The English mathematician, physicist, and astronomer Sir James Hopwood Jeans (1877-1946) made important contributions to the development of quantum theory and to theoretical astrophysics, especially to the theory of stellar structure.

On Sept. 11, 1877, James Jeans was born in Ormskirk, Lancashire, the son of a parliamentary journalist. He was brought up in a strict, very religious Victorian home atmosphere. A precocious child, he was reading by age 4 and had a remarkable ability to memorize numbers. At an early age he also became interested in physics, as well as in mechanical devices, especially clocks--the subject of a short book he wrote at age 9.

In 1897 Jeans entered Trinity College, Cambridge, and in 1903 received his master's degree. In 1904 he was appointed university lecturer in mathematics at Cambridge; and in 1906, at the very early age of 28, he was elected a fellow of the Royal Society--all this in spite of the fact that during 1902-1903 tuberculosis of the joints forced him to go to several sanatoriums. During his illness, from which he completely recovered, he wrote his first book, The Dynamical Theory of Gases.

Jeans taught applied mathematics at Princeton University, N.J., from 1905 to 1909. He returned to Cambridge as Stokes lecturer in 1910 but 2 years later relinquished the position and thereafter devoted full time to research and writing.

In 1907 Jeans married Charlotte Tiffany Mitchell; she died in 1934, leaving one daughter. The following year he married Suzanne Hock, a concert organist, with whom Jeans wrote his very popular and informative book Science and Music (1938). They had two sons and a daughter.

In the first period of his scientific life (1901-1914), Jeans's interests were centered mainly on the kinetic theory of gases and the theory of radiation, especially applied to the new quantum theory of Max Planck and others. Through a vigorous interchange of ideas, Lord Rayleigh and Jeans, in 1905, separately derived what later came to be called the Rayleigh-Jeans law. Despite the fact that this law implied a failure of classical theory when applied to blackbody radiation, Jeans, during the ensuing years, repeatedly attempted to sustain classical theory instead of accepting quantum theory. Only after Henri Poincaré's 1912 paper on the quantum theory did Jeans become convinced. Two years later Jeans wrote a brief but comprehensive Report on Radiation and the Quantum Theory, which, after World War I, was extremely influential in convincing physicists of the importance of the new quantum ideas.

During the war years Jeans experienced his finest hour as a scientist--now a theoretical astrophysicist. His researches on stellar structure were most significant, especially his proof that a rotating incompressible mass will, with increasing rotational velocity, first become pearshaped and then cataclysmically fission into two parts (one model for a single star evolving into a double-star system). This and other important results, including a tidal encounter nebular hypothesis that replaced the classical Kant-Laplace nebular hypothesis, were published in his 1919 Adams Prize essay, Problems of Cosmogony and Stellar Dynamics.

The next decade of Jeans's life (1918-1928) was marked by a rather sharp decrease in his reputation as a theoretical astrophysicist. Already, in 1917, he had a famous debate with Arthur S. Eddington on stellar structure and, though not really apparent at the time, Jeans by and large emerged the loser. In 1929 Jeans turned to popular science writing, especially in astronomy, and soon became very successful. His Universe around Us ushered in a series of eight books between 1929 and 1942. All are stimulating expositions, though they suffer in one degree or another from presenting the results of scientific research a bit too dogmatically, thereby giving a distorted picture of such research in progress.

Jeans was awarded numerous honorary degrees and professional offices. He was knighted in 1928 and won the coveted Order of Merit in 1939. He was a modest and unassuming man and a devoted father. Jeans died on Sept. 16, 1946, at his home in Dorking, Surrey.

Further Reading

• A study of Jeans is E. A. Milne, Sir James Jeans (1952). Milne also wrote a short obituary notice of Jeans in Biographical Memoirs of the Fellows of the Royal Society, 1945-1948, vol. 5 (1947). There is a bibliography of Jeans's writings in both of these works.