# Niels Bohr Danish physicist (1885–1962) whose 1913 model of the atom applied Energy Quantization to electron orbits, whose institute in Copenhagen became the organizing center of The Quantum Revolution, and who was, for thirty years, [[Albert Einstein]]'s antagonist in the argument over what the theory meant (The Bohr-Einstein Debates). He won the Nobel Prize in 1922, formulated the principle of complementarity — that wave and particle descriptions are each complete and mutually exclusive — and is the principal author of the Copenhagen Interpretation, the working orthodoxy of the field. He is in this vault, like Einstein, for the politics. ## The escape and the bomb Bohr's mother was Jewish; in September 1943, warned of his imminent arrest, he crossed the Øresund to Sweden by fishing boat, was flown to Britain in the bomb bay of a Mosquito (he lost consciousness for want of oxygen), and joined the Manhattan Project at Los Alamos as "Nicholas Baker." He contributed little to the engineering and a great deal to the argument: from 1944 he pressed Roosevelt and Churchill to tell the Soviet Union about the bomb before it was used, on the ground that a secret could not be kept and that an arms race could be prevented only by an "open world" of shared scientific information. Churchill, after a disastrous meeting, wanted him locked up; Roosevelt listened and did nothing. His 1950 open letter to the United Nations made the case in public. The [[Nuclear Science]] page carries the arms-control lineage his argument began; [[The Manhattan Project]] the program. ## The Heisenberg question In September 1941 Werner Heisenberg, running the German nuclear effort, visited Bohr in occupied Copenhagen. What was said has never been settled — Heisenberg's later account was that he sought Bohr's help in getting physicists on both sides to withhold the bomb; Bohr's unsent letters, released in 2002, say he understood Heisenberg to be telling him Germany was building one — and the episode is the subject of Michael Frayn's *Copenhagen*. It matters here as the vault's cleanest case of the scientist's responsibility under a regime: two men with the same knowledge and opposite governments, and a conversation neither could afford to have plainly. ## See Also - [[The Manhattan Project]] · [[Nuclear Science]] · [[History of Science Hub]]