George Gamow (1904-1968) was a Russian theoretical physicist and cosmologist. He contributed to the idea of the Big Bang origin of the universe by demonstrating alpha decay via quantum tunneling, radioactive decay of atoms, star formation and stellar nucleosynthesis.
Essentially, Gamow showed how atoms in the sun are formed and how their nucleus eventually decays to release the radiation (light and heath) that we pick up on earth.
This understanding of the formation and decay of stars and by generalization the galaxies and the universe contributed to our understanding of the origin of the universe and how it would eventually die.
Gamow defected to America and dabbled in other kinds of work, including genetics. His primary contribution lies in his work on stellar nucleosynthesis and the fact that he was a popular science writer and wrote for the public on many aspects of science. He made physics and science in general readable for the general public and helped sell the mystique of science to the public.
Georges Gamow. The Birth and death of the Sun. (1940)
George Gamow. The Biography of the Earth. (1941)