Niels Bohr

Niels Henrik David Bohr (7 October 1885 - 18 November 1962) was a Nobel Prize winning Danish physicist. He made important contributions to understanding the structure of atoms and the development of quantum mechanics.

Bohr was born in Copenhagen, to parents Christian Bohr and Ellen Bohr (née Adler). Educated at the University of Copenhagen, he completed his doctorate in physics in 1911, before continuing his studies in Manchester, England with Ernest Rutherford and at the University of Cambridge with Sir Joseph John Thompson. In 1913, Bohr published the Bohr model of atomic structure, developed from his earlier collaboration with Rutherford. The Bohr model introduced the concept of a quantized shell surrounding an atom, to explain how electrons can possess a stable orbit around a nucleus. Bohr also proposed that an electron could move from an outer orbit to an inner orbit, emitting a photon of discrete energy, or conversely move from an inner orbit to an outer one, absorbing energy. This also became the basis for quantum theory.

Returning to the University of Copenhagen in 1916, Bohr was appointed professor of physics, and established the Institute of Theoretical Physics in 1920 as founding director. He was awarded the Nobel Prize in Physics in 1922, for 'his services in the investigation of the structure of atoms and of the radiation emanating from them'.

During September 1941, Bohr was visited by former student Werner Heisenberg, who was now one of the leading theoretical physicists in Germany. Bohr and Heisenberg reportedly one evening discussed the feasibility of atomic weapons, although there is much debate on what exactly was said. This meeting was the basis of a 1998 play by Michael Frayn, Copenhagen, which speculated on the nature of the conversation. In September 1943, Bohr escaped from occupied Denmark and travelled to Sweden, before flying to London to work on the British Tube Alloys nuclear weapons development project, with his son Aage. In 1943, Bohr was invited to the United States of America to work on the Manhattan Project, and made contributions to the development of modulated neutron initiators. It was in April 1944, when receiving correspondence from Soviet physicist Peter Kapitza, that he became aware that the Soviet Union knew of the advances the British and American scientists had made on the development of an atomic bomb. Following the end of the Second World War, Bohr returned to Copenhagen, and fearing that the weapon would change international relations, advocated the peaceful use of nuclear energy. He was the inaugural recipient of the Atoms for Peace Award in 1957.

Bohr died from heart failure at his Carlsberg residence.

The element bohrium (Bh), discovered in 1981, is named in his honour.