After he graduated from MIT in 1958, Jim Simons and his friends Jimmy Mayer ’58 and Joe Rosenshein ’57, PhD ’63, rode from Boston to Bogotá on motor scooters. The trip took seven weeks and required some creativity, given the travelers’ tight budget. “Mostly we camped out,” Simons recalls. But “if it was a little town and it had a jail, we asked if we could sleep there, because we knew we’d be safe.” Frequently, the jailers agreed, allowing them to stay the night in a cell. By the time the group reached Costa Rica, they had run out of money and were “subsisting on bananas,” Simons says. Although Rosenshein stopped in Barranquilla, in northern Colombia, Simons and Mayer eventually reached Bogotá, where they were welcomed by Edmundo Esquenazi ’58 and spent the summer hanging out and playing croquet.

Simons’s love of travel—and his personal daring—have been matched throughout his life by intellectual adventure. Though trained in mathematics, he ventures frequently into other fields. He has earned billions as a hedge fund manager and, through the work of the charitable foundation bearing his name, has delved into the research of other academics, from molecular biologists to cosmologists. Today, in addition to managing his foundation’s investments, he spends much of his time talking with researchers whose work he funds. “When I get a new result, I prefer to talk with him than my colleagues,” says Michael Wigler, a molecular biologist at Cold Spring Harbor Laboratory, whose research on autism Simons has supported for over a decade. “I find him intellectually curious and consider him a collaborator.”

Simons grew up in Brookline, Massachusetts, where as a child he liked to “just sort of ponder,” he says. He liked doubling numbers; he liked Zeno’s paradoxes; he liked climbing trees and watching the other kids play. As a freshman at MIT, he enrolled in a graduate math class, and after three years he had accumulated enough credits to earn a bachelor’s degree. “I liked MIT,” he says. “They just let me do what I wanted.”

After graduation—and the motor scooter escapade—Simons focused on mathematics for the next several years. In 1961, at age 23, he earned a PhD from Berkeley, working on mathematical geometry. Then, after another brief stint at MIT as a Moore Instructor, and a short time as an assistant professor at Harvard, he took a position with the Institute for Defense Analyses in Princeton, New Jersey. In this role, he worked quietly to crack codes on behalf of the National Security Agency, while more visibly pursuing independent mathematical research. “If you took a wire frame, twisted it around, and dipped it in soap solution, you’d create a surface with minimal surface area,” he says, by way of explaining an analogous puzzle involving higher dimensions that he worked on. When his boss, a retired general, defended the Vietnam War in the New York Times, Simons issued a sharp refutation in a letter to the editor that also appeared in that paper. Soon after, he spoke to a Newsweek reporter about how he split his time at the Institute for Defense Analyses and was forced to leave. He became chair of Stony Brook University’s math department at age 30. There, in 1974, he completed the mathematical work for which he is best known: he and Shiing-Shen Chern published the landmark Chern-Simons invariants, which have applications in quantum field theory, condensed-matter physics, and even string theory. In 1976, he won the American Mathematical Society’s Oswald Veblen Prize—geometry’s most coveted honor—for his work on area-minimizing surfaces.

At the same time, however, he had grown restless with academic work. He was frustrated with a mathematical puzzle that involved trying to prove that a particular number was irrational, he recalls, adding that it remains unsolved today. He and his father had also “come into some money,” thanks to an investment they had made in a business founded in Colombia by Simons’s old friends Mayer and Esquenazi. The business had focused at first on vinyl floor tiles but then moved into PVC piping as well; when the piping business took off, it led to a windfall for investors. Thus Simons moved on to the second phase of his career: business.

He turned his attention initially to foreign currency trading. “I didn’t bring much math into it at first,” he says. Eventually, though, “I could see we needed it.” In 1978, he founded the hedge fund company that would ultimately be called Renaissance Technologies. Today, the company is known for hiring mathematicians and scientists to create computer models designed to predict the behavior of financial markets. (Simons himself is often regarded as an early champion of these math-minded “quants.”) Simons is famously opaque about his modeling strategies, but they involve ferreting out patterns within large data sets. His team has conducted empirical studies assessing the importance of different variables in making predictions. And over time, his models have come to include “more and more inputs and different ways of looking at those inputs,” he says. That gives the company an edge—“a small edge, but still an edge.” In early 2016, Simons’s personal fortune was estimated at over $15 billion.

These days, Simons focuses mainly on giving that money away. In his airy office in Manhattan’s Flatiron district, he offers a morning visitor coffee or a gin and tonic. He chain-smokes or sometimes just lets a cigarette dangle from his lip as he discusses his philanthropic work. In 1994, he and his wife, Marilyn, founded the Simons Foundation, which has donated generously to an eclectic mix of projects. They also started two other foundations in the wake of family tragedies. After his son Paul was hit and killed by a car when bicycling, they established a foundation to create and maintain a nature preserve in Stony Brook in his memory; after their son, Nick, drowned on a trip to Bali, they set up the Nick Simons Foundation to improve health care in Nepal, a country he’d worked in and grew to love.

The projects funded by the Simons Foundation reflect Simons’s deep and varied interests, one of which is quite personal. Having a family member on the autism spectrum led to the launch of MIT’s Simons Center for the Social Brain, which studies the underlying mechanisms of autism spectrum disorders with the aim of improving diagnosis and treatment. It also inspired the support of new research by Wigler at Cold Spring Harbor.

In the 1990s and early 2000s, most researchers studying the genetics of autism were focusing on inherited mutations, transmitted from parent to child. Influenced largely by Wigler, however, Simons became convinced that new mutations, present in children with autism but not in their parents, were an underappreciated cause of the disorder. The Simons Foundation began funding extensive basic research with families in which only one person was affected by autism. Thanks to that support, a genetic repository of 2,600 such families is now available to researchers around the world. And different scientists have used that data to home in on roughly 200 genes with a wide range of functions that might be disrupted in some cases of autism. The work has “really changed the paradigm” regarding the disorder’s causes, says Wigler, who was the first advocate of the idea that new mutations could lead to autism (see “Solving the Autism Puzzle,” January/February 2015).

Simons, an MIT Corporation life member emeritus who was named a member of the National Academy of Sciences in 2014, is a major supporter of the math department and scientific research at MIT (Building 2 now bears the Simons name, thanks to his and Marilyn’s support of recent renovations). But he’s just as passionate about supporting math and science teaching at the middle school and high school levels. In 2004, the Simons Foundation established Math for America, an organization that identifies and supports outstanding math and science teachers in the New York City public schools through renewable four-year fellowships. These teachers receive annual $15,000 stipends on top of their salaries and join a powerful network of other “master teachers,” all of whom can exchange ideas and support one another.

“I’ve never been anywhere where I see so many smart teachers passionately talking about how to improve their classes or how to teach specific topics,” says Bushra Makiya, a middle school math teacher in the Bronx. “Math for America is the reason I’m not burning out.” Indeed, one of the organization’s explicit goals is to improve retention among public school teachers whose quantitative skills might make them attractive candidates for other, more lucrative jobs. “We put our teachers on a pedestal,” says Megan Roberts, executive director of the organization, adding that among the more than 1,000 public school math and science teachers supported by Math for America, the attrition rate is only 4 percent, compared with 9 percent for comparable teachers without the organization’s backing. Math for America currently supports around 10 percent of math and science teachers in New York City, and now that the model has proved successful, inspiring a statewide program in New York, Simons thinks there’s a chance other states or the federal government might create similar programs.

Simons and his foundation are also passionately engaged in basic research on cosmology. For several years, the foundation has supported the ultrasensitive work of detecting gravitational waves, the minuscule distortions in the space-time continuum predicted by Albert Einstein. While gravitational waves generated by the collision of two black holes were detected in September 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO), researchers in the mountains of Chile are looking for primordial gravitational waves from the Big Bang, which could open a window into the earliest moments of the universe. In 2012, the Simons Foundation provided funding to construct and install two additional telescopes at the observation site in Chile. “We climb up to 17,500 feet above sea level and can see far-off volcanoes still active and an inky indigo sky above us,” says Brian Keating, a physicist at the University of California, San Diego. It’s “as close as you can get to being on another planet” while on Earth. Now Simons is supporting the creation of a more elaborate observatory with additional telescopes and equipment—“the world’s highest cosmology observatory,” ­Keating says. As always, Simons is personally immersed in the scientific detail. He asks questions that are “completely on point” and deeply penetrating, says physicist Suzanne Staggs, whose group at Princeton collaborates on the project.

“He wants to understand the science on the deepest level,” Keating says, and “when he decides something is a worthy project, he backs it one hundred percent.”