The 1887 Michelson-Morley experiment, named after Albert Michelson and Edward Morley, was conducted in the basement of a dormitory at what is now Case Western Reserve University in Cleveland, disproved the existence of the so-called “luminiferous ether,” which was a hypothesized medium through which light was thought to be propagated. The experimenters set out to prove the existence of the ether by measuring fringe shifts it would supposedly cause in a beam of light that was intentionally split, then reunited to have its patterns measured on a telescope detector.
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INTERFEROMETER
The experiment’s primary apparatus, named for Michelson, as he developed it for an earlier experiment, was an interferometer, which simply unites two sources of light to make measurements using their interference patterns. The 1887 experiment’s two sources of light actually originated from the single beam of a sodium lamp, were split by a half-silvered mirror, then ultimately reunited to have their interference pattern measured after reflecting off a pair of perpendicular mirrors. The entire device was placed atop a marble slab floating in a pool of mercury designed to allow for free movement and the elimination of any confounding effects due to friction.
FIZEAU EXPERIMENT
The Michelson-Morley experiment contradicted the findings of an 1851 study of the speed of light in water by Hippolyte Fizeau. Because light was certainly traveling through a medium in that test, its speed, and, therefore, wave pattern, was altered. Michelson and Morley expected to see a similar shift because they set out on their experiment under the assumption that light was traveling through a medium, the ether, in their test.
DAYTON MILLER
Morley continued to work to prove the existence of the ether with Dayton Miller, a major proponent of its existence, but their work also yielded null results. Another experiment where Miller claimed to have discredited the Michelson-Morley experiment was itself discredited by the work of the Shankland team.
SPECIAL RELATIVITY
The Michelson-Morley experiment’s results held major implications for the development of Albert Einstein’s theory of special relativity because they were aligned with the idea that the speed of light, often denoted with the abbreviation c, appears universally constant, no matter the inertial reference frame. This also helps to explain length contraction at relativistic speeds (i.e., speeds at or near the speed of light), postulated by Hendrik Lorentz and George Francis FitzGerald.
RELATED EXPERIMENTS
The 1901-1903 Trouton-Noble experiment and the 1932 Kennedy-Thorndike experiment built upon and helped to reinforce the findings of Michelson-Morley. The latter had major implications for proving the special-relativity effect of time dilation.
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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:
* Learn about the world’s largest interferometer, LIGO, which is being used in an effort to detect the existence of gravity waves.
* Khan Academy explains the idea behind the luminiferous ether, which was upheld by many renowned scientists until the Michelson-Morley experiment disproved it: * Minute Physics delves into the special-relativity concepts of length contraction and time dilation:
* Famed astrophysicist Neil deGrasse Tyson helps to explain the Michelson-Morley experiment:
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