Light was thought to travel through a medium filling all space, the luminiferous aether, and if the Earth moved through it then light should run measurably faster with the current than across it. Between April and July 1887, in the basement of the Adelbert dormitory at Western Reserve University in Cleveland, Albert Michelson and Edward Morley built the instrument to catch it: a half-silvered mirror splitting one beam into two at right angles, each running eleven metres back and forth, the whole apparatus floated on mercury so it could be turned without shaking. They found nothing. The shift came in at about one fortieth of what the aether required, and they put Earth’s speed through the medium at less than a sixth of what it should have been, certainly less than a quarter. It is one of the most consequential negative results ever recorded and it cleared the ground for relativity. The dormitory became Pierce Hall and was demolished in 1962, so there is nothing of the room left; the campus is still there and so is the story.
Cleveland, Ohio
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