I The invariance of the speed of light is not only a hypothesis?

[externo]

Einstein disagrees with you.

I think Einstein thought it was a physical reality.

Reichenbach is non-isotropic. That is exactly what I would assume (although I would use Anderson’s approach).

It's a convention, it's not a natural isotropy that depends on relative velocities.

How do you propose to avoid it?

Simply assuming the clocks are out of sync. If two clocks are synchronized and then they accelerate to high speed, they are out of sync, why artificially resynchronize them?

In SR postulate 2, Einstein speaks only of the invariant "speed of light in vacuum".

He does not need to distinguish there between round-trip- and one-way speed. Both have there the same value because of his clock-synchronization scheme for defining the time coordinates of the inertial reference coordinate systems.

So isotropic speed of light is only a convention.
Thus acording to you there is no Einstein's special theory of relativity, Einstein only made mathematical abstractions about relativity.
Here is my point of view : Either BU is a physical theory and it opposes LET, or it is only a convention and in this case LET is the only physical theory.

 

[Ibix]

I do no want to choose any simultaneity convention. Why do you want a simultaneity convention? How do you know there is such a thing ?

How do you tell if two clocks show the same time or not? The answer to that is a synchronisation convention. You can't not have one unless you simply refuse to look at more than one clock.

 

[Dale]

why artificially resynchronize them?

So that you can measure one way speeds with them.

Still dodging the challenge, I see. So are you going to rescind your claim or just hope I ignore your avoidance? It isn’t a bad bet, I will probably forget at some point, but by then I think the message will be clear enough anyway.

 

[Ibix]

So that you can measure one way speeds with them.

Indeed. If you don't, you could have one clock at one end of your experiment and two at the other end, all three showing different times. You could get two one way speeds out of one experiment!

 

[externo]

How do you tell if two clocks show the same time or not? The answer to that is a synchronisation convention. You can't not have one unless you simply refuse to look at more than one clock.

In fact we cannot tell if two clocks show the same time. I am quite willing to establish a convention of simultaneity, but you must not give this convention physical consequences that it does not possess.

 

[Ibix]

I am quite willing to establish a convention of simultaneity, but you must not give this convention physical consequences that it does not possess.

It has no physical consequences; it only changes your interpretation of your measurements.

 

[Sagittarius A-Star]

So isotropic speed of light is only a convention.

No, that is only correct for the one-way-speed of light. The isotropy of the two-way speed of light in vacuum is not only a convention. It was tested in the MM experiment.

Thus acording to you there is no Einstein's special theory of relativity, Einstein only made mathematical abstractions about relativity.

That' not correct, see above.

 

[Dale]

So isotropic speed of light is only a convention.
Thus acording to you there is no Einstein's special theory of relativity, Einstein only made mathematical abstractions about relativity.
Here is my point of view : Either BU is a physical theory and it opposes LET, or it is only a convention and in this case LET is the only physical theory

This is an absolutely silly objection. You object to the use of a synchronization convention in BU, and assert that the use of such a convention makes the theory only a mathematical abstraction. But your absurd solution is to push LET which not only uses the same synchronization convention but also adds an undetectable aether and a convention about which frame it is at rest. If you want to use LET that is fine, but the idea that it is somehow superior on the grounds of physicality is ridiculous. It makes all of the same assumptions as BU, plus some more.

In any case, making testable assumptions and arbitrary conventions is part of all physical theories. The idea that the existence of a convention precludes a theory from being physical displays a profound ignorance of science. But, I guess it doesn’t matter much any more.