In June, 2007, a thirty-nine-year-old unemployed physicist named Garrett Lisi arrived at a professional conference in Morelia, Mexico, to give a twenty-minute talk. The conference was attended by all the top researchers in a field called loop quantum gravity, which had emerged as a leading challenger to string theory. Morelia is in a region susceptible to earthquakes, and it occurred to Lisi that if there was an earthquake string theory might predominate for the next twenty years. This thought was not pleasing to him.

Garrett Lisi seemed a model of the hermit genius. Photograph by Martin Schoeller

Lisi had not been to a professional conference in eight years, and he was anxious about speaking in public. He has since learned that he can conquer this fear if he writes out all his remarks and reads from the script. But he hadn’t yet learned that tactic, and so he overcame his nerves by submerging his ideas in a mass of equations.

In the audience was a physicist named Lee Smolin, one of the three founders of the field of loop quantum gravity and a prominent member of the faculty at the Perimeter Institute for Theoretical Physics, in Ontario. Smolin had a bad cold that day, and so, through the double fog of his illness and of Lisi’s exceedingly technical language, he grasped only the contours of what he was listening to. Lisi believed that he had discovered what physicists call a Theory of Everything—a unifying idea that aims to incorporate all the universe’s forces in a single mathematical framework. The Theory of Everything has been the holy grail of theoretical physics for a century; Nobels are won for partial contributions to it. Here was somebody, with no reputation, saying that he might have figured out the key to the whole thing. Within four months, however, and after a second talk, Smolin was telling Lisi that he had “one of the most compelling unification models I’ve seen in years.”

“There’s a dream that underlying the physical universe is some beautiful mathematical structure, and that the job of physics is to discover that,” Smolin told me later. “The dream is in bad shape,” he added. “And it’s a dream that most of us are like recovering alcoholics from.” Lisi’s talk, he said, “was like being offered a drink.”

There is a persistent legend in physics of the hermit genius, the scientist who drops out of academia and then returns, many years later, with an insight that moves the discipline forward. The brilliant outsider has become almost a stock character. David Deutsch, a British pioneer of quantum computer theory, had dropped out of paid academia several years before his theories won wide acclaim. Julian Barbour, whose theories helped pioneer a key physics concept known as background independence, left the university and never returned, holding forth in a farmhouse twenty miles outside Oxford and receiving graduate students as pilgrims. The most famous outsider genius was the patent clerk Albert Einstein. “Look, in my experience, the style of a well-trained Ph.D. going away, thinking hard about something for a long time, and coming back with something very original, something that’s a well-worked-out and well-thought-through point of view, is an essential, if rare, part of how theoretical physics progresses,” Smolin said. “Garrett fit the pattern.”

But Lisi, when he arrived in Morelia, was so obscure that he could not think of a single reputable physicist who might recommend him for a job. Einstein at least had a weekly discussion club in Bern, where he muddled through Poincaré and Hume. Lisi had got his Ph.D. from the University of California at San Diego, completing his dissertation on the mathematics of the movement of water over a swimming dolphin’s skin, and then, at thirty-one, dropped out of academia and nearly out of society.

For almost a decade, Lisi moved on no fixed schedule between Maui, where he likes to surf, and the mountains of the West, where he snowboards. Four years ago, Lisi persuaded his girlfriend, Crystal Baranyk, who is an artist, to move with him into an old Colorado ski-shuttle van; he remodelled it himself, shipped it to Maui, and parked it by the beach. They lived in the van for a year, with no toilet. He worked intermittently, sometimes as a snowboard instructor, once on a short-term consulting contract when a friend’s software company needed an algorithm solved, but mostly he tried to think about physics. When Lisi arrived in Morelia, it was as if the Sierra Nevada and the physical sciences had joined to produce their own version of Sidd Finch.

“I am forty years old and most of my net worth is in snowboards and surfboards, and that’s kind of weird,” Lisi said. He wasn’t even particularly careful with these items. At one point, he was living in a yurt on a plantation in Maui with some people from the group World Wide Opportunities on Organic Farms when he found himself gripped by the urge to snowboard. He had no place to store his surfboards, so he just left them there. When he returned, a year later, he found that a new group had moved into the yurt, discovered the surfboards, and put them to use.

Five months after Morelia, Lisi finally published his theory online, in a thirty-one-page paper called “An Exceptionally Simple Theory of Everything.” The paper is hard for a nontechnical reader to penetrate; it consists mostly of equations and boasts. As physicists began to examine Lisi’s paper, they found it alternately sublime and just strange.

For half a century, scientists have tried, unsuccessfully, to unify the two governing theories of the physical world: general relativity, which explains the behavior of very large objects, like stars, and quantum mechanics, which precisely describes the phenomena of very small objects, like particles. The two theories are written in distinct mathematical languages, and scientists have not found a way to unify them—a common syntax. This makes it hard to describe certain crossover phenomena, like the horizons of black holes. Most physicists believe that the problem isn’t that the universe is incoherent but that there is something missing in the math.

Scientists have long hoped that new experiments in cosmology or particle physics would break this impasse. But discoveries on this scale haven’t been forthcoming, and it’s not clear that some of the most compelling modern theories can even be tested by experiment. This is particularly true of string theory. The appeal of the theory lies in its high-end math, but it also twists the real world in unusual ways. String theorists believe that the world has ten or eleven dimensions, depending on the version of the theory, with the extra ones balled up in “compactifications” too tiny to perceive.

Garrett Lisi, willfully cut loose from the world of academic physics, built his theory as an outsider might, relying on a grab bag of component parts: a hand-built mathematical structure, an unconventional way of describing gravity, and a mysterious mathematical entity known as E8. With the publication of his theory, Lisi wandered into a mill of expectations and press attention, in an unusually politicized moment in physics. His supporters include prominent physicists, but some of his antagonists, particularly among string theorists, thought his math was fishy and found the entire episode outrageous. When I asked the Nobel laureate David Gross, a professor of physics and an influential string theorist at the University of California at Santa Barbara, about Lisi, he said that he was “extremely reluctant to add fuel to this silly story.”

But Smolin, after meeting Lisi and talking to him, became convinced that it was at least possible that Lisi had made a fundamental breakthrough. “It is of the nature of a high-risk shot on goal from way down the field,” Smolin said. He wondered if a position within the academic world might buy Lisi time to develop his theory and asked if he was interested in applying for a university fellowship. Lisi said no.

In the acknowledgments to “An Exceptionally Simple Theory of Everything,” Lisi begins by thanking a mathematician from Columbia named Peter Woit. The two men had never met, and their only previous interaction was a slim exchange of e-mails that had ended some months earlier, in which Lisi sent Woit a description of the problems he was working on and Woit responded with some general words of encouragement. But in physics the invocation of Woit’s name was a smoke signal, a declaration of partisan affinities. Woit was best known for his zealous one-man campaign to discredit string theory. By thanking him, Lisi had enlisted in the string wars. “It was probably not the most politic thing to do,” Woit said.

Lisi had long harbored a deep skepticism about string theory. As a graduate student in theoretical physics at U.C. San Diego in the nineties, he was briefed on a recent string-theory development called the Maldacena conjecture by a young member of the physics department. “It was very interesting mathematics,” Lisi said. “But I remember walking out of this office and wondering what it had to do with any physical reality. And, as far as I could tell, it didn’t.” The influence of string theorists was growing at the time, and Lisi felt the academy closing in on him. “If you share an office next to a guy for twenty years, and you like him and you’re friends with him, it’s hard to tell him that you think that his whole idea of how the universe works is completely wrong,” he said. String theory, Lisi had come to believe, was “a mess.”

First during the nineteen-seventies, but with increasing momentum during the eighties, a loose community of physics researchers had begun to postulate that the disparate small particles that we learned about in high-school science class—electrons, for instance—were actually the varied vibrations of tiny open and closed looped strings. String theorists believed that this basic component allowed them to fit all the forces of nature into a single mathematical framework. By 1999, Steven Weinberg, a physicist and Nobel laureate at the University of Texas, could say that string theory was “the only game in town.”

One good way to prove string theory would be to look and see whether strings exist. But the vibrations, according to the hypothesis, take place at a frequency too high for existing equipment to detect. String theorists have still not been able to resolve their equations into testable hypotheses. Instead, they have built their case on the compelling quality of their mathematics, which some find almost incomprehensibly beautiful.

Physicists have long looked to higher math for insights into the workings of the universe. “If a figure is so beautiful and intricate and clear, you figure it must not exist for itself alone,” John Baez, a professor of mathematics at the University of California at Riverside, said. “It must correspond to something in the physical world.” This instinct—the assumption that beauty will stand in for truth—has become a habit. Some physicists now worry that string theory’s mathematics have grown permanently unmoored from the real world—an exercise in its own complexity. And so modern theoretical physics has become, in part, an argument about aesthetics.