October 7 - Niels Bohr

Danish physicist Niels Bohr was born on October 7, 1885, in Copenhagen. Two years after earning his doctorate at the University of Copenhagen, he developed the Bohr model of atomic structure, involving his theory that electrons orbit around an atom’s nucleus. An element’s chemical properties are largely determined by the number of electrons in the outer orbits. He also theorized that an electron can drop from a higher-energy orbit to a lower one, thereby releasing a “quantum” of energy. In the 1920s, Bohr, Werner Heisenberg and others devised the “Copenhagen interpretation” of quantum physics, which involved ideas of probability, uncertainty and observation. Bohr and Albert Einstein famously debated the complex issues arising from theories of quantum mechanics. The latter declared, "I, at any rate, am convinced that He [God] does not throw dice." Bohr is said to have replied, "Einstein, stop telling God what to do!" Bohr barely escaped arrest by the Nazis in 1943 and went on to consult with the Manhattan Project that built the atomic bomb.