Nuclear Physics to Fission

Ernest Rutherford

• 1911-1912: Rutherford proposed nuclear model of atom

• 1919: Succeeded J. J. Thomson as director of Cavendish Laboratory at Cambridge

• 1920s and 1930s: Made Cavendish a “Mecca” of nuclear physics

James Chadwick and Neutron

• Irene and Frederick Joliot-Curie and others discovered new penetrating rays

• James Chadwick proved in 1932 that the rays were new fundamental particles that Rutherford had speculated on: a neutral particle with mass similar to protons

• Rutherford: Nobel for Chadwick and the Curies would surely win theirs

• Curies: discovery of artificial radioactivity in 1934 and Nobel

• Also in 1932: Discovery of Positron by Carl Anderson

Path to Fission

• Slow neutron effects: Enrico Fermi in 1930s

• Lise Meitner, Otto Hahn, and Fritz Strassmann

• Bombardment of uranium with neutrons• Meitner forced to flee Germany in 1938• Christmas 1938: Hahn and Strassmann’s

experimental results and Meitner and Frisch’s theoretical explanation