Luminiferous Aether

In the late 19th century, luminiferous aether, æther or ether, meaning light-bearing aether, was the postulated medium for the propagation of light.

Following the negative outcome of aether-drift experiments like the Michelson-Morley experiment, the concept of aether as a mechanical medium having a state of motion lost adherents. It has been replaced in modern physics by the theory of relativity and quantum theory.