Ether-Drift Experiments at Mount Wilson

Abstract

THE Michelson-Morley experiment for determining the relative motion of the earth and the luminiferous ether, the “ether-drift experiment,” was first performed in Cleveland in the year 1887, by Prof. Albert A. Michelson and the late Prof. Edward W. Morley. The theory of the experiment and a description of the apparatus was published in the Philosophical Magazine for 1887, and has been repeated in many text-books since that time. They announced their conclusions as follows: “Considering the motion of the earth in its orbit only... the observations show that the relative motion of the earth and the ether is probably less than one-sixth the earth's orbital velocity and certainly less than one-fourth.”(That is, it is less than 7.5 kilometres per second.) This result was considered by many as a null result, often called a negative result, and by some was thought to throw grave doubts upon the validity of the hypothesis of the luminiferous ether.