Ben Roy Mottelson

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Chicago, Illinois
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Chicago, Illinois

Ben Roy Mottelson is a nuclear physicist who is half-American and half-Danish. He grew up in the Chicago suburbs and graduated from high school during the height of World War II, where he was immediately drafted into the military. He did, however, spend the war years at Purdue University, where he studied to become a Navy officer. He received his bachelor’s degree from Purdue University and his PhD from Harvard University after the war. He next moved to Copenhagen, where he accepted a fellowship at the Institute for Theoretical Physics (later the Niels Bohr Institute). He began working with Aage Bohr there, and they experimentally demonstrated that subatomic particle movement can change the form of the nucleus. This study, for which they were awarded the Nobel Prize in Physics two decades later, not only challenged accepted hypotheses but also sparked new research in the subject. He found work soon after, first at the European Organization for Nuclear Research’s Theoretical Study Group, then at the Nordisk Institut för Teoretisk Atomfysik, both in Copenhagen. He later became a naturalized Danish citizen and now resides in Copenhagen.

Childhood and Adolescence

Ben Roy Mottelson was born on July 9, 1926, in Chicago, Illinois, USA. His father, Goodman Mottelson, was an engineer with a university degree. Georgia Mottelson (née Blum) was his mother’s name. He was the second of three children born to his parents.

Ben was up in La Grange, Illinois, a suburb located just outside of Chicago. The hamlet had a very healthy climate at the time when political, moral, and scientific concerns were freely and fiercely debated, and young Ben was greatly inspired by this.

Ben Roy Mottelson attended Lyons Township High School in La Grange. He joined the US Navy as part of his war service after graduating from there in 1943 and was sent to Purdue University to be trained as an officer under the V-12 Navy College Training Program.

He returned to Purdue University after the war to finish his undergraduate studies, getting his Bachelor of Science degree in 1947. After that, he went to Harvard University for graduate school, where he got his Ph.D. in nuclear physics in 1950 while working under Professor Julian Schwinger.

Ben Roy’s Career

Mottelson won a one-year Sheldon Traveling Fellowship from Harvard University shortly after receiving his Ph.D. in 1950. He took it with him to Copenhagen, where he joined the Institute for Theoretical Physics (later the Niels Bohr Institute).

He had only intended to spend the 1950-1951 term in Copenhagen. The Institute was then led by Nobel Laureate and prominent scientist Niels Bohr. The institute developed a tradition of international cooperation under his leadership, and Mottelson appreciated the culture there.

He was fortunate enough to earn another fellowship in 1951, this time from the United States Atomic Energy Commission. It allowed him to continue in Copenhagen for two more years and begin working on the aberrations in the shape of nuclei alongside Aage N. Bohr.

There were two main theories floating about at the time. Independent particles are grouped in shells in a nucleus, according to Maria Goeppert-Mayer. Shell hypothesis was the name for this. The liquid drop model, which portrays the nucleus as a semi-classical fluid made up of neutrons and protons, was the other.

None of them, however, could explain all of an atomic nucleus’ attributes. James Rainwater proposed in 1950 that a nucleus resembled a balloon with balls inside.

Subatomic particles moving inside a nucleus, he theorized, produce deformation on its surface in the same way that moving balls alter the shape of the balloon. Aage Bohr, working independently, had reached the same conclusion.
Mottelson and Bohr collaborated to test this hypothesis experimentally from 1951 forward. They presented the results of these tests in three papers between 1952 and 1953.

He joined the European Organization for Nuclear Research (CERN) as a staff member in 1953 and was assigned to the Theoretical Study Group in Copenhagen. At the same time, he continued to work with Bohr.

He was at CERN until 1957. In the same year, the Nordisk Institut för Teoretisk Atomfysik (NORDITA) was formed on the grounds of the Institute of Theoretical Physics, and Mottelson was hired as a professor there, a position he kept until his retirement.

He was a visiting professor at the University of California in Berkeley for the spring semester of 1959. Meanwhile, he continued to work with Bohr and co-authored a two-volume monograph with him titled “Nuclear Structure.”

The first volume, titled ‘Single-Particle Motion,’ was published in 1969, followed by the second volume, titled ‘Nuclear Deformations,’ in 1975. Meanwhile, Mottelson was granted Danish citizenship in 1971. He also has dual citizenship in the United States.

His Major Projects

Mottelson is well known for his experiments with Aage Bohr, which proved that subatomic particle movement may deform nucleus shape. Not only did the research cast doubt on the widely held belief that all nuclei are exactly spherical, but it also combined Maria Goeppert-shell Mayer’s model with James Rainwater’s liquid drop model.

Achievements and Awards

Ben R. Mottelson, Aage Bohr, and James Rainwater shared the Nobel Prize in Physics in 1975 for “discovering the relationship between collective motion and particle motion in atomic nuclei and developing the hypothesis of the structure of the atomic nucleus based on this connection.”

He also earned the Atoms for Peace Award in 1969 and the John Price Wetherill Medal in 1974, in addition to the Nobel Prize.

Mottelson is a foreign fellow of both the Norwegian and Bangladesh Academies of Science and Letters. He is also a member of the Bulletin of the Atomic Scientists Board of Sponsors.
Purdue University and the University of Heidelberg have given him honorary degrees.

His Private Life

Mottelson married Nancy Jane Reno in December 1948. The marriage had three children: Malcolm Graham and Daniel John, two males, and Martha, a daughter. Nancy Jane Reno died of cancer in 1975, just before Mottelson earned his Nobel Prize.

Britta Marger Siegumfeldt was Mottelson’s second wife, whom he married in 1983.Mottelson enjoys listening to music in his spare time. He also enjoys swimming and bicycling.

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