McCrea, William Hunter (1904–1999)

Irish theoretical astrophysicist and mathematician. In 1934, together with his colleague Edward Milne, McCrea established modern Newtonian cosmology, by applying classical physics to the primordial gas cloud that condensed to form the galaxies. He later made important contributions to Einstein's relativity theory and to the ‘uncertainty principle’ first propounded by the German physicist Werner Heisenberg.

McCrea's work on the uncertainty principle suggested that it applies to light as it travels (thereby expanding on both Heisenberg's work and the theories of the Austrian physicist Ernst Mach). He also emphasized the effect of turbulence in condensing gas clouds and its role in the formation of planets and stars, and studied low-probability transitions of electrons between atomic energy states. In 1975, he proposed that comets may have been formed in the galactic spiral arms, and that the Earth, Moon, and Mars were formed from a single body that differentiated and then split up.

McCrea was born in Dublin, and educated at Cambridge University. He lectured in mathematics at Edinburgh University and at Imperial College, London, before being appointed professor of mathematics at Queen's University, Belfast, in 1936. After World War II, he moved to Royal Holloway College, London, and then to the University of Sussex (1966). McCrea was elected a Fellow of the Royal Society in 1952 and was knighted in 1985.