Theoretical physics and emigration
Bethe studied in Frankfurt and Munich, completing his doctorate with Arnold Sommerfeld in 1928. After losing his Tübingen position under the Nazi regime, he moved to Britain and then joined Cornell in 1935.
Nuclear reactions and stellar energy
He applied nuclear-reaction theory to stellar interiors, analysing processes capable of sustained energy production, including proton–proton reactions and the carbon–nitrogen cycle. Comparing their operating conditions and excluding unsuitable alternatives formed an important part of this work.
References: [1]
A broad physics programme
Bethe also investigated charged-particle energy loss, nuclear structure and quantum electrodynamics. During the Second World War he worked on atomic-bomb development at Los Alamos. He later continued research at Cornell and participated in debates over nuclear weapons.