An experiment, conducted in 1887 by the US physicists Albert Michelson (1852–1931) and Edward Morley (1838–1923), that attempted to measure the velocity of the earth through the ether. Using a modified Michelson interferometer they expected to observe a shift in the interference fringes formed when the instrument was rotated through 90°, showing that the speed of light measured in the direction of the earth’s rotation, or orbital motion, is not identical to its speed at right angles to this direction. No shift was observed. An explanation was subsequently provided by the Lorentz–Fitzgerald contraction, which provided an important step in the formulation of Einstein’s special theory of relativity and the abandonment of the ether concept.
Michelson–Morley experiment. Michelson interferometer.
https://history.aip.org/history/exhibits/gap/Michelson/01_Michelson.html The original 1887 paper in The American Journal of Science
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.
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