Aether (classical element)

According to ancient and medieval science, aether (/ˈiːθər/, alternative spellings include æther, aither, and ether), also known as the fifth element or quintessence, is the material that fills the region of the universe beyond the terrestrial sphere.

[2] The word αἰθήρ (aithḗr) in Homeric Greek means "pure, fresh air" or "clear sky".

Aristotle, who had been Plato's student at the Academy, agreed on this point with his former mentor, emphasizing additionally that fire has sometimes been mistaken for aether.

With this addition the system of elements was extended to five and later commentators started referring to the new first one as the fifth and also called it aether, a word that Aristotle had used in On the Heavens and the Meteorology.

[1][11] Medieval scholastic philosophers granted aether changes of density, in which the bodies of the planets were considered to be more dense than the medium which filled the rest of the universe.

[13] Quintessence (𝓠) is the Latinate name of the fifth element used by medieval alchemists for a medium similar or identical to that thought to make up the heavenly bodies.

Due to the low presence of quintessence, earth could be affected by what takes place within the heavenly bodies.

[14] Due to quintessence's pure and heavenly quality, it was thought that through consumption one may rid oneself of any impurities or illnesses.

Einstein noted that his own model which replaced these theories could itself be thought of as an aether, as it implied that the empty space between objects had its own physical properties.

[21] This idea relates to the hypothetical form of dark energy postulated as an explanation of observations of an accelerating universe.

The use of aether to describe this motion was popular during the 17th and 18th centuries, including a theory proposed by Johann II Bernoulli, who was recognized in 1736 with the prize of the French Academy.

At the time, it was thought that in order for light to travel through a vacuum, there must have been a medium filling the void through which it could propagate, as sound through air or ripples in a pool.

[23] The results of the experiment influenced many physicists of the time and contributed to the eventual development of Einstein's theory of special relativity.

He renounced standing attempts at accounting for this particular form of interaction between distant bodies by introducing a mechanism of propagation through an intervening medium.