.

Edward Arthur Milne FRS[1] (14 February 1896 – 21 September 1950) was a British astrophysicist and mathematician.[2]

Biography

Milne was born in Hull, Yorkshire, England. He attended Hymers College and from there he won an open scholarship in mathematics and natural science to study at Trinity College, Cambridge in 1914, gaining the largest number of marks which had ever been awarded in the examination. 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 was, as would be the next Rouse Ball Professor of Mathematics, Charles Coulson, a pioneer in religion and science discussions.

He died of a heart attack in Dublin, Ireland, while preparing to give a set of lectures. These can be found written down in one of his last published books: Modern Cosmology and the Christian Idea of God (1952).
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. He did not include the gravitation interaction into the model either.

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. However, if each observer measures its local density at the same agreed-upon proper time, the measured density should be the same. In Minkowskian coordinates, this constant proper time forms a hyperbolic surface which extends infinitely to the light-cone of the event of creation. This is true even when proper time approaches 0, the time of the creation. The universe is already infinite at the creation time!

Milne's model 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. It can be shown that this infinite density is actually the density of the universe when at the time of the big bang. The spherical 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.

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.
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

Books by Milne

The White Dwarf Stars, Oxford: Clarendon Press, 1932.
Relativity, gravitation and world-structure, Oxford: Clarendon Press, 1935.
The Inverse Square Law of Gravitation, London: Harrison and Son, 1936.
The Fundamental Concepts of Natural Philosophy, Edinburgh: Oliver & Boyd, 1943.
Kinematic relativity; a sequel to Relativity, gravitation and world structure, Oxford: Clarendon Press, 1948.
Vectorial Mechanics, New York: Interscience Publishers, 1948.
Modern Cosmology and the Christian Idea of God, Oxford: Clarendon Press, 1952.
Sir James Jeans: A Biography, Cambridge University Press, 1952.