Chapter 2 The light dawns
The years following Max Planck’s pioneering proposal were a time of confusion and darkness for the physics community. Light was waves; light was particles. Tantalizingly successful models, such as the Bohr atom, held out the promise that a new physical theory was in the offing, but the imperfect imposition of these quantum patches on the battered ruins of classical physics showed that more insight was needed before a consistent picture could emerge. When eventually the light did dawn, it did so with all the suddenness of a tropical sunrise. In the years 1925 and 1926 modern quantum theory came into being fully fledged. These anni mirabiles remain an episode of great significance in the folk memory of the theoretical physics community, still recalled with awe despite the fact that living memory no longer has access to those heroic times. When there are contemporary stirrings in fundamental aspects of physical theory, people may be heard to say, ‘I have the feeling that it is 1925 all over again’. There is a wistful note present in such a remark. As Wordsworth said about the French Revolution, ‘Bliss it was in that dawn to be alive, but to be young was very heaven!’ In fact, though many important advances have been made in the last 75 years, there has not yet been a second time when radical revision of physical principles has been necessary on the scale that attended the birth of quantum theory. 15
