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This splendid book explains both the triumph and the mystery that is quantum theory. It is a triumph because of its towering mathematical structure, and amazing empirical accuracy. It is a mystery because of the conundrums about how to interpret it.
[...]... his big breakthrough The calculations looked pretty complicated but, when the mathematical dust settled, it became apparent that what had been involved was the manipulation of mathematical entities called matrices (arrays of numbers that multiply together in a particular way) Hence Heisenberg’s discovery came to be known as matrix mechanics The underlying ideas will reappear a little later in a yet more... important physical significance connected with what quantities could simultaneously be measured in quantum mechanics [See 4 for a further mathematical generalization that proved necessary for the full development of quantum theory.] In 1925 matrices were as mathematically exotic to the average theoretical physicist as they may be today to the average nonmathematical reader of this book Much more familiar... they a persistent feature of radiation or simply an aspect of the way that radiation happened to interact with a black body? After all, drips from a tap form a sequence of aqueous quanta, but they merge with the rest of the water and lose their individual identity as soon as they fall into the basin The photoelectric effect The next advance was made by a young man with time on his hands as he worked as... electron According to the Planck prescription, change of energy is the same as change of frequency Compton was thus able to give a quantitative explanation of his 13 Classical cracks The Bohr atom was a great triumph But it had arisen from an act of inspired tinkering with what was still, in many respects, classical physics Bohr’s pioneering work was, in reality, a substantial repair, patched on to the shattered... 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... time was the mathematics associated with wave motion (involving partial differential equations) This used techniques that were standard in classical physics of the kind that Maxwell had developed Hard on the heels of Heisenberg’s discovery came a very different-looking version of quantum theory, based on the much more friendly mathematics of wave equations Quantum theory Wave mechanics Appropriately... discovery has been regarded as the greatest triumph of 19th-century physics The fact that light was electromagnetic waves seemed as firmly established as it could possibly be Maxwell and his contemporaries regarded these waves as being oscillations in an all-pervading elastic medium, which came to be called ether In an 3 Classical cracks 1 Adding waves: (a) in step; (b) out of step encyclopedia article,... the details with increased accuracy In the last quarter of the century, a young man in Germany contemplating an academic career was warned against going into physics It would be better to look elsewhere, for physics was at the end of the road, with so little really worthwhile left to do The young man’s name was Max Planck, and fortunately he ignored the advice he had been given As a matter of fact, some... radiation falling on it and then reemits all of that radiation The issue of the spectrum of radiation in equilibrium with a black body might seem a rather exotic kind of question to raise but, in fact, there are excellent approximations to black bodies available, so this is a matter that can be investigated experimentally as well as theoretically, for example by studying radiation in the interior of a. .. not make any sense at all It predicted that an infinite amount of energy would be found concentrated in the very highest frequencies, an embarrassing conclusion that came to be called ‘the ultraviolet catastrophe’ The catastrophic nature of this conclusion is clear enough: ‘ultraviolet’ is then a way of saying ‘high frequencies’ The disaster arose because classical statistical physics predicts that each