Quarks, Leptons and the Big Bang

Abstract

Particle physics has always been recognized as one of the topics that draws students into physics, but physics teachers at all levels have often shown a strange reluctance, or perhaps even an inability, to cash in on its popularity. Jonathan Allday's excellent book Quarks, Leptons and the Big Bang should help to sweep away such reticence. His position as a teacher at The King's School in Canterbury ensures that he has a clear grasp of the level of knowledge that might reasonably be expected of a sixth-former, while his involvement with the Institute of Physics' initiative to introduce more particle physics into the A-level curriculum shows where his educational interests are focused. Eschewing the traditional historical approach to the subject, Allday takes an unrelentingly `modern' attitude, emphasizing quarks and downplaying hadronic reactions. By starting with an overview of the standard model he is able to provide readers with key facts about quarks, leptons, fundamental forces and the big bang within the first 15 pages of Chapter 1; only then does he start assembling the background that will be needed for a deeper appreciation of the subject. One of the advantages of writing about particle physics is that even the background - relativity and quantum theory, in this case - is interesting. Both of these subjects are handled well and with the light touch that is essential in a book of this kind. The discussion of Feynman's `sum over paths' approach to quantum physics is particularly good - one of the best I have seen at this level. The chapters that follow, on leptons, antimatter, hadrons, hadronic reactions, particle decays and the evidence for quarks, provide good coverage of the basic concepts of particle physics and pave the way for a well placed chapter on experimental techniques. This in turn leads to a chapter on exchange forces that contains a valuable discussion of Feynman diagrams - one that properly recognizes their importance, but does not overplay their physical significance. This chapter also introduces some of the more speculative ideas of particle physics, such as grand unification and supersymmetry. But here I have one of my few real criticisms of the book. Although the discussion of `exotic theories' proceeds at pretty much the same pace as the rest of the book, I greatly regret the fact that it does not say more about string theory. Whatever the ultimate value of string theory, if any, there can be no doubt that it generates a good deal of interest and many readers will be disappointed not to find a more extensive discussion of it. The remaining chapters of the book are mainly concerned with the big bang. The treatment manages to maintain the high standard that characterizes the rest of the work, yet somehow I felt it was a bit more of a struggle. Allday certainly seemed happier writing about the core of particle physics rather than its astrophysical implications, and it was noticeable that one of the book's very few `obvious' minor errors was to be found here (the distance to the Andromeda galaxy in millions of light years is about 2.2 not 22). Allday's writing is not brilliant, but it is exceptionally clear and is lightened from time to time by well judged touches of humour. Another sign of good judgement is the inclusion of occasional `interludes' to deliberately break up the generally smooth flow of the text. Although there are only two `official' interludes, one on CERN and another on the formation of antihydrogen, and both are located towards the end of the text, there are less formal breaks at earlier points, including one labelled as a `coffee point' at the end of a relatively demanding discussion of lepton number conservation. Despite being somewhat artificial these devices help to convey the feeling that the author is a genuinely concerned teacher who really wants to educate his readers, and would not be content merely to report recent developments. Jonathan Allday's clearly written and well produced Quarks, Leptons and the Big Bang will be warmly welcomed by a number of general science readers, and should also find a place in all school and college libraries. It would constitute valuable and enjoyable summer reading for anyone embarking on a physics degree, and should be seriously considered as recommended supplementary reading by those university lecturers teaching specialized courses on particle physics who think that their students might benefit from a simple non-mathematical overview of the subject.