ABSTRACT

From left to right : Robert Millikan, Georges Lemaître and Albert Einstein

Niels Bohr

He studied physics at the University of Copenhagen where his father taught physiology. In 1911 he received his doctorate and then stayed at Cavendish Laboratory with

Joseph J. Thomson at the head, as well as Manchester University, directed by Ernest Rutherford (1908 Nobel Prize for Chemistry). Bohr's first scientific work was devoted to the study of the surface tension of water droplets in a jet of air, a model which he used later to

explain the excitation of atomic nuclei (1937) and the mechanism of uranium fission (1939). Between 1916 and 1962 he taught at the University of Copenhagen. In 1920 Bohr was appointed Head of the Institute of Theoretical Physics and he occupied this post until 1962. In 1943, when Denmark was occupied by Germany, Bohr and his family fled to Sweden and then to the United States. But in 1945 they returned to their home country. Niels Bohr and his son Aage worked on the Manhattan Project. It was during a trip to the United States in 1939 that he brought the news that Otto Hahn (1944 Nobel Prize for Chemistry) and Lise Meitner, in Germany, had probably succeeded in uranium fission by slow neutrons. In 1994,

rumours circulated, wrongly, that he had given confidential information, in 1945, on the American nuclear project to the Soviets: in fact the writings and diagrams related to discussions that he had had with Werner Heisenberg had been discovered. Being a pacifist, Bohr was also President of the Danish Atomic Energy Commission and in 1955 he took an active part in the first Atom for Peace Conference in Geneva. Bohr was one of the founders of CERN. He also took an interest in biology and launched the project of the Institute of Genetics in Cologne, but failed to accomplish this task and to bring the project to life. In his college years he was a brilliant physicist, and at the same time a superb soccer player. In 1922 Bohr was granted the Nobel Pr ize in physics . The same year, the Nobel commit tee presented the Nobel Prize to Albert Einstein, who won i t in 1921

Stationary orbitals. When the wavelength associated with the circular motion of an electron is a submultiple of the length of its (classical) trajectory, the particle undergoing a centripetal acceleration (due to the electric force of the nucleus) does not radiate energy.