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{{Infobox scientist
| name = Edward Arthur Milne
| birth_date = {{birth date|1896|2|14|df=y}}
| birth_place = Hull, Yorkshire, England
| death_date = {{death date and age|1950|9|21|1896|2|14|df=y}}
| death_place = Dublin, Ireland
| nationality = British
| fields = Astrophysics, Mathematics, Cosmology
| workplaces = University of Cambridge; University of Manchester; University of Oxford
| known_for = Kinematic relativity, the cosmological principle, stellar atmospheres
| prizes = Gold Medal of the Royal Astronomical Society (1935)
}}

'''Edward Arthur Milne''' (14 February 1896 &ndash; 21 September 1950) was a British astrophysicist and mathematician, Rouse Ball Professor of Mathematics at Oxford from 1928, who built a complete cosmology out of the [[Special Relativity|special theory of relativity]] and a symmetry postulate, without using general relativity or curved space at all. He named that postulate the '''cosmological principle'''.

Milne's first career was in stellar physics. He worked out the theory of radiative transfer in stellar atmospheres, the Milne&ndash;Eddington approximation for line formation, the theory of the outer layers of stars, and the escape of atoms from stellar surfaces. He disagreed sharply with [[Arthur Eddington|Eddington]] over the internal constitution of stars, arguing for degenerate cores against Eddington's standard model. He was awarded the Gold Medal of the Royal Astronomical Society in 1935 and was its President from 1943 to 1945.

==Kinematic relativity==

From 1932 Milne turned to cosmology. His starting point was that the general theory of relativity smuggles in far more structure than the evidence warrants, and that a cosmology should be deduced from as little as possible. He assumed only special relativity, a set of equivalent fundamental observers, and the requirement that the universe look the same to all of them &mdash; his cosmological principle.

From this alone he derived a linear velocity&ndash;distance relation of Hubble's form. The resulting '''Milne model''' is a uniformly expanding swarm of particles in ordinary flat Minkowski space: no curvature, no expanding space, no gravitating matter. In modern terms it is the empty limit of the Friedmann models, and it is still used as a reference case for exactly that reason.

Milne then introduced his most characteristic idea, two time scales. Atomic or "kinematic" time ''t'', measured by light signals, and dynamical time ''τ'', in which Newtonian mechanics holds exactly, are related logarithmically. In ''t'' the universe expands from a singular origin; in ''τ'' it is static and infinitely old, with the gravitational constant varying instead. The same physical universe, on this account, can be described as expanding or as unchanging depending on which clock is used &mdash; the two are not rival hypotheses but rival conventions.

His main works are ''Relativity, Gravitation and World-Structure'' (1935) and ''Kinematic Relativity'' (1948). A devout Anglican, he also gave the Cadbury lectures published posthumously as ''Modern Cosmology and the Christian Idea of God'' (1952).

Kinematic relativity did not prevail. The observational tests of the 1930s and 1940s were not decisive against it, but general relativistic cosmology absorbed the field, and Milne's death at 54 removed its only serious advocate.

==On this wiki==

Milne matters here because he is the standing proof that a Hubble law can be derived without expanding space, and because his two time scales offer a way of taking cosmic time as conventional rather than absolute. Both points are made repeatedly by the cosmic-time and expanding-space critics catalogued on this wiki.

[[Mogens True Wegener]] is Milne's principal interpreter here. His "[[Milne's Kinematic Relativity]]" (2000) sets out the theory and Walker's analysis of it, and connects it to theories of continued creation. He develops the same line in "[[The Idea of a Cosmic Time]]" (''[[Foundations of Physics]]'', 2004), "[[New Axioms for Cosmology]]" (2011), "[[Eternal Universe]]" and "[[Non Standard Relativity: A Philosopher's Handbook of Heresies in Physics]]".

The cosmological principle itself &mdash; Milne's coinage &mdash; is examined at length by [[Toivo Jaakkola]] in "[[The Cosmological Principle: Theoretical and Empirical Foundations]]" (''[[Apeiron]]'', 1989), which argues for the perfect cosmological principle (same in time as well as in space) and treats the evolving-universe picture as an unfinished Copernican revolution. That position connects directly to [[Fred Hoyle]] and the steady-state tradition, and to the non-expansion arguments in [[:Category:Big Bang]] and [[:Category:Redshift]].

'''A caution for editors.''' This wiki also holds a substantial body of work by [[Harold W Milnes]], an electrodynamics researcher with no connection to E. A. Milne. Papers here with "Milnes" in the title &mdash; on Ampère's law, charged poles and the Toth-Maatian Review &mdash; refer to him, not to the cosmologist.

==See also==

* [[Cosmology]]
* [[Expanding Universe]]
* [[Hubble Constant]]
* [[Arthur Eddington]]
* [[Fred Hoyle]]
* [[Mogens True Wegener]]

[[Category:Scientist|Milne Edward Arthur]]
[[Category:Cosmology]]
[[Category:Relativity]]
[[Category:Astronomy]]
[[Category:Big Bang]]