If I would define the one-way speed as non-isotropic, then the transformation formula would be come more complicated, whithout added value:
https://en.wikipedia.org/wiki/One-w...ansformations_with_anisotropic_one-way_speeds
I do not agree with that definition, but as you use it then indeed length contraction is not “real”. Nor is electrical charge, the magnetic field, the electrical field, gravity, kinetic energy, potential energy, momentum, and I am sure other things. So I am perfectly content with length contraction being not “real” with your meaning. It is in good company with lots of other important but not-“real” things.The real is that which has practical consequences and which does not depend on a convention
Nonsense. You cannot avoid making assumptions. You can only be clear on what you have assumed. By believing that you have not made any assumptions you are tricking yourself.I'm not making any assumptions
The two SR postulates are physical hypotheses.If Einstein's theory is based on a convention and not on a physical hypothesis it seems to me it has no physical value.
Closing rate between you and light does vary with your speed relative to whoever is measuring. This is true in Einsteinian relativity as well as Galilean relativity. Assuming that closing rate and relative speed are the same thing, though, is assuming Galilean relativity.I'm not making any assumptions, it's the reality of the closing speed, which is something that can be verified experimentally. Why make other assumptions?
I thought so too but Dale and others say that isotropic speed of light is a convention.The two SR postulates are physical hypotheses.
It is particularly amusing to hear a LET proponent disparage making assumptions
The assumption in LET is existence of the eather. In BU it is isotropic speed of light.As Dale says, you cannot avoid assumptions, but you need to be clear about what they are.
You seem to think that those are mutually exclusive. The list of important physical quantities that are defined by some convention is quite substantialI thought so too but Dale and others say that isotropic speed of light is a convention.
We can choose by convention that the speed of light is 1, but that will have no physical consequence, only a mathematical consequence.You seem to think that those are mutually exclusive. The list of important physical quantities that are defined by some convention is quite substantial
Correct. As long as the 2-way speed is the experimentally confirmed invariant speed, the one way speed is a matter of convention with no physical consequence (the synchronization convention). So we may as well postulate the simplest convention consistent with the observations.We can choose by convention that the speed of light is 1, but that will have no physical consequence, only a mathematical consequence.
This is where I disagree, I think the invariance of the one-way speed has physical consequences compared to non-invariance. So it can't be used as a convention. It can only be used as a physical hypothesis.Correct. As long as the 2-way speed is the experimentally confirmed invariant speed, the one way speed is a matter of convention with no physical consequence. So we may as well postulate the simplest convention consistent with the observations.
Then you are wrong. Consider doing some maths to determine what the effect on a measurement would be if you chose a different simultaneity convention.This is where I disagree, I think the invariance of the one-way speed has physical consequences compared to non-invariance.
Can you show how and where?This is where I disagree, I think the invariance of the one-way speed has physical consequences compared to non-invariance.
You need a clock at the emission and clock at the detection to measure the speed. If those clocks are not at the same place in space (are spacelike separated) the clocks need to be synchronized -> need to have a simultaneity convention -> one way speed of light is a convention.So it can't be used as a convention.
OK. So please identify and calculate any measurement that could detect any such physical consequence. I will then show that such a measurement is also consistent with a different one-way speed.I think the invariance of the one-way speed has physical consequences compared to non-invariance.
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 ?Then you are wrong. Consider doing some maths to determine what the effect on a measurement would be if you chose a different simultaneity convention.
Time dilation, length contraction for example. Thess are physical consequence.Can you show how and where?
But if it's a convention, you can't derive from it the origin of physical phenomena like time dilation. When you measure the world line that represents proper time on a Minkowski diagram, is this world line physical or is it just a mathematical representation in your opinion? If this is just a mathematical representation, then what is the true origin of time dilation?You need a clock at the emission and clock at the detection to measure the speed. If those clocks are not at the same place in space (are spacelike separated) the clocks need to be synchronized -> need to have a simultaneity convention -> one way speed of light is a convention.
If you don't assume isotropy (or other similar convention like Reichenbach), how do you derive time dilation, contraction, etc ?OK. So please identify and calculate any measurement that could detect any such consequence. I will then show that such a measurement is also consistent with a different one-way speed.
Reichenbach is non-isotropic. That is exactly what I would assume (although I would use Anderson’s approach). However, you have avoided answering the challenge. You claimed that “the invariance of the one-way speed has physical consequences compared to non-invariance”.If you don't assume isotropy (or other similar convention like Reichenbach), how do you derive time dilation, contraction, etc ?
How do you propose to avoid it?I do no want to choose any simultaneity convention.
Einstein disagrees with you.But if it's a convention, you can't derive from it the origin of physical phenomena like time dilation.
In SR postulate 2, Einstein speaks only of the invariant "speed of light in vacuum".I thought so too but Dale and others say that isotropic speed of light is a convention.
I think Einstein thought it was a physical reality.Einstein disagrees with you.
It's a convention, it's not a natural isotropy that depends on relative velocities.Reichenbach is non-isotropic. That is exactly what I would assume (although I would use Anderson’s approach).
How do you propose to avoid it?
So isotropic speed of light is only a convention.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.
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.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 ?
So that you can measure one way speeds with them.why artificially resynchronize 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!So that you can measure one way speeds with them.
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.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.
It has no physical consequences; it only changes your interpretation of your measurements.I am quite willing to establish a convention of simultaneity, but you must not give this convention physical consequences that it does not possess.
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.So isotropic speed of light is only a convention.
That' not correct, see above.Thus acording to you there is no Einstein's special theory of relativity, Einstein only made mathematical abstractions about relativity.
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.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