Willis Lamb was awarded half the Nobel prize in physics in 1955 "for his discoveries concerning the fine structure of the hydrogen spectrum." The other half was awarded to Polykarp Kusch "for his precision determination of the magnetic moment of the electron.” Willis Lamb studied nuclear physics and made many contributions the field of nuclear physics. He became interested in measuring the fine structure of hydrogen, deuterium, and helium after working on some molecular beam experiments and teaching a class on atomic physics. Lamb decided he would try to measure the energy levels which were of interest in the advent of quantum electrodynamics. Lamb and Retheford measured the tiny shift due to an interaction between the electron and the vacuum. This shift is now called the Lamb shift. Theoretical descriptions were provided by Feynmann, Schwinger, and Tomonaga, the founders of quantum electrodynamic theory (see the1965 prize).