We know from countless experiments in astronomy, satellite orbital dynamics, and particle and accelerator physics, that Einstein's formulation of special relativity is physically correct, and that any concept of a fixed, physically real, universally constant field or frame of reference must be either a coarse approximation or false.
Here is a derivation of the proposition that the speed of light, c, is the limiting velocity. It assumes causality and is based on the observation that the speed of light is the same to all observers.
Naturally, it is not rational to claim that one can prove all ones assumptions. To reason logically, one must adopt axioms, which are assumptions accepted without proof.
In this work, we accept the usual assumptions of space and measurable distances, and we assume always that events are occurring in vacuum.
Vacuum is a complex concept. All we mean by it here, is a region of space devoid of all particles except those specified in the proofs. We know from quantum physics that this is not a reasonable assumption: The vacuum has a definite ground-state energy.
The ground-state, or zero-point, energy is ignored in this work. Computations based on observation indicate that the best laboratory vacuum must be seething and boiling with a sea of virtual particles which pop in and out of existence for microscopic periods of time. Notice the metaphors here ("sea", "boiling", "seething", etc.) which are taking the place of precise reasoning. We accept this without further logic.
We take "vacuum" for granted here, although the precise value of the speed of light, c, undoubtedly depends to some extent upon the zero-point energy density.
The Pulfrich Effect, SIU-C. Last updated 2007-04-05