From an article by G E Stedman Ring laser tests of fundamental physics and geophysics Competition Gyros LaserRingGyro Steadman StedmanReview1997 pdf In a 1953 letter to Shankland Shankland 1974 Einstein said my admiration for Michelson s experiment is for the ingenious method to compare the location of the interference pattern with the location of the image of the light source In this way he overcomes the difficulty that we are not able to change the direction of the earth s rotation