Is there an ultimate theory of nature—a “Final Theory”—from whose principles all laws that govern the workings of the physical universe may be deduced? Such a theory would provide the complete underlying rules that control, in finest detail, every action of inanimate or animate matter—including all the (non-random) activities of our very selves. Might such a theory even be within the actual grasp of today’s physicists? Steven Weinberg, in his new book, Dreams of a Final Theory, provides an unqualified “yes” in answer to the first of these questions, and he also gives expression to a belief in the genuine plausibility of the suggestion put forward in the second. Should we be persuaded by these striking claims? Wherever our sympathies initially lie, we must, indeed, pay close attention to what Weinberg says; for, probably among all of today’s theoretical scientists, he most authoritatively represents the viewpoint of established fundamental physics.
Weinberg himself supplied some of the essential theoretical underpinnings to the standard theory of modern particle physics. With Abdus Salam and Sheldon Glashow, he received the Nobel Prize for that important ingredient of particle physics known as “electroweak theory”—which provides a theoretical unification of the weak nuclear force, which causes radioactive decay, with the electro-magnetic force. (I shall have more to say about this theory shortly.) But his expertise lies more broadly than this. He has written two highly authoritative and widely acclaimed books on another extensive area of fundamental physics—that encompassed by general relativity and cosmology. Thus, he is an expert not only on the physics that controls the tiniest ingredients of matter but also on the theory of space-time itself—from Einstein—which governs the structure of the universe on its largest scales.
In his semi-popular 1977 classic The First Three Minutes, Weinberg presented a vivid and well-authenticated account of the first three minutes of our universe’s very existence, and of the specific nature of its (now observed) contents. For the comprehensive picture of what is believed to have gone on at that very early time, detailed theories of both particle physics and cosmology are needed simultaneously. This picture is now referred to as the “standard model of the big bang.” Weinberg’s own most important theoretical contributions (to the electroweak model referred to above) must be combined with another theory of modern particle physics, worked out by others, that describes strong nuclear forces. These two schemes together provide what is known as the “standard model of particle physics.” To round off his powerful command of physics, Weinberg is well read in matters of history and philosophy (though he regards the latter discipline as having little direct positive influence on the progress of science).
These credentials do not, by themselves, compel us to accept Weinberg’s views on the ultimate nature of reality; but if we are interested in such issues in any serious way, we must indeed pay due attention to his arguments. There is also the question of why we should be interested in the issues that relate to this putative ultimate theory. For myself, it seems clear that these issues are important. They have a profound bearing on the deepest questions of our philosophy and on the basis of whatever religious beliefs we might choose to adhere to. They also have importance to another matter—a practical matter of money! The question is raised: Should the US government continue to authorize the expenditure of many thousands of millions of dollars on one particular scientific project? It is this latter issue that provides an important underlying theme of Weinberg’s Dreams. I shall try to address these matters in as dispassionate a way as I am able—although my own personal opinions will undoubtedly strongly color what I shall have to say.
First, what is this immensely expensive scientific project? It is the proposal to construct, and subsequently operate, the vast particle accelerator referred to as the Superconducting Super Collider, or SSC. It will require a ten-foot-wide underground tunnel, which is to be built in Ellis County in Texas, forming an oval ring some fiftyfour miles long. Along this tunnel, traveling in opposite directions, would be sent two narrow beams of protons, their paths bent and focused by powerful superconducting magnets. These would be arranged so that the oppositely traveling protons would collide with each other with tremendous energy at certain specified places. Multitudes of new particles would inevitably be produced as a result of these collisions, but the physicists would be most interested in one species of particle in particular—a putative entity referred to as a Higgs particle.
No Higgs particle has ever been produced in any of the powerful particle accelerators that have been built to date. It could not have been, because the anticipated mass of this particle is too large. In order to be conjured into existence, it needs the kind of enormous energies which the Texas machine is designed to achieve, but which none of its predecessors could muster. Why are physicists so interested in the “Higgs” (as this putative particle is sometimes succinctly described)? Indeed, their interest sometimes borders on passion. Weinberg’s book makes a reasoned and not overstated case for the SSC, but some others have allowed themselves to be carried away in expressions of hyperbole. “The God Particle,” cries out the title of a recent book by the distinguished Nobel Prize-winning experimentalist Leon Lederman and his associate Dick Teresi.* It is clear from such terminology that some researchers must indeed feel that there is something awesomely fundamental about this putative particle. The Higgs is not to be just another of the long list of successfully predicted particles, like the positron, omega-minus, neutrino, anti-proton, or tau-particle—nor is its status comparable even with the yet-unobserved elusive top-quark. No, the Higgs is seen as something with a fundamentally more honored status than any of these.
To a (presumably) dispassionate outside observer such as myself, there are many things that seem odd about this passionate interest in the Higgs. When I first learned about this object, it was presented to me as something that had a theoretical “existence” only. It was not necessarily intended to be a real, observable particle at all, but just a term in a mathematical expression, with a certain formal similarity to the kind of term that would have arisen had an actually real particle been involved. The Higgs object appeared, at that time, to be an ingenious theoretical device, and not necessarily appearing as an actual particle. As a device, it allowed other particles to acquire mass, where all particles were described according to a theoretical scheme in which everything was initially massless. This seems to have been the original viewpoint of Peter Higgs himself, who (along with Tom Kibble) first postulated the hypothetical procedure that now leads physicists to predict the existence of an actual Higgs particle. Higgs is a mild-mannered and modest Englishman who is now a professor at the University of Edinburgh, and who finds himself somewhat disconcerted—even embarrassed—by all the hype and controversy surrounding the SSC project.
Yet, as time has moved forward, this original viewpoint has shifted, because the theories themselves have evolved from some original but tentative ideas into something with a much more specific purpose. The Higgs procedure is still to be the magic wand that dispatches a mass to all those other particles that we now find actually do possess mass. But also it yields forth a special actual particle whose own large mass is there from the start, and which is believed to lie within the projected scope of physical experiment. The Higgs mechanism, in its specific new role, is still the giver of mass to other particles, but it also provides a new, real, observable particle with a finite intrinsic mass of its own. Its complete role is not just as a God in Heaven, but as a God who also deigns to live among His mortal subjects.
There seems, indeed, to be an odd tendency for people to assign some kind of mystical or religious significance to the Higgs particle and to the aims of the SSC. In an exchange between two representatives at the House Committee on Science, Space, and Technology, following a testimony by Weinberg in support of SSC funding, one of them commented: “[W]ill this make us find God?” Weinberg wisely abstained from this exchange. Yet the grand terms in which he had put forward his testimony must have elicited that Representative’s particular question.
With arguments presented in such forceful terms, one may begin to perceive why the proposed discovery of the Higgs indeed raises such great passions and conflict. As Weinberg comments, the executive director of the American Physical Society’s office of public affairs remarked in 1987 that the SSC project “is perhaps the most divisive issue ever to confront the physics community.” If the Higgs is regarded by some as so fundamental as to have religious implications, then its discovery might be well worth the spending of such vast sums of taxpayer’s money. Indeed, if it actually does provide the key to the mystery of mass, then its status is surely unique among fundamental particles. The importance of the Higgs within the scheme of particle physics would, accordingly, be quite different from those of the particles which had been studied before. Perhaps the Higgs will supply the remaining key unlocking the secrets of the Final Theory of fundamental physics. If so, then a vastly expensive machine designed solely for the actual discovery of this magical particle could seem almost to serve as a shrine to science itself, where the discovery of the Higgs ties up the loose ends of this Final Theory and represents the ultimate achievement of fundamental science.
There are obvious dangers in presenting the case for the SSC in this grossly overstated way, and Weinberg wisely refrains from doing so in his book. (I should mention, however, that in a lecture I attended in 1987 that Weinberg gave in Cambridge. England, in honor of the three-hundredth anniversary of Newton’s Principia, he did argue the case for the SSC as a vital quest for a single particle: the Higgs.) In Dreams, Weinberg’s case is a much more balanced one. He does not regard the Higgs as the one remaining link we need for forging the Final Theory; he views the search for it in much more appropriately modest terms. There might be a single Higgs particle, or there might be a number of different ones. There might even be no Higgs particle at all, and some unanticipated phenomenon shows up instead, such as a mysterious hidden extra-strong force. But whatever turns out to be the case, there should be something of fundamental importance to be learned from the collisions between protons at the enormous energies that the SSC will provide. Specifically, the SSC energies should be sufficient either to create a Higgs particle (whose mass is considered to be “almost certainly” no greater than one thousand times that of a proton, so that it is supposed not to be outside the SSC’s range) or else to reveal some phenomenon other than an actual Higgs particle, but which serves a corresponding purpose. Whatever is indeed found, it must elucidate the status of the Higgs mechanism and the “spontaneous symmetry breaking” that is crucial to its use in “electroweak theory.”
Houghton Mifflin, 1993.↩
Houghton Mifflin, 1993.↩