American Scientist

ELUSIVE: How Peter Higgs Solved the Mystery of Mass. Frank Close. xi + 287 pp. Basic Books, 2022. $30.

When Royal Swedish Academy officials tried to telephone Peter Higgs late on the morning of October 8, 2013, to inform him that he had won the Nobel Prize in Physics, the 84-year-old British theoretical physicist was nowhere to be found. They tried to reach him at his Edinburgh apartment and at his university office for half an hour, to no avail, and finally gave up. Anticipating that he might win and wanting to evade the likely media frenzy, Higgs had headed off earlier to his favorite seaside seafood bar in nearby Leith for lunch and a pint of ale.

Higgs and Belgian theorist François Englert were to be honored the following December for “discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles”—the so-called Higgs mechanism they had independently elucidated almost a half century earlier, in 1964. But as Oxford University physicist Frank Close, who knew Higgs well, recounts in detail in his latest book, Elusive, the painfully shy Higgs wanted none of the fame and public exposure that came inevitably with making one of the most profound theoretical breakthroughs of the 20th century.

The great strength of the book is Close’s intimate portrait of Higgs, made possible by the decades-long friendship between the two. During the first couple of years of the coronavirus pandemic, they exchanged letters and talked on the phone, and those (appropriately referenced) interactions undergird this account. Although I have followed the Higgs boson search for decades, I learned much that I had not known.

There has been significant contention, for example, that Englert and his (now deceased) coauthor Robert Brout have not received sufficient credit for their prior paper on the same topic—and that perhaps the particle should instead have been named the Brout-Englert-Higgs boson. (The mechanism was also discovered independently by another trio of theorists—Gerald Guralnik, Carl Hagen, and Tom Kibble—later that year.) But as Close amply demonstrates, it was Higgs alone who in a second 1964 paper unambiguously stated that the spontaneous symmetry-breaking phenomenon that they were all discussing required the existence of this massive, spinless particle. In fact, Close provides exacting readers (for example, science historians like me) with appendices that reprint both of Higgs’s 1964 papers and explain them in detail. What a treat!

To understand spontaneous symmetry breaking better, consider a pencil somehow balanced on its point. This system is rotationally symmetric around a line drawn through the center of the pencil. But a tiny force will cause it to topple into a lower-energy state in which the pencil points in a specific but random direction. Due to the Higgs mechanism, particles in a symmetric universe that were initially massless can acquire a variety of nonzero masses while the symmetry of the underlying equations governing their behavior remains intact.

A chapter about Higgs’s visit to the University of North Carolina at Chapel Hill for the 1966–1967 academic year notes that while Higgs was there, he published a third, longer paper in Physical Review titled “Spontaneous Symmetry Breakdown without Massless Bosons,” which really established his claim to the massive boson as his personal conception. As Close explains, “What he did—uniquely among the six theorists who had constructed the mass mechanism—was to predict that the boson exists and provide a means to identify it, which is why the boson was later given his name.”

What doesn’t come through so clearly in Elusive is that these contributions ran counter to the dominant currents of theoretical physics at the time. The subdiscipline of quantum field theory in which Brout, Englert, and Higgs were then working was in deep decline in the early 1960s. Although quantum field theorists had triumphed in accounting for the electromagnetic interactions among subatomic particles, they had largely been stumped by the strong interactions binding atomic nuclei and the weak interactions responsible for radioactivity. Frustrated theorists had moved on to (what then seemed to be) greener pastures, such as S-matrix theory, the bootstrap model, and SU3 symmetry. Beyond the taut clique of quantum field theorists, nobody paid much attention to Higgs’s obscure papers.

Close’s account therefore falls into the category of what British historian Herbert Butterfield long ago dubbed “Whiggish history”—history as recounted by the winners, with a sense of inevitability about the outcome. And sociologist of science Andrew Pickering has called this tendency “retrospective realism”: What had been a tentative, speculative hypothesis at the time has been retroactively imbued with the seeming weight and authority of reality. But the Higgs mechanism (much like the quark hypothesis, also published in 1964) had to struggle for attention and acceptance by the majority of particle physicists.

A crucial advance came in 1967, when Abdus Salam and Steven Weinberg independently adopted this mechanism for generating particle masses in a new theory that unified the weak and electromagnetic forces into what eventually became known as the electroweak force. But their theory received scant attention until 1970, when Dutch graduate student Gerard ’t Hooft proved that it was indeed calculable—that infinities that cropped up in calculations using the theory could be eliminated by a theoretical sleight of hand known as renormalization.

Close can craft crystalline metaphors, but he sometimes drifts into technical expositions you’d need a graduate course in quantum theory to understand.

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Together with the discovery of quarks in experiments at the Stanford Linear Accelerator Center and of neutral currents (an aspect of the weak force that had been predicted by electroweak theory) at CERN (the European Center for Nuclear Research), these theoretical advances culminated during the late 1970s in the recognition of the so-called Standard Model as the dominant paradigm of particle physics, able to explain essentially all observed subatomic phenomena. As that theory predicted, the W and Z boson carriers of the weak force were discovered at CERN in 1983 with masses—also generated by the Higgs mechanism—equal to 85 and 97 times the proton mass.

What remained to be discovered was the Higgs boson itself, whose mass was exceedingly difficult for theorists to pin down. Without that information, experimental physicists were basically casting about in the dark, remaining alert for this neutral boson’s appearance. As Close recounts, three CERN theorists—John Ellis, Mary Gaillard, and Dimitri Nanopoulos—took an initial stab in 1976 at predicting how it might show up in experiments. But they concluded their long, rambling paper “with an apology to experimentalists, for having no idea what is the mass of the Higgs boson.”

Thus began a 36-year pursuit that finally culminated in the July 4, 2012, announcement of the boson’s discovery in two lectures at CERN attended by Englert and Higgs, the latter wiping tears from his eyes as everyone else in the hall cheered. It had been a long, winding road that involved spending 2 billion dollars fruitlessly on partial construction of the Superconducting Super Collider (which project was terminated by the U.S. Congress in 1993), and something like 10 billion euros on CERN’s successful Large Hadron Collider facility. Thousands of physicists from more than 60 nations had been involved in the search, and several false sightings had occurred along the way.

Close touches on this epic hunt, but it would take another entire book to do it justice. His strength as a writer lies in recounting the evolution of theoretical physics ideas, which he does admirably well, for the most part.

If I had to voice a major criticism of Elusive, it would be the unevenness of Close’s narrative. In some places he crafts crystalline metaphors, as when he describes the all-pervading Higgs field as “cosmic treacle” (molasses) that gives rise to mass by creating a kind of drag on particles moving through it. In other parts, he drifts into technical expositions you’d need a graduate course in quantum theory to understand; I found the same to be true of his earlier book, The Infinity Puzzle.

But the enduring value of Elusive is the intimate portrait it offers of Peter Higgs. After finishing the book, I came away wondering how such a shy, self-effacing scientist could ever endure having a subatomic particle named after him—the only particle named after a human being in the entire discipline.

In fact, “the Higgs boson” is often shortened to “the Higgs”—a phrase I studiously avoid. A far better sobriquet for this capstone of the Standard Model is “the higgson,” which California Institute of Technology theorist Murray Gell-Mann suggested long ago and others (including myself) have advocated. But as with the phrase “Standard Model,” which Close wants to replace with “Core Theory,” the discipline seems mired in long-standing usages that it stubbornly refuses to relinquish.

It is particularly intriguing, at least to me, that the prediction of this mass-inducing mechanism—and its consequent boson—was the only major contribution that Higgs made during a long scientific career. But it turned out to be one of the crucial theoretical physics advances of the century.