The English astronomer Sir Arthur Stanley Eddington (1882-1944) greatly advanced theoretical astrophysics as a consequence of his original contributions to the theory of relativity and his studies on the internal constitution of stars.
Arthur S. Eddington was born on Dec. 28, 1882, at Kendal, Westmorland. His father was the headmaster and proprietor of a school where John Dalton once taught. Arthur was a precocious child, and by his own account had mastered the 24 x 24 multiplication table before he could read. He received his bachelor's degree in 1902 from Owens College, Manchester, and immediately proceeded to Trinity College, Cambridge. At Cambridge he placed first in the mathematical tripos examination in his second year, an unprecedented achievement. In 1905 he took his bachelor's degree from Cambridge University; in 1907 he became Smith's Prize winner and was elected a fellow of Trinity College; and in 1909 he obtained his master's degree.
In 1906 Eddington was appointed chief assistant at the Royal Observatory at Greenwich. He remained there for 7 years, gaining much practical astronomical experience. While there he initiated a program for determining latitude variation of stars which, with modifications, is still in force today, and engaged in theoretical researches on the systematic motions and distributions of the stars recorded in the Groombridge Catalog. These last studies formed the basis of his Smith's Prize essay and culminated in his book Stellar Movements and the Structure of the Universe (1914). One important result was that he confirmed Jacobus Kapteyn's 1904 conclusion that there are two star streams in the Milky Way.
In 1913 Eddington was appointed Plumian professor of astronomy at Cambridge; a year later he became director of the Cambridge Observatory and was elected a fellow of the Royal Society. During World War I he began studies on Albert Einstein's general theory of relativity and on stellar structure. As secretary of the Royal Astronomical Society, Eddington received for publication a copy of Einstein's paper of 1915, the only one to reach England during the war. By the end of the war Eddington had become one of the few men to master Einstein's general theory, had made original contributions to it, and had written the first account of it in English.
In 1919 Eddington led the famous solar eclipse expedition to West Africa and proved, as Einstein's theory demanded, that starlight is deflected in passing close to a massive body such as the sun. Later, Eddington generalized H. Weyl's theory of the electromagnetic field, and in 1925 W. S. Adams spectroscopically verified Eddington's 1924 prediction of a large gravitational red shift of the light emitted by Sirius's white dwarf companion. In 1930 Eddington proved that an Einstein universe is unstable, thereby lending support to the concept of an expanding universe.
In 1915 Eddington also began studying the internal constitution of stars, a subject largely of his own creation. During the ensuing years he demonstrated, for example, the importance of radiation pressure in helping thermal pressure maintain a star's stability against gravitational collapse. He, as well as Harlow Shapley, showed that variable stars change their brightness because they pulsate. He also derived his famous mass-luminosity law, which shows that the more massive a star, the brighter it is.
Eddington was a master of popular science writing, a talent which he exploited especially after 1927. He also increasingly expounded his controversial philosophical and theological convictions. Moreover, spurred on by Paul Dirac's 1928 discovery of the relativistic wave equation for the electron, Eddington during the last 16 years of his life attempted to wed relativity to quantum theory in what came to be called his fundamental theory. Undisturbed by the criticism that this elegant but speculative theory evoked, Eddington pursued it to the end. Few today accept it, but its positive elements may one day be reborn in different form.
Eddington was knighted in 1930 and received numerous honors throughout his life, including the coveted Order of Merit in 1938. He remained a bachelor and died in Cambridge on Nov. 22, 1944.
A full-length biography of Eddington is Allie Vibert Douglas, The Life of Arthur Stanley Eddington (1956). For a shorter biographical sketch see H. C. Plummer's obituary notice in the Biographical Memoirs of the Fellows of the Royal Society, vol. 5 (1945-1948). See also John W. Yolton, The Philosophy of A. S. Eddington (1960).
Chandrasekhar, S. (Subrahmanyan), Eddington, the most distinguished astrophysicist of his time, Cambridge; New York: Cambridge University Press, 1983.