An experiment, conducted in 1887 by 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 (see illustration) 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 finally 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 interferometer
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