The Function of the Second Postulate in Special Relativity
Abstract
Many authors noted that the principle of relativity, together with space-time symmetries, suffices to derive Lorentz-like coordinate transformations between inertial frames. These contain a free parameter, , (equal to in special relativity) which is usually claimed to be empirically determinable, so that special relativity does not need the postulate of constancy of the speed of light. I analyze this claim and find that all methods destined to measure fail without further assumptions, similar to the second postulate. Specifically, measuring requires a signal that travels identically in opposite directions (this is unrelated to the conventionality of synchronization, as the one-postulate program implicitly selects the standard synchronization convention). Positing such a property about light is logically weaker than Einstein's second postulate but suffices to recover special relativity in full.
Cite
@article{arxiv.1408.3142,
title = {The Function of the Second Postulate in Special Relativity},
author = {Alon Drory},
journal= {arXiv preprint arXiv:1408.3142},
year = {2016}
}