Niels Bohr (1885–1962) was the Danish physicist whose 1913 model of the atom — electrons circling the nucleus in fixed shells — explained the structure of matter, opened the first era of quantum theory, and won him the 1922 Nobel Prize in Physics.
Founder of the Copenhagen institute that became the world capital of quantum physics, he spent the 1920s in famous debate with Einstein over what quantum mechanics means — and the 1940s helping, then warning, the atomic age he had made possible.
