The One-Way Speed of Light on Rotating Earth and the Definition of the Meter

Abstract

Since 1983 the meter is defined to be the "length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second". If there was exactly one single consistent method of synchronizing clocks, or if all corresponding methods were equivalent, one could infer from the validity of special relativity theory on a definite value of the one-way speed of light c in inertial frames. It is true that sufficiently slowly separated clocks always show middle in time reflection when sending and receiving light signals. But a simple consideration proves that the one-way speed of light is not a constant in rotating systems, in principle detectable with only one clock. On basis of a new internal synchronization method, this also affects all local inertial frames on rotating Earth, too, violating an absolute constancy of the one-way speed of light. This is not a contradiction to Einstein's original theory of relativity but to the present definition of the meter. Based on the constant local average value c of light going there and back, however, a modification for the definition of the meter is suggested, which would not depend on synchronization of any distant clocks. Appendix: FitzGerald-Lorentz contraction and time dilation, according to Einstein's generally accepted understanding, should be purely kinematic effects and would not need any dynamic explanation. But an analysis of Ehrenfest's paradox of the rotating disk shows that it is not possible to separate exactly relativistic kinematics from dynamics. The necessity of such a fundamental restriction is well known for a long time - though only from quantum mechanics till now.