Foreword to first edition

Professor Sir Brian Pippard, FRS

One of the greatest transformations of physics began about 70 years ago, when quantum mechanics was formulated. Many of the outstanding puzzles of atomic structure suddenly became clear, and it was not long before a start was made on understanding the chemical bond. Before 1930 the new ideas were applied to solids; one of the first successes was to explain how electrons can move so easily between the closely-packed atoms of a metal, and soon after this came the explanation of why some solids conduct electricity well, but others are insulators. Since then there has been no slackening of effort; many more phenomena have been revealed and explained, and new technologies have grown up out of the successes, to transform our lives. One example will suffice. The transistor was invented in 1947 by solid-state physicists, and without it modern communication and information systems would never have been developed.

There are more people engaged in research into condensed matter, and its applications, than on any other branch of physics. One consequence of this activity is that the assimilation of new facts and theories is an almost overwhelming task, and we are forced to rely on the efforts of those who can put together a readable account of the main themes. It is not surprising that most of the recent text books meet the challenge by concentrating on general principles and the theoretical treatment of rather simple examples, to such a degree that a casual reader might consider that the whole subject is dominated by theory. One cannot deny that without theory we should be left with a miscellaneous ragbag of facts, lacking the means to find any underlying structure. On the other hand, without the challenge of the facts, the deep general theories like quantum mechanics would never have been looked for.

Nowadays most physicists specialise in either experiment or theory, and there are few to rival those of earlier days who, like Maxwell, Rayleigh, Helmholtz and Fermi, were superlatively good at both. Nevertheless, all modern specialists acknowledge their dependence on the different skills of others. A theoretician ignorant of facts is no more to be trusted than an engineer who takes a textbook diagram of a bridge as the basis for a design, never having seen the real thing or tested a model. Unfortunately the prevalence of software packages for almost every conceivable task encourages the mistaken belief that they incorporate all the experience needed for success in their application. If you read Michael de Podesta’s book seriously you are unlikely to fall into such a grievous error. Once its lesson has been learnt, it will remain a source of information and, more important still, an incentive to continue with the process of self-education, which is the key to achievement.

Of all the messages that this book conveys there is especially one with which I feel the strongest sympathy. It is not that facts are things you have to assimilate before you settle down to interesting theories – rather, it is that the facts themselves, if well presented, are interesting in their own right and raise a host of questions that make you want to find out how everything ties together. All too rarely do most of us stop to think about apparently trivial everyday observations. How often, for example, do we wonder why there are such things as liquids? You will not find a complete answer here because the complete answer is not known (and perhaps least understood about water, that most extraordinary of liquids) but you will discover the beginning of an answer, and you will find that the beautiful simplicities of thermodynamics help you to see what happens when a solid melts, and give hints of the difficulties that one may yet hope to eventually overcome. And this is only one of the tantalising problems discussed here in the hope that you will discover (if you have not done so already) both the lovely certainties and the stimulating mysteries that together make physicists enjoy their work, and continue to enjoy it as long as they can carry on with physics.