Speed of light vs speed of sound

[wabbit]

@PeroK fine, light isn't fundamental to the theory we currently use under the name of SR - but I think we agree on that.

And "we can reformulate the theory without it " or "the theory works without it" is pretty much what I mean by "it is not fundamental to the theory"

 

[doaaron]

The assumption that there exists some observable phenomenon (it doesn't have to be light) that propagates at the same speed relative to all inertial observers and without a medium is sufficient to derive the entire panoply of special relativity: Lorentz transforms, relativity of simultaneity, universal speed limit, relativistic velocity addition, length contraction, time dilation, Minkowski space-time, all that good stuff.

Hi Nugatory,that's a good point. Actually that is kind of why I was originally interested to know whether the fact that light travels at "c" for a moving receiver has been proven experimentally. With emphasis on, "propagates at the same speed relative to all inertial observers and without a medium".

Fizeau:
1) With a medium.
2) Medium is moving relative to observer.
3) Conclusion is that the observer is moving relative to the medium and therefore all inertial observers are taken into account.

De Sitter:
1) Moving source.
2) No medium (space).
3) Moving observer (the Earth), but irrelevant based on the experimental setup?
4) Conclusion is that a moving source has no effect on the speed of light.

Michelson Morley:
1) Source moving together with observer inside what was thought to be a fixed medium.
2) No fixed medium was detected so vacuum was hypothesized.

As I understand it, these three experiments could be used to prove SR. But in these three experiements, you don't explicitly fulfill the conditions in bold (above). We have a moving source in De Sitter, and a moving medium in Fizeau, but I'm not sure if its fair to extrapolate a "moving observer" from Fizeau.regards,
Aaron

EDIT: On the other hand, SR does correctly predict the observed speed in the Fizeau experiment which uses relativistic velocity addition... just confused :(

 

[PeroK]

@PeroK fine, light isn't fundamental to the theory we currently use under the name of SR - but I think we agree on that.

And "we can reformulate the theory without it " or "the theory works without it" is pretty much what I mean by "it is not fundamental to the theory"

@wabbit

I think I see what you're saying now. That's beyond my knowledge of SR.