Niels Bohr was one of the pioneers of quantum physics and was one of the twentieth century's most widely respected thinkers. Bohr was only 21 when he won the gold medal of the Danish Academy of Sciences for his first research project in which he carried out a precise determination of the surface tension of water. Five years later he was awarded his doctorate for a theory explaining the behaviour of electrons in a metal. In 1911, on a scholarship from the Carlsberg Brewery, he went to the University of Cambridge to study under J. J. Thomson, but he soon left Cambridge to work with Ernest Rutherford at the University of Manchester. There he worked on 'quantum' models of the atom, which were developments of Rutherford's ideas. After a few months Bohr returned to Denmark where he married and took up a new post in the Institute of Technology. In 1913 he published the details of his quantum theory of the atom, and later that same year started to present the ideas that would eventually constitute the correspondence principle.
Bohr returned to Manchester in 1914, shortly after the outbreak of the First World War and stayed there until 1916 when he was offered a professorial appointment in Denmark. In 1920, he became the founding director of the Institute of Theoretical Physics in Copenhagen, where he continued to work on atomic physics and on the fundamental interpretation of quantum mechanics, particularly the development of the Copenhagen interpretation (his discussion with Einstein on this topic are legendary). He was awarded the Nobel Prize for Physics in 1922. Bohr was still in Copenhagen in 1940, when the Germans invaded. He stayed there until 1943, when, in imminent danger of arrest by the Gestapo, he escaped to Sweden by boat, and thence to Britain. He returned to Denmark in 1945 and lived there until his death.
Like many of the leading physicists of his generation, Bohr became interested in the physics of the nucleus. Using his liquid drop model (1936), he explained how a heavy nucleus could undergo fission following the capture of a neutron and demonstrated that the only isotope that would undergo fission with slow neutrons was uranium-235. Bohr subsequently became involved in the development of the atomic bomb and later became a strong supporter for strict control over nuclear weapons. He often tried to persuade statesmen to adopt rational and peaceful solutions rather than force. Throughout his working life, Bohr was enormously influential in his own professional field and also in the wider world of politics. It was partly through his political skills that a European laboratory for fundamental nuclear research (CERN) was set up in 1952. Following Bohr's death in 1962, the Copenhagen Institute for Theoretical Physics was renamed the Niels Bohr Institute in his honour.
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