The function of waves

摘要

In 1887 Albert Michelson and Edward Morley used an interferometer (a device that splits and recombines a beam of waves, to determine whether the recom-bined beam is still coherent) to measure the speed of light. It was thought at the time that light was the result of vibrations in an invisible "aether" that pervaded the universe. Since the Earth, as it journeyed through space, must move relative to that aether, Michelson and Morley expected that the daughter beams, which took different paths relative to the Earth's movement, would move at different speeds.