The addition-of-velocities hypothesis, which Kantor recently claimed to have verified, has been investigated using a different experimental arrangement. A laser beam was passed through a moving mica window, which might be considered as a Huygens-type moving source of light. An interferometer was built with which to detect and measure any change in speed of the emitted light. The apparatus allowed investigation of: the effects of window speed, which could be varied continuously up to 63m/sec; direction of window motion with respect to direction of propagation; and the effects of air in the beam path. Emission theory as used by Kantor predicted a ⅓ fringe shift; however, no shift was observed under any conditions. The estimated sensitivity of the method is 1/20 fringe. Our results are therefore consistent with the second postulate of special relativity, but not with Kantor’s hypothesis.
RAY O. WADDOUPS, W. FARRELL EDWARDS, and JOHN J. MERRILL, "Experimental Investigation of the Second Postulate of Special Relativity," J. Opt. Soc. Am. 55, 142-142 (1965)