Niels Bohr
Niels Henrik David Bohr (October 7, 1885 - November 18, 1962) was a Danish physicist. He made essential contributions to understanding atom structure and quantum mechanics.
Born in Copenhagen, Denmark to Christian Bohr and Ellen Adler, Bohr received his doctorate from Copenhagen University in 1911. He then studied under Ernest Rutherford in Manchester, England. Based on Rutherford's theories, Bohr published his Bohr model about atom structure in 1913, introducing the theory of electrons travelling on orbits around the atom's nucleus, with the outer orbits holding more electrons than the inner ones, thereby determining the chemical properties of the atom. Also, an electron could drop from an outer orbit to an inner one, emitting a photon (light) of discrete energy. This became the basis for quantum theory.
In 1916, Bohr became professor at the University of Copenhagen, and director of the newly constructed "Institute of Theoretical Physics" in 1920. In 1922, he was awarded the Nobel Prize in physics for developing the Copenhagen interpretation of quantum mechanics.
Bohr also conceived the principle of complimentarity: that items could be separately analyzed as having several contradictory properties. For example, physicists currently conclude that light is both a wave and a stream of particles--two seemingly mutually exclusive properties--based on this principle. Bohr also found philosophical applications for this daringly original principle. Albert Einstein much preferred the clarity of classical physics over the new physics of Bohr and Max Planck. He and Bohr had good-natured arguments over the verity of this principle throughout their lives.
One of Bohr's most famous students was Werner Heisenberg, who became head of the German atomic bomb project. In 1941, during the German occupation of Denmark in World War II, Bohr was visted by Heisenberg in Copenhagen and apparently learned something of the German plans. In 1943 he escaped to Sweden to avoid arrest by the German police, then travelled to London. He worked at Los Alamos, New Mexico, USA, on the Manhattan Project, however his role was minor. He is quoted as saying "That is why I went to America. They didn't need my help in making the atom bomb." He was seen as a knowledgeable consultant or "father confessor" on the project [1]. After the war he returned to Copenhagen, advocating for a peaceful use of nuclear energy. He died in Copenhagen.
The element Bohrium is named in his honor.
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Heisenberg claimed in an interview after the war when the author Robert Jungk was working with the book Brighter than a thousand suns, that he had tried to establish a pact with Bohr, so that scientists on neither side should help develop the atomic bomb. He also said that the German attempts were entirely focused on energy production, and that his circle of colleagues tried to keep it that way.
When Bohr saw this claim he disagreed wholeheartedly. He said, that Heisenberg had indeed let him know in Copenhagen that he was working on an atomic bomb project, and that he thought that Germany would win the war. He dismissed the idea of any pact as an after-the-fact construction. He drafted several letters to inform Heisenberg about this but never sent any of them.
The play Copenhagen, which ran on Broadway for a time, written by Michael Frayn, was about what might have happened at the 1941 meeting between Heisenberg and Bohr.
On the relation to Heisenberg
Books about Bohr
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