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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.

Alice has no way of knowing which situation is the true situation - as per the Galilean Principle of Relativity.

Bob's bodycam footage provides observational evidence to the contrary.

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"

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.

Coordinate systems and references are for essential understanding measurements, be those coordinates latitude/longitude etc, so it is reasonable to introduce them.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.

Quote from: the_roosh on 11/06/2019 11:12:47Bob'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.

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.

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.

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.

They assume that it must rely on an Ether and that it can only be formulated as a dynamical theory.

Essentially, we don't need an absolute reference frame, we need a privileged referece frame that defines "true time".

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.

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.

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.

@Halc: this point needs addressing before we can proceed.Quote from: Halc on 11/06/2019 13:40:40Einstein 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.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.

I genuinely do not.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.

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.

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.

Quote from: Halc on 12/06/2019 14:53:03I genuinely do not.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.The light clock set-up is based on two clocks equidistant from the emitter, so this analogy is a misrepresentation of it.

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.

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.

Quote from: Halc 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.One must take the comment in the context in which A and B were defined as Einstein defined them.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.

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.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.

Einstein was talking about 2 spatially separated clocks A and B.

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.So, Einstein's synchronisation convention talked about two trips for the single llight signal" from1) clock A to clock B2) clock B to clock Athe 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.

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.

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.

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.So, Einstein's synchronisation convention talked about two trips for the single llight signal" from1) clock A to clock B2) clock B to clock Athe 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.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.

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"

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.

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 this

What can be demonstrated otherwise; which statement is false?

So, Einstein's synchronisation convention talked about two trips for the single llight signal" from1) clock A to clock B2) clock B to clock Athe 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.

Quote from: the_roosh on 12/06/2019 16:59:34I 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.Quote 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.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" from1) clock A to clock B2) clock B to clock Athe 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 sameThere 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.QuoteBear 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.

Does this clarification suffice: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.

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?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.

Secondly, frames do not provide coordinates, only relative ones. One needs to specify an origin to make it into a coordinate system.

QuoteDoes this clarification suffice:In the "stationary system" i.e. Alice's spaceship, Alice marks out (with chalk/spraypaint/whatever) three points A, B1 and B2.That works, sure.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.Quote from: Halc on 13/06/2019 12:16:34None. 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?

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.

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.

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.

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?

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.

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.

If B1 is distance d away from A, then C0 reads d/c at a time simultaneous with events B1 and B2.

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.

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.

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).

Alice's computation represents a mathematical prediction that needs to be verified against observations in the physical world.

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?

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.

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??

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.

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.

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.

]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.

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.

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.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.

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.

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 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.

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.

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.

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.

Quote from: Halc on 13/06/2019 20:25:16Their 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.

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.

It is a crucial prediction because the conclusion that simultaneity is relativity rests entirely upon it.

Given that it is an untestable prediction it can only be assumed to be true.

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.

Without this assumption we are left with the underlined part of the conclusion above, whic is derived from the totality of empirical evidence.

If Alice's assumption is dropped - in the face of this overwhelming evidence - the RoS simply disappears.

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.

Her calculation represents a prediction - in this case an untestable/unfalsifiable one.

Alice is required to make observations to test the predictions of the theory.

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?

The thought experiment represents a [plausible] real world experiment. As such, it allows us to make certain inferences and deductions.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.

The issue is that there will remain an alternative interpretation of those results, one which doesn't assume the Simultaneity of events.

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?

C0 is baggage.

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.

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.

Alice assumes that she lives in an SR world, but only bcos she assumes her conclusions.

How does she know it's true? It's certainly not on the basis of empirical evidence.

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.

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.

It therefore assumes its conclusion that simultaneity is relative.

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....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....[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.

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?

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.

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.

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.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....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 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 an SR 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.

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.

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.

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.

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.

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.

More like the other way around, but yes, it is sort of circular.

Alice is doing things the relative way because we're testing that interpretation via this thought experiment.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.

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.

QuoteIt 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.

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.

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.

The mathematical description is open to interpretation;

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.

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.

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?

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.

Quote from: Halc 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.

It is assumed under SR, not tested. Meaning the conclusion of RoS (in SR) is assumed.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.

That is, the first part of the conclusion is assumed (in bold above).

Without this assumption there is no conclusion of RoS - hence, it is circular, hence SR assumes its conclusion.

As you have pretty explicitly agreed that RoS is based on circular reasoning i.e. that the conclusion is 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.

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.

Albert Einstein chose a synchronization convention (see Einstein synchronization) that made the one-way speed equal to the two-way speed

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.

Quote from: Halc If 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.

Quote from: Halc 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.

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.

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 preponderance of evidence is against the assumption of Simultaneity of events in the stationary system.

Remember, as you have repeatedly stated, the Simultaneity of those events must be assumed not observered empirically.

All other observers provide empirical evidence that the events weren't simultaneous.

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

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.

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.

I've clarified this above. Alice represents us trying to determine what kind of Universe she/we live in.

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 can simply drop any assumptions about the Simultaneity of events in a stationary system.

The conclusion that simultaneity is relative requires the conclusion to be assumed.

The conclusion that it isn't relative simply require us to not make the assumption that it is.

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.