Editing Albert A. Michelson (section)

=== Michelson–Morley interferometry experiment ===
{{main|Michelson–Morley experiment}}

In 1887 he collaborated with colleague [[Edward Morley|Edward Williams Morley]] of Western Reserve University, now part of [[Case Western Reserve University]], in the [[Michelson–Morley experiment]]. Their experiment for the expected motion of the [[Earth]] relative to the [[luminiferous aether|aether]], the hypothetical medium in which light was supposed to travel, resulted in a [[null result]]. Surprised, Michelson repeated the experiment with greater and greater precision over the next years, but continued to find no ability to measure the aether. The Michelson–Morley results were immensely influential in the physics community, leading [[Hendrik Lorentz]] to devise his now-famous [[Lorentz contraction]] equations as a means of explaining the null result.

There has been some historical controversy over whether [[Albert Einstein]] was aware of the Michelson–Morley results when he developed his theory of [[special relativity]], which pronounced the aether to be "superfluous". In a later interview, Einstein said of the Michelson–Morley experiment, "I was not conscious it had influenced me directly&nbsp;... I guess I just took it for granted that it was true."<ref>Swenson, Loyd S. Jr., ''The Ethereal Aether: A History of the Michelson–Morley–Miller Aether-Drift Experiments, 1880–1930'', University of Texas Press, 1972</ref>  Regardless of Einstein's specific knowledge, the experiment is today considered the canonical experiment in regards to showing the lack of a detectable aether.<ref>Note that while Einstein's 1905 paper ''[[On the Electrodynamics of Moving Bodies]]'' appears to reference the experiment on first glance—"together with the unsuccessful attempts to discover any motion of the earth relatively to the 'light medium', suggest that the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest"—it has been shown that Einstein was referring to a different category of experiments here.</ref><ref>[[Gerald Holton|Holton, Gerald]], "Einstein, Michelson, and the 'Crucial' Experiment", ''Isis'', Vol. 60, No. 2 (Summer, 1969), pp. 133–197 {{doi|10.1086/350468}}</ref>

The precision of their equipment allowed Michelson and Morley to be the first to get precise values  for the [[fine structure]] in the atomic spectral lines<ref>AA.  Michelson  and  E.  W.  Morley,  Amer. J.  Sci.34,  427  (1887);  Phil  Mag.  24,  463 (1887).</ref> for which in 1916 [[Arnold Sommerfeld]] gave a theoretical explanation, introducing the [[fine-structure constant]].