Bohr, Niels Henrik David
Rutherford had discovered the nucleus of the atom in 1911, but classical theory was unable to explain the stability of the nuclear model of the atom. Bohr provided the solution to this problem in 1913, when he postulated that electrons move around the nucleus of the atom in restricted orbits and explained the manner in which the atom absorbs and emits energy. He thus combined the quantum theory with this concept of atomic structure. Much of the knowledge of modern physics was made possible by Bohr's initial revolutionary assumption that atomic processes cannot be explained by classical laws alone. Bohr was a leading figure in the continuing development of the quantum theory over the next twenty years. He received the 1922 Nobel Prize in Physics.
When Bohr visited the United States in 1938 and 1939, Bohr told American scientists of his belief, based on experiments reported by German scientists, that the uranium atom could be split into approximately equal halves. This was verified by scientists at Columbia. Bohr returned to Denmark but fled from the Nazi-occupied country in 1943. He gave valuable assistance in the atomic bomb research at Los Alamos, N.Mex., and in 1945 again returned to Denmark. His writings include
See biographies by R. E. Moore (1966) and N. Blaedel (1988); studies by A. P. French and P. J. Kennedy, ed. (1987), D. R. Murdoch (1987), F. Aaserud (1989), and A. Pais (1991).
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