English astrophysicist and mathematician who formulated a theory of relativity which he called kinematic relativity, parallel to Albert Einstein's general theory.
Milne was born in Hull, Yorkshire, and studied at Cambridge, where he spent his academic career until 1925. He then moved to Manchester as professor of mathematics. From 1929 he was professor at Oxford.
Studying stellar structure, Milne suggested that a decrease in luminosity might cause the collapse of a star, and that this would be associated with nova formation. Some of his cosmological theories were developed with Irish astrophysicist William McCrea.
In 1932, Milne began his attempt to explain the properties of the universe by kinematics (the movement of bodies). Basing his theory on Euclidean space and on Einstein's special theory of relativity alone, Milne was able to formulate systems of theoretical cosmology, dynamics, and electrodynamics. He also gave a more acceptable estimate for the overall age of the universe (10,000 million years) than that provided by the general theory of relativity.