Niels Bohr was born in Copenhagen, Denmark. He received a doctors degree in physics at the University of Copenhagen in 1911. In the same year he traveled to London to study, and in 1912, to work with the physicist Rutherford.

Rutherford had postulated an atom which was a miniature solar system, with the positive nucleus as the sun, and the negative electrons as planets. See the the gold foil experiment.
It was impossible, however, in terms of classical physics to imagine that in such a sytem the electrons could revolve without radiating energy, which meant that the system must be unstable.

In 1913 Bohr combined the ideas of Rutherford with Planck's quantum theory in a new and radical solution. He suggested that a certain distances from the nucleus there are stationary positions or states, and as long as one or more electrons is in such a position it can revolve around the nucleus without radiating. He postulated that the arrangement of the electrons in their orbits must depend on the position of the atom in the periodic table. He also showed that the spectral lines characteristic of each atom could be explained as the energy radiated by an exited electron in moving from one state or orbit to another.

Niels Bohr was Director of the Institute for Theoretical Physics in Copenhagen from 1916 until 1943 when he fled from German occupied Denmark to the United States. He returned to Copenhagen after the war in 1945.

In 1922 Bohr was awarded the Nobel Prize for Physics.

People: 1500-2000 Events: 1913