Michelson-Morley+Experiment



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**Aether ** People of the 19th century (1800s) believed that there was a mysterious substance in space called "aether." This substance was thought to be both rigid (to transport light waves) and fluid (so planets can pass through it). The Michelson-Morley experiment proved that there is no aether because the speed of light is constant.======

**The Apparatus**
The scheme of the experiment is as follows: a pulse of light is directed at an angle of 45 degrees at a half-silvered, half transparent mirror, so that half the pulse goes on through the glass, half is reflected. They both go on to distant mirrors which reflect them back to the half-silvered mirror. At this point, they are again half reflected and half transmitted, but a telescope is placed behind the half-silvered mirror as shown in the figure so that half of each half-pulse will arrive in this telescope. Now, if there is an aether wind blowing, someone looking through the telescope should see the halves of the two half-pulses to arrive at slightly different times, since one would have gone more upstream and back, one more across stream in general. To maximize the effect, the whole apparatus, including the distant mirrors, was placed on a large turntable so it could be swung around.