Bohr, Niels Henrik David (1885–1962), Danish physicist. Bohr was the foremost influence on and major contributor to the development of quantum theory in the first half of the 20th century. In 1913 he postulated the theory that bears his name and that laid the groundwork for modern atomic physics. During World War II he worked in Britain and the United States on atomic bomb projects. Bohr was awarded the Nobel Prize for Physics in 1922.