Abstract

Both VLBI (Very Long Baseline Interferometry) and GPS (Global Positioning System) indicate that earth-based clocks are biased as a function of their position in the direction of the earth?s orbital velocity. The evidence for these biases is discussed, and the result is confirmed by comparison of earth-based clocks with millisecond pulsars. These clock biases are precisely such as to cause the speed of light to appear as ??c?? in the earth?s inertial frame. This shows that the speed of light is not isotropic in the earth?s frame and that the Lorentz transformation is only an apparent transformation that results from Selleri?s inertial transformations combined with clock biases.