Niels Bohr

On August 1, 1912, he married Margrethe Nørlund, sister of the mathematician Niels Erik Nørlund. The couple was blessed with six sons, of which two died in unfortunate circumstances.

He died on November 18, 1962, at his home in Carlsberg, Copenhagen, Denmark, after having a stroke. His body was cremated, and his ashes were buried in the family plot in the Assistens Cemetery in the Nørrebro section of Copenhagen.

He was born on October 7, 1885 in Copenhagen, Denmark, to Christian Bohr, a physiology professor, and his wife, Ellen Adler Bohr, daughter of a wealthy Danish Jewish family. He had an elder sister, Jenny, and a younger brother, Harald.

He received his early education from the Gammelholm Latin School which he joined when he was seven. From 1903 he attended the Copenhagen University where his major was physics, which he studied under Professor Christian Christiansen.

In 1909, he earned a master’s degree in physics and went on to complete his PhD in physics in 1911, both from the University of Copenhagen. His doctoral dissertation was on the electron theory of metals.

In 1911, he traveled to England and met J. J. Thompson of the Cavendish Laboratory at the Cambridge University. He conducted some research on cathode rays, but failed to impress Thomson. Later, Ernest Rutherford invited him to conduct post-doctoral research in England on the atomic structures.

In 1913, Bohr’s paper on atomic structure was published which became the basis of the famous ‘old quantum theory’.

From 1914 to 1916, he worked as a lecturer of physics at the Victoria University of Manchester, UK.

In 1916, he became a professor of theoretical physics at the University of Copenhagen, a post he held for 46 years. He founded the ‘Institute of Theoretical Physics’ at the Copenhagen University in 1920 and also served as its administrator until 1962.

During World War II, he fled from Denmark to America, where he worked on the Manhattan Project. After the war he became an outspoken activist against nuclear weapons and for the peaceful use of atomic energy.

He proposed an atomic model in which he postulated that electrons travel in fixed orbits around the atom's nucleus, and further explained how electrons emit or absorb energy. He introduced the idea that an electron could drop from a higher-energy orbit to a lower one, in the process emitting a quantum of discrete energy.

He is also known for conceiving ‘the complementarity principle’ which defined that wave and particle aspects of nature are complementary, and can never be experienced simultaneously. The principle states that items could be separately analyzed in terms of contradictory properties, like behaving as a wave or a stream of particles.