Ten years later, by now a professor at the Case School in Cleveland, Michelson became interested in trying to measure something called the ether drift—a kind of headwind produced by moving objects as they ploughed through space. One of the predictions of Newtonian physics was that the speed of light as it pushed through the ether should vary with respect to an observer depending on whether the observer was moving towards the source of light or away from it, but no-one had figured out a way to measure this. It occurred to Michelson that if you took careful measurements, with a very precise
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