The atomic model proposed by Niels Bohr in 1913 was an important milestone in the history of science for two quite different reasons. First, the Bohr theory answered some fundamental questions about the location and behavior of electrons in an atom. In a sense it provided the final step in the development of the modern theory of the atom that had begun with Joseph J. Thomson's discovery of the electron.

For all its success, however, the Bohr model confronted physicists with a somewhat disturbing situation. Bohr had not so much devised a new way of looking at the atom as he had pieced together ideas from classical physics with new, ad hoc assumptions that "explained" empirical observations. A number of physicists felt that some new--perhaps revolutionary--theory of matter was needed to provide a more sound basis for the Bohr model.

Interestingly enough, a number of ideas needed...