October 7, 1885, Copenhagen (Denmark) - November 18, 1962, Copenhagen (Denmark)
Son of Christian Bohr, a devout Lutheran, professor of physiology at the city's University, and Ellen Adler, from a wealthy Jewish family of great importance in Danish banking and ‘parliamentary circles’.
After receiving his doctorate in physics from the University of Copenhagen in 1911, he sought to further his studies at the Cavendish Laboratory in Cambridge with Joseph J. Thomson, discoverer of the electron and winner of the Nobel Prize in 1906. This was a subject of great interest to Bohr, as it was the subject of his doctoral thesis, which he hoped would be translated into English. However, Thomson was not very enthusiastic about Bohr's work, so he decided to go to Manchester and complete his studies with Ernest Rutherford, another Nobel Prize winner and expert in radioactivity and atomic models, as his teacher, with whom he established a long-lasting scientific and friendly relationship.
Rutherford had worked out a theory of the atom which was entirely valid on a speculative level, but which could not be sustained within the laws of classical physics. Borh, in a display of boldness that was unpredictable in his shy and retiring character, dared to circumvent these problems that were hindering Rutherford's progress with a solution as simple as it was risky: he simply stated that the movements inside the atom were governed by laws that were alien to those of traditional physics.
In 1913, Niels Bohr achieved worldwide fame in the field of physics by publishing a series of essays in which he revealed his particular model of the structure of the atom. It was a modification of Rutherford's atomic model in which the atom is like a ‘microscopic solar system’ in which the electrons orbit the nucleus. Bohr assumed that the electrons moved in circular orbits around the nucleus.
Niels Bohr developed his model according to three fundamental postulates:
- Electrons describe circular orbits around the nucleus of the atom without radiating energy.
- The only orbits allowed for an electron are those for which the angular momentum of the electron is a certain integer multiple.
- The electron only emits or absorbs energy in the jumps from one allowed orbit to another.
Three years later, the Danish scientist returned to his hometown to take up a professorship in theoretical physics at the University of Copenhagen and secured the funds to set up the Nordic Institute for Theoretical Physics, which he directed from 1920 until his death.
In a very short time, this Institute, together with the German universities of Munich and Göttingen, became one of the three corners of the European triangle where the main research on the physics of the atom was being carried out.
In 1922, the year in which Bohr definitively established himself as a scientist of universal renown by winning the Nobel Prize ‘for his research into the structure of atoms and the radiation emanating from them’, his son Aage Niels Bohr was born, who followed in his father's footsteps and collaborated with him on several research projects. He also received a PhD in physics and, like his father, was a university professor of physics and director of the Nordic Institute for Theoretical Physics, and was awarded the Nobel Prize in 1975.
Immersed in his research on the atom and quantum mechanics, Niels Bohr enunciated the principle of correspondence in 1923, to which he added the principle of complementarity in 1928. As a result of this last contribution, the so-called ‘Copenhagen school of quantum mechanics’ grew up around him, whose theories were fiercely contested by Albert Einstein. Despite these differences, the father of the theory of relativity recognised by the Danish physicist as ‘one of the greatest scientific researchers of our time’.
In the 1930s, Niels Bohr spent long periods in the United States, where he brought the first news of nuclear fission, discovered in Berlin in 1938 by Otto Hahn and Fritz Strassmann. For five months, he worked with J. A. Wheeler at the Institute for Advanced Study in Princeton, New Jersey, and announced with his collaborator that plutonium, like uranium, would be fissionable.
His life and those of his family were so threatened that he was forced to take his family on a small fishing boat to Sweden. A few days later, Bohr took refuge in the United States and, under the pseudonym Nicholas Baker, began to collaborate actively in the so-called ‘Manhattan Project’, developed at the Los Alamos laboratory in New Mexico, which resulted in the manufacture of the first atomic bomb.
At the end of World War II, in 1945, he returned to Denmark and once again headed the Nordic Institute for Theoretical Physics. From then on, aware of the potentially devastating applications of his research, he devoted himself to convincing his colleagues of the need to use the findings of nuclear physics for beneficial purposes.
A pioneer in the organization of international symposia and conferences on the peaceful use of atomic energy, in 1951 he published and disseminated throughout the world a manifesto signed by more than a hundred eminent scientists, stating that the public authorities should guarantee the use of atomic energy for peaceful purposes. For this, in 1957, he received the Atoms for Peace Prize, awarded by the Ford Foundation to promote scientific research for the betterment of mankind.
Director, since 1953, of the European Organisation for Nuclear Research, Niels Henrik David Bohr died in Copenhagen in the autumn of 1962, aged seventy-seven, after having printed such valuable works as 'The Theory of Spectra and Atomic Constitution' (1922), 'Light and Life' (1933), 'Atomic Theory and Description of Nature' (1934), 'The Mechanism of Nuclear Fission' (1939) and 'Atomic Physics and Human Knowledge' (1958).
