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ether. We wish to calculate the transit times of a light ray in each arm in the moving system. The length of arm 1 in Fig. 1 is contracted by the Lorentz contraction: where c is the vacuum velocity of light. The velocity of light in this arm is Here we used eq. (2); the (+ ) sign referring to the velocity parallel to v while (—) to the velocity antiparallel to v. During the light transit, mirror M where t (t is the transit time of the light from B to M The light ray striking M ## (3)W ## (5)## (6)or using eq. (1) (7) The overall transit time through arm 1 is given by ## (8)The length of arm 2, l (9) X=vt Fig. 2. - Demonstration of the dragging effect. (10) c'= c/n vb . | Multiplying this equation by t we obtain the relation between the distances Z ## (11)Using eq. (1), we can express y by (12) Again, from Fig. 1 or (13) We obtain then that the overall transit time through arm 2 is (14) The difference in transit times between the two arms is given by (15) Expanding and retaining only terms of second order in /? we have (16) If the frequency of light is v and its wave length in vacuum A, the phase difference of the two beams will be (17) A rotation of 90° will interchange arms 1 and 2, but will not affect the frequency v of the light source [a laser] due to our assumption that the MME gives a negative result in vacuum. We thus have for the total observed fringe shift for a 90° rotation of the system, ## (IB)## 3. - The experimental system.The Michelson-interferometer arms consisted of perspex rods, and the light source was a He-Ne laser. For sensitive detection of fringe shifts, the fringes |