On November 1, 1952, the US detonated the first thermonuclear weapon, dubbed “Ivy Mike,” off the Enewetak Atoll in what is now the Marshall Islands. Most of us consider the late physicist Edward Teller to be the “father of the hydrogen bomb”—and Teller did indeed champion the notion of a fusion-based “super bomb.” But hardly anyone outside of physics has heard of Stanislaw Ulam, the Polish mathematician and physicist who helped realize Teller’s objective, although the extent of their respective contributions to the breakthrough Teller-Ulam design remains both highly classified and controversial.

Ulam is also the mastermind behind what is known as the Monte Carlo method of computation, and along with his Hungarian-born colleague John von Neumann, he was a pioneer of early computing technology. He proposed a novel nuclear pulse propulsion method for starships that led to the formation of Project Orion in 1958, with the goal of achieving interplanetary travel. And he was a formidable poker player, as many of his Los Alamos colleagues learned to their detriment.

The life of this extraordinary yet largely unsung scientist is the focus of *Adventures of a Mathematician*, a new film from German director Thor Klein. Klein’s thoughtful, haunting film is less a straightforward biopic and more an elegant, impromptu narrative composed out of key events in Ulam’s life, set against the backdrop of World War II and its immediate aftermath.

(**Some spoilers for the film below.)**

What was it about Ulam that made him so special in the eyes of his colleagues? “The key is having the right idea at the right time,” George Dyson, a science historian who consulted on the film, told Ars. “Ulam is one of the lead characters in three of my books. He keeps appearing because he did so many different things. A lot of ideas that we credit to other people came from their bouncing them off of Ulam.” Apart from his research in pure mathematics and logic, Ulam is known for a handful of particularly influential ideas.

First and foremost is the Teller-Ulam design for thermonuclear weapons. It was Enrico Fermi who first mentioned to Edward Teller in the fall of 1941 the possibility of using the energy from a fission device to begin a fusion reaction. Even after the Trinity Test and bombings of Hiroshima and Nagasaki in 1945, Teller was convinced there would be a need for a nuclear “super bomb.” When the Soviet Union detonated its first atomic bomb in August 1949—an implosion design similar to the Fat Man bomb detonated over Nagasaki, courtesy of information provided by Soviet spy Klaus Fuchs—President Harry S. Truman greenlit a US program to develop a hydrogen bomb.

The sticking point for the hydrogen bomb was how to ignite the fusion material, which required tremendous temperatures and pressures. The original idea was to use a fission “trigger,” but the heat from that explosion alone turned out to be insufficient. Ulam and Teller’s ingenious 1951 solution is now called “staged implosion,” and it’s believed to be the basis for most thermonuclear weapons today.

While Teller later denied Ulam’s contribution, other physicists, like nuclear weapons designer Ted Taylor, contend that Ulam deserves credit for ideas about compression and basic staging of the weapon, while Teller realized that radiation—rather than hydrodynamic pressure—was the key to ignition. (Since many of the relevant files remain classified, the controversy is unlikely to be resolved any time soon.)

Ulam got the idea for his MonteCarlo method while recuperating from surgery. This was when scientists were developing ENIAC, the first programmable, electronic general-purpose digital computer. Ulam had been playing a lot of solitaire during his recovery, trying to estimate the odds of, say, a successful Canfield solitaire game using abstract combinatorial calculations. He came up with a more practical method, laying out the game a hundred times, for example, and then observing and counting the number of successful plays. Ulam quickly recognized that a computer like ENIAC would make such methods feasible. When he mentioned it to von Neumann, they began planning actual calculations, and the Monte Carlo method was born.

Dyson also credits Ulam with having the vision to foresee the digital universe. “Ulam had this very clear picture that once you had enough computers, you would effectively have a two-dimensional universe,” said Dyson. “Ulam had the insight that you could look at this in a biological way. These arrays of cells could become ‘Turing complete’ and become their own universal machines. So you could have free-floating computers in this digital space, which at the time seemed like an insanely crazy idea. It took many years for that to even become science fiction. That’s the digital universe we live in now, what we call the cloud.”

Much of this is touched upon, albeit briefly, in *Adventures of a Mathematician*. Director Klein has had a lifelong love of mathematics, ever since he read a book called *Who Got Einstein’s Office* (by Edward Regis), telling the story of Princeton’s Institute of Advanced Study. Ulam and John von Neumann both figured prominently. “They were throwing parties and driving fast cars, in Johnny’s case,” Klein told Ars. “They were so different from the math teachers I had in school.”

Initially, Klein dreamed of becoming a mathematician himself, but he eventually realized math wasn’t his strength. “I had a great literature teacher who made me aware that I was probably more interested in these people and their ideas than doing the actual math,” he said. “And I realized when I got older that the parties and fast cars were on the surface. Underneath it was deep tragedy, because they lost their families and just had each other to rely on.”

Klein encountered Ulam’s memoir, *Adventures of a Mathematician*, while still in film school and decided to base his film on that. Of course, the story about the Manhattan Project and the birth of the atomic age has been told and retold many times on-screen in many different ways. But Ulam was a relatively minor character at Los Alamos. True, his insights proved crucial, particularly for the later hydrogen bomb, but he is not one of the famous names associated with the project in popular culture, like Robert Oppenheimer and Teller.

“Stan was on the periphery of the place,” said Klein. “[Ulam’s story] opened up visually an interesting way to portray this, to show a different layer [to the story].” The fact that so many of the Los Alamos scientists were European immigrants who had fled the Nazi occupations of their home countries also appealed to Klein.