. Falsification isn't something that is done one over the other. Both interpretations might get falsified by a single test.
The assumptions being made are empirical assumptions.Not the assumptions of the interpretations. Only the theory proper makes only empirical assumptions, which are thus not really assumptions at all since they are empirically tested.
They are assumptions about the configuration of the physical system for which there is no empirical evidence.You seem to be talking about the interpretations now. Yes, the interpretations make some physical assumptions like actual constant light speed for instance, not just empirically constant measurements. If you consider that to be a configuration, then you can call it that. If you say that any interpretation makes any mention of a specific physical system, I deny that. No such premise is made.
A theory which includes an assumption about the one-way speed of lightI can't think of an interpretation that doesn't, but I agree that it is an assumption. I am unconvinced that an interpretation with light moving at not-c would be valid. I don't know of one that has been validated.
carries with it an implicit (or tacit) statement about the configuration of a physical system i.e. a prediction; it is a prediction which cannot be verified experimentallly and so it represents an empirical assumption i.e. an assumption about the configuration of the physical system.Nonsense. An empirical assumption is about what can be tested, and that assumption cannot be tested. Any assumed configuration of the physical system is a metaphysical assumption, not an empirical one. Learn the meaning of the terms.
Contrast this with an interpretation which doesn't include that assumption but is based rather on the empirically determined round-trip speed of light. This interpretation doesn't imply, tacitly or otherwise, the same statement about the configuration of the physical system i.e. it doesn't make the same untestable prediction. It therefore makes fewer assummptions about the physical system and doesn't assume that part of its conclusion.No metaphysical assumption is testable, so none of them are predictions at all. Just assertions. An interpretation that doesn't posit constant light speed indeed doesn't make the same metaphysical statements. It makes damn few as a matter of fact. The theory proper is like that. It makes damn few such assumptions about the physical system.
allow me to quote from Michael Tooley's Time, Tense, and Causation.My conclusion is bias (see my bold). If both formulations of the SToR posit this One-Way Light Principle, why does the inability to measure it have any weight in the choice of one formulation (interpretation) over the other?
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I'll allow you to draw your own conclusions.QuoteThe fact that the modiﬁed theory* does not entail the One-Way Light Principle would seem to be a reason,therefore, for preferring it to standard formulations of the Special Theory of Relativity—though not,of course, to formulations of the ∈-Lorentz variety."
Bold is mine. Now, I know that you're just itching to isolate the emboldened part and tell me how you don't disagree with this and that it is the premise upon which the theory is based and the conclusions are derived from this, but we can extrapolate from there to show the further tacit, empirical assumptions that the interpretation entails.I agreed with (and didn't bother to keep) the part you bolded. I agreed with it all. The part I bolded was to illustrate naked bias. I've said what I thought were the premises of the typical absolute interpretation, and it wasn't that. If you don't assume fixed light speed, that's fine. Very few of the usual definitions apply then, so you'll have to come up with your own new ones.
The clock synchronisation convention establishing by definition that the time for a light signal from A to B is equal to that of B to A can be restated as, the simultaneity of clock synchronisation events is established by definition. I know, I know, Einstein doesn't say it like this, but that's the beauty of logic, we can deduce it. In assuming that the time from A to B is the same from B to A so the simultaneity of the clock synchronisation events are assumed along with it.I cannot really comment on something not actually said except to repeat that the absolute interpretation uses the exact same convention/definition as does Einstein. This is one of those points that don't differ between interpretations. The variable-speed interpretation does not use this convention.
So, given that there is "absolutely no experimental support" for the assumption that the time from A to B equals the time from B to A, there is, by definition, "absolutely no experimental support" that the clocks are synchronised.By Einstein's definition, there is, but that definition makes that assumption. So again, I agree that the convention doesn't work if that assumption is not made.
If there is absolutely no experimental support then it can only be an empirical assumption.There is no such thing as an empirical assumption. There are empirical facts. If it can't be measured, then it isn't empirical.
Similarly, the circularity claim you repeat, when SR is not circular. It does not assume its conclusions nor does it conclude any of its premises. Either of those would be an example of circularity, yes, but it doesn't do either of them. Your argument commits the strawman fallacy when you assert that RoS is assumed for instance. It isn't. Read the paper. It is derived. It follows from the premises.It is a simple matter of fact - call it a brute fact - that if you make a conclusion about something which you have not empirically observed, then you are assuming that conclusion. Put any adjective you like in front of it, to qualify it in any way - "...a rose by any other name..." - it doesn't change the fact that, if you conclude it but you haven't observed it, then you are assuming it.
Fine. Alice still shows that her clocks are synced in her frame, even if that statement is not one of being actually synced in an absolute interpretation. She never claimed the clocks were actually synced. OK, she did assume isotropy to make her claim. If she can't assume that, there's really nothing that can meaningfully be known about the relative state of a pair of clocks, so there's no point in doing a procedure involving them.She can assume isotropy all she wants but assuming isotropy doesn't show her that her clocks are synced in her frame, it only means that she assumes they are synced in her frame. If she doesn't assume isotropy then she won't make claim that the clocks are synced, in her frame. That's because assuming that the time from A to B1 equals that from A too B2 implicitly assumes the simultaneity of clock synchronisation events, in the given frame.
And they can't get further, can they?They can. Alice can see that assuming isotropy leads her to assume that her clocks are synced in her frame. This, shows her that she is assuming the first part of the conclusion that is RoS.
In no known interpretation do they see that. Not even in your funny one.When you clarify what you mean by "stationary system" above, we can go through the differences in the interpretations. They actualy do make slightly different predictions, but predictions which cannot be tested. We can see how both (or all) intepretations actually necessitate a privileged reference frame - but not in the sense of an absolute reference frame, which can be discarded without affecting the predictions or the mathematics.
That also has not been determined. In any interpretation, they don't know if the pair of clocks is synced. If the results were different, then not-in-sync could be known in some interpretations, but not the results you describe in the experiments they ran.Again, you freudianly prove my point. If they don't know that the pair of clocks are syned in any interpretaion (inluding SR) then they must be assuming that the clocks are syned - in the given frame. But I suspect you'll be in a hurry to change that statement too.
If you find a single animal hair on the sofa and the evidence apparently fits the interpretation that it was left by dog and the interpretation that it was left by a cat (imagine you can't test it for whatever reason). The fact that you don't know which is true doesn't make it likely or possible that both are true. The two interpretations are mutually exclusive. So no, it isn't a case of "I don't know is mutually exclusive with I don't know", it's that "the hair was left by a dog" and "the hair was left by a cat" are mutully exclusive.QuoteThe same empirical evidence fits both interpretations so, the empirical evidence doesn't falsify either - but both cannot be true bcos they are mutually exclusive.I don't know is mutually exclusive with I don't know? I don't think so. I maintain that the isotropic interpretations might both be true.
Oh, I don't know, the idea that simultaneity is reltive maybe.Just a different definition, an abstract, not physical difference. They're not mutually exclusive. Points A being closer to one arbitrarily chosen line than point B, but B being the same distance as A to another such line, does contradict a statement that point B is in fact the closer to some actual real line. That's what I mean by saying the two statements are not mutually exclusive.
That's an empirical claim. So the Hafele–Keating experiment is predicted to have different results in a different interpretation. Sure you want to go with that?Nope, but a sneak preview of a later argument (if we get that far) is that the Haefele-Keating experiment, along with many other empirical tests of relativity (and deductions from the thought experiments) provide justification for a privileged reference frame interpretation - not one where the absolute rest frame is the privileged frame. I believe that is the line of argument "my peers" usually take, but it's not the one I take bcos I'm saying we can do away with the absolute reference frame.
This is a rule for theories, yes. No so for interpretations. This is a lot of the reason why physics courses in college don't dwell on interpretations. Take a QM class if you don't believe this. They might touch on the interpretations, but debating them explains nothing at all. The class focuses on empirical facts.I can appreciate the "shut-up and calculate" approach, but inspite of this, interpretations of physical theories abound. As humans I think it's innate within us to seek such interpretations. I also think that such interpretations can often inform theoretical physics. As such, these interpretations represent our attempts to build intuitive models based on the data and evidence which can help us to look at problems in different ways, and possibly make intuitive connections that the mathematics might not enable us to do. I would see the math as the 99% perspiration and (occasionally) the intuitive interpretation might be able to provide 1% inspiration.
Again, verification consists of inability to falsify. Passing all tests is part of that. If two both pass the test, then neither is falsified by that test, but might be falsified by some other test. Falsification isn't something that is done one over the other. Both interpretations might get falsified by a single test.I just meant that if one theory passed while the other failed, the theory that passed woul be "verified" over the other.
No interpretatoin/theory is ever fully verified since there always might be a new test someday that falsifies it. The standard relative and absolute interpretations have both yet to be falsified, but SR does have an asterisk that it is only for a special case that only occurs locally in the universe. I found that it also works at the largest scales (where space once again becomes flat), but not on the scales in between.
You seem to be talking about the interpretations now. Yes, the interpretations make some physical assumptions like actual constant light speed for instance, not just empirically constant measurements. If you consider that to be a configuration, then you can call it that. If you say that any interpretation makes any mention of a specific physical system, I deny that. No such premise is made.As we discussed, we can derive a statement about the configuration of the physical system that Alice is in, which says that the reading d/c (on the clock at the midpoint) co-incides with the clock synchronisation events at B1 and B2.
Nonsense. An empirical assumption is about what can be tested, and that assumption cannot be tested. Any assumed configuration of the physical system is a metaphysical assumption, not an empirical one. Learn the meaning of the terms.Apply any adjective that you like to it, "...a rose by any other name...". The conclusion of Relativity of Simultnaeity rests entirely on this empirical/metaphysical/tacit/unjustified assumption.
You don't seem to have expressed any ideas. The whole thread has been what I take to be false statements being made about the relative interpretation, such as it assuming its conclusions. All such statements have been refuted.I'm not surprised you think I haven't expressed, nor am I able to express, any ideas of my own, because for the past 4 pages you've been shadowboxing against the strawman that you've mistakenly assumed is my position. It's hard for you to see the ideas being put forward when you've got such a big cognitive blind spot. Indeed, we haven't had a chance to progress precisely bcos you've been arguing against a strawman and we still need to get you up to speed with the first basic point.
My examples have not been refuted. Not saying I'm right about them. They can be refuted. You just don't seem up to the task on your own.
It's a really simple case that came up due to the usage of a different sync convention than the one Einstein uses. But your reaction to it made it into a little test to see if you can think through a simple scenario on your own. So far I've not seen you do it.
What would I say? They did this thing, and I agree that they did it. How is that possible?Pretty lame thread.You could state how you believe it is pertinent to modern day attempts to measure the isotropic one-way speed of light, as it pertains to SR and how the peer reviewed literature that addresses the question of that issue does not apply to Romer.
What is relevant to this thread? You're certainly not going about pushing your new interpretation. Haven't heard a word of it. Just pages of asserting that the one interpretation is not the only valid one, and nobody has disagreed with that. Why the continued discussion if nobody has disagreed with this 2nd point you're supposedly trying to make?I posted the paper in the OP, this thread has been spent addressing the objections that you have raised. We haven't gotten past the first hurdle yet. The focus of the paper was the problem of time, reinterpreting the theory of relativity was just one part. In the discussions I've had, understandably, the main contention has been the points I've made about Einsteinian relativity. Discussions like this have actually lead me to further develop my own thinking on that and flesh out ideas that I didn't flesh out in the paper (I still don't feel comfortable using the word "paper" bcos I know it's not up to any sort of rigorous standard).
I'm in it because you're having Alice making strawman conclusions like "the relative interpretation says my clocks are in sync".
My defense of SR rests on its lack of being falsified. What Alice and Bob are doing is irrelevant to that unless what they actually conclude (not your strawman conclusions) is found to be in contradiction with the premises of SR.Unfortuntely, there was nothing in Kahneman's book on how, after repeatedly pointing out the error that someone is making, how to make them recognise that error and to stop making it.
I am pointing out the statements that I feel are doing just that. You making those statements makes my claims actual, not strawman.You have repeatedly demonstrated that you are arguing against a strawman by repeated references to the issue of contradiction of the premises of SR. So, it is not surprising that you genuinely believe that your statements are addressing that issue, and indeed they do. The problem is, however, that isn't the actual issue; that isn't the point of contention.
You joke, but its real. There's quite an industry set up to separate this crowd from their money, same as it done for any fanatic group. The religions don't have a monopoly on doing that. OK, they do if you consider it a religion, which it probably is since the sites are often religion based. Apparently Einstein and God have become mutually exclusive, despite my school teaching the exact opposite.I've been peripheraly aware of such sites, but I've never really frequented them (despite how it might seem) - luckily, it would seem. I have gotten a vague notion of what seemed like a somewhat cultish mentality among some of "my peers", but I find my time and effort is better served in discussions like this where my theses are rigorously challenged.
Shall we do that? It might be instructive. Alice is in the stationary system, but it hasn't been specified if she knows that. If she doesn't know, then her clocks are synced but she has no no way to determine that. Bob once again agrees with everything and makes no contradictory conclusions.By "stationary system" here do you mean the absolute rest frame? As in, are we starting with Alice in the absolute rest frame with Bob moving relatively - even though Alice cannot determine that she is in the absolute rest frame?
What's the point? I never said it wasn't. Einstein's sync convention still works even. It doesn't with your non-isotropic interpretation, but that's a third (unverified) interpretation.Just to be clear, the interpretation Im advocating is one that employs a round-trip speed of light principle, so it will be empirically equivalent to the other interpretations.
I can't think of an interpretation that doesn't, but I agree that it is an assumption. I am unconvinced that an interpretation with light moving at not-c would be valid. I don't know of one that has been validated.That's fair enough. The mathematics for all the various interpretations appears to be the same. It is the Einsteinian interpretation that I am challenging - and the absolutist one for that matter, as I am saying the absolute reference frame can be discarded.
That said, the theory (not any interpretation) does not make this assumption. The theory defines the empirical tests, and those don't rely on any assumption of one-way SoL. If they did, there wouldn't be all these sites saying it cannot be measured, would there?
No metaphysical assumption is testable, so none of them are predictions at all. Just assertions. An interpretation that doesn't posit constant light speed indeed doesn't make the same metaphysical statements. It makes damn few as a matter of fact. The theory proper is like that. It makes damn few such assumptions about the physical system.You can have round-trip light speed principle which is empirically justified and leaves you with an empirically equivalent interpretation. It doesn't lead to conclusions like RoS though and real physical reciprocal length contractions or reciprocal time dilation.
In case you don't see it, I'm agreeing with you. An interpretation that goes light on the assumptions is open to anything, but it also concludes little more than does the theory proper.
You may have misread the part I quoted, it says that the modified theory does not entail the One-Way Light Principle. The theory that pooley proposes, and which I would borrow the phrasing from, employs a round-trip light principle.My conclusion is bias (see my bold). If both formulations of the SToR posit this One-Way Light Principle, why does the inability to measure it have any weight in the choice of one formulation (interpretation) over the other?QuoteThe fact that the modiﬁed theory* does not entail the One-Way Light Principle would seem to be a reason,therefore, for preferring it to standard formulations of the Special Theory of Relativity—though not,of course, to formulations of the ∈-Lorentz variety."
I agreed with (and didn't bother to keep) the part you bolded. I agreed with it all. The part I bolded was to illustrate naked bias. I've said what I thought were the premises of the typical absolute interpretation, and it wasn't that. If you don't assume fixed light speed, that's fine. Very few of the usual definitions apply then, so you'll have to come up with your own new ones.As you have quite righly intimated, I don't have the requisite background to develop such a theory on my own, which is why I am stuck with debating the philosophical interpretations. In the course of our discussion I came across the work of Michael Tooley (literally a few day ago). In it, he lays out an absolute interpretation of relativity (seemingly based solely on an absoolute reference frame) that sounds - to the untrained mind - pretty convincing. Unfortunately, I can't fully evaluate it myself, just to say that if his claims hold up, it is a solid interpretation. He also addresses the issue of the undetectability of the absolute reference frame thusly:
This is,I believe, the most forceful objection that can be mounted against any theory that entails the existence of absolute rest. But there is a perfectly satisfactory answer,the gist of which is that, if it is true that the modiﬁed theory entails that there is,in nature, a conspiracy of silence with respect to the existence of absolute rest, this is so only because,and precisely because, the Special Theory of Relativity itself entails that there is,in nature, a conspiracy of silence with respect to a certain matter—namely,the one-way speed of light.
Suppose that an experiment is possible that would enable one to measure the one-way speed of light. If the outcome of that experiment were that the one-way speed of light was the same in all directions in all inertial frames,then the modiﬁed theory would be conclusively refuted,since,
as we have just seen, it entails that this will not be the case. If,on the other hand,it turned out that the oneway speed of light not only was not the same,but varied in accordance with the above relation, then it would be possible to determine the velocity of any inertial frame relative to absolute space. So,unless there is a conspiracy in nature that prevents any measurement of the one-way speed of light,the choice between the modiﬁed theory and standard formulations of the Special Theory of Relativity is experimentally decidable.
Suppose,however, that there is no experimental way of measuring the one-way speed of light. Then there will be no way of determining the velocity of any inertial frame relative to absolute space,and there will be the conspiracy of silence that Zahar contends is an objection to theories that postulate absolute space. But we have just seen that a conspiracy of silence with respect to absolute rest and motion can obtain only if,and precisely because, there is a conspiracy within nature with respect to the measurement of the one-way speed of light. So any conspiracy of silence within nature that one must countenance,on the modiﬁed theory,is either identical with, or derives from, a conspiracy of silence that one must countenance according to any version of the Special Theory of Relativity
It is a simple matter of fact - call it a brute fact - that if you make a conclusion about something which you have not empirically observed, then you are assuming that conclusion.If that were true, all mathematical proofs would be rendered circular since none of them are based on any empirical observation.
Take Alice on her trip to Loch Ness. Standing by the lake, she sees bubbles rising to the surface and she concludes that the Loch Ness Monster is in the lake. Alice is assuming her conclusion.That she would be.
these clever people - who are not my peersI've apparently struck a nerve. Must be on to something.
...
Thanks to these very clever people
we have a number of more intuitive and intelligible thought experiments which can help us draw conclusions about the competing and mutually exclusive interpretations.I can't think of any thought experiments that demonstrate a preference for one interpretation over the other. Perhaps they're not clever enough.
the process of synchronising 2 clocks, in the given frameAt given locations, not 'in a given frame'.
in this particular set-up, is done by establishing by definition that the time from A to B1 equals the time from A to B2 (together with the time for the return trips being the same).What definition is now being referenced? I agree that we set it up for the times to be the same, but I am unaware of a definition being utilized this time.
If we take the contention that the simultaneity of clock synchronisation events is derived and not assumedI didn't say that. I said RoS is derived from SR premises. The above statement is not a statement of RoS.
If we establish by definition that the time from A to B1 equals the time from A to B2 (and likewise for the return jounrey)Again, what definition?
then there are 2 things that we can "derive" from that:Actually, only number 2 is a physical statement. #1 involves only a statement concerning abstract coordinate time.
1) the clock synchronisation events are simultaneous, in the given frame i.e. they co-incide with the reading d/2 on the clock at the mid-point.
2) the light pulses will return to the mid-point simultaneously.
Here, we have derived two statements about the configuration of the physical system.
While the two statements have been derived from the same information, there is a key difference between them. That difference pertains to their empirical verifiability. As we know, statement #2 above can easily be tested and indeed it is. It represents a testable prediction of all of the various interpretations.Because that one is a physical statement, yes. The other is not.
As we both know, as you have stated on numerous occasions, #1 above simply cannot be tested.I can perform the in-sync test, but that test again only verifies an abstract coordinate concept. No physical (or even metaphysical) statement is made in #1, so there is nothing to verify.
While the fact that it can't be tested puts it into a different class than statement #2, this different classification doesn't explain away the fact that it represents an untestable prediction.It doesn't represent a prediction at all.
The fact that the conclusion, that simultaneity is relative.That conclusion is contingent on the premises, not concluded absent them. If premises, then RoS. No ∴RoS period. Your insistence on the latter is a strawman. I'm well aware of the validity of the interpretation that posits actual simultaneity, and that it is absolute. The relative interpretation makes no statement concerning actual simultaneity, only abstract coordinate simultaneity. The interpretation is very light on metaphysical additions (like preferred frames, locations, moments, aether, whatever) , which is why it is the mainstream interpretation. All those additions seem like Loch Ness monsters to me. Not asserting no monster, but it seems just silly to posit one or several.
OK, she did assume isotropy to make her claim.I take this back. Reading carefully, she doesn't. She utilizes a convention to make her claim. No isotropy is assumed. The clocks are defined to be in sync in that frame by that convention, and no assumptions need be made at all. This is why her (completely abstract) claim does not conflict with interpretations that make different assumptions. No assumption with which to conflict. That's the beauty of a theory that makes no metaphysical assumptions. None of the conclusions are metaphysical ones, and all your attempts at conflict are on the metaphysical level.
She can assume isotropy all she wants but assuming isotropy doesn't show her that her clocks are synced in her frame, it only means that she assumes they are synced in her frame.Read the paper. No assumption is needed at all. She's shown it. You're problem is that you keep assuming she's made a metaphysical claim, but she hasn't.
When you clarify what you mean by "stationary system" above, we can go through the differences in the interpretations.You seem to have edited out the 'above'. If I say 'the stationary system', the term only has meaning in an absolute interpretation, so I probably meant actually stationary.
They actualy do make slightly different predictions, but predictions which cannot be tested.You and I have a different definition of 'prediction' then. You apparently mean different metaphysical descriptions of the system. I don't call those predictions. The relative interpretation doesn't make many such statements, only empirical predictions and abstract relations with coordinate systems such as an abstract line being above a rock.
We can see how both (or all) intepretations actually necessitate a privileged reference frameAh: An assertion that the relative interpretation requires a metaphysical addition despite never using it. I can see no such thing. The interpretation makes no conclusions/statements concerning this privileged frame.
Again, you freudianly prove my point. If they don't know that the pair of clocks are syned in any interpretaion (inluding SR) then they must be assuming that the clocks are syned - in the given frame.This comment makes no logical sense. If I don't know whats in my left hand, then I must assume that I have a coin in my right. The one just doesn't follow from the other.
If you find a single animal hair on the sofa and the evidence apparently fits the interpretation that it was left by dog and the interpretation that it was left by a cat (imagine you can't test it for whatever reason).An animal hair is physical evidence. Alice hasn't got that and has thus made no metaphysical claim. A non-metaphysical claim does not conflict with a metaphysical claim. That claim is sort of like positing the dog, except without even finding the hair.
I'm not sure which interpretation your advocating there where absolute simultaneity and the relativity of simultaneity re not mutually exclusive.I'm comparing (not advocating) the SR theory with no additional metaphysical assumptions (not even fixed one-way light speed), with the absolute interpretation. Only the latter adds all these metaphysical assumptions. Since the former interpretation doesn't deny any of them, it isn't incompatible.
As you progress thru your history book (trust me, it gets even more exciting than Romer) you will see that Einstein's SR overturned Newton's absolute time and space and with it, the concept of relativity of simultaneity overturned absolute simultaneity.Since the absolute interpretation lives on, he did no such thing, history books notwithstanding.
You seem to be basing it on the idea that the mathematics for both theories is identical and so the mathematics is compatible with both.I've not been discussing Newton's theories. If you don't mean that one, then which two theories?
You might be advocating the less well known Schroedingers Cat interepretation of relativity, as outlined by Fie Lyne, which says that simultaneity is both relative and absolute and the wave function is only collapsed with the measurement of the isortropic one-way speed of light, as it pertains to Einstein's theory.That's a thing? Never heard of it. Sounds pretty hokey.
Nope, but a sneak preview of a later argument (if we get that far) is that the Haefele-Keating experiment, along with many other empirical tests of relativity (and deductions from the thought experiments) provide justification for a privileged reference frame interpretation - not one where the absolute rest frame is the privileged frame.Perhaps you can distinguish the two. I tend to use the two terms interchangably, which I would not wish to do if they mean different things.
I can appreciate the "shut-up and calculate" approach, but inspite of this, interpretations of physical theories abound.That they do. Most people even have preferences. Some go too far and claim theirs must be the correct one.
I just meant that if one theory passed while the other failed, the theory that passed woul be "verified" over the other.OK. I would have simply said that the other theory had been falsified. There's little more evidence that the 'verified' theory is any more correct other than a smaller list of alternate theories. But even if there are not, the reamining one is not necessarily proven. Sometimes all of them are falsified, in which case we know we need to keep looking for a better answer. Unified field theory comes to mind.
As we discussed, we can derive a statement about the configuration of the physical system that Alice is in, which says that the reading d/c (on the clock at the midpoint) co-incides with the clock synchronisation events at B1 and B2.That's not a physical statement about the state of her system. It is a pure abstract statement about it.
You see, you've mistaken my recognition of the fact, that your point about Romer is a meaningless irrelevancy in the context of this discussionDepends what you think my point was concerning it. There were two in fact, both relevant. Neither had anything to do with measurement of the one-way speed of light.
When the fact of the matter is, I have addressed it, in the context of the discussion pertaining to the isoptropic one-way speeed of light as it pertains to Einsteinian relativity. I have addressed it by presenting peer reviewed references that pertain to the isoptropic one-way speed of light as is relevant to Einsteinian relativity, which demonstrate that it hasn't yet been measured to a satsisfactory degreeWow, that statement makes it sound like it was measured at all, just not very accurately.
If however, you find it difficult to give up continual references to your [seeming] hero, feel free to state the point you are trying to make, clearly and coherently, and be explicit in how you believe it is relevant to the discussion of Einsteinian relativity, bcos I am saying that it isn't relevant.The first point was brought up when the subject first came up: An illustration of a different sync convention that the one Einstein (and Lorentz) uses.
You could state how you believe it is pertinent to modern day attempts to measure the isotropic one-way speed of lightI would be lying if I said that. It isn't pertinent at all. You said that, not me.
Which nobody has discussed. Colin2B (post 20) said something on the order of if it being your intention to discuss an idea or a paper (which I haven't seen), misrepresenting the mainstream theory might not be the best route to achieve this purpose. No attempt has been made to steer things onto that track. Your purpose appears to be the debate, and not the discussion of your idea.Quote from: HalcWhat is relevant to this thread?I posted the paper in the OP, this thread has been spent addressing the objections that you have raised.
Are you saying I'm making an error in the statement above? Or just an error in realization of your purposes here?Quote from: HalcMy defense of SR rests on its lack of being falsified. What Alice and Bob are doing is irrelevant to that unless what they actually conclude (not your strawman conclusions) is found to be in contradiction with the premises of SR.Unfortuntely, there was nothing in Kahneman's book on how, after repeatedly pointing out the error that someone is making, how to make them recognise that error and to stop making it.
I am not trying to demonstrate a contradiction in SR!!Fine. I believe you. But I'll still comment whenever I think the position is being misrepresented, for whatever purpose. If you're trying to argue that other interpretations are valid, nobody has disagreed with that. If you have a different interpretation than one of the usual ones, then I've yet to render an opinion of the validity of it on the surface.
===================This is the absolute interpretation, so there is one meaning to 'stationary system'. It means her position is not changing. Bob is moving. Not relatively. Moving period. That's how the absolute interpretation words things. Motion is property, not a relation under the interpretation.
Absolute Interpretation
===================Quote from: HalcShall we do that? It might be instructive. Alice is in the stationary system, but it hasn't been specified if she knows that. If she doesn't know, then her clocks are synced but she has no no way to determine that. Bob once again agrees with everything and makes no contradictory conclusions.By "stationary system" here do you mean the absolute rest frame? As in, are we starting with Alice in the absolute rest frame with Bob moving relatively - even though Alice cannot determine that she is in the absolute rest frame?
It's an important distinction.What distinction? There seems to be only one way to use those words. You had suggested before a possible difference between the absolute frame and the preferred one. I presume those to be the same, so feel free to clarify if they're not.
Just to be clear, the interpretation Im advocating is one that employs a round-trip speed of light principle, so it will be empirically equivalent to the other interpretations.That remains to be seen. I've not seen it.
That's fair enough. The mathematics for all the various interpretations appears to be the same.That's not true. Simpler in some ways, more complicated in others. Try to imagine implementing a speed limit sign on the side of the road using the absolute interpretation. Can be done, but it wouldn't be very helpful to the guy reading it. Such examples is why physics is far simpler with the relative interpretation.
It is the Einsteinian interpretation that I am challenging - and the absolutist one for that matter, as I am saying the absolute reference frame can be discarded.Could be interesting.
So, it's not that nature privileges a particular reference frame, its that we must privilege one particular reference frame as a matter of operational necessityThat's exactly what Alice has done when she selects her abstract coordinate system. How is it going to be different than the standard interpretation then?
for us, by default, that is the reference frame of the Earth (for obvious reasons).That frame isn't inertial. In fact it is an accelerating/rotating reference frame, with a funny set of properties all its own.
We also privilege the Earth reference frame by designating it our chosen reference frame for the definition of the units of measurement that we use in our experiments.Hate to be picky, but frames don't define units. They don't even define origins. OK, the rotating frame could define a unit of time period, even though we don't use it. We cut up time from a standard one rotation plus nearly 236 seconds. The meter? Somebody pulled that out of his arse. I don't think anything on Earth really suggests it.
You may have misread the part I quoted, it says that the modified theory does not entail the One-Way Light Principle. The theory that pooley proposes, and which I would borrow the phrasing from, employs a round-trip light principle.It wasn't clear what was meant by '∈-Lorentz variety'.
the Round-Trip Light Principle—where this is the principle, not that the round-trip speed of light is a constant relative to all inertial frames,but rather that the round-trip speed of light is a constant as measured within all inertial frames.Empirical measurements agree with that and much more. Why not take the full statement that all of EM is included in principle of relativity? That doesn't assume anything, and it includes your subset principle. Why go for the weak premise when there's a stronger empirical one?
He also addresses the issue of the undetectability of the absolute reference frameThe quote doesn't say much. It says you can't tell. Nothing in it was news to me. Sounds like "A conspiriacy to hide the invisible pink elephant is equivalent to a conspiracy to posit an invisible pink elephant, therefore there is as much reason to posit the invisible pink elephant as there is to not do so.
Poincare started with the absolute reference frame and had two inertial frames moving relative to that absolute frame, S and S'. Galilean transformations were used between the absolute reference frame and each of S and S', but the Lorentz transformation was used between S and S' themselves. In these reference frames Alice's clocks would not be synced, in her frame.In this interpretation, I don't know what it means to be synced in a frame. Synced is an absolute thing, not a frame thing, so those words have no meaning. I can't follow this.
If that were true, all mathematical proofs would be rendered circular since none of them are based on any empirical observation.
Alice has not made a claim of proof of anything. She has made a simple abstract statement that if she draws a line here, the rock is below it, and maybe above this other line drawn. The fact that nobody can empirically see her line doesn't alter her statement.
That she would be.The intepretation makes a claim about the configuration of the physical system. It claims that the reading d/c, on clock C0 is co-incident with the two clock synchronisation events at C1 and C2. It also makes a claim about the reading (2d/c) on C0 that corresponds to the return of light signals.
The claim in the example is not like that, and thus your Ness example is an inappropriate analogy. She's made no physical claim. Never does she conclude that any of her premises are true, or that any of the conclusions are true sans contingency on the premises.
In short, she never concludes that the clocks are in sync, which is arguably a physical claim (and arguably not).
I've apparently struck a nerve. Must be on to something.hahaha I think you may have misread the tone of that one (which wouldn't be completely out of character). I was emphasising the fact that those "very clever people" (your peers maybe?) derived a number of insights about the Einsteinian intepretation, which weren't expressly stated in the 1905 paper. I labored the point to try and avoid things like this:
What definition is now being referenced? I agree that we set it up for the times to be the same, but I am unaware of a definition being utilized this time.You seem to have difficulty extrapolating from the 1905 paper. As I mentioned, there was no mention of atomic clocks or airliners, or Alice and Bob, in the 1905 paper, but those "very clever people" (am I being too presumptuous to call them your peers?) were able to extrapolate from Einstein's paper so that we could have a clock synchronisation convention as opposed to just a verification procedure.
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Again, what definition?
I can't think of any thought experiments that demonstrate a preference for one interpretation over the other. Perhaps they're not clever enough.It's probably more a case that the the thought experiments were used, during the course of their education on the subject, to demonstrate the empirical consequences of SR; as opposed to being used to draw further deductions between interpretations that are generally considered to be historical footnotes in the development of SR.
Again, we can extrapolate the statement about the simutaneity of clock synchronisation events (in the given frame).QuoteIf we take the contention that the simultaneity of clock synchronisation events is derived and not assumedI didn't say that. I said RoS is derived from SR premises. The above statement is not a statement of RoS.
Actually, only number 2 is a physical statement. #1 involves only a statement concerning abstract coordinate time.OK, then we can conclude that RoS isn't an accurate representation of the physical world. Its an abstract mathematical proposition which is compatiblle which in no way contradicts absolute simultaneity.
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Because that one is a physical statement, yes. The other is not.
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I can perform the in-sync test, but that test again only verifies an abstract coordinate concept. No physical (or even metaphysical) statement is made in #1, so there is nothing to verify.There might be one small matter to verify.
It doesn't represent a prediction at all.Oh but it does! If I say to you that at the very moment you and I are standing in the same room, at that very moment there is a clock in the next room which reads d/c, that is a prediction. If the clock is then brought into our room but it no longer reads d/c - bcos of the time taken to bring it into the room - that doesn't make my first statement any less of a prediction, it just makes it an untestable one.
That conclusion is contingent on the premises, not concluded absent them. If premises, then RoS. No ∴RoS period. Your insistence on the latter is a strawman. I'm well aware of the validity of the interpretation that posits actual simultaneity, and that it is absolute. The relative interpretation makes no statement concerning actual simultaneity, only abstract coordinate simultaneity. The interpretation is very light on metaphysical additions (like preferred frames, locations, moments, aether, whatever) , which is why it is the mainstream interpretation. All those additions seem like Loch Ness monsters to me. Not asserting no monster, but it seems just silly to posit one or several.If you want to peddle the idea that the relativity of simultaneity is perfectly compatibile with and in no way whatsover contradicts absolute simultaneity, then go right ahead. We can progress onto the next part of the atemporal argument.
I take this back. Reading carefully, she doesn't. She utilizes a convention to make her claim. No isotropy is assumed. The clocks are defined to be in sync in that frame by that convention, and no assumptions need be made at all. This is why her (completely abstract) claim does not conflict with interpretations that make different assumptions. No assumption with which to conflict. That's the beauty of a theory that makes no metaphysical assumptions. None of the conclusions are metaphysical ones, and all your attempts at conflict are on the metaphysical level.I didn't predict your retraction, I derived it (from observtion).
Lloyd (1988: 2), a philosopher of evolutionary biology, stated that, ―Under a general hypothetico-deductive view of theories, a theory is understood as offering hypotheses from which, in combination with empirical assumptions, deductions can be made regarding empirical results.
Why look at the deflection of a particle’s trajectory in an electromagnetic field in order to measure its charge? – and doing so will demand a large number of auxiliary empirical assumptions.Cartwright, Nancy D. (2009) 'What is this thing called 'ecacy'?',
The model solves for the mass evolution based on what are thought to be the dominant input boundary conditions. Some empirical assumptions are made to predict the behavior of lower order physics.//proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1605299
By identifying the energy that must be absorbed through deformation of the vehicle’s roof using the FMVSS 216 five inches (127 mm) of roof crush strength limit as a constraint, it was possible to calculate theoretically using some broad empirical assumptions generated from rollover crash test data, Vehicle roof strength as it relates to contained occupant injury prevention during rollover crashesYoung, D. P., Grzebieta R.H
one word of caution is that the Doppler Dimming method strongly depends on empirical assumptions of the electron density and ion temperature, thus possibly leading to different results with different assumptions (Wilhelm et al. 2011).//iopscience.iop.org/article/10.1088/0004-637X/794/2/109/meta
You seem to have edited out the 'above'. If I say 'the stationary system', the term only has meaning in an absolute interpretation, so I probably meant actually stationary.Apologies, I didn't think I had missed anything. But yes, that is the point that I wanted to clarify, whether or not you were talking about absolute rest.
You and I have a different definition of 'prediction' then. You apparently mean different metaphysical descriptions of the system. I don't call those predictions. The relative interpretation doesn't make many such statements, only empirical predictions and abstract relations with coordinate systems such as an abstract line being above a rock.I mean statements about the physical configuration of the system. Just as Einstein talked about the hands on a watch physical watch being simultaneous with the arrival of a physical train, so am I talking about the reading on a physical clock being simultaneous with a physical photon making physical contact with another physical clock. But you seem to be of the opinion that this isn't a physical statement.
Ah: An assertion that the relative interpretation requires a metaphysical addition despite never using it. I can see no such thing. The interpretation makes no conclusions/statements concerning this privileged frame.I did distinguish between the two, it must just not have registered.
This is akin to asserting that a triangle cannot be discussed in a geometry class without assigning it to the actual coordinate system (as opposed to any other coordinate system, or no coordinate system).
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Perhaps you can distinguish the two. I tend to use the two terms interchangably, which I would not wish to do if they mean different things.
This comment makes no logical sense. If I don't know whats in my left hand, then I must assume that I have a coin in my right. The one just doesn't follow from the other.It makes no logical sense bcos you haven't understood it, as is clear by your misrepresentation of it here.
An animal hair is physical evidence. Alice hasn't got that and has thus made no metaphysical claim. A non-metaphysical claim does not conflict with a metaphysical claim. That claim is sort of like positing the dog, except without even finding the hair.Again, inadvertently making my point. Exactly, she doesn't have any physical evidence of the synchrony of the clocks. However, her lack of evidence doesn't mean that she "thus" hasn't made a physical (or metaphysical) claim it simply means that she has no evidence for her claim about the synchrony of the clocks.
I'm comparing (not advocating) the SR theory with no additional metaphysical assumptions (not even fixed one-way light speed), with the absolute interpretation. Only the latter adds all these metaphysical assumptions. Since the former interpretation doesn't deny any of them, it isn't incompatible.You mean you are comparing the Lorentz transformation and other mathematical artefacts with the absolute interpretation? Then you are arguing a new kind of strawman.
Etherless Lorentz-Poincare theory or the forumulation as outlined by Michael Tooley. You know absolute interpretations of relativity.QuoteYou seem to be basing it on the idea that the mathematics for both theories is identical and so the mathematics is compatible with both.I've not been discussing Newton's theories. If you don't mean that one, then which two theories?
That's a thing? Never heard of it. Sounds pretty hokey.hahaha of course it isn't......not yet ;)
As we discussed, we can derive a statement about the configuration of the physical system that Alice is in, which says that the reading d/c (on the clock at the midpoint) co-incides with the clock synchronisation events at B1 and B2.That's not a physical statement about the state of her system. It is a pure abstract statement about it.
I wasn't sure what point you were trying to make. My intuitive response was to present references to information which was pertinent to the question of the one-way speed of light, as it pertains to SR - because that was topic under consideration. I knew that the information I posted was relevant to the question of one-way light speed in the context of SR partly bcos "your peers" had linked me to similar such information in the past. I knew, therefore, that your point must have been a red-herring and so I gave it little to no consideration.You see, you've mistaken my recognition of the fact, that your point about Romer is a meaningless irrelevancy in the context of this discussionDepends what you think my point was concerning it. There were two in fact, both relevant. Neither had anything to do with measurement of the one-way speed of light.
I said precisely the opposite. I called you on your red-herring. Yet, you tried to persist with it. It's a level of intellectual dishonesty I haven't encountered before but at least when it came down to it, you have admitted its irrelevance to the topic of this discussion.QuoteYou could state how you believe it is pertinent to modern day attempts to measure the isotropic one-way speed of lightI would be lying if I said that. It isn't pertinent at all. You said that, not me.
Wow, that statement makes it sound like it was measured at all, just not very accurately.It's a separate philosophical discussion to determine in what sense one can say he actually measured the speed of light. He made measurements and got a value, did he actually measure the speed of light tho?
The first point was brought up when the subject first came up: An illustration of a different sync convention that the one Einstein (and Lorentz) uses.But not free of the same issues that all sync conventions apparently fall foul of.
The 2nd point was my suggestion that you consider the experiment being done in a system where light speed is 3x in one direction as it is in the opposite, and what result would be measured if the experiment was done in both directions in attempt to test this. I'm not sure about that one myself. Barring that funny interpretation, perhaps just describe the experiment in standard absolute terms where light speed is constant in all directions, but the test system is moving at half light speed. I want to see if you have any idea what you're talking about.You're basically asking what would happen if we actually measured the one-way speed of light, specifically, if we measured it to be anisotropic. Why not just ask that question without trying to obfuscate the issue with red-herrings.
Are you saying I'm making an error in the statement above? Or just an error in realization of your purposes here?I'm saying you are making an error in interpreting the argument I am presenting. As you have repeatedly demonstrated, you have presumed I am questioning the internal consistency of SR, despite it being repeatedly stated that this is not the case. Indeed, you perceive me to repeat errors that you have pointed out, but you have been pointing out errors as they pertain to the claim of the contradictory nature of SR. You've been beating a strawman over the head with a red herring while I've been tapping you on the shoulder to tell you that you've been beating a strawman over the head with a red herring.
Anyway, yes, I've had trouble with exactly that. You repeat errors that I've pointed out.
Fine. I believe you. But I'll still comment whenever I think the position is being misrepresented, for whatever purpose. If you're trying to argue that other interpretations are valid, nobody has disagreed with that. If you have a different interpretation than one of the usual ones, then I've yet to render an opinion of the validity of it on the surface.As long as you aren't commenting to highlight how I'm misprepresenting the internal consistency of SR then there should be no problem.
This is the absolute interpretation, so there is one meaning to 'stationary system'. It means her position is not changing. Bob is moving. Not relatively. Moving period. That's how the absolute interpretation words things. Motion is property, not a relation under the interpretation.I just wanted to double check before misrepresenting you.
Feel free to tell me I'm misrepresenting the interpretation. It is waters I don't usually find myself in. Wording things in such a manner is not second nature to me.
The transformations involved three reference frames. Frame S0 is at rest in the ether, S is a Galilean frame moving with velocity v with respect to S0 , and S' is an auxiliary frame that also moves with velocity v with respect to S0 . S0 and S are connected by the Galilean transformations, whereas S and S' are connected by the transformations [symbols didn't render] . Combining these two transformations we obtain the transformations connecting S and S'.On the Empirical Equivalence between Special Relativity and Lorentz’s Ether Theory by Pabo Accuna.
In this paper I argue that the case of Einstein‘s special relativity vs. Hendrik Lorentz‘s ether theory can be decided in terms of empirical evidence, in spite of the predictive equivalence between the theories. In the historical and philosophical literature this case has been typically addressed focusing on non-empirical features (non-empirical virtues in special relativity and/or non-empirical flaws in the ether theory). I claim that non-empirical features are not enough to provide a fully objective and uniquely determined choice in instances of empirical equivalence. However, I argue that if we consider arguments proposed by Richard Boyd and by Larry Laudan and Jarret Leplin, a choice based on non-consequential empirical evidence favoring Einstein‘s theory can be made.
That is what is generally meant by the term preferred reference frame. As I outlined in the other post, a preferred reference frame need only be the frame where instruments are reuinited for comparison. Or the frame in which measurement units are defined (I see you point on this below and will answer it there).QuoteIt's an important distinction.What distinction? There seems to be only one way to use those words. You had suggested before a possible difference between the absolute frame and the preferred one. I presume those to be the same, so feel free to clarify if they're not.
All of the theories, in effect, operate a round-trip light principle, including SR. SR just goes a step further and says that thee one-way speed of light is also a constant.QuoteJust to be clear, the interpretation Im advocating is one that employs a round-trip speed of light principle, so it will be empirically equivalent to the other interpretations.That remains to be seen. I've not seen it.
That's not true. Simpler in some ways, more complicated in others. Try to imagine implementing a speed limit sign on the side of the road using the absolute interpretation. Can be done, but it wouldn't be very helpful to the guy reading it. Such examples is why physics is far simpler with the relative interpretation.Apologies, I don't really understand the analogy. The speed limit sign can still imply relative to the road.
Could be interesting.If its undetectable and plays no role in predictions then, just like the Ether, it can be discarded, without affecting the mathematics of the theory. Imagine, Alice in the absolute reference frame and Bob moving relative to her. Now imagine that Alice moves too. There's no observer at absolute rest and hence, no absolute reference frame.
That's a redefinition of how the term is used in physics. Perhaps you should choose another one. Why do reunited instruments need a frame? They can reunite on the fly, comparing results at some event as they pass. Events don't have frames.It's not necessarily a redefinition of it, rather a different interpretation of it. Instead of nature doing the privileging, we do it as a matter of operational necessity.
That's exactly what Alice has done when she selects her abstract coordinate system. How is it going to be different than the standard interpretation then?Yep, and Bob does the same, but, as we can from things like the Twin-paradox and Hafele-Keating experiments, measuring instruments must be reunited in a single frame - that could be Alice's or it could be Bob's. In practical terms, the reference frame at rest relative to the Earth is the one used in the HK experiment and others.
Indeed, but it doesn't stop us from defining an Earth Centered Inertial frame. As I'm sure you will have learned from "my peers", this is the frame that is arguably used in GPS.Quotefor us, by default, that is the reference frame of the Earth (for obvious reasons).That frame isn't inertial. In fact it is an accelerating/rotating reference frame, with a funny set of properties all its own.
Hate to be picky, but frames don't define units. They don't even define origins. OK, the rotating frame could define a unit of time period, even though we don't use it. We cut up time from a standard one rotation plus nearly 236 seconds. The meter? Somebody pulled that out of his arse. I don't think anything on Earth really suggests it.Nope, frames don't define units, we define them in specific frames. Take "the Second" for example, that is defined by an atomic clock at rest, relative to the Earth (in a lab in Colorado).
Empirical measurements agree with that and much more. Why not take the full statement that all of EM is included in principle of relativity? That doesn't assume anything, and it includes your subset principle. Why go for the weak premise when there's a stronger empirical one?I am familiar with the idea, but only in the context of SR. If it implies the one-way speed of light, then I've stated the issues with that.
The quote doesn't say much. It says you can't tell. Nothing in it was news to me. Sounds like "A conspiriacy to hide the invisible pink elephant is equivalent to a conspiracy to posit an invisible pink elephant, therefore there is as much reason to posit the invisible pink elephant as there is to not do so.Basically it says, if you can measure the one-way speed of light, as it pertains to SR, then you can distinguish between SR and absolutist theories - eseentially rendering the objection to positing undetectable quantities equal across the two interpretations.
The reasoning seems to be a refutation to some (not included, but probably involving conspiracy to hide) argument against the absolute interpretation, but none of it seems relevant to actually finding a logical flaw in any of them.
In this interpretation, I don't know what it means to be synced in a frame. Synced is an absolute thing, not a frame thing, so those words have no meaning. I can't follow this.It's a statement about the simultaneity of events in an inertial frame.
I don't know the base premises. You talk about starting with an absolute frame, but then use relative, not absolute terminology. Most absolute interpretations don't talk about frames at all. Alice and Bob are moving, with different velocities. That's all. This is obviously a different interpretation, but I don't know what any of the terminology means.I posted an excerpt from a paper above which outlines how Poincare derived the Lorentz transform and it makes use of the term "frame". Take a read of the paper.
The rules of empiricism do not apply to mathematic bcos, as has been repeatedly stated (by both of us) mathematics is abstractsAgree, but then why are you applying rules of empiricism to a mathematical statement?
But, just as the rules of empiricism do not govern mathematics, neither do the rules of mathematics govern empiricism.You probably don't mean that mathematics cannot be used in physics, so not sure what you mean by this. Most of SR theory is mathematical. There are some empirical predictions of course, but we don't seem to be in disagreement about those, only the mathematical parts.
That is why mathematically derived predictions are required to be verified/falsified by way of empirical observation. Empirical observation trumps mathematical derivation.No it doesn't. If the model predicts one thing and empirical measurement yields another, then the model does not correspond to reality, but the mathematics in the model is not wrong because of it. The model is the wrong one, not the mathematics.
Theory and InterpretationNot all theories have mathematical formalization, and not all mathematical formalism is part of theories. The hard sciences (like we're discussing here) tend to be quite mathematical, but something like psychological theory might not as much. What defines a theory is empirical predictions. Hence something like string theory (insanely heavy on the mathematics) is arguably not a theory since it has yet to make a prediction. Quantum field theory is a theory, but pilot wave theory is not.
Forgive me if I'm using the terms imprecisely here, but I'm hoping you will understand the point that I am trying to make, as opposed to getting caught up in any imprecise usage of terms.
If I understand your usage of terms correctly, the "theory" appears to represent the mathematical formalism, sans metaphysical assumptions. Essentially, the Lorentz transformation, metric, etc. Am I correct in that?
If so, then we can conclude that the relativity of simultaneity isn't derived from the mathematics.No idea how you conclude that. I challenge you to derive it without mathematics.
How can we conclude this? Bcos the absolutist interpretations are mathematically equivalent but do not incorporate RoS.They're not equivalent at all. Again, trying implementing a speed limit sign using the alternate interpretation, and you'll see the difference in the mathematics. I notice you didn't respond to that.
We can still use the term "derive" to describe the statements that each interpretation necessitates, bcos they can be derived from the mathematics together with the mataphysical assumptions.I'm considering the interpretation that makes no additional metaphysical assumptions (raw SR theory). Lacking a conflicting assumption, I can hope this prevents conflict with an interpretation that makes some.
But - and I'm stating the obvious bcos it appears to be part of the issue - scientists (as opposed to mathematicians) are in the domain of empiricism. This is why they didn't simply accept what Einstein had derived mathematically as a given, instead they derived predictions from Einstein's interpretation (theory??) and then sought to test those empiricallyThe predictions were not derived from any interpretation, which makes none. You describe no predictions above except the simultaneous return of the signals. The rest is just abstract mathematical statements. They could become metaphysical statements had there been any metaphysical premises, but I'm avoiding them for the moment to make the point that the definitions don't require them.
And, while SR stood up to every single test, it appears to be less well understood that so too did all of the mathematically equivalent, absolutist interpretations.SR is a theory. The absolute interpretation of it is still SR.
In comes the thought experiment with Alice and Bob. Usually, these thought experiments are used as a means to demonstrate the empirical consequences of Einstein's interpretation.Interpretations don't have empirical consequences.
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They represent real-world scenarios which is why they are employed to demonstrate the empirical consequences logically necessitated by the different interpretations.
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As they represent an idealised experimental set-up, they demonstrate to us the empirical consequences that are logically necessitated by the different interpretations. In this manner we can apply the rules of empiricism - not the rules of mathematics - and see what empirical derivations we can make.
This is partly the reason why the intuitive response to reading Alice and Bob is to make the assumption that the premises of SR are implied. But we're not doing that. We're assuming the premises of no interpretation.That's what I've been doing as well. Still assuming the premises of the theory, which is OK since they're empirical premises.
Yes, the thought experiments are abstract but they are not abstract in the sense of being purely, mathematical abstractions.The conclusions they draw are often pure mathematical abstract conclusions. 'Clock at A is in sync with clock at B' is a pure mathematical abstract conclusion, not a metaphysical one. 'Clock A is in sync with Clock B' on the other hand is worded as a metaphysical statement. Hence me being picky about the difference.
They are abstract in the sense that talking about and describing the Hafele-Keating experiment (or any other such test of relativity) is abstract, but not in a mathematical sense. They are abstract descriptions of real-world experiments.H-K was an empirical exercise, not an abstract one or a thought experiment. It is in fact the first empirical verification of the twins experiment. One may be free to interpret the results in different ways, but the point was the empirical comparison done at the end coupled with an empirical history of the journey taken by each device.
The power of a thought experiment is that it allows us to represent a real-world experimental set-up which cannot be carried out for practical reasons - we aren't able to accelerate spaceships up to the speeds involved.Beg to differ. There are spaceships out there whose navigation depends on GR. There are clocks moved at very high speeds with predicted results. One can call them space ships if it satisfies some requirement. The thought experiments might help initially work out the details of the theory, but in a thread like this, those thought experiments are just illustrations of the established theory, not means by which new discoveries are expected to be made. We both assume the theory to be sound when we discuss them. I have little personal means to verify it myself.
Empirical AssumptionsWhat ever might be an empirical assumption? I assume I observe X?? I observe it or I observe something else. I don't see where assumptions come in.
See the bottom of this post for contextual examples of the term "empirical assumptions". You might use the term "metaphysical assumption", but we will see why the semantical difference is immaterial.OK, so you mean metaphysical assumption when you say this. Perhaps you also mean metaphysical consequences when speaking of 'empirical consequences of interpretations'. This sort of language abuse is rapidly destroying our ability to communicate. 'Empirical' and 'metaphysical' are mutually exclusive. As soon as some finding becomes empirical, it ceases to be interpretation. You walk out of the cave and see what causes the shadows on the wall for the first time. The various interpretations of those shadows are now empirically validated or falsified theories and are no longer interpretations.
An empirical assumption is an assumption about how the physical world is/should/must be in order for a given interpretation of empirical evidence to be made to fit the conclusions drawn from that evidence. If the empirical assumptions aren't granted, then the conclusions, drawn by the given interpretation, don't stand-up.Understood, but I refuse to use this wording myself. It seems intentionally designed to mislead.
As has been stated repeatedly, we can derive 2 statements about the physical configuration of Alice's system:Again, the 2nd is a physical statement, the 1st an abstract one. Both are statements about the physical configuration, so I agree with you as you word it.
1) the reading d/c on clock at C0 must co-incide with the clock synchronisation events at C1 and C2.
2) the light signals [must] return to the mid-point simultaneously and co-incide with the reading 2d/c on clock C0.
On the other hand, statement #1 above, which has been derived from Einstein's interpretation of the mathematicsIt is derived from his convention. There is no interpretational component to that.
cannot be verified empirically. It is therefore an untestable prediction; it is unfalsifiable*.It's entirely testable. He put a way to do it in his paper. That demonstration involves purely empirical methods, so it can very much be verified empirically.
It is unobserved. Not only is it unobserved, it would appear to be unobservable.A metaphysical assertion (had one been made) would not be observable. The abstract thing is quite observable. You're confusing the two. No such statement of the former has been made, nor derived.
In the domain of empiricism, something which is unobserved or unobservable constitutes an "empirical assumption".As I said, I understand what you mean by this, but will not accept the language since doing so would deprive me of a word I need for its defined purpose.
The intepretation makes a claim about the configuration of the physical system.The theory (not any interpretation) makes this abstract claim about the configuration of the physical system. The theory isn't based on any new assumptions, so it is hard to contest.
1) Reading [d/c] on clock C0 = physical claimThat's an empty physical claim, standing in opposition to one where the clock doesn't read that at some point, like it skips over some times or something. It wouldn't be a clock if this claim was unrealistic. And it's clock at C0 BTW.
2) Light signal making contact with C1 (synchronisation event at C1) = physical claimAgain, all empty claims, in opposition to an interpretation that the light signals were diverted elsewhere. None of these are claims. They're descriptions of events, using wording that frames (most of) them in an abstract coordinate system.
3) Light signal making contact with C2 (synchronisation event C2) = physical claim
4) 2 & 3 coinciding with 1 = physical claimAbstract (neither physical nor metaphysical) claim. Your insistence otherwise seems the source of our disagreement, and the source of my labeling your wording as strawman.
5) Reading [2d/c] on clock C0 = physical claimJust another event description, not a claim.
6) Light signals returning and co-inciding with 5 = physical claim.Wow, I agree on one 1 of 6.
Her conclusion of RoS can be stated as:In relatively moving frames, 1,2,3,5 are not established. #4 is demonstrated only in one frame and unknown (without employing further methods) in other frames. The sync test cannot be performed in other frames, and we've not devised a means here to demonstrate whether or not they're in sync in a given one. But I deny that at this point b) has been demonstrated. Bob hasn't done this.
a) #4 above
together with
b) not #4 in relatively moving frames
I was emphasising the fact that those "very clever people" (your peers maybe?) derived a number of insights about the Einsteinian intepretation, which weren't expressly stated in the 1905 paper.I'm mostly talking about the theory here, not somebody else's interpretation of it. I won't go so far as to assert that there is no metaphysical language used in Einstein's works, but I'm not relying on it.
I agree, RoS is derived from SR premises. The one-way speed of light is assumedIt is not. It is never concluded from SR. Only certain (most/all) interpretations assume this, but not the theory itself, and RoS is derived from the theory, not any interpretation.
OK, then we can conclude that RoS isn't an accurate representation of the physical world.Of course not. RoS isn't such a statement at all, as I've said for countless posts. You're just now getting that?
Its an abstract mathematical proposition which is compatiblle which in no way contradicts absolute simultaneity.Since absolute simultaneity is a metaphysical premise, it doesn't conflict since they're in unrelated realms. So agree.
Assuming clock at C0, sure, using the same method.Quote from: HalcI can perform the in-sync test, but that test again only verifies an abstract coordinate concept. No physical (or even metaphysical) statement is made in #1, so there is nothing to verify.There might be one small matter to verify.
Can you empirically verify that the reading d/c, on clock C0, coincides with the synchronisation events at C1 and C2, thereby confirming that your co-ordinate system is an accurate representation of the physical system it purports to describe;
can you verify that, in the real-world, the physical world, that the time co-ordinate (d/c) - as provided by the physical clock C0 - can reliably be ascribed to the events at C1 and C2No such concept has been introduced by the theory. The absolute interpretation introduces that concept and thus gives meaning to a variant to that question, and yes, even that can be verified by Einstein's convention (if you choose to use the convention). What cannot be verified is the clocks being at respective locations C0, C1, and C2, so the test can at best assume they are at those locations, or not assume it and declare that this physical sync cannot be determined.
can you verify that both events coinicde with the same reading on clock C0, given that there is an alternative, mathematically equivalent co-ordinate system which implies that both events do not coinncide with the same reading on clock C0?Hard to parse that. I presume we're using Einstein's definitions here, in which case, yes, of course. The events are simultaneous in one coordinate system and not the other. Both are abstract statements.
I didn't say the clock in the next room reads d/c. I said it does in the coordinate system where the rooms are at a fixed location. The latter is not a physical statement, but an abstract one.Quote from: HalcIt doesn't represent a prediction at all.Oh but it does! If I say to you that at the very moment you and I are standing in the same room, at that very moment there is a clock in the next room which reads d/c, that is a prediction.
are you saying that SR does not confict with, or make any claims/statements/etc. which contradict the absolutist interpretations?The theory doesn't, no. An interpretation of it might, but I have a hard time thinking even of that one.
Btw, the premises of SR assume isotropy and as you have been so eager to point out, "she is assuming the premises of SR" ergo isotropy is assumed and with it, the conclusion of RoS.I said I took that back. It isn't concluded nor even assumed, and there are all these sites that show it can't be done, so it obviously isn't needed by the theory at all, which needed no modification due to the inability to show this. It uses a convention with coordinate systems with orthogonal axes. It is a definition of a convention, not an assumption about the underlying reality that isn't needed for statements not concerning that underlying reality.
If you're arguing that she doesn't assume isoptropyIf she's using just the theory and no interpretational baggage, then yes, I'm arguing that.
But yes, that is the point that I wanted to clarify, whether or not you were talking about absolute rest.He does not give it that meaning, which is why of course all the denial sites gather like flies around that passage.
Btw, as we have already covered, Einstein uses the term "stationary system" in his paper.
I meant that also. A statement is not a prediction. A prediction is an anticipated result of a measurement. The word implies the measurement has not yet been performed.Quote from: HalcYou and I have a different definition of 'prediction' then. You apparently mean different metaphysical descriptions of the system. I don't call those predictions.I mean statements about the physical configuration of the system.
I talking about the reading on a physical clock being simultaneous with a physical photon making physical contact with another physical clock. But you seem to be of the opinion that this isn't a physical statement.I said it wasn't a prediction, not that it wasn't a physical statement. Predictions are used to verify/falsify a theory. A theory that doesn't make a distinct prediction isn't a theory, however blue in the face it might turn describing a physical system.
Again, contemplate the twin-paradox and the Hafele-Keating experiment. How do they end? They end with the twins/measuring instruments being reuinited in a single reference frame for comparison.A local comparison is not frame dependent. That comparison can be (and was) done in any frame. It isn't possible to not be in the other frames. H-K beginning and end events were not done by equipment that was stationary in the same frame as each other. It was an unnecessary requirement and no care was taken to do so. Likewise with the twins at both ends of the journey. The requirement is that they be together. That's all. Comparisons are objective if they're local. I suppose mass comparisons are not.
Reuiniting the measuring equipment like that in a single reference frame privileges that reference frame.Again, you are redefining the term from the way say Minkowski or Galileo define it, but since we have an alternate term, communication isn't as hampered.
It doesnt mean it is an absolute reference frame, it just means that there is an automatically ascribed asymmetry where one inertial frame is "forced" to undergo acceleration while the other isn't.An intertial frame cannot be accelerated. An accelerated frame can, but it has different properties.
The hair represents the physical evidencce of the light signal returning simultaneously, from which she cannot conclude that the clocks in her frame are synchronised.That's fine. She didn't conclude it from that since it is true in any frame, and the clocks are not synced in them all.
I mean what I said and not what you said. I'm not even sure what you're trying to say here. I'm not comitting the strawman fallacy since the statement makes no claims (false or otherwise) about what some interpretation might assert. Not sure what you think a strawman is. I just made a claim and invite being corrected. I might be wrong on this one.Quote from: HalcI'm comparing (not advocating) the SR theory with no additional metaphysical assumptions (not even fixed one-way light speed), with the absolute interpretation. Only the latter adds all these metaphysical assumptions. Since the former interpretation doesn't deny any of them, it isn't incompatible.You mean you are comparing the Lorentz transformation and other mathematical artefacts with the absolute interpretation? Then you are arguing a new kind of strawman.
Neither a theory. If either is a theory, what prediction does it make? It's an interpretation until it has a falsification test.Quote from: HalcIf you don't mean that one, then which two theories?Etherless Lorentz-Poincare theory or the forumulation as outlined by Michael Tooley. You know absolute interpretations of relativity.
It was brought up due to its relevance to a sync convention being discussed. Sync convention is relevant to this thread topic.Quote from: HalcI said precisely the opposite. I called you on your red-herring. Yet, you tried to persist with it. It's a level of intellectual dishonesty I haven't encountered before but at least when it came down to it, you have admitted its irrelevance to the topic of this discussion.QuoteYou could state how you believe it is pertinent to modern day attempts to measure the isotropic one-way speed of lightI would be lying if I said that. It isn't pertinent at all. You said that, not me.
It's a separate philosophical discussion to determine in what sense one can say he actually measured the speed of light. He made measurements and got a value, did he actually measure the speed of light tho?You still deny it! This is the 2nd reason why I didn't let it drop. SR says the method is valid and should yield exactly c. The theory says that, not any interpretation. It follows trivially from the empirical premises of SR. If your interpretation denies this, it is wrong.
But not free of the same issues that all sync conventions apparently fall foul of.Your claim of there being issues with a defined convention is noted. What do you think a convention is? Is that another word that is going to get redefined?
You're basically asking what would happen if we actually measured the one-way speed of lightI never meant that. He was measuring SoL using a one way method.
As per the Michael Tooley quote, if you could measure this then you could detect your absolute motion relative to the abssolute frame.If you could meausre 1WSoL, yes, but that doesn't mean that SoL cannot be measured using a one way method. If it yields c every time (as PoR say it must), then no absolute motion can be detected. Tooley is quite right about this.
This leads to slightly different conclusions than SR, but not in terms of things that can actually be tested.Yes, they're different conclusions, but not conflicting ones. All interpretations (if they add premises) make additional conclusions based on those added premises. You have been calling this circular reasoning, but I have not.
Agree, but then why are you applying rules of empiricism to a mathematical statement?
I meant as I said. The rules of empiricism do not govern mathematics. We don't make observations in mathematics bcos mathematics isn't an empirical discipline. Mathematics is a tool that can be used in physics, although its usefulness appears to have lead some - not necessarily you - to conflate mathematics with empiricism. The term "physics" is a broad term which covers the theoretical and the empirical part. Mathematics falls into the former category. But mathematics on its own isn't science. Science is an empirical discipline. Mathematics is a tool which can be used to derive predictions and model the physical world. If the predictions derived from the mathematics is contradicted by empirical tests then it is the mathematics which needs adjusting. Empirical observation trumps mathematically derived predictions.QuoteBut, just as the rules of empiricism do not govern mathematics, neither do the rules of mathematics govern empiricism.You probably don't mean that mathematics cannot be used in physics, so not sure what you mean by this. Most of SR theory is mathematical. There are some empirical predictions of course, but we don't seem to be in disagreement about those, only the mathematical parts.
No it doesn't. If the model predicts one thing and empirical measurement yields another, then the model does not correspond to reality, but the mathematics in the model is not wrong because of it. The model is the wrong one, not the mathematics.The corresponence of the model to the physical reality is precisely the point.
Not all theories have mathematical formalization, and not all mathematical formalism is part of theories. The hard sciences (like we're discussing here) tend to be quite mathematical, but something like psychological theory might not as much. What defines a theory is empirical predictions. Hence something like string theory (insanely heavy on the mathematics) is arguably not a theory since it has yet to make a prediction. Quantum field theory is a theory, but pilot wave theory is not.That is fine. What we are doing is discussing the intepretations. The SR interpretation and those other interpretations that are mathematically and empirically equivalent to SR.
Interpretations get into the metaphysics. One can choose to totally skip the metaphysics and just work with the theory raw. That's what Alice could be said to be doing if you keep metaphysical claims out of her conclusions.
Bcos Lorentz-Poincare theory employs the same mathematics but doesn't include RoS.QuoteIf so, then we can conclude that the relativity of simultaneity isn't derived from the mathematics.No idea how you conclude that. I challenge you to derive it without mathematics.
They're not equivalent at all. Again, trying implementing a speed limit sign using the alternate interpretation, and you'll see the difference in the mathematics. I notice you didn't respond to that.See how Poincare derived Lorentz transformation and you will see how there is no difference.
RoS is derived from the theory which defines simultaneity in a empirical (physical) way.Except that it can't be determined empirically - in any of the interpretations.See Romer and the finite speed of light.
An absolute interpretation.discards that definition (and several others) in favor of metaphysical ones.
I'm considering the interpretation that makes no additional metaphysical assumptions (raw SR theory). Lacking a conflicting assumption, I can hope this prevents conflict with an interpretation that makes some.When you say "raw SR theory" do you mean the mathematics of the Lorentz Transformation?
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The predictions were not derived from any interpretation, which makes none. You describe no predictions above except the simultaneous return of the signals. The rest is just abstract mathematical statements. They could become metaphysical statements had there been any metaphysical premises, but I'm avoiding them for the moment to make the point that the definitions don't require them.
Anyway, I more or less agree with the description until it got into a description of what the scientists may or may not have accepted or decided needed testing. The philosophers maybe. Their job is to sort out the sorts of things being debated in this thread.
SR is a theory. The absolute interpretation of it is still SR. If SR fails in a prediction, any absolute interpretation goes down with it.If both are referred to as SR theory, then SR theory cannot imply relativity of simultaneity because simultaneity is absolute in the absolutist interpretation. If SR theory implied RoS then RoS would - by necessity - be implicit in any absolute intepretation. This simply isn't the case - unless you're positing Schroedingers Special Relativity.
Interestingly, SR claims up front not to correspond to reality except locally, so there are plenty of non-local tests to falsify it as a model of the universe at medium scales. Simplest test is the inability to sync a pair of clocks on different floors of a building. So there likewise needs to be an absolute interpretation of GR theory.I'm arguing that it doesn't correspond to reality locally.
Interpretations don't have empirical consequences.They imply empirical consequences. The returning of the light signals simultaneously is an empirically testable consequence in all interpretations.
We're talking about the interpretations. But, given that you believe that RoS is a consequence of the mathematics, it is understandable how you might make that mistake.QuoteThis is partly the reason why the intuitive response to reading Alice and Bob is to make the assumption that the premises of SR are implied. But we're not doing that. We're assuming the premises of no interpretation.That's what I've been doing as well. Still assuming the premises of the theory, which is OK since they're empirical premises.
The conclusions they draw are often pure mathematical abstract conclusions. 'Clock at A is in sync with clock at B' is a pure mathematical abstract conclusion, not a metaphysical one. 'Clock A is in sync with Clock B' on the other hand is worded as a metaphysical statement. Hence me being picky about the difference.When we jump into the real world, "Clock at A" represents a physical clock which can be labelled "Clock A". Indeed, the location "A" is represented by a mark on the floor of a spaceship whos inertial motion cannot be determined.
H-K was an empirical exercise, not an abstract one or a thought experiment. It is in fact the first empirical verification of the twins experiment. One may be free to interpret the results in different ways, but the point was the empirical comparison done at the end coupled with an empirical history of the journey taken by each device.Our discussing the H-K experiment is abstract bcos we are not in commerical airliners with atomic clocks. The thought experiments are abstract in this sense, not in a mathematical sense. If it were logistically possible, the thought experiment could be carried out as an empirical exercise. So, it is not abstract in the sense that mathematics is abstract, which was the implication of your statement (whether you realised it or not).
Beg to differ. There are spaceships out there whose navigation depends on GR. There are clocks moved at very high speeds with predicted results. One can call them space ships if it satisfies some requirement. The thought experiments might help initially work out the details of the theory, but in a thread like this, those thought experiments are just illustrations of the established theory, not means by which new discoveries are expected to be made. We both assume the theory to be sound when we discuss them. I have little personal means to verify it myself.We're not making new discoveries through the thought experiments, we are deducing what the different interpretations imply, and what they have implied all along.
OK, so you mean metaphysical assumption when you say this. Perhaps you also mean metaphysical consequences when speaking of 'empirical consequences of interpretations'. This sort of language abuse is rapidly destroying our ability to communicate. 'Empirical' and 'metaphysical' are mutually exclusive. As soon as some finding becomes empirical, it ceases to be interpretation. You walk out of the cave and see what causes the shadows on the wall for the first time. The various interpretations of those shadows are now empirically validated or falsified theories and are no longer interpretations.Maybe you had started replying before I had a chance to edit the post bcos I had forgotten to include the contextual examples. They have been included again here. See below.
Understood, but I refuse to use this wording myself. It seems intentionally designed to mislead. We need a word to replace 'empirical' then, something to mean what actually can be observed, because you're destroyed that meaning. Communication not possible with no word that means that anymore.See contextual examples below
Lloyd (1988: 2), a philosopher of evolutionary biology, stated that, ―Under a general hypothetico-deductive view of theories, a theory is understood as offering hypotheses from which, in combination with empirical assumptions, deductions can be made regarding empirical results.
Why look at the deflection of a particle’s trajectory in an electromagnetic field in order to measure its charge? – and doing so will demand a large number of auxiliary empirical assumptions.Cartwright, Nancy D. (2009) 'What is this thing called 'ecacy'?',
The model solves for the mass evolution based on what are thought to be the dominant input boundary conditions. Some empirical assumptions are made to predict the behavior of lower order physics.//proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1605299
By identifying the energy that must be absorbed through deformation of the vehicle’s roof using the FMVSS 216 five inches (127 mm) of roof crush strength limit as a constraint, it was possible to calculate theoretically using some broad empirical assumptions generated from rollover crash test data, Vehicle roof strength as it relates to contained occupant injury prevention during rollover crashesYoung, D. P., Grzebieta R.H
one word of caution is that the Doppler Dimming method strongly depends on empirical assumptions of the electron density and ion temperature, thus possibly leading to different results with different assumptions (Wilhelm et al. 2011).//iopscience.iop.org/article/10.1088/0004-637X/794/2/109/meta
Again, the 2nd is a physical statement, the 1st an abstract one. Both are statements about the physical configuration, so I agree with you as you word it.Both are statements about the physical system. Only one of them can be verified empirically, therefore the other is a statement about the physical system whose validity can only be assumed.
It is derived from his convention. There is no interpretational component to that.The convention depends on the isotropic one-way speed of light reltive to all co-ordinate systems. That is only part off the SR interpretation.
It's entirely testable. He put a way to do it in his paper. That demonstration involves purely empirical methods, so it can very much be verified empirically.Put yourself in Alice's shoes. Send the light signal to the clock at A and B (the points marked on the floor of your spaceship). Now, what is the empirical evidence that allows you to verify that Clock A located at point A (on your spaceship) is synced with Clock B located at point B (on your spaceship)?
Your problem seems to be an assumption that Einstein is making a sort of metaphysical statement by #1. But it's just an abstract statement, and one that can be tested.
A metaphysical assertion (had one been made) would not be observable. The abstract thing is quite observable. You're confusing the two. No such statement of the former has been made, nor derived.How does Alice observe that the physical photons make physical contact with the physical clocks located at the points A and B on her physical spaceship at the moment that coincides with the reading d/c on clock C0?
See the contextual examples.QuoteIn the domain of empiricism, something which is unobserved or unobservable constitutes an "empirical assumption".As I said, I understand what you mean by this, but will not accept the language since doing so would deprive me of a word I need for its defined purpose.
The abstract claim is based on the one-way speed of light. The theory, as you define the term, doesn't make this metaphysical assumption, the interpretation does.QuoteThe intepretation makes a claim about the configuration of the physical system.The theory (not any interpretation) makes this abstract claim about the configuration of the physical system. The theory isn't based on any new assumptions, so it is hard to contest.
That clock C0 located at C0 on the physical spaceship will read d/c is a physical claim. It is a claim that says this will be a reading on the physical clock which will not be skipped over.Quote1) Reading [d/c] on clock C0 = physical claimThat's an empty physical claim, standing in opposition to one where the clock doesn't read that at some point, like it skips over some times or something. It wouldn't be a clock if this claim was unrealistic. And it's clock at C0 BTW.
Again, all empty claims, in opposition to an interpretation that the light signals were diverted elsewhere. None of these are claims. They're descriptions of events, using wording that frames (most of) them in an abstract coordinate system.Indeed, in opposition to an interpretation that the light signals were diverted elsewhere, the physical claim implies that they aren't deflected elsewhere and that such an interpretation isn't under consideration.
The sourse of the misunderstanding is that you cannot recognise that the abstract mathematical claim is a claim about a physical system. If it remains in the abstract mathematical domain and isn't put forward as a model of the pyhsical system, that is, if it is stated categorically that it does not represent an accurate model of the physical world, then yes it is a purely abstract claim.Quote4) 2 & 3 coinciding with 1 = physical claimAbstract (neither physical nor metaphysical) claim. Your insistence otherwise seems the source of our disagreement, and the source of my labeling your wording as strawman.
In relatively moving frames, 1,2,3,5 are not established. #4 is demonstrated only in one frame and unknown (without employing further methods) in other frames. The sync test cannot be performed in other frames, and we've not devised a means here to demonstrate whether or not they're in sync in a given one. But I deny that at this point b) has been demonstrated. Bob hasn't done this.Except, #4 isn't demonstrated in that one frame, it is assumed - which is the point entirely.
Alice has not concluded RoS. That comes from the SR, not from new experimentation. If you don't assume the empirical premises of SR, it doesn't follow. Newton didn't posit RoS because he was unaware of the empirical premises in question. It follows quite trivially from empirical evidence. You don't need to do any arithmetic to conclude it.Making your way thru the history book I see. Get back to me when you reach Lorentz and Poincare and the empirical equivalence of their interpretation and SR.
I'm mostly talking about the theory here, not somebody else's interpretation of it. I won't go so far as to assert that there is no metaphysical language used in Einstein's works, but I'm not relying on it.You inadvertentyl are though. You are conflating Eisntein's intepretation with the underlying mathematics. This is completely understsandable, given how it is taught and given the mainstream adoption of Einstein's interpretation.
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It is not. It is never concluded from SR. Only certain (most/all) interpretations assume this, but not the theory itself, and RoS is derived from the theory, not any interpretation.
An interpretation that has metaphysically direction-dependent light speed is functionally equivalent to a coordinate system with non-orthogonal axes. While it is mathematically valid to do this, one might wonder why one would wish to adopt such an interpretation.
Anyway, in such an interpretation, Einstein's convention still works and Alice's clocks are still in sync in her frame by that convention. It works because the convention doesn't reference any metaphysical assumptions.You're assuming the validity of the convention, which is not a given.
Of course not. RoS isn't such a statement at all, as I've said for countless posts. You're just now getting that?So simultaneity is both absolute and relative?
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Since absolute simultaneity is a metaphysical premise, it doesn't conflict since they're in unrelated realms. So agree.
No such concept has been introduced by the theory. The absolute interpretation introduces that concept and thus gives meaning to a variant to that question, and yes, even that can be verified by Einstein's convention (if you choose to use the convention). What cannot be verified is the clocks being at respective locations C0, C1, and C2, so the test can at best assume they are at those locations, or not assume it and declare that this physical sync cannot be determined."If you choose to use that convention" means, if you assume the validity of the convention.
Hard to parse that. I presume we're using Einstein's definitions here, in which case, yes, of course. The events are simultaneous in one coordinate system and not the other. Both are abstract statements.You're back to assuming that Alice is an SR girl, living in an SR world - I've repeatedly stated, that is not a given.
Abstract simultaneity convention is something like this: You select an arbitrary coordinate system of 4 orthogonal axes in spacetime and draw a line from each event tangent to the temporal axis. If the two tangent lines meet the arbitrarily selected axis at the same point, they will also have that property with any line parallel to the selected one. It is the orientation, not location, that counts. Anyway, if that abstract condition is met, the events are simultaneous by definition of the convention. There is no metaphysical statement of simultaneity implied by that. It is an abstract statement made about a physical system. The description here speaks of events and not of synced clocks. The latter are not events.OK, outline how this correesponds to the real-world, making reference to physical clocks, physical photons, and physical readings on physical clocks.
All such coordinate systems are mathematically equivalent, and the property will not be met with some of them using the same two events. That is another way of answering your question above.
I didn't say the clock in the next room reads d/c. I said it does in the coordinate system where the rooms are at a fixed location. The latter is not a physical statement, but an abstract one.The point of physics is to describe the physical world, not an abstract world that has no correspondence to reality.
If by the theory you mean the underlying mathematics then agreed, but only bcos the mathematics doesn't imply anything about the simultaneity of events. The mathematics provides a co-ordinate description of events, metaphysica assumptions about the nature of time determine claims about simultaneity.Quoteare you saying that SR does not confict with, or make any claims/statements/etc. which contradict the absolutist interpretations?The theory doesn't, no. An interpretation of it might, but I have a hard time thinking even of that one.
It isn't concluded nor even assumed, and there are all these sites that show it can't be done, so it obviously isn't needed by the theory at all, which needed no modification due to the inability to show this. It uses a convention with coordinate systems with orthogonal axes. It is a definition of a convention, not an assumption about the underlying reality that isn't needed for statements not concerning that underlying reality.Not sure I've parsed this one correctly, but if we are still talking about Einstein's convention here, then we are not granting its validity.
Then she doesn't conclude RoS bcos the L-P interpretation uses the same theory/mathematics and doesn't include RoSQuoteIf you're arguing that she doesn't assume isoptropyIf she's using just the theory and no interpretational baggage, then yes, I'm arguing that.
He does not give it that meaning, which is why of course all the denial sites gather like flies around that passage.I may have misundestood when you said "...'the stationary system', the term only has meaning in an absolute interpretation". I was just pointing out that it doesn't only have meaning in an absolute interpretation.
I meant that also. A statement is not a prediction. A prediction is an anticipated result of a measurement. The word implies the measurement has not yet been performed.If the one-way speed of light can be measured - a proposition you and others seem to be optimisic about - then it represents a prediction. If the one-way speed of light cannot be measured, then the simultaneity of clock syncing events is an untestable prediction. Just bcos something cannot be measured it doesn't mean its not a prediction, it just means that it is an untestable one.
I said it wasn't a prediction, not that it wasn't a physical statement. Predictions are used to verify/falsify a theory. A theory that doesn't make a distinct prediction isn't a theory, however blue in the face it might turn describing a physical system.
Some of the string theorists' tribulations regarding untestable predictions are shared by epidemiologists and other researchers//academic.oup.com/aje/article-abstract/162/7/618/204321
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When the causal effect of interest is ill defined, the counterfactual theory of causal inference from observational data and the elegant statistical methods derived from it lead to predictions that are untestable.
Untestable predictions and hypotheses lie outside the realm of science. Suppose someone told you, for example, that lightning storms are caused by angry ghosts. If this is true, you would predict that when ghosts are angry, there will be more lightning storms. It's not a valid scientific hypothesis, however, because neither the proposed explanation nor its predictions are testable. There is no possible experiment you can design to determine whether ghosts are angry and whether their wrath is correlated with the incidence of thunderstorms, so the hypothesis and its predictions are completely untestable.//sciencing.com/testable-prediction-8646215.html
A local comparison is not frame dependent. That comparison can be (and was) done in any frame. It isn't possible to not be in the other frames. H-K beginning and end events were not done by equipment that was stationary in the same frame as each other. It was an unnecessary requirement and no care was taken to do so. Likewise with the twins at both ends of the journey. The requirement is that they be together. That's all. Comparisons are objective if they're local. I suppose mass comparisons are not.I didn't say it was frame dependent, I said that it privileges the reference frame in which the local comparison is made. The H-K comparison was done in the "at rest relative to the Earth frame", where the Airplanes had to accelerate and decelerate to come to be at rest reltive to the earth. It wouldn't have been practical to accelerate and decelerate the Earth while the airplane was in the air - as I'm sure you understand.
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Again, you are redefining the term from the way say Minkowski or Galileo define it, but since we have an alternate term, communication isn't as hampered.
If we apply Occam‘s razor and excise the ether from Lorentz‘s theory, what we obtain is not special relativity. It is still possible to retain the Newtonian space-time plus conspiring dynamical effects by defining by fiat a privileged reference frame. For example, the Lorentzian could baldly say that the privileged frame is the one in which the real time is measured, period.On the Empirical Equivalence between Special Relativity and Lorentz’s Ether Theory by Pablo Acuna. I can send a copy of the paper if you like - is it possible to add attachments to PMs on here?
An intertial frame cannot be accelerated. An accelerated frame can, but it has different properties.A spaceship represents an inertial frame - perhaps you mean inertial co-orddinate frame - a spaceship can be accelerated.
That's fine. She didn't conclude it from that since it is true in any frame, and the clocks are not synced in them all.That is the only empirical evidence available to her. If she didn't conclude it from empirical evidence, then she must be be assuming it.
I mean what I said and not what you said. I'm not even sure what you're trying to say here. I'm not comitting the strawman fallacy since the statement makes no claims (false or otherwise) about what some interpretation might assert. Not sure what you think a strawman is. I just made a claim and invite being corrected. I might be wrong on this one.I believe you are wrong about this one. Given that you don't usually find yourself "in these waters" it is not surprising that you might not realise the fact that that the underlying mathematics or "the theory" is the same for both interpretations - Poincare derived the Lorentz contraction independently of Einstein and from Lorentz's theory.
Neither a theory. If either is a theory, what prediction does it make? It's an interpretation until it has a falsification test.I quoted the prediction it makes, it predicts that the one-way speed of light is not isotropic relative to all reference frames. Esseentially, it predicts that, if the one-way speed of light can be measured then absolute motion could be determined. If the one-way speed of light is found to be isotropic relative to all inertial frames, the theory is falsified.
It was brought up due to its relevance to a sync convention being discussed. Sync convention is relevant to this thread topic.And I referened literature that highlighted the problem that has, thus far, beset all such sync conventions. Conventions much more sophisticated that Romers.
So to repeat, I brought it up as a relevant example of a different sync convention. I persisted with it because you suggested that he cannot have done what he did (which was measuring light speed utilizing a one-way method, not measuring the one-way speed of light).And I repeat, measuring the one-way speed of light requires the syncing of two spatially separated clocks, which requires an accurate measurement of the one-way speed of light which requires the syncing of two spatially separated clocks, which requires a an accurate measurement of the one-way speed of light which requires.....
You still deny it! This is the 2nd reason why I didn't let it drop. SR says the method is valid and should yield exactly c. The theory says that, not any interpretation. It follows trivially from the empirical premises of SR. If your interpretation denies this, it is wrong.SR says Romers method is valid and should yield exactly c? How did that work out can you tell me?
Your claim of there being issues with a defined convention is noted. What do you think a convention is? Is that another word that is going to get redefined?In the context of Einstein's sync convention it means something which is established without being empirical verified/verifiable.
I never meant that. He was measuring SoL using a one way method.He was demonstrating that the speed of light was finite as opposed to the assumption at the time, that it was infinite/instantaneous. I'm not even sure he was trying to measure the speed of light, but given the measurements he did make, he arrived at a value.
If you could meausre 1WSoL, yes, but that doesn't mean that SoL cannot be measured using a one way method. If it yields c every time (as PoR say it must), then no absolute motion can be detected. Tooley is quite right about this.If you can propose a method of measuring the 1WSoL that doesn't require the syncing of spatially separated clocks (by convention) or that doesn't make assumptions pertaining to the rigidy of the bodies used in the measurement, then fame and notoriety await you.
We might be talking about slightly different things here. I'm talking about the idea that an interpretation of relativity that incorporates an absolute reference frame - with two frames moving relatively to that, where the Lorentz Transformation is used between the absolutely moving frames - does not predict reciprocal time dilation the way Einstein's interpretation does. In the absolute interpretations both Alice and Bob's clocks are slowed.QuoteThis leads to slightly different conclusions than SR, but not in terms of things that can actually be tested.Yes, they're different conclusions, but not conflicting ones. All interpretations (if they add premises) make additional conclusions based on those added premises. You have been calling this circular reasoning, but I have not.
Apologies, I don't really understand the analogy. The speed limit sign can still imply relative to the road.Yes it can, and is, because the mathematics is far simpler if a relative interpretation is used. That was my point. You claim the mathematics is the same.
That's a redefinition of how the term is used in physics. Perhaps you should choose another one. Why do reunited instruments need a frame? They can reunite on the fly, comparing results at some event as they pass. Events don't have frames.If they could compare on the fly then we could have Alice and Bob compare recciprocal time dilation on the fly[/quote]What is 'reciprocal time dilation' and how is it different from the comparison made with everybody with identical motion?
but that would, of course give rise to a paradox bcos it would require Alice to show that Bob's clock ticks slower than hers, while Bob shows that Alice's clock ticks slower than his.A comparison of respective elapsed time has nothing to do with the tick rates of either clock. You read what each clock says and subtract. The rates of the clocks play no rote in that calculation. The twins experiment can be described without any acceleration at all using nothing but pure inertial clocks that are never stationary relative to each other and never accelerated.
but, as we can from things like the Twin-paradox and Hafele-Keating experiments, measuring instruments must be reunited in a single frameThat is a requirement of neither test. I don't think you know your theory at all.
are you from the UK btw?I'd say 'maths' and 'centre' if I was.
And yep, the meter was ... relative to the Earth, calculating the circumference.OK, 1/40000000th of the circumference of Earth as it was known at the time. If that's so, it is based on some Earth dimension. You'd think they'd make it divisible by 360 or something.
It doesn't obviously since it's been well pointed out that there is no empirical test for that.Quote from: HalcEmpirical measurements agree with that and much more. Why not take the full statement that all of EM is included in principle of relativity? That doesn't assume anything, and it includes your subset principle. Why go for the weak premise when there's a stronger empirical one?I am familiar with the idea, but only in the context of SR. If it implies the one-way speed of light, then I've stated the issues with that.
Just put yourself in Alice's shoes. You've finished all the math, you'e derived all your statements, now your ready to jump back into the real-world, the physical world, the world where the rules of empiricism apply.No, since she cannot determine that she remains at that location. Good thing she never claimed to have done what you ask.
You are located at the mid-point between two clocks; you have your own clock; you send out a light pulse from the mid-point to each clock. Can you be sure that the light pulses reached each clock simultaneously?
Yes it can, and is, because the mathematics is far simpler if a relative interpretation is used. That was my point. You claim the mathematics is the same.I meant both use the Mathematics of the Lorentz transformations to make predictions. I'm not aware of any attempt by the city council to implement road signage in the absolute reference frame - mind you, I wouldn't be surprised to hear of some sort of executive committee charged with the tast of using public fuding to find the absolute reference frame.
What is 'reciprocal time dilation' and how is it different from the comparison made with everybody with identical motion?://lmgtfy.com/?q=reciprocal+time+dilation
A comparison of respective elapsed time has nothing to do with the tick rates of either clock. You read what each clock says and subtract. The rates of the clocks play no rote in that calculation. The twins experiment can be described without any acceleration at all using nothing but pure inertial clocks that are never stationary relative to each other and never accelerated.Alice and Bob moving relative to each other. Alice sees Bob's clock running slow. Bob sees Alice's clock running slow.
That is a requirement of neither test. I don't think you know your theory at all.So, in the H-K experiment the clocks aren't brought back together to a position at rest relative to the Earth?
I'd say 'maths' and 'centre' if I was.It was your use of the term "arse" as opposed to "ass" that had me wondering.
OK, 1/40000000th of the circumference of Earth as it was known at the time. If that's so, it is based on some Earth dimension. You'd think they'd make it divisible by 360 or something.Yep, both it and "the second" are defined in a geocentric reference frame.
No, since she cannot determine that she remains at that location. Good thing she never claimed to have done what you ask.I presume you mean that she cannot determine that she, along with the spaceship and everything on board, remains at the same location, yes? Bcos she can obviously determine that she has stayed in the same location on the spaceship.
If you are saying that RoS is a purely mathematical artefact which bears no resemblance to the physical world then you will find I'm in agreement.And yet pages later you go on about it. It may or may not bear a resemblance to the physical world. I'm not claiming it one way or the other. Such would be a metaphysical claim.
If the model makes a prediction about the physical world which cannot be observed it is an untestable prediction. If an oberver makes a conlusion about the physical world that relies on that untestable prediction, then they are assuming a conclusion about the physical world.Again we agree.
You are either confusing the conclusions of the mathematical model with the conclusions drawn from the actual empirical evidence, or you are saying that certain aspects of the model does not represent the physical reality of the physical reality it purports to model.I'm not the one calling unobservables 'predictions'. I made none of those, having laid no claim of correspondence of an abstract thing to physical reality.
What we are doing is discussing the intepretations. The SR interpretation and those other interpretations that are mathematically and empirically equivalent to SR.I don't know which SR interpretation you are referencing. I'm talking about the blank interpretation that makes no additional premises from the ones in the theory. So there is no 'the SR interpretation'. All (even the absolute ones) are SR interpretations.
The empirical equivalence might be a bit of a misnomer bcos it could be taken to suuggest that they predict the same things, when in actuality it means that all empirical tests to date have falsified none of the interpretations.By definition, yes.
The Michael Tooley interpretation (which appears to be the same as an Etherless Lorentz-Poincare interpretation) doesn't predict reciprocal time dilation in the manner that SR does.In fact it doesn't predict anything at all, else it would not be an interpretation.
Lorentz-Poincare theory employs the same mathematics but doesn't include RoS.Poincare derived RoS before anybody else, but their interpretation uses a non-empirically defined coordinate system to define simultaneity. Einstein used a defined coordinate system. Lorentz-Poincare does not.
I mean the entire theory, not one little part of it. The theory only uses empirical premises. No assumptions.Quote from: HalcI'm considering the interpretation that makes no additional metaphysical assumptions (raw SR theory).When you say "raw SR theory" do you mean the mathematics of the Lorentz Transformation?
If both are referred to as SR theory, then SR theory cannot imply relativity of simultaneity because simultaneity is absolute in the absolutist interpretation.Again, it uses a non-empirical coordinate system to conclude that.
If SR theory implied RoSIt deduces RoS using the empirical convention to define simultaneity. It doesn't imply it. One is free to choose a different convention, but the convention is not a physical or metaphysical assumption of any sort. Some interpretations use the same convention, but an undefined coordinate system posited by a non-empirical assumption. That different kind of simultaneity may or may not be relative, but being based on an assumed premise, that kind of simultaneity becomes assumed and not testable.
I'm sure you will have been able to deduce that we are discussing Einstein's interpretation versus absolute interpretations.Not talking about Einstein's interpretation because I don't have a list of his additional premises, so I'm going with just his theory sans additional premises. I know he held additional premises, but the changed over time. SR theory did not. GR needed adjustments, but startlingly few.
By corresponding, I mean empirical correspondence, as SR is an empirical theory. If you argue it doesn't do this, then you claim a falsification test. But I think you simply claim it doesn't correspond to metaphysical reality, which is fine since SR is a scientific theory and makes no metaphysical claims about the underlying reality. Reality indeed has no correspondence to a theory that is mute on the subject.Quote from: HalcSR claims up front not to correspond to reality except locally, so there are plenty of non-local tests to falsify it as a model of the universe at medium scalesI'm arguing that it doesn't correspond to reality locally.
No it isn't. It is a consequence of the theory upon which the interpretation is based. An empirical consequence of an interpretation would be an additional prediction not made by the underlying theory. If one were to exist, the 'interpretation' would cease to be an interpretation by definition.Quote from: HalcInterpretations don't have empirical consequences.They imply empirical consequences. The returning of the light signals simultaneously is an empirically testable consequence in all interpretations.
A mark on the floor does not designate a location since no definition of the floor being stationary has been established. A coordinate system is required to do that, and 'Clock A' makes no reference at all to that essential coordinate system. Thus no empirical conclusion can be drawn about Clock A, but one can be made about 'Clock at A'.Quote from: Halc'Clock at A is in sync with clock at B' is a pure mathematical abstract conclusion, not a metaphysical one. 'Clock A is in sync with Clock B' on the other hand is worded as a metaphysical statement. Hence me being picky about the difference.When we jump into the real world, "Clock at A" represents a physical clock which can be labelled "Clock A". Indeed, the location "A" is represented by a mark on the floor of a spaceship whos inertial motion cannot be determined.
We don't need to interpret the results any differently, we can just recognise that one reference frame is privileged over the other. The mountain cannot go to Mohammed, so Mohammed has to go to the mountain.1) Any experiment (twins, H-K) anything at all, can be done and analyzed in any frame. It doesn't change the result. 2) Mohammad need not stop at the mountain any more than the mountain need stop at Mohammed.
It would appear that the issue lies in your mispprehension of the idea that RoS is part of the "raw" mathematics of the theory.If you are saying that RoS is a purely mathematical artefact which bears no resemblance to the physical world then you will find I'm in agreement.And yet pages later you go on about it. It may or may not bear a resemblance to the physical world. I'm not claiming it one way or the other. Such would be a metaphysical claim.QuoteIf the model makes a prediction about the physical world which cannot be observed it is an untestable prediction. If an oberver makes a conlusion about the physical world that relies on that untestable prediction, then they are assuming a conclusion about the physical world.Again we agree.QuoteWhat we are doing is discussing the intepretations. The SR interpretation and those other interpretations that are mathematically and empirically equivalent to SR.I don't know which SR interpretation you are referencing. I'm talking about the blank interpretation that makes no additional premises from the ones in the theory. So there is no 'the SR interpretation'. All (even the absolute ones) are SR interpretations.QuoteThe empirical equivalence might be a bit of a misnomer bcos it could be taken to suuggest that they predict the same things, when in actuality it means that all empirical tests to date have falsified none of the interpretations.By definition, yes.QuoteThe Michael Tooley interpretation (which appears to be the same as an Etherless Lorentz-Poincare interpretation) doesn't predict reciprocal time dilation in the manner that SR does.In fact it doesn't predict anything at all, else it would not be an interpretation.
I'm not the one calling unobservables 'predictions'. I made none of those, having laid no claim of correspondence of an abstract thing to physical reality.The key word is untestabl predictions. I've posted contextual examples. Just as I did for "empirical assumptions". Did you read them?
The convention depends on the isotropic one-way speed of light reltive to all co-ordinate systems. That is only part off the SR interpretation.That would be an interpretational assumption. No, it doesn't assume that. The convention is simply established by definition. That's what a convention is.
It's entirely testable.Put yourself in Alice's shoes. Send the light signal to the clock at A and B (the points marked on the floor of your spaceship). Now, what is the empirical evidence that allows you to verify that Clock A located at point A (on your spaceship) is synced with Clock B located at point B (on your spaceship)?
How does Alice observe that the physical photons make physical contact with the physical clocks located at the points A and B on her physical spaceship at the moment that coincides with the reading d/c on clock C0?By using the method described by Einstein. Are you suggesting I'm referring to different events than the ones where these physical occurrences take place?
Poincare derived RoS before anybody else, but their interpretation uses a different convention to define simultaneity. Einstein used an empirical convention. Lorentz-Poincare does not.
In a contribution for a volume celebrating the 25th anniversary of Lorentz‘s doctorate, Poincaré explained his point by means of an illustration that strikingly resembles Einstein‘s method for the synchronization of clocks. He showed that if two observers at rest with respect to each other, but in motion with respect to the ether, try to synchronize their clocks by means of light pulses, the result is that their synchronized clocks are late with respect to the real time.His convention to define simultaneity is, in effect, the same as Einstein's. Indeed, it is indiscgernible from Einstein's treatment of cco-ordinate systems.
Imagine two observers who wish to adjust their watches by optics signals; they exchange signals, but as they know that the transmission of light is not instantaneous, they take care to cross them. When the station B perceives the signal from the station A, its clock should not mark the same hour as that of station A at the moment of sending the signal, but this hour augmented by a constant representing the duration of the transmission. Suppose, for example, that the station A sends its signal when its clock marks the hour 0, and that the station B perceives it when its clockChange station A and Station B for Clock at A and Clock at B and you've effectively got Einsein's sync convention. This is in Alice's "stationary system".
marks the hour t. The clocks are adjusted if the slowness equal to t represents the duration of the transmission, and to verify it the station B sends in turn a signal when its clock marks 0; then the station A should perceive it when its
clock marks t. The time pieces are then adjusted. And in fact, they mark the same hour at the same physical instant, but on one condition, namely, that the two stations are fixed
In the contrary case the duration of the transmission will not be the same in the two senses, since the station A, for example, moves forward to meet the optical perturbation emanating from B, while the station B flies away before the perturbation emanating from A. The watches adjusted in that manner do not mark, therefore, the true time; they mark what one may call the local time, so that one of them goes slow on the other. It matters little, since we have no means of perceiving it.This is what Alice see's from the stationary system.
I mean the entire theory, not one little part of it. The theory only uses empirical premises. No assumptions.OK, well then you aren't discussing RoS bcos RoS is part of one interpretation and not part of the others, so it by way of logical necessity, cannot be derived from the "raw" mathematics.
You use the term "non-empirical" as though it means something other than "assumption".QuoteIf both are referred to as SR theory, then SR theory cannot imply relativity of simultaneity because simultaneity is absolute in the absolutist interpretation.Again, it uses a non-empirical convention to conclude that.
It deduces RoS using the empirical convention to define simultaneity.Is it an empirical convention or a non-empirical convention? Either way, you are now in the domain of interpretation.
It doesn't imply it. One is free to choose a different convention, but the convention is not a physical or metaphysical assumption of any sort. Some interpretations use a different convention, but those are usually not empirical conventions, but rather based on a non-empirical assumption. That different kind of simultaneity may or may not be relative, but being based on an assumed premise, that kind of simultaneity becomes assumed and not testable.You seem to be a bit all over the place here. Is RoS derived from the "raw" mathematics or is it derived using the convention of one of the interpretations and therefore not part of the "raw" theory? I'll give you a hint, it's the latter.
standard formulations of the Special Theory of Relativity involve an assumption that is not even in principle testable if the rest of the theory is true: the status of the One-Way Light Principle will be that of a gratuitous metaphysical assumption.
Not talking about Einstein's interpretation because I don't have a list of his additional premises, so I'm going with just his theory sans additional premises.Then you're arguing a strawman again, bcoss RoS is an interpretational artefact based on an "assumed premise", a "metaphysical assumption". It's not derived from the "raw" mathematics bcos if it were, it would form part of all interpretations and not just one!
No it isn't. It is a consequence of the theory upon which the interpretation is based. An empirical consequence of an interpretation would be an additional prediction not made by the underlying theory. If one were to exist, the 'interpretation' would cease to be an interpretation by definition.Perhaps that is why people refer to them as Einstein's theory of Special Relativity and Lorentz-Poincare theory. Bcos, in case you hadn't noticed, they do make some pretty different predictions, it just appears as though they are not testable.
A mark on the floor does not designate a location since no definition of the floor being stationary has been established. A coordinate system is required to do that, and 'Clock A' makes no reference at all to that essential coordinate system. Thus no empirical conclusion can be drawn about Clock A, but one can be made about 'Clock at A'.There's that word "stationary" again. Relative to what, would you like to say the physical floor of the spaceship is "stationary"?
1) Any experiment (twins, H-K) anything at all, can be done and analyzed in any frame. It doesn't change the result. 2) Mohammad need not stop at the mountain any more than the mountain need stop at Mohammed.Yep, can be done in any frame, but it must be done in the same frame. Specifying which reference frame doesn't need to undergo acceleration/deceleration privileges it. Any frame can be chosen, but just you try and accelerate the Earth all the way to another where the other "twin" is. That any frame can be chosen shows that it isn't all that privileged.
Rotate the system until you find the direction in which the one-way speed of light is not constant. There you go, implied isotropy demonstrated.The convention depends on the isotropic one-way speed of light reltive to all co-ordinate systems. That is only part off the SR interpretation.That would be an interpretational assumption. No, it doesn't assume that. The convention is simply established by definition. That's what a convention is.
Wrong. Subtracting the values and getting identical figures demonstrates that the clocks at those locations are in sync, by the established convention. Your counter examples use a different convention, but no claims about those other conventions have been made.Ooops, youre back to assuming that Alice is an
By using the method described by Einstein. Are you suggesting I'm referring to different events than the ones where these physical occurrences take place?You're here, the clocks are over there. You send a light signal from here to there. How can you determine empirically, when the light signals arrive "over there"? How can you determine that the arrival of the light signals to the clocks "over there" coincide with the reading [d/c] on your clock C0?
Or are you suggesting that no such event exists and the light was intercepted or something? I am admittedly assume that the latter is not occurring, but there are interpretations that suggest exactly that. The events you describe represent counterfactuals, which, under certain interpretations, do not exist until measured at a later time. Einstein's comment about the moon not existing if not observed was along the lines of denial of the principle of counterfactual definiteness. Since I'm avoiding metaphysical assumptions, I cannot assume that one.
By corresponding, I mean empirical correspondence, as SR is an empirical theory. If you argue it doesn't do this, then you claim a falsification test. But I think you simply claim it doesn't correspond to metaphysical reality, which is fine since SR is a scientific theory and makes no metaphysical claims about the underlying reality. Reality indeed has no correspondence to a theory that is mute on the subject.You've just been arguing how SR is an abstract mathematical theory to which the rules of empiricism do not apply. Now you are stating that it is an empirical theory, which claims emprical correspondence. Therefore, we are back in the domain of empiricism where the rules of empiricism apply.
The abstract claim is based on the one-way speed of light.Then the interpretation you're comparing is a different one than I am using. Conclude what you wish about it. My Alice is utilizing the theory which makes no such assumption.
If the contention is that the co-ordinate reference system in no way represents the physical world, then there is no issue.No assertion about the coordinate system representing the real world is made. Any such assertion would be an additional premise, and I've made none.
The sourse of the misunderstanding is that you cannot recognise that the abstract mathematical claim is a claim about a physical system.I don't recognize it because I am making no such claim. You insisting that I am making this claim commits the strawman fallacy. I'm not defending an interpretation that makes such a claim.
If it remains in the abstract mathematical domain and isn't put forward as a model of the pyhsical system, that is, if it is stated categorically that it does not represent an accurate model of the physical world, then yes it is a purely abstract claim.I didn't say it does not represent an accurate model of the physical world. Such a statement would be a physical claim, and I'm not making one. I simply said I've made no claim that it represents an accurate model of the physical world. It may or may not be accurate. Nobody can know.
You're assuming the validity of the convention, which is not a given.I is a pure mathematical convention. If you can find an error in the mathematics, be my guest and point it out. Else you've no grounds for a claim of it being invalid.
Then the interpretation you're comparing is a different one than I am using. Conclude what you wish about it. My Alice is utilizing the theory which makes no such assumption.You're discussing RoS. RoS is derived from the mathematis + the metaphysical assumption about the isotropic one-way speed of light relative to all reference frames.
No assertion about the coordinate system representing the real world is made. Any such assertion would be an additional premise, and I've made none.See the post addressing "empirical correspondence"
Does the "raw" mathematical theory correspond empirically to the physical world?QuoteThe sourse of the misunderstanding is that you cannot recognise that the abstract mathematical claim is a claim about a physical system.I don't recognize it because I am making no such claim. You insisting that I am making this claim commits the strawman fallacy. I'm not defending an interpretation that makes such a claim.
I didn't say it does not represent an accurate model of the physical world. Such a statement would be a physical claim, and I'm not making one. I simply said I've made no claim that it represents an accurate model of the physical world. It may or may not be accurate. Nobody can know.So, no one can know if a model of the world which incorporates RoS is an accurate model of the world?
I is a pure mathematical convention. If you can find an error in the mathematics, be my guest and point it out. Else you've no grounds for a claim of it being invalid.It makes reference to light signals which are not "purely mathematical". They may be represented mathematically, but they are not"purely" mathematical.
It wouldn't be a specific prediction, but it would be a prediction of a sort had I (and others) asserted that.Quote from: HalcA statement is not a prediction. A prediction is an anticipated result of a measurement. The word implies the measurement has not yet been performed.If the one-way speed of light can be measured - a proposition you and others seem to be optimisic about - then it represents a prediction.
If the one-way speed of light cannot be measured, then the simultaneity of clock syncing events is an untestable prediction.Not true if the convention by which the simultaneity is measured does not depend on an untestable metaphysical assumption like that. This is the most trivial logic you're failing here.
That's the problem with counterfactuals: they produce untestable conclusions. It's one of the primary reason the alternate interpretations are less mainstream.QuoteWhen the causal effect of interest is ill defined, the counterfactual theory of causal inference from observational data and the elegant statistical methods derived from it lead to predictions that are untestable.//academic.oup.com/aje/article-abstract/162/7/618/204321
All local comparisons are made in all frames, so this doesn't make syntactic sense. It is not possible to exit a frame.A local comparison is not frame dependent. That comparison can be (and was) done in any frame. It isn't possible to not be in the other frames. H-K beginning and end events were not done by equipment that was stationary in the same frame as each other. It was an unnecessary requirement and no care was taken to do so. Likewise with the twins at both ends of the journey. The requirement is that they be together. That's all. Comparisons are objective if they're local. I suppose mass comparisons are not.I didn't say it was frame dependent, I said that it privileges the reference frame in which the local comparison is made.
The H-K comparison was done in the "at rest relative to the Earth frame", where the Airplanes had to accelerate and decelerate to come to be at rest reltive to the earth. It wouldn't have been practical to accelerate and decelerate the Earth while the airplane was in the air - as I'm sure you understand.I disagree with all of this. OK, the comparison was done in all frames, the Earth one included. At no point was the equipment stationary relative to Earth, only to the Earth's local surface, which is a different inertial frame at every point on the surface*. There were at least 4 comparisons, all done at different locations on that surface, so each of the 4 was performed using equipment stationary in different inertial frames. Coupled with that, the surface of the Earth very much was accelerated while the aircraft was aloft, more so than was one of the aircraft. It is quite practical to do so, and actually rather impractical to prevent. The least accelerated aircraft (the one that accelerated less than the surface below it, as measured by moment of acceleration) logged a larger time than the ground one. The aircraft that accelerated more (by the same metric) logged less time. The former difference was larger than the latter difference. SR predicted these results, but also predicted that the differences would be more similar. GR explains the discrepancy.
This is from the Pablo Acuna paper I have referenced several times:No thanks on the paper. I find it ironic that he discards the ether (a counterfactual) by invoking Occam (which I applaud, it being my reasoning as well) but then violates this by retaining the privileged frame, another couterfactual. That's OK. I've not been working with the ether ever in any of my posts in this thread.QuoteIf we apply Occam‘s razor and excise the ether from Lorentz‘s theory, what we obtain is not special relativity. It is still possible to retain the Newtonian space-time plus conspiring dynamical effects by defining by fiat a privileged reference frame. For example, the Lorentzian could baldly say that the privileged frame is the one in which the real time is measured, period.On the Empirical Equivalence between Special Relativity and Lorentz’s Ether Theory by Pablo Acuna. I can send a copy of the paper if you like.
So, as you can see the privileged reference frame can be any reference frame where "real time" is defined, it isn't a requirement that it be the absolute rest frame.The thing you took from that quote is the one thing he says is stated badly??
The context of this comment is lost, but accelerated frames is a term (ARF, as opposed to IRF). I've not heard the term 'inertial coordinate frame', and don't know how it is distinct from a regular inertial frame. The term doesn't sound like something that implies acceleration.Quote from: HalcAn inertial frame cannot be accelerated. An accelerated frame can, but it has different properties.A spaceship represents an inertial frame - perhaps you mean inertial co-orddinate frame - a spaceship can be accelerated.
So, if you say you are comparing the "raw theory" to the mathematics of the absolute interpretation, then you are in actual fact not comparing one thing to another, because there is only one thing and no other. It's the same mathematics for both.I'm not. I'm comparing the conclusions of the raw theory with the conclusions (not just the empirical ones) of an absolute interpretation of that theory.
If you are comparing the "raw theory" to the absolute interpretation (not just the mathematics) then you are comparing apples to oranges. You need to be comparing one interpretation to the other.OK, I called it the raw interpretation, the one that posits no counterfactuals (such as one way speed of light, since that seems important to you). Now it's an interpretation. Apples to apples. I think the absolute interpretation adds considerable mathematics to deal with the additions it posits, but none of that mathematics contradicts the raw interpretation since it all concerns concepts undefined in that interpretation.
Context gone from this, so not sure what interpretations were being referenced here. You didn't specify a test, so it's an interpretation. An assertion is not a test.Quote from: HalcNeither a theory. If either is a theory, what prediction does it make? It's an interpretation until it has a falsification test.I quoted the prediction it makes, it predicts that the one-way speed of light is not isotropic relative to all reference frames. Esseentially, it predicts that, if the one-way speed of light can be measured then absolute motion could be determined. If the one-way speed of light is found to be isotropic relative to all inertial frames, the theory is falsified.
I do. I see that you cannot read. See the bolded part. Roemer was not measuring the one way speed of light, despite your continuous reference to it to refute what he was actually doing, which is the italicized part.Quote from: HalcI persisted with it because you suggested that he cannot have done what he did (which was measuring light speed utilizing a one-way method, not measuring the one-way speed of light).And I repeat, measuring the one-way speed of light requires the syncing of two spatially separated clocks, which requires an accurate measurement of the one-way speed of light which requires the syncing of two spatially separated clocks, which requires a an accurate measurement of the one-way speed of light which requires.....
see where I'm going with this?
Impressively well. He measured a many month duration within an accuracy of 5 minutes using 17th century technology.Quote from: HalcYou still deny it! This is the 2nd reason why I didn't let it drop. SR says the method is valid and should yield exactly c. The theory says that, not any interpretation. It follows trivially from the empirical premises of SR. If your interpretation denies this, it is wrong.SR says Romers method is valid and should yield exactly c? How did that work out can you tell me?
Since he gave an empirical method to verify it, your understanding is wrong. It's like talking to a child. I'm getting behind in my posts because you seem to not understand even the simplest concepts.Quote from: HalcWhat do you think a convention is? Is that another word that is going to get redefined?In the context of Einstein's sync convention it means something which is established without being empirical verified/verifiable.
If I'm measuring Usain Bolt's speed as he runs the 100m and I use imprecise methods of time keeping and get a value 25% less than the official Olympic measurement, have I really measured Usain Bolt's speed? Or have I just arrived at some value that doesn't actually represent his speed?Depends on the convention of time keeping you choose to use, but I agree that a comparison between measurement taken via different conventions are meaningless, neither conflicting with the other.
Would I have a better chance of measuring his speed if I could use and sync two spatially separated clocks - one at the starting line and one at the finish line?One requires a coordinate system to do that. One is typically presumed, but since we're being precise, I'm pointing it out. One can posit speed to be a property and not require a coordinate system, but then your methods as described don't work. The method you suggest requires an abstract coordinate system.
Again with the inability to read.Quote from: HalcIf you could meausre 1WSoL, yes, but that doesn't mean that SoL cannot be measured using a one way method. If it yields c every time (as PoR say it must), then no absolute motion can be detected. Tooley is quite right about this.If you can propose a method of measuring the 1WSoL that doesn't require the syncing of spatially separated clocks (by convention) or that doesn't make assumptions pertaining to the rigidy of the bodies used in the measurement, then fame and notoriety await you.
Tooley's point is that any philosophical reason for favoring Einstein's interpretation over an interpretation based on an absolute reference frame is rendered null and void, because the testing of the 1WSoL represents the falsification test for both.That is but one reason to not choose interpretation over the other. There are other philosophical reasons, and some of these very much favor one interpretation or the other. Your choice might depend heavily on which reasons carry more weight with you.
We might be talking about slightly different things here. I'm talking about the idea that an interpretation of relativity that incorporates an absolute reference frame - with two frames moving relatively to that, where the Lorentz Transformation is used between the absolutely moving frames - does not predict reciprocal time dilation the way Einstein's interpretation does. In the absolute interpretations both Alice and Bob's clocks are slowed.As does Einstein's interpretation when considered from any 3rd frame, be it labeled absolute or not. I see no difference.
If it were a simple case of comparing the two clocks without needing to reuinite them, Alice would see the photon in her light clock travel the perpendicular distance between the mirrors of her light clock, while she would see the photon in Bob's clock travel the longer perpendicular distance.Not sure of the scenario here, but you're talking about separated events occurring 'at the same instant' without defining a frame in which that assessment is taken. Relative to some 3rd frame (be it absolute or not), if Alice and Bob's systems (light clocks now?) are moving at the same speed but different velocities, this would be true, but you haven't specified all that clearly.
The critical difference is that the duration of both would be the same. That is, the photon in Alice's clock would reach the opposite mirror at the same instant as it does in Bob's clock.
From this Alice would either conclude that the photon travels faster in Bob's clock or that the photon in her clock actually travels the longer distance too.She's using a different coordinate system and making a different abstract conclusion.
It is the need to reuinte the measurement instruments which circumvents this fact and which reduces it to the kind of privileged reference frame theory I have been "redefininig". The same is true for Einstein's interpretation.Reuniting is fine, but then your interpretation cannot be used for any situation where such a thing is not practical, such as scheduling of interplanetary commerce without collisions. They had this problem with railroads, and real trains were wrecked due to lack of model that based on more than one location. The train people thus were the first to adopt widespread use of standard clocks and worldwide time zones as opposed so locally defined ones.
Rates are not being compared. The reading (one value) on each clock is being taken, and a common frame is not required to do that.A comparison of respective elapsed time has nothing to do with the tick rates of either clock. You read what each clock says and subtract. The rates of the clocks play no rote in that calculation.Alice and Bob moving relative to each other. Alice sees Bob's clock running slow. Bob sees Alice's clock running slow.
How do you compare clocks on the fly to show that Alice's clock runs slower than Bob's and that Bob's clock runs slower than Alice's?
So, in the H-K experiment the clocks aren't brought back together to a position at rest relative to the Earth?Relative to the local surface at the time, yes, not the frame of Earth ever and not the same as the frame of other events where the readings were taken (four in all, all different frames).
I presume you mean that she cannot determine that she, along with the spaceship and everything on board, remains at the same location, yes?She can because she's selected a coordinate system where this is true. That makes her items at known locations.
It would appear that the issue lies in your mispprehension of the idea that RoS is part of the "raw" mathematics of the theory.It is part of both interpretation. The absolutists might choose not to use that one as much, but it's there in the toolkit. Alice's conclusion is still valid given the absolute interpretation. She just didn't make any absolute statement about the sync of her clocks.
The problem is that it isn't. The reason we can deduce that it isn't derived from the "raw" mathematics is bcos it forms part of one interpretation but doesn't form part of the other. If it was part of the "raw theory" i.e. the mathematics it would, by necessity, form part of both interpretations.
Under SR, you're right. I stand corrected. I've even made posts to that effect, so I contradicted myself there.Poincare derived RoS before anybody else, but their interpretation uses a different convention to define simultaneity. Einstein used an empirical convention. Lorentz-Poincare does not.Quote from: UAIn a contribution for a volume celebrating the 25th anniversary of Lorentz‘s doctorate, Poincaré explained his point by means of an illustration that strikingly resembles Einstein‘s method for the synchronization of clocks. He showed that if two observers at rest with respect to each other, but in motion with respect to the ether, try to synchronize their clocks by means of light pulses, the result is that their synchronized clocks are late with respect to the real time.His convention to define simultaneity is, in effect, the same as Einstein's. Indeed, it is indiscgernible from Einstein's treatment of cco-ordinate systems.
Imagine Poincare starting with the absolute reference frame, then adding one relatively moving inertial frame. Now stop. You've got something that is indiscernible from Einstein's treatment of co-ordinate systems.Well, it has that absolute frame that Einstein's didn't, which seems discernible. Einstein just treats it like just another frame. That's a weak statement since the absolute frame is most often (but not always) posited to not be an inertial one. It doesn't need to be, but typically it is none of the usual inertial, rotating, or accelerated reference frame. They instead use (for the absolute 'frame') what might be called a comoving foliation which requires a different sync convention than the one suggested by Einstein. Under this (most typical) interpretation, I have Alice with her clock and Bob with his, both at equal gravitational potentials. They are both stationary (absolutely), but not local. Their clocks are in sync. Alice sends a signal at T1 (on her clock), which is received at Bob at T2 (on his clock) and reflected back to Alice who logs T3. T3-T2 will be a larger value than T2-T1. They require a different convention to verify that their clocks are actually in sync: They both have to send signals simultaneously (at T1) and both note the T2 time when the signals are received. Then the verification has been made. Doing by reflecting doesn't work since the distance between Alice and Bob is increasing despite them both being stationary. Such is the nature of the comoving foliation. Space is expanding under GR, but not under SR.
I notice both signals are sent at time 0, which works even in an expanding universe, so long as the clocks are close enough. Of course if the time pieces need adjusting, the procedure does not suffice to actually get them in sync. Yes, he mentions the stations needing to be fixed (at a location) and a coordinate systems is needed to do that. I presume he's using the preferred coordinate system above, but it isn't stated. Maybe we're still taking about the example where these guys are not at fixed locations. The author is being sloppy. This seems to be a pop publication, not a scientific one.QuoteImagine two observers who wish to adjust their watches by optics signals; they exchange signals, but as they know that the transmission of light is not instantaneous, they take care to cross them. When the station B perceives the signal from the station A, its clock should not mark the same hour as that of station A at the moment of sending the signal, but this hour augmented by a constant representing the duration of the transmission. Suppose, for example, that the station A sends its signal when its clock marks the hour 0, and that the station B perceives it when its clock marks the hour t. The clocks are adjusted if the slowness equal to t represents the duration of the transmission, and to verify it the station B sends in turn a signal when its clock marks 0; then the station A should perceive it when its clock marks t. The time pieces are then adjusted. And in fact, they mark the same hour at the same physical instant, but on one condition, namely, that the two stations are fixedChange station A and Station B for Clock at A and Clock at B and you've effectively got Einsein's sync convention. This is in Alice's "stationary system".
Not necessarily. Hard to follow what exactly this scenario speaks of, but UA says the one watch 'goes slow on the other' (a wording I suspect Poincare would never use) which implies relative motion between the two. Alice's clocks are stationary relative to each other and neither 'goes slow on the other'. Maybe he just means they're not actually in sync, in which case yes, it is pretty much Alice's scenario. Funny way to say they're not in sync. It is worded like a dilation statement.QuoteIn the contrary case the duration of the transmission will not be the same in the two senses, since the station A, for example, moves forward to meet the optical perturbation emanating from B, while the station B flies away before the perturbation emanating from A. The watches adjusted in that manner do not mark, therefore, the true time; they mark what one may call the local time, so that one of them goes slow on the other. It matters little, since we have no means of perceiving it.This is what Alice see's from the stationary system.
Now, imagine that neither Alice nor Bob is in the absolute rest frame, both are moving relative to it. What do you think will be the case there?You mean they're not at rest in that frame. They cannot be 'not in it'. Don't know what you mean by what I think will be the case there. I thought it was the case being discussed already. The two clocks are watches on separate observers. The Alice case has one observer (Alice) and her two clocks. What Alice is doing is irrelevant. The clocks record the times of the various events. UA puts watches on people so the clocks track the observer wherever they go, so he needs more observers to get the required number of watches in play. The observers however play no role, so we don't even need them or Alice.
You use the term "non-empirical" as though it means something other than "assumption".OK, first of all, I misstated that, as you point out above. The same convention is used, but different coordinate systems are selected. The interpretations both have RoS: The abstract notion of clocks being in sync relative to an abstract coordinate system is still dependent on the coordinate system. But an absolute interpretation selects only one of those coordinate systems (or a different kind of coordinate system altogether) as being the one corresponding to reality, so actual time corresponds only to that one coordinate system and not the others, hence actual simultaneity is absolute. Yes, it is based on the premise of reality corresponding to one such coordinate system (by virtue of the ether or something else), and lacking a way to detect it, that makes said premise an assumption.
Are you now saying that the one-way speed of light cannot be measured?I've repeated over and over that I agree that it cannot.
You sounded pretty optimistic earlier that it couldThen you didn't read what I said. I said the speed of light can be (and has been) measured via a one-way method. That's a different claim than being able to measure the one-way speed of light.
The thing you quoted says directly. You're giving me serious doubts that you read my posts at all. Maybe you're just a contradicting-bot.Quote from: HalcIt deduces RoS using the empirical convention to define simultaneity.Is it an empirical convention or a non-empirical convention?
Is RoS derived from the "raw" mathematics or is it derived using the convention of one of the interpretations and therefore not part of the "raw" theory?The convention is defined by the theory, not by any interpretation of it. RoS is derived utilizing that defined convention, and not utilizing any assumptions that some interpretation might add.
Also, with regard to the convention being an assumption (of any kind).Definitions are not assumptions. They are just that: definitions.
standard formulations of the Special Theory of Relativity involve an assumption that is not even in principle testable if the rest of the theory is true: the status of the One-Way Light Principle will be that of a gratuitous metaphysical assumption.Yes, standard formulations typically assume it. UA I see assumes it above, as presumably does Poincare. But I'm leaving it off because I said my raw interpretation makes no metaphysical assumptions, just to illustrate what the theory itself shows.
Also, you use a term there, that I'm not familiar with, "non-empirical assumption". Perhaps if you tell me what the opposite of that would be, then I might better understand it.The opposite would be an empirical fact. 'It rained here today'. Constant one-way speed of light is often assumed, but barring a way to test it, it becomes a non-empirical assumption. The term is admittedly redundant.
Also, are you suggesting that the Einstein convention is not based on an assumed premise?That's right. There are premises, but being empirical, they're not assumed.
Bcos, in case you hadn't noticed, they do make some pretty different predictions, it just appears as though they are not testable.Interesting assertion. The predictions are testable, they just don't appear to be.
Relative to the abstract coordinate system we've selected.Quote from: HalcA mark on the floor does not designate a location since no definition of the floor being stationary has been established. A coordinate system is required to do that, and 'Clock A' makes no reference at all to that essential coordinate system.There's that word "stationary" again. Relative to what, would you like to say the physical floor of the spaceship is "stationary"?
Step back into the "physical-world" for a second. You're onboard Alice's ship and she calls out, "Where are you Halc?" and you answer "I'm at the point marked A on the floor". Alice now knows your location.Only if we've agreed on a coordinate system, which in this case intuitively corresponds to the ship, and would be an accelerating or rotating coordinate system if the ship was doing either of those things. The statement also usually suggests that I am reasonably stationary relative to the thing referenced. Alice isn't going to be able to find me at point A on the floor if I'm moving at several km/sec relative to it, or point A on the floor is moving at several km/sec relative to the coordinate system I've selected. Alice needs to know (or at least assume) all these things to know where I am. Else she only knows of one past event, and not where I am now.
1) Any experiment (twins, H-K) anything at all, can be done and analyzed in any frame. It doesn't change the result. 2) Mohammad need not stop at the mountain any more than the mountain need stop at Mohammed.Yep, can be done in any frame, but it must be done in the same frame.[/quote]Disagree. Kindly provide an example where the result is incorrect due to a pair of measurements not being done in the same frame. It needs to be something that can be objectively measured like the value displayed by a clock or the mark on the floor getting noted. Your prior attempted example was a clock rate, but no clock displays its rate. The rate is an abstract value, computed, not objectively measured.
Specifying which reference frame doesn't need to undergo acceleration/deceleration privileges it.I agree that given a pair of events separated in a time-like manner, there is but one inertial frame where those two events occur at the same location. But measurements taken at those events do not need to be done using equipment that is stationary in that frame or stationary relative to other equipment, and any experiment that involves more than 2 events likely has no frame that puts all the events in the same place, thus no such frame may suggest itself. I gave an example of that, and of course got this repeated assertion instead of a response to my example. No progress is made again.
You're here, the clocks are over there.We've not established either fact. Both I and the clocks are straight worldlines, and while I've taken some measurements an determined some relations concerning some known events (points along those worldlines), it is too early to presume that there is a 'here' or 'over there' at which anything in fact is, or at least at which it is remaining.
You send a light signal from here to there.I send a light signal from one event to another. That's a relation, but the signal is sent from/to a pair of events, not from/to a here or there. So a signal goes from A to C.
How can you determine empirically, when the light signals arrive "over there"?That's been the question, hasn't it? It depends on if we're discussing apples (the abstract map, the paper plate) or oranges (reality). The RoS is true for apples, but differently defined for oranges, depending on the premises assumed for reality. So for oranges, RoS is indeed not necessarily true.
How can you determine that the arrival of the light signals to the clocks "over there" coincide with the reading [d/c] on your clock C0?
Are you saying that the clocks and light signals "over there" are not over there bcos you can't see them? Bcos that is what your analogy implies.I've not given my personal interpretation opinion on this thread. I am discussing a blank interpretation that makes no assumption. I do hold personal assumptions, so I've not been discussing my personal view.
If the moon is stil there when you look awayThat's a topic for QM interpretations, not relativity interpretations.
I'm gonna be offline again, for at least 2 weeks (more meditation).Gives me a chance to catch up.
I'll leave you with this one. I felt it deserved a separate post of its own.Quote from: HalcBy corresponding, I mean empirical correspondence, as SR is an empirical theory. If you argue it doesn't do this, then you claim a falsification test. But I think you simply claim it doesn't correspond to metaphysical reality, which is fine since SR is a scientific theory and makes no metaphysical claims about the underlying reality. Reality indeed has no correspondence to a theory that is mute on the subject.