Eric Koch for Anefo · CC0

Co-developed the steady-state model of the universe with Fred Hoyle and Thomas Gold in 1948, proposing that the cosmos looks the same at all times as an alternative to an expanding universe with a single origin — a theory later overturned by the discovery of cosmic microwave background radiation, but one that sharpened the questions cosmologists had to answer. He also did foundational work on general relativity, correctly explaining the nature of gravitational waves and analyzing the behavior of negative mass, work he later called his best.