Rudolf Ortvay

“ In the well known experiment of Sagnac [2] , two light rays traversing in opposite directions the periphery of a rotating circle (more exactly a polygon) , will be brought to interfere, and on that occasion a displacement of the interference fringes in respect to the stationary state was observed, by an amount that corresponds to a phase difference of , where is the length of the periphery, is the velocity of a point of the periphery, is the speed of light. The theory of the experiment for the resting system of earth was given by M. v. Laue, before the experiment was even conducted. ”

“ Since the experiment proves that in the rotating system the propagation of light does not correspond to that of an uniform moving system, a discussion from the standpoint of general relativity is desired. ”

“ We assume with Thirring, that a spherical shell of mass and radius is uniformly rotating around the origin of our coordinate system with the angular velocity around the -axis. Let be large against the circle radius.
In infinity we take for the coefficients of the line element, its values in the pseudo-euclidean case and apply the approximate solution of Einstein with retarded potentials.
When we neglect the terms that include , we obtain for the energy-momentum-tensor [4]
We denote by , speed of light, = mass density. ”