The Nobel Prize winner Niels Henrik David Bohr was born in Copenhagen, Denmark on October 7 1885. The middle of three children, his father Christian Bohr was the professor of physiology at Copenhagen University and his mother was the daughter of the Jewish politician. He had an elder sister Jenny and a younger brother Harald with whom he had a life-long deep friendship.
In 1891, he went to the Grammelholms School where he remained until he finished his secondary education. His last two years at school saw him specializing in physics and mathematics. Niels always credited his father in encouraging his interests in these subjects.
Leaving school, he entered Copenhagen University in 1903 studying physics as his main subject but also taking courses in mathematics, astronomy and chemistry. While still a student, he conducted experiments at his father’s laboratory at the University, producing a paper on “the analysis of vibrations of water jets as a means of determining surface tension”. It was with this paper he won the Gold medal from Royal Danish Academy of Sciences in 1906.
His studies continued at Copenhagen University. He gained a Masters degree in 1909 and a Doctorate in 1911. His thesis for his doctorate was on “Studies on the electron theory of metals”. He dedicated this thesis to his father who had died in February 1911.
After obtaining his doctorate, the Carlsberg Foundation gave Niels Bohr a travel grant, which he used to travel to England. In September 1911, he started working with the Nobel Prize winner Sir Joseph John Thomson at the Cavendish Laboratory in Cambridge. In March 1912, he moved to Manchester to work with another Nobel Prize winner, Ernest Rutherford, on the structure of the atom.
Returning to Copenhagen in July 1912, he continued to work on his theories of atomic structure publishing three papers in 1913. One was on the structure of the hydrogen atom; the other two were on the atomic structure of elements heavier than hydrogen.
On 1 August 1912 he married Margrethe Norlund, a girl he had been engaged to before he left for England. They were to have six sons during their marriage but would lose two.
Copenhagen University appointed him as a docent in July 1913. The following year he wrote to the Department of Educational Affairs suggesting that they create a post of professor of theoretical physics and give him the post. They agreed to this but there were some delays in doing so. These delays led Bohr to accept a post in England with his former mentor Ernest Rutherford as Schuster Reader. He remained in Manchester until 1916 before returning to Copenhagen to take up his professorship.
He started work on plans for an Institute for Theoretical Physics in Copenhagen. This opened in 1921 and with Niels Bohr appointed as its Director. He remained the Director of this institute until his death.
In 1922, he won the Nobel Prize for Physics in recognition of his work on atomic structure.
Over the years, he worked on various aspects of theoretical physics including the quantum theory. Along with his wife and one of his sons, Hans, Niels Bohr went on a world tour in 1937. This tour took him to the United States, Japan, China and the Soviet Union.
The year 1937 saw the death of his mentor and friend Ernest Rutherford. Bohr attended the funeral at Westminster Abbey, at which he gave a speech in tribute to the dead scientist.
With the Second World War, the Nazis occupied Denmark. Although he had been brought up as a Christian, Bohr was half-Jewish. This meant Copenhagen was a very dangerous place for him. In 1943, he escaped Denmark by fishing vessel to Sweden. From there he went first to England then to the United States where he worked on the atomic bomb project at Los Alamos.
Niels Bohr argued in favour of international cooperation in the production of the atomic bomb. He made his views known, in 1944, to both President Roosevelt and Winston Churchill.
Bohr continued to argue for cooperation in the field of atomic weapons when he returned to Copenhagen at the end of the war. In 1950, he sent an open letter to the United Nations stating, “Humanity will be confronted with dangers of unprecedented character unless, in due time, measures can be taken to forestall a disastrous competition in such formidable armaments and to establish an international control of the manufacture and use of powerful materials.” The USA gave him the first Atoms for Peace Prize in 1957.
When he died of a heart attack on 18 November 1962 many scientists and world leaders paid tribute to him. The then President of the United States John F. Kennedy said of him, “American scientists, indeed all American citizens who knew Doctor Bohr’s name and his great contributions, have respected and venerated him for more than two generations.”
His four surviving sons all made successful careers for themselves. Hans Henrik became a doctor, Erik a chemical engineer, and Ernest a lawyer. Aage gained a PhD to become a theoretical physicist like is father. On his fathers death Aage became the Director of the Institute for Theoretical Physics. In 1975, Aage Niels Bohr became the second member of the family to win a Nobel Prize for Physics. His was a third share for his work on “discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection”
Nils Bohr Biography University of St Andrews Website
Nobel Lectures, Physics 1922-1941, Elsevier Publishing Company, Amsterdam, 1965