[Bill S]

There is no such universal absolute frame

Agreed.

The absolute frame is the frame at any point where a stationary object is stationary relative to the local fabric….

So, an “absolute frame” is a local feature?  Doesn’t that seem an odd use of the term “absolute”?
 

….and where light passes that object in all directions at c relative to it.

Isn’t that; everywhere “in a vacuum and outside of any gravity well”?

so the whole universe cannot have a single absolute frame of reference…

OK with that.

….other than within an exterior space within which our space fabric is expanding

You’ve lost me.

[David Cooper]

So, an “absolute frame” is a local feature?  Doesn’t that seem an odd use of the term “absolute”?

The name "absolute frame" is historical. The word "atom" also means indivisible, but we don't trip over that as we don't base the modern definition on the name.

Isn’t that; everywhere “in a vacuum and outside of any gravity well”?

Yes.

….other than within an exterior space within which our space fabric is expanding

You’ve lost me.

There could be an absolute frame of reference in an external space which contains our space fabric where the same frame of reference applies at every location in our space fabric, but there is no such frame within our space fabric. The simplest way to understand how this is mathematically possible is to imagine our space fabric as being the surface of an expanding 3D bubble which exists within a 4D exterior space. The speed of light through the surface of the 3D bubble is the same on every part of the bubble, and it's also the same relative to the 4D exterior space. Using the 4D space, there is a universal absolute frame which governs the speed of light through the entire 3D space fabric contained in the 4D space, but the frames of reference in the 3D space are all curved, so the absolute 3D curved frame at one point in the bubble is not the same frame as the absolute 3D curved frame at any other point.

[alancalverd]

Wow - you're still clinging to that old mistake after all this time! Have you still not bothered to crunch the numbers in the way LET tells you you should so that you take into account length contraction (caused by the phenomenon of relativistic mass) and clocks being slowed by their movement through space (due to the lengthened round-trip communication distances)? When you do that, you find that no experiment will be capable of detecting any difference no matter how widely the one-way speed of light varies relative to the apparatus in opposite directions.

The classic undergraduate experiment only uses one clock, which has no idea where the light is coming from or going to.

Maxwell's equations demonstrate c to be constant from first principles of electrodynamics, which don't involve light or motion at all.

[Bill S]

Don't let what I say sway you. Challenge me!

I can't promise not to let what you say "sway" me.  I respect your views.  However, I'll not be slow to challenge anything, as long as I understand enough to launch a  reasonable challenge. 

[alancalverd]

AFAIK the entire concept of length contraction, time dilation etc arises from the premise that c is independent of direction, so you can't use relativity to suggest that c isn't independent of direction, and any experiment that confirms a relativistic prediction implies that c is indeed constant.

[David Cooper]

The classic undergraduate experiment only uses one clock, which has no idea where the light is coming from or going to.

Which experiment?

Maxwell's equations demonstrate c to be constant from first principles of electrodynamics, which don't involve light or motion at all.

We've covered this before - your measurements of the distances that have to be fed into the equations have to be made in relation to a specific frame of reference, and the answers that you get out of it then assert that the frame you chose has light moving at c relative to it in all directions, but all that's happening is that you're getting the same frame back that you fed in through your distance measurements. The real distances vary depending on whether you're moving or not - we aren't dealing with a static system here, but forces which act at speed c across a distance, and that distance varies depending on how far the force carriers actually have to travel through space to complete the trip. A naive understanding (i.e. a misunderstanding) of what you're doing when you measure these distances leads to you generating incorrect conclusions, and having made this error here, you extend it to every other case and blind yourself to the reality that you cannot measure the speed of light relative to any apparatus in a single direction, and that the actual relative speeds can vary.

AFAIK the entire concept of length contraction, time dilation etc arises from the premise that c is independent of direction, so you can't use relativity to suggest that c isn't independent of direction, and any experiment that confirms a relativistic prediction implies that c is indeed constant.

The concept of length contraction came out of the result of the MMX and it led to Lorentz's relativity (LET). The "time dilation" again comes out of measurements based on the application of LET, so in both cases these come from relativity and are based on c being able to vary relative to the apparatus. All the experiments produce results fully compatible with LET.

[yor_on]

What one can say David is taking the idea of a spatial measurement (e.g a distance) as something unchangingly given may not be the best of ideas. According to relativity a  'rod' one find a length too, will be a result of ones frame of reference relative whatever frame the rod is in. The same goes for 'relative speeds'. In Relativity you have two kinds, uniform motion and accelerations. Both will have a impact on ones definition of the length of that rod.

Then you have 'being at rest' which creates a system in where, let's use the MMX https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment , in where the mirrors are at rest with each other.

what sort of conclusions one can draw from that one is that no matter what 'relative speed' we might want to give Earth 'moving' with the solar system through the universe, the turning table they used showed no difference of 'speed of light' for that experiment. And that's the most interesting thing as it gives us a 'constant' called 'c'.

it's a constant
=

The whole point of something 'being at rest', as this 'system of mirrors' the MMX used, is that you now can disregard any question of 'distance'. It doesn't matter as long as they don't move relative each other. The 'system' is in a same frame of reference. But the Earth on which it was mounted has 'relative speeds', and depending on what you choose to measure it against, the sun, the galactic 'center', whatever, you then find different 'relative motions'. If that mattered the speed of light wouldn't be a constant.

[guest4091]

This is dead and buried. The one way speed of light is always 'c'.

Yet it keeps appearing, like sightings of Elvis!

[guest4091]

AFAIK the entire concept of length contraction, time dilation etc arises from the premise that c is independent of direction, so you can't use relativity to suggest that c isn't independent of direction, and any experiment that confirms a relativistic prediction implies that c is indeed constant.

May I add,independent of direction, implies independent of the source.

[David Cooper]

If that mattered the speed of light wouldn't be a constant.

It isn't a constant - the constant is merely the measured speed of light and not the actual speed of light.

[David Cooper]

This is dead and buried. The one way speed of light is always 'c'.

Yet it keeps appearing, like sightings of Elvis!

It keeps appearing because people keep making unsound assertions about the one way speed of light always being c, and they're basing that on experiments that fail to prove what's being claimed of them. No experiment has ever shown anything about the the speed of light in a single direction relative to the apparatus other than that it's somewhere between 2c and -2c.

What is it with people that they ignore a proof that goes against their beliefs? Which part of my analysis of the MGP experiment don't they understand? We have a ring of fibre optic cable being rotated round the centre of the ring such that the light doing a complete circuit of the loop travels faster relative to the material of the cable in one direction than the other. We can make it red light going clockwise through the ring and blue light going anticlockwise while the ring rotates anticlockwise, so the red light is moving faster relative to that material of the ring than the blue light. It doesn't matter if the ring is stationary on average or moving through space at any speed you care to name; on average, the red light is moving faster through each part of the ring than the blue light relative to the material there. Any attempt to make them equal conflicts with the result of MGP.

How do Einsteinists defend against this? They make up bogus rules about rotating frames of reference which are incompatible with the rules of non-rotating frames, and then they never bother to check to see if they're compatible or not. They aren't compatible - I showed that by mapping the inertial circuit to a non-inertial circuit and explained why the rules of non-rotating frames have to apply to rotating frames too without producing contradictions: the two frames would have to be compatible for the rotating frame rules to be valid. They aren't compatible though, so the rules for the rotating frame are not valid. The speed of light relative to an object has thus been proved to be different in different directions in such cases (and by extension, in most cases), and SR has been mathematically disproved. None of you have been able to take this on to try to show where my proof fails. If you've drawn a blank, why not call in the mathematicians and then we can bury SR officially and rescue physics from its biggest mistake.

[guest4091]

The concept of length contraction came out of the result of the MMX and it led to Lorentz's relativity (LET). The "time dilation" again comes out of measurements based on the application of LET, so in both cases these come from relativity and are based on c being able to vary relative to the apparatus. All the experiments produce results fully compatible with LET.

The concept of lc was developed by Lorentz and Heaviside about 1888. Fitzgerald suggested the idea as a solution for the MMx. The coordinate transformations CT, were deveoped by Lorentz based on an unobservable ether. The identical CT were developed by Einstein without an ether.
They both produce the same results, with light speed being measured as c.

[guest4091]

Can we measure the one way speed of light
part 1

Let's examine the simplest argument first.
Since matter in motion is restricted to <c, a single observer cannot be present at both the emission event and detection event of a light signal, for a 1-way path. 

We can consider the 1905 paper, par. 1, and substitute (our events) where Einstein considers an A-time for A (local emission), and a B-time for B (remote detection), but no common time. He then introduces his synchronization convention. It's critical to any argument concerning c, that the 2-way path, using synchronized clocks (c1 and c2) is symmetrical by definition. Observer A, who perceives a pseudo rest frame for himself (right drawing), would expect the outbound time to equal the inbound time, or equal path lengths. As the graphic shows (left drawing), the axis of simultaneity (s1-s2) is an abstract mathematical device. The A frame is actually moving parallel to the U reference frame. This is another instance of abstraction altering the identity of something. Time becomes a line, and all lines are equal, and to some, the lines become reality .

Notice the 2-way light path for +x (0,s2,D) is the same length as for -x, but with the long and short parts in reverse order. If light speed varied for the long part, the time would vary equally for both + and - directions, and thus be undetectable.

clock synch.gif (7.92 kB . 1005x457 - viewed 1985 times)

[guest4091]

can we measure the one way speed of light
part 2
And then there's Newton.
Newton's first rule (no one knows the law) of motion: "A body remains at rest, or if in motion, remains in motion at a constant speed in a straight line, unless acted upon by an external force."
Here Newton, in typical two valued logic, defines 'rest' and 'motion' as opposites/complements, eg., light-dark, hot-cold, sweet-sour, etc. The earth and its population are moving relative to the sun at approx. 30 km/sec, yet we never consider this in our daily activities. The point is, we are at rest relative to the earth, yet simultaneously in motion relative to the sun. It seems a contradiction of terms.
If Newton's first rule is modified to: "A body is at rest relative to second body, if both have the same velocity", then all bodies are in motion, and rest is just a special case of motion. It works well in a dynamic universe.
The purpose of this idea is to avoid the need to search for the elusive 'absolute rest frame'.
Motion is quantifiable via the definitions for velocity, "the rate of change of position and direction, per unit of time". Rest is not quantifiable. Object 1 can have greater speed than object 2, but cannot have more or less 'rest' than object 2. Complementary properties are measured indirectly. From the examples above, the value of darkness can be expressed as a standard d, minus the value of detected light, dryness depends on the measurable value of wetness. etc. This is a form of "fuzzy logic", a scale of gradations vs an 'all or nothing'/ 'black or white' logic.
Science can only study things it can measure, which excludes 'rest'.

[yor_on]

David, you have to differ between the actual experiment and the abstractions you might infer from it.  " It isn't a constant - the constant is merely the measured speed of light and not the actual speed of light. "


If you have a experiment testing the speed of light, and there are several, and you find it (and every ones else experiments) to give you a same result, then that is a fact.

[yor_on]

The rest of it is actually open for interpretations still, as long as you can fit it to the experiments. Myself I like the idea of light not 'propagating' at all, instead being emanations in a 'field'. But that doesn't mean I know how to test that idea, and prove it :) I just think it might fit. If you really expect yourself to have a experiment proving different speeds of light you should construct it and then present your results.

[David Cooper]

David, you have to differ between the actual experiment and the abstractions you might infer from it.

I agree - if you do the experiments and then build conclusions based on the results where you apply bad reasoning and state that you've measured the one-way speed of light and that the figure you've produced actually is the speed of light relative to the apparatus, you have departed from science.

If you have a experiment testing the speed of light, and there are several, and you find it (and every ones else experiments) to give you a same result, then that is a fact.

Yes - it's a fact that you've produced the same value, if that's what you've done, but in all those cases you're building an assumption of being stationary into your experiment which your experiment is then handing back to you at the end. If you do the experiment based on a different initial assumption, guess what: you get different numbers back for the speed of light relative to the apparatus, but you've completely ignored that.

If you really expect yourself to have a experiment proving different speeds of light you should construct it and then present your results.

I've already pointed to Michelson-Gale-Pearson which does exactly that.

[yor_on]

what you're doing there David is to go out from a 'whole undividable universe'  in where objects must have a defined speed. Relativity does not do that. You can do it as a presumption, but then you also need to refute the experiments relativity use, at least reinterpret them in a way that builds a logic.
=

What's funny about relativity is that almost everyone I've seen do the same, defending it. And it comes from a presumption, not a fact. What Relativity state is that it's observer dependent, it's not a 'whole undividable universe' in that sense at all

[guest4091]

The coordinate transformations reduce to
x’ = γx, and t’ =γt.
Thus speed = distance/time.
If x/t = c, then x’/t’ = x/t = c
The reason, motion alters perception and measurement.
This satisfies the 1st postulate of SR since the expressions using x and t are the same for all inertial frames.

[alancalverd]

Yes - it's a fact that you've produced the same value, if that's what you've done, but in all those cases you're building an assumption of being stationary into your experiment which your experiment is then handing back to you at the end. If you do the experiment based on a different initial assumption, guess what: you get different numbers back for the speed of light relative to the apparatus, but you've completely ignored that.

No. Any terrestrial experiment is conducted with the certain knowledge that we are rotating at about 0.25 degrees per second whilst orbiting the sun at godknowshowmany miles per hour and hurtling away from the center of the galaxy at a significant fraction of c whilst other galaxies are rushing about even faster.

Stationary with respect to what?

And when we bounce lasers off the moon, or radar waves off Venus, no part of the apparatus is stationary with respect to any other, but the value of c remains remarkably constant.

Come to think of it, we can measure the doppler shift of a radar or laser reflection from a body moving in a circle if we are standing outside the circle.  Now the reflector has no idea where we are but we know its radius is fixed, and so is the distance from the observer to the center of rotation, so we can calculate its speed relative to the observer in any direction at any time. Lo and behold, the doppler equation applies exactly and everywhere. So c must be constant regardless of direction.