Special Relativity (SR) is a cornerstone for modern physics and for variety of applications. SR is based on two postulations, the principle of relativity and the principle of constancy of the propagation speed of light wave. However, up to now, the second postulate has not been confirmed experimentally yet. Recently we have shown that light propagate as particles even in “pure” wave experiments. In this article we propose doable modified Michelson’s rotating mirror experiments to test the second postulate for photons.
If the experiments show that the constancy of the speed of light propagating as photons holds, then we, the first time, experimentally confirm the second postulation of SR. If the experiments show that the propagation speed of photons is not constant, then, the second postulate of SR is disproved. Either negative result or positive results would be profoundly significant.