This can be interpreted in regard to our present knowledge only in the sense of Doppler's principle, as an expansive motion of the system of stars in the large as required, according to Friedman, by the field equations of gravitation. Whether the relative separations are due to special relativistic motion in the usual sense of movement, or the dilation of space as is required by Friedman's cosmological solutions based on Einstein's own gravitational field equations, is not in dispute by Einstein. The moment your domain has grown so large that the cosmological effects of spacetime curvature and dilation become important, any statement about the speed of light being a globally-fixed constant in all such reference frames becomes inadequate.
Special relativity is a local approximation to a far more complex global geometry for space-time.
Copyright 1997 Dr. Sten Odenwald Return to Ask the Astronomer .