Ether

Ether is a word derived from the Greek aithēr (αἰθήρ), meaning "pure, fresh air" or "clear sky", and refers to a postulated space-filling substance or field. Aristotle included aether among the four terrestrial elements, thus making of it the fifth element (the quintessence). In the late 19th century the luminiferous aether or ether was a light-bearing element postulated by scientists to describe a medium for the propagation of light, theory that was later discarded.

Further reading

• Ether at Theosopedia