Wolfgang Pauli and Arnold Sommerfeld, physicists, c 1940.

Wolfgang Pauli (1900-1958) developed the Pauli Exclusion Principle in 1924, which required that no two electrons in an atom can be in the same quantum state. Arnold Sommerfeld (1868-1951) worked on a variety of problems, but his most famous work developed Niels Bohr's (1885-1962) theory of atomic structure, replacing circular electron orbits with elliptical orbits in 1915.