Ether

Ether, or aether, in physics, hypothetical substance that was once believed essential for transmission of light waves through space. Scientists assumed that waves required some medium. Observations of stars had suggested that the ether must be stationary in space, and that the earth therefore moved through it. In 1887 the U.S. scientists Albert A. Michelson and Edward W. Morley tried to measure the effect of the “ether wind,” but found no sign of it. The theory of ether was finally abandoned when Albert Einstein's theory of relativity showed that electromagnetic radiation is not a mechanical distortion of a medium, but a type of energy that travels through a vacuum.