A Possible Experimental Test of Einstein's Second Postulate

Abstract

AS is well known, Einstein's special theory of relativity rests on two postulates: (1) the postulate of relativity; (2) the postulate of constant light velocity, which says¹ “that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body”. For the first postulate there is much experimental support; for the second, none. It is not generally appreciated that the experiments often held to confirm the kinematical part of Einstein's theory are, in fact, evidence that the Maxwell–Lorentz electromagnetic equations are invariant to the Lorentz transformation, since the forces and velocities concerned are determined from those equations and not by direct measurement.