Hans Albrecht Bethe
Born: 2 July 1906, Strassburg (now Strasbourg), Germany (now France)
Died: 6 March 2005, Ithaca, NY, USA
Affiliation at the time of the award: Cornell University, Ithaca, NY, USA
Prize motivation: "for his contributions to the theory of nuclear reactions, especially his discoveries concerning the energy production in stars"
Prize share: 1/1
Hans Bethe was born in Strasbourg and studied in Frankfurt and Munich. When the Nazis took power in 1933, Hans Bethe was dismissed from his post in Tübingen and emigrated via England to the U.S. He became a professor at Cornell University in Ithaca, New York, where he stayed for the rest of his career. During World War II, he took part in developing the atomic bomb and introductory work on the hydrogen bomb, but he subsequently opposed nuclear weapons. In 1939 he married Rose Ewald, with whom he had two daughters.
The discovery of fission - the splitting of heavy nuclei - revealed the liberation of large quantities of energy; an effect now exploited in nuclear reactors. This energy is generated by differences in mass. Energy is also liberated when light nuclei combine to form heavier ones, i.e. fusion. In 1938, Hans Bethe proved that fusion produces the enormous energy emitted by stars. He proposed two different processes, both of which result in hydrogen nuclei fusing with helium nuclei.