Aether (science)

Light is a wave, and the luminiferous aether (or ether) is defined to be whatever medium transmits the light waves.

The Michelson-Morley experiment in 1887 failed to detect any motion of the aether relative to the Earth. Henri Poincaré conjectured that the aether may be unobservable, and invented special relativity based on the notion that the aether may be superfluous. Albert Einstein published conflicting opinions on whether the aether exists.

Quantum electrodynamics (QED) teaches that when light goes through a vacuum, it is really going through a sea of virtual particles. Cosmologists say that the vacuum is really filled with dark energy, and it is unknown whether that has any relation to the aether concept. According to these theories, there is no such thing as empty space. The aether describes space when it is as empty as possible.

The existence of luminiferous aether is a counterexample to relativity as it is sometimes described, as it is sometimes said that Einstein abolished the aether.

A.N. Whitehead states 5 reasons that had provided for long time the support for acceptance of aether hypothesis:

1. The wave theory of light required existence of ether as one of its postulates
2. Maxwell's Equations describe electrostatic and magnetic attractions by means of describing the status changes of ether
3. Maxwell's Equations assume events in a space that is evidently void. There must be something to which these properties could be ascribed.
4. The identification of light with electromagnetic waves performed by C.Maxwell shows that the same entity (aether) is implied by at first glance different optical and electromagnetic phenomena thus should be able to unify their interpretation
5. The possibility to perceive static "ether sea" which homogeneously penetrates all space of cosmos as absolute frame of reference towards which the Newton's laws of motion are referenced. Ether acquires this special character in Lorentz's and Larmore's theory however such extrapolation is discouraged by Whitehead as it is rooted in solely speculative entity lacking any experimental evidence.