Born: 8 January 1891, Oranienburg, Germany
Died: 8 February 1957, Heidelberg, West Germany (now Germany)
Affiliation at the time of the award: University of Heidelberg, Heidelberg, Federal Republic of Germany, Max-Planck-Institut für medizinische Forschung, Heidelberg, Federal Republic of Germany
Prize motivation: "for the coincidence method and his discoveries made therewith"
Prize share: 1/2
In a counter tube, particles passing through the tube generate an electric pulse. In 1925 Walter Bothe connected two counter tubes together so that only simultaneous passages were registered. This meant that either the passages were caused by particles that originated from the same event or by a particle that moved so fast that the time for movement between the tubes was negligible. Walther Bothe used the method to show that energy is conserved in impacts between particles and photons and to study cosmic radiation.