Nielsen studied at the University of Minnesota, completing a bachelor's degree in electrical engineering in 1922 and a Ph.D. in physics in 1925.
[1] He was the third person to join the physics department at the newly endowed Duke University.
[1] His promotion of research and leadership brought Duke University's physics department "into international prominence.
"[5] Under his influence, Duke University's physics department appointed a number of outstanding physicists, including Martin M. Block, William M. Fairbank, Walter Gordy, Fritz London, Henry W. Newson, Lothar Wolfgang Nordheim, and Hertha Sponer.
[1] Nielsen chaired the Duke University Council for many years, the Council of the Oak Ridge Institute of Nuclear Studies[1] (of which he was a member from 1946 to 1959), and the Southeastern Section of the American Physical Society (APS) for one year.