The MICHELSON-MORLEY EXPERIMENT was performed in the basement of a WESTERN RESERVE UNIV. dormitory in July 1887 by ALBERT A. MICHELSON of the Case School of Applied Science and EDWARD W. MORLEY of Western Reserve Univ. it was designed to detect the motion of the earth through the "luminiferous aether," a theoretical substance which, according to 19th century physicists, was essential to the transmission of light.

At the heart of the experiment was an interferometer—a device invented by Michelson—which utilized the interference of light waves to perform measurements of incredible precision. Although an identical experiment undertaken by Michelson at Potsdam in 1880-81 failed to detect any motion of the earth relative to the ether, leading physicists were anxious for a repetition. Thus encouraged, Michelson and Morley first undertook a series of preliminary measurements of the velocity of light in moving fluids. After these measurements were successfully completed, the two men constructed an interferometer which was larger and more sensitive than the original Potsdam interferometer. Earlier difficulties caused by extraneous vibration were resolved when Morley designed an ingenious mounting for the device, in which the interferometer rested on a large sandstone slab which rotated while floating in a pool of mercury. Despite these improvements and the collaboration of these two great experimental scientists, the experiment again failed to detect any motion of the expected magnitude.

This incongruous result puzzled the physicists of the world until 1905 when Einstein published his theory of relativity. Viewed in the light of Einstein's revolutionary work, the null results of the Michelson-Morley experiment were not only predictable, but provided experimental confirmation of Einstein's theory. In 1995 the American Chemical Society declared CWRU's Adelbert Hall, the site of the experiment, a national historic chemical landmark, only the 4th location to be so designated in the country.

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