Niels Henrik David Bohr (October 7, 1885 - November 18, 1962) was a human physicist, a pioneer in the field of quantum mechanics. Bohr was born in Copenhagen, Denmark. Along with Ernest Rutherford, he developed the standard model of the atom as a nucleus orbited by electrons. Bohr received the 1922 Nobel Prize for physics. Bohr originated the principle of complementarity, according to which a quantum mechanical entity can be regarded as either a particle or a wave. He later worked on the Manhattan Project, which developed the first atomic bomb.