Prior to 1938, scientists were puzzled about how stars produce their light and energy. One popular theory about the production of stellar energy relied on chemical combustion; others proposed gravitational forces or electrical fields. In 1938, German-American physicist Hans Bethe finally provided the answer: nuclear fusion.

Bethe was born in Strassburg, Germany on July 2, 1906. He studied physics at universities in Frankfurt and Munich, and received his Ph.D. in 1928. He went on to work with the eminent physicists Ernest Rutherford in England and Enrico Fermi in Italy. When Adolph Hitler (1889-1945) rose to power in 1933, Bethe left Germany and went to England, where he taught for two years. He then moved to Cornell University in Ithaca, New York to teach.

Bethe, who was one of the scientists who worked on the development of the atomic bomb, combined Henri Becquerel 's information about subatomic physics with Sir Arthur Eddington's theory about...