Pauli and Bohr (right) watching a tippe top toy on the floor. Wolfgang Pauli (1900-1958), Austrian- Swiss physicist, and Niels Henrik David Bohr (1885-1962), Danish physicist, both worked on the newly developed quantum theory. Pauli proposed both a fourth quantum number 's' (for the spin of an electron), and his exclusion principle (1924). Bohr developed a quantum hydrogen atom model (1913). They won the 1945 and 1922 Physics Nobel Prizes respectively. Photographed in 1955 at the opening of the Institute of Physics, Lund, Sweden.