Ether

in physics and astronomy, the name given to the substance which it is assumed fills all space beyond our atmosphere. It is thought that light is a vibration of ether. It is thought also that heat, gravity, and electricity are dependent upon ether for their existence as forces of nature. No one knows exactly the nature of this stellar or cosmic ether, and some scientists reject the idea of its existence. Its acceptance has been brought about because it offers a satisfactory explanation of the phenomena of radiation, refraction, diffraction, and polarization of light.