Revelations from Historical Experiments on Constant Speed of Light

The postulate of constant speed of light for all reference frames is the foundation of relativity theories. The resultant time dilation and length contraction are generally accepted but still perplexing for most people. By re-examining the historical evidence, this paper confirms Einstein’s postulate and reveals the mechanism for the constant speed of light: the interaction between photons and matter can impart the speed of an inertial frame to the photons and thus result in the same speed of light for different inertial reference frames. This mechanism can consistently explain all major experiments on the constant speed of light.