Arthur Milne

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For other persons named Edward Milne, see Edward Milne (disambiguation).

Edward Arthur Milne (February 14, 1896 – September 21, 1950) was a British mathematician and astrophysicist.

Milne was born in Hull, Yorks, England. He was a fellow of Trinity College, Cambridge, 1919–1925, being assistant director of the solar physics observatory, 1920–1924, mathematical lecturer at Trinity, 1924–1925, and university lecturer in astrophysics, 1922–1925. He was Beyer professor of applied mathematics, Victoria University of Manchester, 1924–1928, before his appointment as Rouse Ball Professor of Mathematics and to a fellowship at Wadham College, Oxford, in 1928. Milne's earlier work was in mathematical astrophysics. From 1932 he also worked on the problem of the "expanding universe" and in Relativity, Gravitation, and World-Structure (1935), proposed an alternative to Albert Einstein's general relativity theory. His later work, concerned with the interior structure of stars, aroused controversy. Milne was president of the Royal Astronomical Society, 1943–1945.

He died in Dublin, Ireland.

Contents 1 Relativity, Gravitation, and World Structure 2 Honours 3 See also 4 Bibliography (excerpt) 5 External links

[edit] Relativity, Gravitation, and World Structure

The main difference between the Milne model of an expanding universe, and the current (Einstein's) model of an expanding universe was that Milne did not assume a priori that the universe has a homogeneous matter distribution.

Milne argued that under the context of Einstein's special relativity, and the relativity of simultaneity, that it is impossible for a nonstatic universe to be homogeneous. Namely, if the universe is spreading out, its density is decreasing over time, and that if two regions appeared to be at the same density at the same time to one observer, they would not appear to be the same density at the same time to another observer.

Milne's model (shown below) is, therefore, that of a sphere, with an approximately homogeneous matter distribution within several billion light years of the center which then increases to an infinite density. This distribution is unique in that it is essentially the same after a Lorentz transformation, except that a different stationary particle is at the center. As it is the only distribution that has this property, it is the only distribution which could satisfy the cosmological principle of "no preferred reference frame." Based on this cosmological principle Milne created a model that can be described entirely within Euclidean geometry.

The plate below shows that as of 1935, using this model, Milne published a prediction of the cosmic background radiation which appears to be of a much different character than that predicted by Eddington. In fact, many passages in Relativity, Gravitation and World Structure are devoted to attacking Eddington's preconceptions.

[edit] Honours

Awards

• Gold Medal of the Royal Astronomical Society (1935)
• Royal Society's Royal Medal (1941)
• Bruce Medal (1945)

Named after him

• Milne crater on the Moon

[edit] See also

• Gale, George, "Cosmology: Methodological Debates in the 1930s and 1940s," Stanford Encyclopedia of Philosophy. Milne was a major player in the cosmological controversies described in this article.

[edit] Bibliography (excerpt)

• Thermodynamics of the Stars (1930)
• The White Dwarf Stars (1932)
• Relativity, Gravitation and World-Structure (1935)
• Kinematic Relativity (1948)

[edit] External links

• O'Connor, John J., and Edmund F. Robertson. "Arthur Milne". MacTutor History of Mathematics archive.