Jeans, James Hopwood (1877-1946) was a British research scientist. He made important contributions in several fields, including mathematics, physics, and astronomy. He contributed to the understanding of the behavior of gases and suggested a theory of the creation of the universe. He also wrote many popular science books.

Jeans was born on Sept. 11, 1877, in Ormskirk, in Lancashire, England. As a child, he learned to play the piano and the organ, and he developed an early interest in science.

In 1900, Jeans earned a bachelor's degree in mathematics from Cambridge University. He then began work toward a master's degree.

In 1902, Jeans developed tuberculosis of the joints. He left the university and spent about a year in several sanatoriums, medical facilities for treatment and extended rest. During his recovery, Jeans developed a theory about the behavior of gases. Known today as the kinetic theory, it explains that all matter is made of constantly moving particles—atoms or molecules. An atom is one of the basic units of matter, and a molecule is a combination of atoms. The speed of the gas particles' movement depends on their weight and the temperature of the gas. Jeans wrote the book The Dynamical Theory of Gases to explain his work in detail. It was published in 1904.

Jeans received his master's degree from Cambridge in 1903. He served as a lecturer at the university in 1904 and 1905. He also studied the law of radiation developed earlier by Lord Rayleigh and found a numerical error in the mathematical calculations. In 1905, Jeans corrected the error, and the revised theory of radiation became known as the Rayleigh-Jeans law. From 1905 to 1909, Jeans was a professor of applied mathematics at Princeton University in the United States. There he published two textbooks, Theoretical Mechanics (1906) and The Mathematical Theory of Electricity and Magnetism (1908).

In 1906, Jeans was elected a fellow (member) of the Royal Society, the leading scientific organization in the United Kingdom. Jeans became a fellow of the Royal Astronomical Society in 1909.

Jeans returned to Cambridge University in 1910. He served as Stokes lecturer in applied mathematics until 1912, when he retired from teaching so that he could devote more time to research. Jeans turned his attention to cosmogony, the study of the origin of the universe.

Jeans and the British geophysicist Harold Jeffreys developed the tidal theory of cosmogony. According to this theory, the solar system began with hot gas pulled from the sun by the gravity of a passing star. The gas condensed to form the planets. Jeans explained the tidal theory in the essay “Problems of Cosmogony and Stellar Dynamics,” for which he won the Adams prize awarded by Cambridge University. The essay was published as a book in 1919. That year, Jeans won the Royal Medal of the Royal Society. From 1919 to 1929, he served as one of the two honorary secretaries of the society.

Jeans received the Royal Astronomical Society's gold medal in 1922 for his work in cosmogony. He served as president of the society from 1925 to 1927. From 1923 to 1944, he was a research associate at the Mount Wilson Observatory in California.

Jeans was knighted in 1928. That year, he suggested that matter was continuously being created in the universe. This idea contributed to the steady state theory of cosmogony developed later by English astronomer Fred Hoyle and others.

Jeans then devoted his time to writing and delivering radio lectures and published The Universe Around Us (1929), one of the first in a series of books that made science more popular among the general public. In 1939, he received the Order of Merit.