Jeans, Sir James Hopwood, 1887–1946, English mathematician, physicist, and astronomer. He was professor of applied mathematics at Princeton (1905–9), later lectured at Cambridge (1910–12) and Oxford (1922), and was research associate at Mt. Wilson Observatory (1923–44). He was knighted in 1928. He devoted himself to mathematical physics and contributed to the dynamical theory of gases and the mathematical theory of electricity and magnetism. Going on to astrophysics and cosmogony, he solved the problem of the behavior of rotating masses of compressible fluids. He was then able to explain the behavior of certain nebulae, discuss the origins of binary stars, and describe the evolution of gaseous stars. These ideas are presented in Problems of Cosmogony and Stellar Dynamics (1919). With Harold A. Jeffreys he developed the tidal hypothesis of the origin of the earth. In 1929, Jeans abandoned research and became one of the most outstanding popularizers of science and the philosophy of science. His later works include The Universe around Us (1929), The Mysterious Universe (1930), and The Growth of Physical Science (1947).