Abdullahi, Musa Daji
Mechanics / Electrodynamics
August 7, 2018
Fringe shift, light, reflection, rotation, speed, time, velocity.
The speed of light , from a source moving with speed u relative to a point of reference, with respect to an observer moving with speed v relative to the same point of reference, is z = c + (u – v), where c is the speed of light, a constant relative to the source. In the MM and MGP experiments, the source and observer (interferometer) were moving with the same speed (u = v) relative to the centre of the Earth. As such there should have been no time difference between rays, moving with speed c, reflected off the mirrors, to give a null result. A null result was recorded in the MM experiment but not so for the MGP experiment. In the Sagnac experiment, the glass plate acts as a secondary source moving at speed u, with v = 0, relative to the centre of the rotating disc. A refracted (transmitted) ray moving in a circle of radius R, travels with speed z = c + u, while the reflected ray goes at speed z = c - u, making a time difference between the two rays moving in opposite directions, to give a fringe shift, as observed. The fringe shifts said to have been obtained in the MGP experiment were within the experimental error of the apparatus. The Sagnac experiment should have put to rest the relativistic principle of constancy of the speed of light relative to an observer.