Abstract

In a paper in 1910 Tolman pointed out that the light speed invariance postulate of special relativity requires that the time for light to traverse a fixed distance between two points is independent of the movement of those points relative to the light source. The range equation of the GPS is used to directly test this proposition. This equation has been rigorously tested and verified in the Earth-Centred Inertial frame where light signals propagate in straight lines at constant speed c. The result is a simple demonstration of light speed anisotropy that is consistent with light speed variation detected in other experiments and inconsistent with the light speed invariance postulate.

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