William Hunter McCrea was born in Dublin on 13^th December, 1896. The family moved to Chesterfield, Derbyshire in 1907 and it was in that town that he received his schooling. He won an entrance scholarship in Mathematics to Trinity College, Cambridge, becoming a "wrangler" (a first-class honours graduate) in 1926. After graduating he began research under the distinguished physicist and astronomer R.H. Fowler (who supervised fifteen Fellows of the Royal Society and three Nobel Laureates between 1922 and 1939).

Initially he worked on quantum physics and relativity, and also on related problems in pure mathematics, McCrea's interest gradually focused on the application of theoretical physics to the astronomical universe, ranging from the constitution of stellar atmospheres, through the formation of planets and stars, to cosmology, the study of the universe as a whole. Recognition came early with a Cambridge University Rayleigh Prize, a Trinity College Rouse Ball Senior Studentship and Travelling Studentship, a Sheepshanks Exhibition and an Isaac Newton Studentship.

One of his research attainments involved determining the composition of the Sun. In the 1920s, astrophysicists had come to question the accepted proposition that the Sun was made up mostly of iron. A counter-proposition was that the Sun held many of the same gases and materials as the earth. Spectroscopy suggested the presence of hydrogen in the Sun's atmosphere, and the German astronomer and astrophysicist Albrecht Unsöld theorised in 1928 that hydrogen, in fact, was its most common element. McCrea soon worked out the calculations to confirm the hypothesis. Cosmologists eventually established that all stars were composed chiefly of hydrogen, a realisation that turned their science into a new direction. It also pointed toward the Big Bang theory of the origin of the universe though in the late 1960s, McCrea distanced himself from the theory of a single Big Bang, advancing his own interpretations which indicated instead a series of bangs at different times and places in the cosmos.

McCrea studied for one year at Göttingen University in Germany, before in 1930 taking up a post as Lecturer in the Edinburgh University Department of Mathematics, which was headed by Edmund Whittaker, the outstanding mathematician, and where he published his first book, Relativity Physics, then was Reader and Assistant Professor in Mathematics at Imperial College, London from 1932 until 1936.

In 1936 he moved to Queen's University, Belfast, as Professor of Mathematics. While at Queen's, in 1942 he published a book, Analytical Geometry of Three Dimensions, which was based upon a course of lectures to first-year Honours students. A second edition was produced in 1947, in whose preface he explained that, while not a long book, care had been taken "to frame the theory so that it does strictly apply to real space. This explains the avoidance of certain familiar short-cuts, which actually depend on jumping difficulties about reality conditions." His book was republished in 1953, again in 1960 and finally reprinted in 2006. Among other work he published while at Queen's were articles on moving atmospheres, observable relations in relativistic cosmology and random paths in two and three dimensions.

In 1943 McCrea was given leave from Queen's University while doing Operational Research in the Admiralty in the team led by PMS Blackett, the experimental physicist and later Nobel Prize winner. He attained the rank of Temporary Captain in the Royal Naval Volunteer Reserve, and had the task, thanks to his German learned at Göttingen, of interviewing German naval officers. He did not though return to Belfast, having in 1944 been appointed Professor of Mathematics at Royal Holloway College, London, an appointment which he took up at the end of the war. He remained there until 1966; the McCrea Building on Royal Holloway's campus is named for him.

McCrea then took up an appointment as Research Professor of Theoretical Astronomy, supported by the Science Research Council, at the newly-established Sussex University. Sussex had received its Charter in August 1961; Astronomy at Sussex had started in October 1965, with the beginning of a formal collaboration between the University and the Royal Greenwich Observatory, then at nearby Herstmonceux. The first astronomers in post were three visiting staff from Greenwich: the Astronomer Royal, Sir Richard Woolley, was made a visiting professor and there were two visiting readers. McCrea arrived part-time in January 1966 and became full-time later that year as the first Research Professor of Theoretical Astronomy, with Roger Tayler as Professor of Astronomy. With the support of Woolley and his colleagues, McCrea (research) and Tayler (planning) jointly put Sussex on the world astronomy map. McCrea was made Emeritus Professor on his retirement in 1972.

His memoirs and obituaries of many leading astronomers, mathematicians and physicists (many of whom he knew personally) such as Eddington, Milne, Jeans, and Einstein (he wrote a preface to one of Einstein's books, The Meaning of Relativity), are lasting contributions to the history of science. In addition to his many papers and reviews, McCrea wrote the texts Relativity Physics, the less technical Physics of the Sun and Stars and Cosmology, a history of the Royal Greenwich Observatory; together with Tayler, he produced the second volume of History of the Royal Astronomical Society. He also translated Unsöld's The New Cosmos, and wrote an autobiographical essay, Clustering of astronomers.

McCrea's services to astronomy went far beyond his technical contributions. He was successively Council member, Secretary, President, Foreign Correspondent and Treasurer of the Royal Astronomical Society, and for some years he was editor of The Observatory and of the RAS's Monthly Notices. He served on the Councils of the Royal Society, the London Mathematical Society and the Royal Institute of Philosophy. He also served as a school governor.

McCrea was in demand all over the world. He was a bye-Fellow at Caius College, Cambridge, and visiting professor or lecturer at Berkeley, the Case Institute at Cleveland, University of British Columbia at Vancouver, Louvain, Cairo, Istanbul, and Otago, among others. Further recognition came with honorary degrees from the National University of Ireland, the Queen's University at Belfast, the National University at Cordoba, Argentina, and the Universities of Dublin and Sussex; he was Member of the Nationale Akademie der Wissenschaften Leopoldina in Germany, and a Foreign Member of the Accademia delle Scienze di Torino, Italy.

He was successively Council member, Secretary, President, Foreign Correspondent and Treasurer of the Royal Astronomical Society, and for some years he was editor of The Observatory magazine and of the journal Monthly Notices of the Royal Astronomical Society. Some predecessors as President of the Royal Astronomical Society had been William Herschel, Fred Hoyle, James Jeans and Bernard Lovell. In 1976 he was awarded the Society's highest distinction, the Gold Medal, previously awarded to Albert Einstein and subsequently to Stephen Hawking.

He was elected to the Fellowship of the Royal Society of Edinburgh in 1931 and of the Fellowship of the Royal Society in 1952. He was President of the Royal Astronomical Society from 1961 to 1963 and was awarded its Gold Medal in 1976. He was knighted in 1985.

Born:	13 December 1904
Died:	25 April 1999