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Rh XVIII. On the Second Postulate of the Theory of Relativity: Experimental Demonstration of the Constancy of Velocity of the Light reflected from a Moving Mirror.

By , Professor of Physics at the Polytechnic School of Turin.

HE Theory of Relativity is based upon two well-known fundamental postulates. The first affirms the impossibility of discovering the movement of a system without referring this system to other systems; that is to say, it denies the physical reality of absolute motion. The second postulate affirms that the velocity c of propagation of light in vacuo is a universal constant. Both these postulates are generalizations of facts or principles already admitted by physicists.

In fact, we may regard the first as the extension to optical or electrical phenomena of a classical principle of mechanics,