James Jeans (1877-1946), British physicist, astronomer and mathematician. Sir James Hopwood Jeans made many important contributions to the field of physics, including quantum theory, and the theories of radiation and stellar evolution. He was a founder of British excellence in cosmology. He also was the first to propose a steady state cosmology, where the universe is continually being created as it expands. However, this was ruled out in 1965 when the discovery of cosmic microwave background radiation supported the Big Bang, the theory that all matter was created from a single event billions of years ago whose effects are still being observed today.