With the release of the movie Oppenheimer, it’s worth taking a look at the role that California played in one of the most important technological developments of the 20th century: the making of the atomic bomb. The Manhattan Project, the prodigious scientific endeavor that produced the world’s first nuclear weapons, cast a long, dark shadow over the mid-20th century. But amid the mushroom clouds, there lies a tale of innovation and scientific genius that originated from an unlikely source—the University of California, Berkeley.

For years, America’s physics powerhouse resided in the East. But in the post-WWI era, the western horizon blazed with opportunity. Visionary administrators at Caltech and UC Berkeley threw financial muscle behind their bold mission: to make physics research a priority.

By the dawn of the 1930s, their investments bore fruit. The American Physical Society‘s president hailed California as a hotbed of physics innovation, equating it with the East in the academic landscape of the discipline. Universities played high-stakes poker for the talents of up-and-coming physicists like Oppenheimer and Ernest Lawrence, known for his groundbreaking work in photoelectricity and ionization.

J. Robert Oppenheimer, one of the leading physicists of the 20th century, is often remembered as the ‘father of the atomic bomb’. However, his journey toward this formidable title began at Berkeley, an intellectual crucible where his talent for theoretical physics was honed, ultimately leading him to oversee the Manhattan Project, a scientific endeavor that would change the world.

Oppenheimer’s relationship with Berkeley began in 1929 when he joined as an Assistant Professor of Physics. This was an exciting period in the realm of science. Quantum mechanics was in its infancy and a new breed of scientists was emerging, eager to unlock the secrets of the universe. Oppenheimer, with his insatiable curiosity and infectious enthusiasm, was just the right person for this time of exploration.

During his years at Berkeley, Oppenheimer made significant contributions to quantum mechanics, notably his work on the Oppenheimer-Phillips process. This theory describes a particular type of nuclear reaction that occurs during the absorption of a neutron by a nucleus, an understanding that would later prove pivotal to the development of nuclear energy.

Outside the laboratory, Oppenheimer was an adored figure, known for his quick wit and charismatic teaching style. He was instrumental in building the physics program at Berkeley into perhaps the finest in the country by attracting some of the brightest minds of the time. Together, they would be known as dubbed the “luminaries”.

“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, former chair of the Berkeley 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 German-American theoretical physicists of the age said Oppenheimer established UC Berkeley as the “greatest school of theoretical physics the United States has ever known.”

Although he was increasingly recognized as a pivotal figure in theoretical physics, former students say he remained accessible, consistently urging his students to question norms and extend limits. He actively promoted a culture of inquiry among his students, even if his responses occasionally seemed harsh. However, Oppenheimer’s questions to his student speakers were meant to clarify rather than to humiliate, often aimed more at enlightening the audience than himself. His rapport with his students was unexpectedly casual. He provided an open-door policy, inviting his students to visit his office anytime to utilize the physics resources within his personal collection.

Oppenheimer’s life at Berkeley wasn’t all physics. A man of varied interests, he was an avid hiker, horseback rider, and aficionado of literature, poetry, and art. These varied interests made him a multifaceted character and helped him foster connections with many prominent figures across different fields. His unique combination of scientific genius, humanity, and leadership qualities made him a standout candidate for the enormous task that lay ahead – the Manhattan Project.

While no major Manhattan Project facilities graced the Golden State, Berkeley, nestled in the heart of California, emerged as an unsung hero of the project. Berkeley offered more than a tranquil academic setting; it provided an assembly line of experts that would revolutionize nuclear science. Not only was Berkeley home to Oppenheimer the university also attracted other nuclear-era luminaries like Ernest Lawrence, and chemists Glenn Seaborg.

Berkeley had always been special. California’s first land-grant university, founded in 1868, Berkeley underwent a metamorphosis under the leadership of Robert Sproul. From 1930 to 1958, Sproul spearheaded the transformation of Berkeley into a hub of intellectual firepower. The University of California system burgeoned across the state, with Berkeley, the original campus, earning a reputation as one of the nation’s foremost research institutions. Its powerhouse physics department became a beacon in the dark world of the Manhattan Project.

Berkeley’s list of accomplishments in physics is long and distinguished, but one discovery stands out – the identification of plutonium. Edwin McMillan, a promising physicist at Berkeley, ventured into the wilderness of uranium fission products. In 1940, he stumbled upon an unknown substance – element 93, or as he named it, “neptunium,” a hat tip to the distant planet Neptune. McMillan predicted that neptunium decayed into plutonium, the elusive element 94.

Glenn Seaborg, another Berkeley savant, picked up where McMillan left off when the latter migrated east to work at MIT. Seaborg unveiled the heart of plutonium, exposing its fundamental chemical and nuclear properties, including its high propensity for fission. As the world’s leading expert on plutonium, Seaborg directed the ambitious effort to separate plutonium from uranium and other reactor products.

Meanwhile, Ernest Lawrence led a research group that broke boundaries with the cyclotrons at the Rad Lab. They used the 60-inch cyclotron to bombard uranium with neutrons, producing plutonium for scrutiny. But Lawrence had a revelation. In 1941, he realized the cyclotron could also operate as a mass spectrometer, effectively isolating uranium-235 from uranium-238. This technique was later adopted at Oak Ridge’s Y-12 Separation Plant, enabling large-scale separation. The cyclotron, rechristened as a “Calutron” in a nod to the University of California, had revolutionized nuclear science.

While these figures were all played prominent roles in the development of the atomic bomb dropped on Hiroshima and Nagasaki in 1945, it is Oppenheimer who is best remembered. After fourteen years at Berkeley, Oppenheimer was plucked from the physics department at Berkeley by General Leslie Groves to assume leadership of the research program at Los Alamos. Even after his move, Oppenheimer fostered a close alliance between Berkeley and the Manhattan Project. In a shroud of secrecy, the University of California took on the management of the operations at Los Alamos. The university even set up a Los Angeles office that handled material logistics for the lab.

Despite decades passing and the veils of secrecy lifting, the legacy endures. The Los Alamos lab continues to operate under the University of California’s management, preserving Berkeley’s indelible imprint on the atomic age. It’s a testament to the institution’s groundbreaking contributions and a tribute to the remarkable scientists who once walked its hallowed halls.