An experiment performed in 1887 by the American physicists A. A. Michelson and Edward Williams Morley (1838–1923) to establish the presence or absence of an ether, the medium through which light was supposed to travel. The experiment attempted to detect the motion of the Earth relative to the ether by measuring the speed of light in two directions at right angles to each other. No such motion was found. An explanation was provided by the Lorentz–Fitzgerald contraction, and subsequently the special theory of relativity showed that the concept of an ether was unnecessary.