Jun 27, 2023 · By Erik Olsen

Before Los Alamos, Oppenheimer Built the Atomic Age at Berkeley

J. Robert Oppenheimer spent 14 years at UC Berkeley, where he built a world-class physics program and colleagues discovered plutonium and invented the calutron. California’s role in the Manhattan Project.

Updated Oct 12, 2026

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The movie Oppenheimer spends a lot of time in New Mexico, but the story of the atomic bomb really starts in California, at the University of California, Berkeley. That’s where J. Robert Oppenheimer spent 14 years building one of the best physics programs in the world, and where some of the key science behind the Manhattan Project was done.

The film team filmed several scenes at Berkeley, adding a vintage car and 1940s-era lampposts to the campus. Oppenheimer taught at UC Berkeley from 1929 to 1943 — his office was on the third floor of Physics North (then named LeConte Hall)

For a long time, American physics happened back East. After World War I, though, Caltech and UC Berkeley decided to change that, and they spent serious money to do it.

By the early 1930s, it was working. The president of the American Physical Society said California had caught up with the East. Universities were fighting over young stars like Oppenheimer and Ernest Lawrence, who invented the cyclotron at Berkeley and won the Nobel Prize for it in 1939.

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Oppenheimer is remembered as the “father of the atomic bomb,” but before he ran the Manhattan Project’s lab at Los Alamos, he was a Berkeley professor.

J. Robert Oppenheimer, Enrico Fermi and Ernest O. Lawrence at UC Berkeley in 1940. Courtesy: Lawrence Berkeley National Laboratory

Oppenheimer’s relationship with Berkeley began in 1929, when he joined the faculty as an assistant professor. It was a great time to be a physicist. Quantum mechanics was brand new, and Oppenheimer, who had studied in Europe with the people inventing it, brought it to the West Coast.

At Berkeley, he did important work in theoretical physics, including the Oppenheimer-Phillips process, which explains a type of nuclear reaction in which a deuteron (a proton and neutron stuck together) hits a nucleus, and the nucleus grabs the neutron while the proton flies off.

He was also a magnetic teacher, quick and charismatic, and he drew so many bright students that Berkeley’s theoretical physics program became arguably the best in the country. Then, in the summer of 1942, he gathered a small, secret group of top theorists, nicknamed the “luminaries,” to work out the physics of an atomic bomb.

J. Robert Oppenheimer (Ed Westcott/U.S. Department of Energy via Bay City News)

“The group met secretly in his office at the northwest corner of the top floor of ‘old’ LeConte Hall. This office, like others on the top floor, has glass doors opening out onto a balcony,” wrote Raymond T. Birge, who chaired Berkeley’s physics department at the time. “This balcony is readily accessible from the roof. To prevent this method of entry, a very heavy iron netting was placed over the balcony. A special lock was placed on the door to the office and only Oppenheimer had the key. No janitor could enter the office, nor could I, as chairman of the department,”

Hans Bethe, one of the great physicists of the era, said Oppenheimer made Berkeley the “greatest school of theoretical physics the United States has ever known.”

Former students said that even as he got famous, he stayed approachable. He pushed them hard, and his questions in seminars could sound harsh, but they said he was trying to make things clear for everyone in the room, not to humiliate the speaker. He was surprisingly casual with them, and they could drop by his office anytime.

J. Robert Oppenheimer with Glenn T. Seaborg and Ernest O. Lawrence in early 1946. (Photo courtesy of Berkeley Lab)

It wasn’t all physics. Oppenheimer loved literature, poetry and art, read Sanskrit, and rode horses and hiked. That mix of brilliance and breadth is part of why General Leslie Groves eventually picked him to run the bomb lab.

California didn’t get the giant bomb factories, which went to Tennessee, Washington state and New Mexico. But Berkeley’s Radiation Laboratory was a key Manhattan Project site, and the campus supplied a remarkable number of the project’s stars: Oppenheimer, Ernest Lawrence and the chemist Glenn Seaborg, among others.

Berkeley, founded in 1868 as California’s first land-grant university, had grown into a research powerhouse under Robert Sproul, who led the University of California from 1930 to 1958.

Berkeley’s biggest contribution may have been plutonium. Edwin McMillan, a promising physicist at Berkeley, was studying what happens when uranium is hit with neutrons. In 1940, he found a new element, number 93, which he named neptunium, after the planet past Uranus. He predicted it would decay into plutonium, element 94.

Glenn Seaborg (Wikipedia)

When McMillan left for MIT to work on radar, Glenn Seaborg picked up the hunt, and in early 1941 his team identified plutonium and showed that it splits easily, which meant it could fuel a bomb. Seaborg went on to lead the work of separating plutonium from uranium and other reactor waste.

Meanwhile, Lawrence and his team at the Rad Lab used their 60-inch cyclotron to make plutonium for study. Then, in 1941, Lawrence realized he could convert a cyclotron into a giant mass spectrometer to separate the rare uranium-235 that a bomb needs from the far more common uranium-238. That method was scaled up at Oak Ridge’s Y-12 Separation Plant. The machines were called “Calutron” in honor of the University of California, and they enriched uranium for the Hiroshima bomb.

Recording of the “Rainier” shot, Nevada Test Site, Sept. 19, 1957.
Atomic Energy Commission/U.S. Department of Energy via Wikipedia Commons

All of these people played big roles in the bombs dropped on Hiroshima and Nagasaki in 1945, but Oppenheimer is the one we remember. After 14 years at Berkeley, Oppenheimer was picked by General Leslie Groves to run the new weapons laboratory at Los Alamos. And the Berkeley connection stayed. In secret, the University of California agreed to manage Los Alamos, and it even set up an office in Los Angeles to buy and ship supplies to the lab.

The University of California has been tied to Los Alamos ever since. It ran the lab on its own for decades, and since 2018 it has been one of the partners in the consortium that manages it. Oppenheimer’s old office was in LeConte Hall, now called Physics North. If you’re on campus, it’s worth a look.