What is "emission theory"

Emission \E*mis"sion\, n. [L. emissio: cf. F. ['e]mission. See Emit.]

1. The act of sending or throwing out; the act of sending forth or putting into circulation; issue; as, the emission of light from the sun; the emission of heat from a fire; the emission of bank notes.

2. That which is sent out, issued, or put in circulation at one time; issue; as, the emission was mostly blood.

   Emission theory (Physics), the theory of Newton, regarding light as consisting of emitted particles or corpuscles. See Corpuscular theory, under Corpuscular.

n. (context physics English) A discredited scientific theory, once considered an alternative to special relativity, proposing that light is emitted at speed c relative to its source instead of applying the invariance postulate.

Emission theory, also called emitter theory or ballistic theory of light, was a competing theory for the special theory of relativity, explaining the results of the Michelson–Morley experiment of 1887. Emission theories obey the principle of relativity by having no preferred frame for light transmission, but say that light is emitted at speed "c" relative to its source instead of applying the invariance postulate. Thus, emitter theory combines electrodynamics and mechanics with a simple Newtonian theory. Although there are still proponents of this theory outside the scientific mainstream, this theory is considered to be conclusively discredited by most scientists.

Emission theory or extramission theory (variants: extromission, extromittism) is the proposal that visual perception is accomplished by rays of light emitted by the eyes. This theory has been replaced by intromission theory, which states that visual perception comes from something representative of the object (later established to be rays of light reflected from it) entering the eyes. Modern physics has confirmed that light is physically transmitted by photons from a light source, such as the sun, to visible objects, and finishing with the detector, such as a human eye or camera.