Born: 26 January 1911, Blankenburg, Germany
Died: 20 March 1993, Dallas, TX, USA
Affiliation at the time of the award: Columbia University, New York, NY, USA
Prize motivation: "for his precision determination of the magnetic moment of the electron."
Prize share: 1/2
In certain respects, electrons and atoms behave as if they were rotating charged particles that generate a magnetic field. Their magnetic moment provides a way of measuring how strongly they are affected by a magnetic field. Drawing upon quantum mechanics and relativity theory, Paul Dirac developed a theory for the interaction of charged particles with electromagnetic fields. Through precise measurements, Polykarp Kusch showed in 1947 that the electron's magnetic moment was somewhat greater than the theory predicted. This became important for the further development of quantum electrodynamics.