J. Robert Oppenheimer: the man, his science, and the man beyond the science

J. Robert Oppenheimer is best known for his work on the atomic bomb, but it was not the sum of his academic journey. We explore.

American film director Christopher Nolan’s latest work, Oppenheimer, has dominated theatres worldwide (alongside Greta Gerwig’s Barbie), delivering one of the most iconic box office weekends for cinema. The movie has also renewed interest in the life of J. Robert Oppenheimer, played in the film by Cillian Murphy.

Known as the “father of the atomic bomb,” Oppenheimer’s contributions to nuclear physics and science in general not only sparked technological advancements but also raised questions about ethics and science.

Early years and education

Born in New York City in 1904 to wealthy Ashkenazi Jewish immigrants, Oppenheimer proved to be a prodigious scholar right from the start. His younger brother Frank, too, was a physicist.

After finishing school, he enrolled at Harvard University, majoring in chemistry, but soon realised that his real passion was physics. In fact, in a letter to a friend, Oppenheimer wrote, “My two great loves are physics and desert country.” (He spent time recuperating from illnesses on multiple occasions at a ranch in New Mexico, which he later bought too).

After finishing his degree, Oppenheimer moved to Cambridge University’s Christ’s College, where, in 1925, he expressed a desire to work at Ernest Rutherford’s Cavendish Laboratory. . Rutherford, the 1908 Chemistry Nobel Prize winner, asked Percy Bridgman, his professor at Harvard, if he’d recommend that Oppenheimer join his laboratory. His response throws light on the great scientist’s still-uncertain future at the time. As science historian and author David C. Cassidy wrote in his 2005 book, J. Robert Oppenheimer and the American century, “Despite his (Oppenheimer’s) interest in experimental research, the young man displayed little of the dexterity required for laboratory work.”

“His weakness is on the experimental side. His type of mind is analytical, rather than physical, and he is not at home in the manipulations of the laboratory.”

Percy Bridgman, in his recommendation for Oppenheimer to Rutherford

J. Robert Oppenheimer and the American century by David C. Cassidy

While Oppenheimer left for Cambridge in September 1925, in the hopes of earning a doctorate degree in experimental physics, it was not to be.

Scientific work

Niels Bohr, the 1922 Physics Nobel laureate for his work on structure of atoms, was also a visitor at Cambridge in the spring of 1926. At the time, Oppenheimer was working on the motion of two bodies in quantum mechanics. A discussion with Bohr about the same had profound impact on Oppenheimer and sparked his transition to theoretical physics. “I forgot about beryllium and films and decided to try to learn the trade of being a theoretical physicist,” Oppenheimer said, decided, according to Cassidy’s book.

Oppenheimer’s research yielded results and his first ever published paper, which applied principles of quantum mechanics to a rotating and vibrating diatomic molecule. Max Born, a theoretical physics professor at Germany’s University of Göttingen, arrived at Cambridge just in time for a public reading of Oppenheimer’s second paper, on the motion of two bodies in quantum mechanics. Having worked on a similar topic, Born was interested in Oppenheimer’s work; impressed, he invited Oppenheimer to come the next year to Göttingen, where he was the presiding professor of the new quantum mechanics wing.

Oppenheimer was elated. “I felt completely relieved of the responsibility to go back into a laboratory. I hadn’t been good, I hadn’t done anybody any good, and I hadn’t had any fun whatever; and here was something I felt just driven to try,” he reportedly said.

Oppenheimer arrived in Göttingen in the fall of 1926, joined at the institute by other notable scientists of the time, including Karl T. Crompton, Paul Dirac, Wolfgang Pauli, Werner Heisenberg, and more. However, not everyone liked his presence there; Oppenheimer’s wealth reportedly made his peers uncomfortable, and he was known to interrupt seminar speakers, including Born. Despite this, Oppenheimer’s work with Born yielded magnificent results, and he was able to complete his doctoral dissertation within a few months.

He published 12 research papers while at Göttingen, and his association with Born also led to one of his most-valued contributions to the field of quantum mechanics — the Born-Oppenheimer approximation, whichassumes that the motion of electrons can be separated from nuclear motion in molecules to simplify the study of atoms and molecules.

The timing of Oppenheimer’s choice of field can also be attributed as a factor, however small, in his success. Quantum mechanics developed in the 1920s, and Oppenheimer had the chance to associate with stalwarts like Bohr, Dirac, Heisenberg, and other scientists considered pioneers of the field. His knowledge of mathematical tools allowed him to focus on applications rather than their formulation and led to various advancements in quantum mechanics.

Back in the U.S. with his doctorate degree at the age of just 23, Oppenheimer split his time between Harvard University and the California Institute of Technology as a fellow of the National Research Council. He also visited other international centres of scientific learning, like Leiden in the Netherlands and Zurich in Switzerland.

Professor Oppenheimer

In 1929, Oppenheimer became an assistant professor in physics, simultaneously at the University of California in Berkeley and at the California Institute of Technology. He continued to collaborate with scientists and his research students. His notable works include the Oppenheimer-Phillips process, which involves a nuclear reaction that results in breaking the neutron-proton bond in a deuteron (a stable particle consisting of a proton and a neutron)— while the neutron is absorbed into the nucleus, a proton is thrown out.

In 1939, Oppenheimer almost predicted the existence of black holes in a publication titled On Continued Gravitational Contraction, in collaboration with his student Hartland Snyder. In the paper, the scientists pointed out that “when all thermonuclear sources of energy are exhausted a sufficiently heavy star will collapse.” We now know that most black holes were once large stars that died in a supernova explosion.

The research paper also marked the end of Oppenheimer’s brief foray into astrophysics, and the beginning of World War II, which started his journey for the scientific advancement he’s best known for – the atomic bomb.

World War II

The U.S. entered World War II on December 7, 1941, after Japan bombed Pearl Harbour. However, U.S. President Franklin D. Roosevelt had already approved a programme to develop an atomic bomb (which was eventually used on Hiroshima and Nagasaki in Japan, effectively ending the war in 1945).

According to the American Museum of Natural History, a letter written by scientist Albert Einstein to President Roosevelt in 1939 provided the impetus to push the U.S. towards developing an atomic bomb. Consequently, the government launched the Manhattan Project — the scientific and military undertaking to develop the bomb. Einstein himself, however, was denied the security clearance to work on the project because of his left-leaning political views.

In his memoir for Oppenheimer, Nobel Laureate and theoretical physicist Hans Bethe wrote that Oppenheimer felt the urge to “contribute to the American society” in 1942, and the opportunity presented itself soon in the form of leading a theoretical effort to design the atomic bomb.

Oppenheimer assembled a small group of theoretical physicists for the job — Edward Teller (who eventually came to be known as the father of the hydrogen bomb), John Hasbrouck Van Vleck, Hans Bethe, Emil Konopinski, Robert Serber, and three of his own graduate students.

According to Bethe, some members of the group did calculations for the actual project of the study under Serber, while the rest — especially Teller, Oppenheimer, and Bethe himself — worked on the question of whether and how an atomic bomb could be used to trigger a hydrogen bomb.

While working on the Manhattan Project, Oppenheimer circled back to his love for the desert and chose Los Alamos in New Mexico for a remote and permanent facility to develop the bomb. He owned a ranch with his brother in Pecos Valley of New Mexico, situated around an hour away from Los Alamos.

According to Bethe, it wasn’t obvious at first that Oppenheimer would direct the Los Alamos laboratory, given his inexperience in managing a large group. But General Leslie Groves, by then in charge of the Manhattan Project, overruled objections and appointed him director. t “It was a marvellous choice. Los Alamos might have succeeded without him, but certainly only with much greater strain, less enthusiasm, and less speed,” Bethe wrote.

“It (selecting Oppenheimer as director of the Los Alamos laboratory) was a marvellous choice. Los Alamos might have succeeded without him, but certainly only with much greater strain, less enthusiasm, and less speed.”

Hans Bethe

Biographical Memoirs of Fellows of the Royal Society

Science behind atomic bomb

The Manhattan Project experimented to weaponise nuclear fission. When a single atom of an unstable radioactive element like uranium or plutonium is bombarded with neutrons of a specific energy, it causes the nucleus to split. The reaction can release another neutron of similar energy, hence repeating the process and creating a chain reaction capable of releasing tremendous energy in a short time. Strong nuclear force — the force that holds protons and neutrons inside the nucleus — is the strongest among the four fundamental forces, the others being gravitational force, electromagnetism, and weak nuclear force.

In an atomic bomb, fission explosion occurs when the radioactive material within the core of the bomb, like uranium-235 or plutonium, reaches critical mass. Critical mass is the minimum amount of fissile material that will support a self-sustaining chain reaction.

Before the bomb was dropped on Hiroshima and Nagasaki in August 1945, it was tested at the Alamogordo Bombing Range in the New Mexico desert on July 16, 1945. The test was called “Trinity” and provided valuable information on the physical properties of a nuclear explosion.

The ethics of nuclear weapons and its aftermath

According to Bethe, conversations with Bohr, who was asked to help at the Los Alamos laboratory, deeply impressed the scientists working there, including Oppenheimer. Bohr couldn’t influence statesmen as he had hoped to, but the scientists agreed with his views that “international control of the atom was the only way to avoid a pernicious arms race or worse, atomic war”.

After World War II ended, Oppenheimer served as Chairman of the General Advisory Committee (GAC) of the Atomic Energy Commission from 1946 to 1952.

The Soviet Union exploded its first atomic weapon in 1949, and some scientists proposed that the U.S. should develop hydrogen bombs as a response. The GAC recommended against this. It did not want to set up an arms race with the Soviets, and besides, , a key component for this development was invented by Teller only in 1951.

Following President Harry Truman’s approval for the development of a hydrogen bomb anyway, Oppenheimer tried to resign as the chairman of the committee, but his resignation was not approved.

This wasn’t the only trouble Oppenheimer was going to face. In 1953, he was accused of being a Communist and working against the interests of the country. President Dwight Eisenhower ordered that his security clearance for government operations be terminated. Though he was cleared of the charges, he lost security access as well as his position with the Atomic Energy Commission. The decision was majorly prompted by his “close ties” with the Communist movement between 1939 and 1942.

It wasn’t until 1961 that the U.S. government, under President John F. Kennedy, made amends to Oppenheimer and presented him the Fermi Award (which he eventually received in 1963).

Oppenheimer’s politics

According to Bethe’s memoir, Oppenheimer’s interest in politics began around 1936, shortly before World War II. Some of his Jewish relatives in Germany bore the brunt of Hitler’s antisemitic policies, and he was also affected by how the American depression impacted his students, which shaped his political bent towards the left. Although he never joined the Communist Party, his brother and sister-in-law were members. However, he seemed to move away from its influence after Hitler and Stalin, the Soviet leader, signed the German-Soviet pact, essentially allowing Hitler to start the war.

Oppenheimer, beyond the science

In his memoir, Bethe described Oppenheimer, or “Oppie”, as a “creative scientist”. “He worried about the increasing gap between specialised knowledge and common sense, the increasing gap between neighbouring sciences, and even between different branches within his own science of physics. He said: ”Even in physics we do not entirely succeed in spite of a passion for unity which is very strong.’”

Oppenheimer’s interest in Hinduism, especially the sacred text Bhagavad Gita, is also well documented. According to Cassidy, he studied the scripture in Sanskrit, and also studied Plato in his original Greek. At Berkeley, he studied Sanskrit with the chair and only member of the Sanskrit department, Arthur Ryder. An article published in Time magazine in November 1948 identified, “Scholarship is less than sense, therefore seek intelligence,” as one of Oppenheimer’s favourite couplets.

When the Trinity test was conducted in New Mexico, Oppenheimer is famously known to have quoted, “Now I am become death, the destroyer of worlds,” from the Gita.

According to Time, Oppenheimer would often treat his students to expensive dinners. Bethe wrote about their evening parties, where they “drank, talked, and danced until late, and, when Oppie was supplying the food, the novices suffered from the hot chilli that social example required them to eat”.

Oppenheimer married Katherine Harrison in 1940. They had a son named Peter and a daughter named Katherine.

Last years

Oppenheimer served as the director of the Institute for Advanced Study in Princeton from 1947 to 1966. He was diagnosed with throat cancer in 1965, subsequently undergoing surgery and radiation therapy. However, he fell into a coma on February 15, 1967, and died at his home in Princeton, New Jersey, on February 18, aged 62.

In 2022, the Joe Biden administration reversed the 1954 decision revoking Oppenheimer’s security clearance for U.S. government projects. In a press release, the U.S. Department of Energy (the successor of the Atomic Energy Commission) announced that the 1954 decision was vacated.

“When Dr. Oppenheimer died in 1967, Senator J. William Fulbright took to the Senate floor and said ‘Let us remember not only what his special genius did for us; let us also remember what we did to him.’ Today we remember how the United States government treated a man who served it with the highest distinction. We remember that political motives have no proper place in matters of personnel security. And we remember that living up to our ideals requires unerring attention to the fair and consistent application of our laws,” Secretary of Energy Jennifer Granholm said.

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