The Physicist Who Made Sense of the Universe

https://www.nytimes.com/2019/05/28/opinion/gell-mann-physics.html

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There is nothing physicists love more than a mess of puzzling, apparently contradictory experimental results. Physicists are convinced that nature is fundamentally simple, and that they can discover hidden principles which bring order to the chaos — if they just think about it hard enough. Nobody was better at finding order amid apparent chaos than Murray Gell-Mann, who died on Friday.

The 1950s and 60s were a Golden Age of particle physics, as accelerators produced a plethora of new particles with unpredictable properties. This presented a problem: There were too many of these new particles, which appeared in collisions without any evident rhyme or reason. They didn’t look anything like the kind of simple, elegant structure scientists expect from the laws of nature.

With a series of brilliant strokes, Dr. Gell-Mann revealed the secret pattern that made everything snap into place. His Eightfold Way, mischievously named after a Buddhist doctrine of liberation, made sense of the new particles that had been discovered and predicted ones that hadn’t been. The Eightfold Way is to elementary particles what the Periodic Table is to chemical elements. Ultimately, he proposed “quarks,” unobserved particles that are bound together in groups of two or three, to account for almost all of the new discoveries.

But that wasn’t all.

Dr. Gell-Mann was at the center of a whirlwind of theoretical activity. He showed how quantum mechanics allowed a particle to transform into a different particle and then back again. He demonstrated that the strength of particle interactions would depend on the energy with which they were colliding. With his colleague Richard Feynman, he explicated the symmetry structure of the weak nuclear force, one of the four forces of nature. He proposed a physical quantity — “strangeness” — that would explain why some particles lasted longer than others. He, along with Harald Fritzsch, hypothesized that there were force-carrying particles, which they called “gluons,” that hold quarks together. Each of these ideas has subsequently been triumphantly confirmed by experiment.

Any one of these achievements would have served as the high point in the career of any physicist. And there were many others he could have received credit for, as he often waited too long to publish and was occasionally scooped; the Eightfold Way was proposed independently by Yuval Ne’eman, and quarks were theorized by George Zweig. Dr. Gell-Mann’s perfectionism could get the best of him.

Where Dr. Gell-Mann almost always came out ahead was in giving names to his ideas. Dr. Ne’eman simply referred to his proposal by its mathematical label, “SU(3).” That was never going to compete with the romance of “the Eightfold Way,” even if Dr. Gell-Mann did later regret providing an opening to those who would connect quantum physics with Eastern mysticism. Dr. Zweig, on the other hand, called his hypothetical particles “aces,” which lacked the enigmatic heft of “quarks.” Dr. Gell-Mann actually had the sound “kwork” first, and then later noticed the sentence “Three quarks for Muster Mark!” in James Joyce’s novel “Finnegans Wake.” There was no connection to particle physics, but Dr. Gell-Mann didn’t let that get in the way of a colorful coinage.

Today, the situation in particle physics is the opposite of that in the postwar boom. All of the data being produced in high-energy accelerators is beautifully explained by a single theory with a highly unromantic name: the Standard Model. It was put together over years by numerous talented scientists, but nobody had a greater part in its construction than Dr. Gell-Mann.

There are many ways to become an influential theoretical physicist. Some produce creative new ideas, while others are masters of intricate calculations. Some are best at speculating about the unknown, while others bring clarity and insight to established lore. Part of what made Dr. Gell-Mann special was his mastery of all these modes. His work with Francis Low on the “renormalization group” taught physicists how phenomena at high energies and short distances could be elegantly related to what happens at low energies and long distances. This philosophy remains the central organizing principle of much of modern physics.

Once the Standard Model triumphed in the 1970s and 80s, Dr. Gell-Mann didn’t rest on his laurels. He became convinced of a pressing need for more interdisciplinary work on complex systems. He consequently helped found the Santa Fe Institute, which is today the world’s leading research center on complexity, and which was Dr. Gell-Mann’s research home for the last decades of his life.

It was an interesting move for someone who had garnered so much fame working as a particle physicist at the California Institute of Technology. Elementary particles are the most fundamental building blocks of nature, and their study would seem to be an expression of simplification in its purest form. The essence of complexity research, by contrast, is the emergence of new kinds of order that are only manifest when systems are large and messy.

But this shift of perspective suited Dr. Gell-Mann, who was never comfortable with narrow disciplinary boundaries. He was a rare breed of wide-ranging polymath, well-versed in archaeology, history and ornithology. With his former student James Hartle, he proposed a way of understanding the foundations of quantum mechanics, a puzzle that has bothered physicists since the days of Niels Bohr and Albert Einstein. His final research program was an expansive project to study the evolution of human languages.

He was also infamously cantankerous. At a workshop celebrating the centenary of the birth of Enrico Fermi, the great physicist, a series of speakers told fond stories with the common subtext of how they thought they were so smart until they first met Fermi. The one exception was Dr. Gell-Mann, who said it was the other way round: It was Fermi who thought he was so smart — until he met Dr. Gell-Mann. He was fond of referring to people he didn’t think highly of as “ignoramuses.” He was the kind of language maven who would correct people on the pronunciation of their own names, and complain to servers at French and Spanish restaurants about misspellings on their menus.

But beneath the prickly exterior lay genuine warmth. Dr. Gell-Mann could criticize others mercilessly, but would readily change his mind when he was proved wrong. At the end of his speech at the centenary celebration of Fermi, after taking the audience through a tour of his own achievements from that time, Dr. Gell-Mann choked up, remembering his fondness for Fermi and the influence the elder physicist had on him as a mentor. He in turn was known to vigorously support young scientists and their wild ideas.

The novelist Cormac McCarthy, who is a Fellow at the Santa Fe Institute, said that Murray Gell-Mann “knew more things about more things than anyone I’ve ever met.” His genius and enthusiasm for seeking order amid the chaos will be sorely missed.

Sean Carroll (@seanmcarroll) is a theoretical physicist at the California Institute of Technology and the author of “The Big Picture: On the Origins of Life, Meaning, and the Universe Itself.”

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