Niels Bohr
Niels Henrik David Bohr (Danish: [ˈne̝ls ˈpoɐ̯ˀ]; 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.
"Bohr" redirects here. For other uses, see Bohr (disambiguation).
Niels Bohr
18 November 1962 (aged 77)
Nobel Prize in Physics (1922)
- Hughes Medal (1921)
- Matteucci Medal (1923)
- Franklin Medal (1926)
- Foreign Member of the Royal Society (1926)
- Max Planck Medal (1930)
- Faraday Lectureship Prize (1930)
- Copley Medal (1938)
- Order of the Elephant (1947)
- Atoms for Peace Award (1957)
- Sonning Prize (1957)
Team
Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid. He conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr's thinking in both science and philosophy.
Bohr founded the Institute of Theoretical Physics at the University of Copenhagen, now known as the Niels Bohr Institute, which opened in 1920. Bohr mentored and collaborated with physicists including Hans Kramers, Oskar Klein, George de Hevesy, and Werner Heisenberg. He predicted the properties of a new zirconium-like element, which was named hafnium, after the Latin name for Copenhagen, where it was discovered. Later, the synthetic element bohrium was named after him.
During the 1930s, Bohr helped refugees from Nazism. After Denmark was occupied by the Germans, he met with Heisenberg, who had become the head of the German nuclear weapon project. In September 1943 word reached Bohr that he was about to be arrested by the Germans, so he fled to Sweden. From there, he was flown to Britain, where he joined the British Tube Alloys nuclear weapons project, and was part of the British mission to the Manhattan Project. After the war, Bohr called for international cooperation on nuclear energy. He was involved with the establishment of CERN and the Research Establishment Risø of the Danish Atomic Energy Commission and became the first chairman of the Nordic Institute for Theoretical Physics in 1957.
Second World War
Assistance to refugee scholars
The rise of Nazism in Germany prompted many scholars to flee their countries, either because they were Jewish or because they were political opponents of the Nazi regime. In 1933, the Rockefeller Foundation created a fund to help support refugee academics, and Bohr discussed this programme with the President of the Rockefeller Foundation, Max Mason, in May 1933 during a visit to the United States. Bohr offered the refugees temporary jobs at the institute, provided them with financial support, arranged for them to be awarded fellowships from the Rockefeller Foundation, and ultimately found them places at institutions around the world. Those that he helped included Guido Beck, Felix Bloch, James Franck, George de Hevesy, Otto Frisch, Hilde Levi, Lise Meitner, George Placzek, Eugene Rabinowitch, Stefan Rozental, Erich Ernst Schneider, Edward Teller, Arthur von Hippel and Victor Weisskopf.[98]
In April 1940, early in the Second World War, Nazi Germany invaded and occupied Denmark.[99] To prevent the Germans from discovering Max von Laue's and James Franck's gold Nobel medals, Bohr had de Hevesy dissolve them in aqua regia. In this form, they were stored on a shelf at the Institute until after the war, when the gold was precipitated and the medals re-struck by the Nobel Foundation. Bohr's own medal had been donated to an auction to the Finnish Relief Fund, and was auctioned off in March 1940, along with the medal of August Krogh. The buyer later donated the two medals to the Danish Historical Museum in Frederiksborg Castle, where they are still kept,[100] although Bohr's medal temporarily went to space with Andreas Mogensen on ISS Expedition 70 in 2023-2024.[101][102]
Bohr kept the Institute running, but all the foreign scholars departed.[103]