Prior to Michelson’s experiment, the theory of ‘luminiferous aether’ was widely accepted by physicists. It suggested that much like the propagation of sound waves through matter, light waves must also travel through a fixed medium named the ‘aether’, which permeates all of space. This would mean that as Earth travels through the aether, the speed of light measured from its surface should vary, depending on the direction in which it is measured.
