Foundations of Physics, Vol. 18, No, 5, 1988

Book Review

Constructing Quarks. By Andrew Picketing. University of Chicago Press, Chicago, 1984, x +468 pp., $30.00 (cloth), $17.95 (paperback).

Andrew Pickering's Constructing Quarks reminds me of a sandwich made with fine meat placed between two slices of processed white bread. My advice is throw away the bread and eat only the meat. What Pickering has given us is a rather complete and admirable history of the development of quark theories and models, but embedded it within the strong program in the sociology of science. This program undervalues the role of experimental evidence and constructs explanations in terms of the interests and practices of the ~cie~tific community. In Pickering's view, the science that results is a mere social construction that has no rational warrant as knowledge. "On ~.he view advocated in this chapter, there is no obligation upon anyone framing a view of the world to take account of what twentieth-centory science has to say." (P. 4t3.)

Before discussing and criticizing this view I wish to comment on some of the considerable virtues of this book. Picketing has managed to take a rather technical history, involving complex and advanced physics, and make it understandable to a reader without an extensive background in quantum field theory and particle physics. I believe this book can be read with profit by both undergraduates in physics and even by general readers. Although there are times when Pickering's discussions of renormalizability, constituent quark models, GIM mechanisms, and the like will be too much for such readers, overall the story is quite clear. I should add that Pickering's style conveys much of the excitement of the physics. His dis- cussions of "the R crisis," the slaying of the mutants," "the November revolution," etc. keep the reader interested in what happens next. He tells a cracking good story.

Pickering begins his history with a good survey of what he calls the ~otd" physics, the study of particle resonances and soft-scattering processes,

585

0015-9018/88/0500-0585506,00/0 © 1988 Plenum Publishing Corporation

586 Book Review

during the period 1945-1964. In 1964, with the invention of quark models by Zweig and by Gell-mann, the "new" physics began. Although these early models had success in classifying particles, Pickering argues that it was only with the analysis of deep inelastic electron scattering and Feynman's patton model that quarks began to be taken seriously. He suggests here and elsewhere that, although other possible theoretical explanations were available, because the quark-patton view allowed both theorists and experimentalists to continue their work, these were not investigated. Pickering never specifies what these alternatives were, what experimental support they had, and why they should have been taken seriously. In his analysis, Picketing does not seem to understand the idea that not all theories are equally supported by experimental evidence, the idea of partial but not complete confirmation, and that testability by future experiment is a good reason for investigating a successful theory. He also does not seem to distinguish between the context of justification, the decision to accept a theory, and the context of pursuit.

Pickering continues with a discussion of the rise of gauge theories, in particular the Weinberg-Salam unified theory of electroweak interactions. I found his presentation of this theory particularly clear and understandable, although directed primarily at readers with a knowledge of physics. He points out that, until 't Hooft showed that such gauge theories were renor- malizable, there was almost no interest in this work. During the period 1967-1971 there were only five citations of Weinberg's paper. After 't Hooft's work there were 64 citations in 1972 and 162 in 1973. The impor- tance of renormalizability as a condition for a successful theory is clear. It is here that Pickering emphasizes his distrust of experimental evidence in theory choice. His discussion centers on the 1970s experiments demonstrating the existence of the weak neutral currents predicted by the Weinberg-Salam theory. He notes that earlier experiments had interpreted such events as neutron background. It was only after the theoretical predic- tions that the hew experiments changed their "interpretive practice" and found the neutral currents. Picketing emphasizes, I believe correctly, the importance of theory as a guide to new phenomena, but he does not seem to understand that theoretical belief, no matter how strong, cannot put the appropriate events in a spark or bubble chamber.

The increasing success of the standard model--quantum chromo- dynamics (QCD) and Weinberg-Salam electroweak unification--is discussed next. Pickering includes the "R crisis," the fact that the ratio of hadron production to muon pair production in e+e - collisions was too high, the solution of that problem by the discovery of the J/O with the suggestion of a charmed quark, and the further discovery of naked charm,

Book Review 587

the D mesons. He notes that at this point quarks became real. He attributes this to the interests of physicists and the future utility of this model for the work of both theorists and experimentalists. I would argue that at this point the theory had received considerable confirmation, and that this explains the behavior of the physics community. The story continues with the further success of the standard model and the discovery of the v lepton and the upsilon particle, evidence for the bottom quark. Pickering argues that physicists chose their experimental evidence selectively, preferring the SLAC results on the scattering of polarized electrons, which supported the Weinberg-Satam theory, and rejecting the atomic parity-violating experiments, which did not. He ignores the experimenter's own caveat that the calculation of such atomic effects was uncertain, and relegates the subsequent experimental results, which helped resolve the discrepancy, to a footnote. He also does not discuss the arguments for the validity of the experimental results that appeared in these papers.

Pickering continues his story through the late 1970s and early 1980s during which experiments were centered on phenomena of interest to QCD theorists. He emphasizes the fruitful interaction of theory and experiment, but seems to regard it as somewhat sinister and not as the good practice of science. There is, of course, a legitimate fear that, as the number of accelerators decreases and experiments become larger, more expensive, and fewer in number, only phenomena of current theoretical interest will be investigated. The history of modern physics seems to show that this fear is unfounded. Results that do not fit currently accepted theories are always being found. As one of Pickering's own heroes, Thomas Kuhn, notes, an accepted paradigm is a very useful guide for investigating nature in depth and detail and for leading to the discovery of anomalies for that very paradigm. Pickering also seems to long for the "old" physics in which obvious phenomena such as resonance production and soft scattering were investigated, rather than the somewhat rarer phenomena of interest to current theories. How and why these phenomena came to be obvious is never discussed. One might imagine a Picketing-like scenario for gravitational physics in the 1920s. One might complain that physicists, instead of investigating obvious phenomena such as falling bodies and planetary positions, were, under the baleful influence of the new general theory of relativity, looking at such esoteric phenomena as the advance of the perihelion of Mercury, the bending of light in a gravitational field, and the gravitational red shift. The point is clear. New theories tend to make new phenomena of interest.

If this review has been critical of Pickering's approach to the study of science, it is because I believe his book should be read by physicists. In

588 Book Review

addition to giving us a very good history of an episode in contemporary physics, he has also asked important questions about how science works. I do not agree with his answers to these questions, but ! do think that physicists should think about the issues he has raised.

Allan Franklin Department of Physics University of Colorado Boulder, Colorado 80309