Mottelson does graduate studies at Harvard University and completes his PhD work about nuclear physics in 1950.

The U.S. Navy sends him to Purdue University for officer’s training. He receives a Bachelor of Science degree in 1947.

With the founding of the Nordic Institute for Theoretical Atomic Physics in 1957, he receives a position as professor in Copenhagen. He begins a close collaboration with Aage Bohr (the son of Niels Bohr) and becomes a Danish citizen in 1971.

He spends one year as a postdoc at the Institute of Theoretical Physics in Copenhagen (later the Niels Bohr institute). After that, he joins a theoretical study group that accompanies the founding phase of CERN.

His childhood home is a place where scientific, political and moral issues are freely and vigorously discussed. He attends primary school and high school in the village of La Grange, IL, graduating during World War II.

Ben Mottelson shares the 1975 Nobel Prize in Physics with Aage Bohr and James Rainwater "for the discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection".

He marries Nancy Jane Reno in 1948. She dies in 1975. He marries a second time (Britta Marger Siegumfeldt) in 1983.

Ben Roy Mottelson is born in Chicago, IL.