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Physics, Astronomy & Cosmology / Re: Why does vacuum affect frames of reference?
« on: 19/02/2024 19:11:40 »Why does vacuum affect frames of reference?'Why questions' only beget more why questions.
A frame of reference is an abstract choice of coordinate system. Vacuum has little effect on that, except that in a vacuum, a human is quickly going to be rendered incapable of making such an abstract choice.
That's probably not an answer to what you had in mind, but it answers the question actually asked in the title.
Why is it it that light's speed has to be constant all the time no matter what frame of reference it is observed in?It doesn't have to be, it's just that observation seem to suggest it.
SR postulates that locally (as Kryptid correctly points out), the speed of light in a vacuum is frame independent, and it postulates this because such an assumption is consistent with all experimentation. That experimentation also shows it not being invariant for a medium other than a vacuum.
But it is just a postulate, not something ever actually proven, and it only works for inertial coordinates in Minkowskian spacetime, and spacetime is Minkowskian (has Lorentz symmetry) only locally, so light in a vacuum moves at other speeds depending on your coordinate system of choice and the curvature of the spacetime being considered.
There are alternate theories that deny the postulates of SR, and according to those theories, light speed is not frame independent, and the physics of one frame is not the same as another.
For a comprehensive experimental basis for the postulates of special relativity, see here:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html