ABSTRACT
Interferometry does not allow direct measurement of time intervals. However, it does enable one to measure optical path lengths and thus the time that it takes light to travel along the path. e classical series of experiments conducted by Michelson and Morley provides a textbook example of such measurements. e so-called Michelson-Morley experiment paved the way toward relativity theory and is regarded as one of the most important experiments in the history of science. It was the time difference of the propagation of two light beams, which had simultaneously emerged from the same origin in two dierent directions and returned aer having been reected by mirrors, which was measured in
these experiments. e measurement accuracy was equal to 3 × 10−17 s. At the time, it was an unprecedented world record!
