Coming of Age in the Milky Way (47 page)

Glashow, on the other hand, was naturally gregarious, easygoing to the point of indolence, and a stranger to the rigors of study. If Weinberg excelled at Cornell, missing Phi Beta Kappa only because he failed physical education, Glashow barely scraped by; in accepting the Nobel Prize, he thanked “my high school friends Gary Feinberg and Steven Weinberg for making me learn too much too soon of what I might otherwise have never learned at all.”
¹³
He spoke indistinctly, in fragmentary sentences built on an unimposing vocabulary, and smiled perpetually, as if contemplating a private joke. Physics seemed to come to him as naturally and effortlessly as a dream.

Glashow studied at Harvard under the elegant and venturesome Julian Schwinger, called “the Mozart of physics” both for his
brilliance and for the uncaring way he wore it. A child prodigy, Schwinger as an adult remained impatient with the fragmented state of quantum physics, and he implored his students and colleagues never to rest until they had arrived at unified theories capable of describing a far wider scope of phenomena through fewer precepts. Even in the 1950s, when the quantum electrodynamics he had helped to create was the rising sun of quantum field theory, Schwinger was writing that

Glashow absorbed from Schwinger the conviction that the weak and electromagnetic interactions ought to be explicable by means of a single, unified gauge theory.
^*
“A fully acceptable theory” of the two forces, Glashow wrote in his graduate thesis, echoing Schwinger, “… may only be achieved if they are treated together.”
¹⁵

His thesis completed, Glashow went to Copenhagen to study with Niels Bohr. There he pieced together a unified Yang-Mills theory of the weak and electromagnetic forces. The glaring problem with this theory, as would be the case for Weinberg and others later, was that its equations produced nonsensical infinities. Glashow tried to solve this problem by “renormalizing” his equations. Renormalization is a mathematical procedure that involves canceling the unwanted infinities by introducing other infinities; it smacks of mathematical trickery, but when adroitly manipulated can produce the desired, finite results. Among other credentials, renormalization had played an essential role in the perfection of quantum electrodynamics—which had made some of the most precise predictions ever confirmed by experiment, and had become a model
of what a quantum field theory ought to be.
^*
By late 1958 Glashow was satisfied that he had renormalized his unified theory, and he presented a paper saying so the following spring, in London.

In the audience was the Pakistani physicist Abdus Salam, seven years Glashow’s senior but seemingly older, a dignified, composed man in whom strong intellectual currents flowed beneath an exterior of oceanic calm. Born in 1926, the son of a high school English teacher who had prayed nightly to Allah for a son of intellectual brilliance, Salam at age fourteen scored the highest marks in the history of the Punjab University matriculation examination, a feat that brought cheering throngs out to greet him when he bicycled home to the little town of Jhang in what is now Pakistan. While working for his Ph.D., Salam managed to prove the renormalizability of quantum electrodynamics as applied to mesons, an accomplishment that garnered him a reputation as an expert on renormalization. Since then, he and a colleague, John Ward, had devoted considerable effort to the renormalization of a unified theory of the electromagnetic and weak interactions, without success. So when Glashow claimed that he had solved the problem, he got Salam’s attention.

“My God! This young boy was claiming that this theory was renormalizable!” Salam recalled, in a 1984 interview with Robert Crease and Charles Mann.

Glashow, however, was not easily discouraged, and despite any embarrassment he may have felt at having mistakenly claimed to have solved the renormalization problem, he persisted in searching for links between electromagnetism and the weak force. In this
effort he was encouraged by Gell-Mann if by few others. (“What you’re doing is good,” Gell-Mann recalled having told Glashow, over a seafood lunch in Paris, “but people will be very stupid about it.”)
¹⁷
In 1961, Glashow produced a paper, “Partial-Symmetries of Weak Interactions,”
¹⁸
that called attention to “remarkable parallels” between electromagnetism and the weak force, depicted them as linked by a broken symmetry, and predicted the existence of the W and Z force-carrying particles—later known as the W
⁺
, W
⁻
, and Z°. These hitherto undetected particles were to play an important role in experimental tests of the unified electroweak theory, but Glashow was unable to predict their masses, which left the experimenters with nothing to go on. Glashow and Gell-Mann then wrote a paper demonstrating that all the symmetries evinced in what are known as noncommutative or Cartan groups correspond to Yang-Mills gauge fields. Their efforts to identify a gauge symmetry group that would embrace both the strong force and Glashow’s protounified electroweak forces, however, came to naught. Glashow, discouraged, set aside his work on electroweak unified theory.

Meanwhile, in 1959, Salam and Ward had, like Glashow, arrived at insights about links between the weak and electromagnetic forces, but had, like Glashow, met with an indifferent response from the scientific community, and likewise grew discouraged. “A broken symmetry breaks your heart,” said Salam.
¹⁹

The situation then brightened, thanks to new insights into the mechanism of spontaneous symmetry-breaking first presented by Yoichiro Nambu, Jeffrey Goldstone, and others and culminating in work published by Peter Higgs in 1964 and 1966. This research demonstrated that symmetry-breaking events could create new kinds of force-carrying particles, some of them massive. (The particles envisioned by Yang-Mills gauge theory had been massless.) If the particles that carry the weak and electromagnetic forces were related by a broken symmetry, these new tools might make it possible to estimate the masses of the W and Z particles characteristic of the unified, more symmetrical force from which the two forces were thought to have arisen.

Weinberg in particular was captivated by the concept of spontaneous symmetry breaking. “I fell in love with this idea,” he said in his Nobel Prize address in 1979, “but as often happens with love affairs, at first I was rather confused about its implications.”
²⁰
Initially
he tried to apply the new symmetry-breaking tools to the strong force. This worked well insofar as global symmetries were concerned—specifically, Weinberg found that he was able to make successful predictions of the scattering of pi mesons—but when he sought to extend the technique to local symmetries, the results were disappointing. “The theory as it was working out was making nonsensical predictions that didn’t look like the strong interactions at all,” Weinberg recalled in a 1985 interview. “I could fiddle with it and make it come out right, but then it looked too ugly to bear.”
²¹
The worst problem was that the particle masses predicted by the breaking of the symmetry group Weinberg was contemplating did not match those of the particles involved in the strong interactions.

But then, in Weinberg’s recollection, “at some point in the fall of 1967, I think while driving to my office at MIT, it occurred to me that I had been applying the right ideas to the wrong problem.”
²²
The particle descriptions that kept bobbing up out of his equations—one set massive, the other massless—resembled nothing in the strong force, but fit perfectly with the particles that carry the weak and electromagnetic forces. The massless particle was the photon, carrier of electromagnetism; the massive particles were the Ws and Zs. Moreover, Weinberg found, he could calculate the approximate masses of the Ws and Zs. Here, finally, was an electroweak theory that made a verifiable prediction. Salam independently reached a similar conclusion the following year—testimony, Weinberg said, to “the naturalness of the whole theory.”
²³

With that, the work that would win the 1979 Nobel Prize in physics was complete. Yet little heed was paid to it at first. Weinberg’s paper, the first complete statement of the electroweak theory, was cited not once in the scientific literature for four full years after it appeared. The main reason was that the theory had not yet been shown to be renormalizable. Once that was accomplished—in 1971, when its dolorous infinities were scotched in a heroic effort by the Dutch physicist Gerard’t Hooft—interest in the electroweak theory intensified, and the focus of attention turned to the question of testing the theory through experiment. This called upon those embodiments of big science, the particle accelerators.

Accelerators are to particle physics what telescopes and spectrographs are to astrophysics—both an exploratory tool for finding new things and a supreme court for testing existing theories. Their operating principle is based on Einstein’s
E = mc
²
. One accelerates
charged particles to nearly the speed of light by propelling them along an electromagnetic wavefront created by pulsing electromagnets, then smashes them into a target, creating tiny explosions of intense power. New particles condense from the tiny fireball, like raindrops precipitating in a storm cloud, and are recorded by surrounding detectors as they come reeling out. The original detectors were photographic plates; later these were replaced by electronic sensors coupled to computers.

Engaged in the race to test the electroweak theory were researchers at two of the world’s most powerful accelerators—CERN, the European center for nuclear research near Geneva, and Fermilab, named after the physicist Enrico Fermi, on the Illinois plains west of Chicago. Both are proton accelerators.
^*
The protons come from a little bottle of hydrogen gas, small enough for a backpacker to carry, that contains a year’s supply of atoms. Computer-controlled valves release the gas in tiny puffs, each scantier than a baby’s sigh but each containing more protons than there are stars in the Milky Way galaxy. The gas enters the electrically charged cavity of what is called a Cockroft-Walton generator.
^†
The field strips the electrons away from the hydrogen atoms and sends the protons speeding down a tunnel and into a pipe the size of a garden hose that describes an enormous circle—three miles in circumference in the case of Fermilab. The protons are accelerated around the ring by pulses sent through surrounding electromagnets, while focusing magnets gather them to a beam thinner than a pencil lead. When they reach a velocity approaching that of light—at which point, thanks to special relativity effects, their mass has increased by some three hundred times—they are diverted from the ring and slammed into a stationary target inside a detector. Their tracks, subjected to yet another magnetic field in the detector, betray their charge and mass and thus their identity.

Though similar in design, the CERN and Fermilab accelerators exemplified rather different styles of doing big science. Fermilab,
built under the direction of the American physicist and sculptor Robert Wilson, was conceived and executed as a work of art, an embodiment of the aesthetics of science. A Wilson sculpture, a looming set of steel arches titled “Broken Symmetry,” was erected at the main entrance. The accelerator tunnel, buried underground, was delineated, for purely aesthetic purposes, by an earthwork berm. Within the ring buffalo grazed; swans swam in the waters employed to cool the electromagnets. The administration building, a sweeping, convex tower, was set against the berm like a diamond on an engagement ring; Wilson modeled it on the proportions of Beauvais Cathedral in France. As he recalled his reasons for this decision:

Wilson defended the aesthetics of his creation—which, it should be added, was completed under budget—by drawing further parallels between art and science:

CERN, for its part, looked about as aesthetically unified as a Bolshevik boiler factory.
Its
administration building, slapped together from prefabricated plastic panels and aluminum alloy window frames that bled pepper-gray corrosives in the rain, called to mind less Beauvais Cathedral than the public housing projects of suburban Gorky. Its laboratories were scattered across the landscape, as haphazardly as the debris from a trucking accident, on a plot of land that straddled the French-Swiss border outside Geneva.
The prevailing style was late Tower of Babel, with scientists switching from French to German to English in mid-sentence while lunching at the laboratory cafeterias, one of which accepted only French currency and the other only Swiss. Yet for all its air of disorder, CERN worked every bit as well as Fermilab, and by the early 1970s was beginning to surpass it.