Born on 5 December 1868 in Königsberg, Prussia, theoretical physicist Arnold Sommerfeld was a pioneer of quantum and atomic physics. Sommerfeld started out studying mathematics, earning his PhD from the University of Königsberg in 1891, when he was just 23 years old. After serving a year in the military, he spent the rest of his career in academia, accepting teaching posts in Göttingen, Clausthal, and Aachen before settling in 1906 at the University of Munich. There he worked over the next three decades to create one of the world’s leading schools for theoretical physics. Sommerfeld is perhaps best known for his 1916 relativistic generalization of Bohr’s model of the atom, in which he proposed that electrons move in elliptical orbits as well as circular ones. He also did groundbreaking research on such topics as the fine-structure constant and the effects of electric and magnetic fields on atomic spectra. Sommerfeld also mentored a number of students who would go on to win the Nobel Prize in Physics, including Wolfgang Pauli, Werner Heisenberg, and Hans Bethe. Sommerfeld himself never received the Nobel, however, despite being nominated more than 80 times. Among the many awards he did receive were the Lorentz Medal, the Max Planck Medal, and the Oersted Medal. He died in 1951 from injuries sustained when he was struck by a car. (Photo credit: AIP Emilio Segrè Visual Archives, Margrethe Bohr Collection)

Info via Physics Today