Who was Niels Bohr's doctoral advisor at the University of Copenhagen?

Niels Bohr’s doctoral advisor at the University of Copenhagen was Christian Christiansen. Christiansen was a Danish physicist known for experimental work in optics and electromagnetic theory, and he supervised Bohr’s doctoral research on the electron theory of metals. Bohr received his doctorate in 1911.

The subject exposed Bohr to difficult questions about how classical physics could explain the behavior of electrons in matter. Those problems helped point him toward the quantum theory of the atom. After completing his doctorate, Bohr traveled to England, where he worked with J.J. Thomson in Cambridge and then Ernest Rutherford in Manchester. Both men later became major influences, but neither was his doctoral advisor.

Another misleading option is Christian Bohr, who was Niels Bohr’s brother, not his academic supervisor. Christian Christiansen therefore fits both the historical record and the specific Copenhagen University relationship asked about here. Bohr went on to formulate his atomic model in 1913 and won the 1922 Nobel Prize in Physics.