He also studied astronomy and mathematics under Professor Thorvald Thiele, and philosophy under Professor Harald Høffding, a friend of his father.In 1905, a gold medal competition was sponsored by the Royal Danish Academy of Sciences and Letters to investigate a method for measuring the surface tension of liquids that had been proposed by Lord Rayleigh in 1879.
In 1903, Bohr enrolled as an undergraduate at Copenhagen University.His major was physics, which he studied under Professor Christian Christiansen, the university's only professor of physics at that time.Harald became the first of the two Bohr brothers to earn a master's degree, which he earned for mathematics in April 1909. Students had to submit a thesis on a subject assigned by their supervisor.Bohr's supervisor was Christiansen, and the topic he chose was the electron theory of metals.Bohr subsequently elaborated his master's thesis into his much-larger Doctor of Philosophy (dr. He surveyed the literature on the subject, settling on a model postulated by Paul Drude and elaborated by Hendrik Lorentz, in which the electrons in a metal are considered to behave like a gas.
Bohr extended Lorentz's model, but was still unable to account for phenomena like the Hall effect, and concluded that electron theory could not fully explain the magnetic properties of metals.
Bohr's thesis was groundbreaking, but attracted little interest outside Scandinavia because it was written in Danish, a Copenhagen University requirement at the time.
In 1921, the Dutch physicist Hendrika Johanna van Leeuwen would independently derive a theorem from Bohr's thesis that is today known as the Bohr–van Leeuwen theorem.
; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922.
Bohr was also a philosopher and a promoter of scientific research.
The thesis was accepted in April 1911, and Bohr conducted his formal defence on 13 May.