From 1703 to 1905, physicists estimated that space contained a fixed and invisible substance called the ether. This substance impregnated the material bodies and vibrated under the action of a light source. They also supposed that a wind of ether influenced wave movements and varied according to earth rotation.
The experiment carried out in 1887 by Albert Abraham Michelson and Edward Williams Morley revealed no sign supporting such theory. In 1905, Albert Einstein simply concluded to the non-existence of an ether wind.