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J. Robert Oppenheimer and the Making of the Atomic Bomb

My writing interests are general, with expertise in science, history, biographies, and how-to topics. I have written over 70 books.

J. Robert Oppenheimer with his signature porkpie hat.

J. Robert Oppenheimer with his signature porkpie hat.

Early Life

Julius Robert Oppenheimer was born in New York City on April 22, 1904. His father was a German immigrant who became a wealthy textile importer. His mother, Ella Freedman, was a gifted painter. Music and art were always prominent in the Oppenheimer household. Robert was a quick learner with a wide-ranging curiosity. He attended the Ethical Culture School in New York, where he was taught to develop his “ethical imagination,” to see “things not as they are, but as they might be.” “I was an unctuous, repulsively good little boy,” he later said. “My life as a child did not prepare me for the fact that the world is full of cruel and bitter things.”

After graduation from the Ethical Culture School, which was equivalent to high school, he went for a summer trip to Germany to visit relatives. On a field trip to collect mineral samples in Bohemia, he contracted dysentery and became very ill. He spent the next winter recovering at his parents’ home in New York. During the summer of 1922 his father sent him with his English teacher, Herbert W. Smith, to explore the trails and plateaus of New Mexico. This trip would instill in him a lifelong love of the desert southwest.

In the fall of 1922, Oppie, as his friends called him, entered Harvard University to study chemistry. A gifted student, he took more than a full load of classes and audited others. By the end of his three years at Harvard his interests had shifted away from chemistry to the study of the underlying physics. In 1925 he graduated with a BA summa cum laude.

Cambridge University

The brilliant young Oppenheimer suffered a personal and professional setback when he went for further study at England’s prestigious Cambridge University. He had applied to work with the renowned experimental physicist Ernest Rutherford at the Cavendish Laboratory, which was part of the university. Rutherford was not impressed with his credentials and did not accept him; rather, Oppenheimer worked under the former director of the Cavendish Laboratory, J.J. Thompson. Oppenheimer was a very talented theoretician, but he was clumsy with his hands, which made him a poor laboratory student. A combination of events in England caused him to unravel: he didn’t like the Cambridge culture or the work with Thompson; he had anxieties caused by some sexual encounters; and there was a growing distance with his old Harvard friends due to their marriages. All these events were catalysts that led to his nervous breakdown.

Not accustomed to failing, he became depressed and jealous of those experimentalists who found success at the Cavendish. His tutor, Patrick Blackett, three years his senior, became the object of Oppenheimer’s obsession. In the fall of 1925, he placed a “poison apple,” possibly laced with cyanide, on Blackett’s desk. Luckily for all involved, the deed was discovered before Blackett could eat the tainted apple. Oppenheimer was brought before university officials and nearly expelled. If it hadn’t been for the intervention of his parents and their promise to seek psychiatric help for their son, he would have been expelled, thus placing a black mark on his sterling academic record. He quickly recovered and began to immerse himself in work on physics theory rather than conducting experiments in the laboratory. Here he excelled and wrote two papers on the application of quantum mechanics to the vibrational and rotational spectra of molecules before leaving Cambridge in the late summer of 1926.

The apparatus used by Ernest Rutherford in his atom-splitting experiments, set up on a small table in the Cavendish Laboratory.

The apparatus used by Ernest Rutherford in his atom-splitting experiments, set up on a small table in the Cavendish Laboratory.

The World of Physics

The world of physics when Oppenheimer graduated from Harvard was undergoing a sea change. The ideas of the classical physics of Isaac Newton were being overthrown by a new model of reality based on the concepts of quantum mechanics. The laws of classical physics work well for macroscopic objects, the world we see and experience in our day-to-day lives; however, classical physics breaks down when it is applied at the atomic and sub-atomic level.

During the first two decades of the 20th century, physicists Max Planck, Albert Einstein, and Niels Bohr were at the cutting edge of this new way of understanding nature. In 1925, German physicist Werner Heisenberg published his first paper on the new quantum mechanics. That same year, Paul Dirac published a paper in which he developed his own version of Heisenberg’s theory. Early the next year, Erwin Schrödinger published his first paper on his wave equation, which would become fundamental to the development of quantum mechanics. The new ideas began to solidify into logically consistent and mathematically clear descriptions of the atomic world. Oppenheimer’s ability to grasp the flood of new theory allowed him to play a part in the maturation of quantum physics, knowledge that would be essential for the development of the atomic bomb.

Finding His Passion in Theoretical Physics

Realizing that his talent in physics was not in the laboratory but rather with paper and pencil making theoretical calculations, he went to the University of Göttingen to study under the theorist Max Born. With Born’s guidance, Oppenheimer developed a quantum theory of molecules that described the motion of electrons around the combined nuclei as well as the motion of the nuclear skeleton. In addition, the pair developed a method of approximation that greatly simplified making calculations concerning electron structures called the Born-Oppenheimer approximation. Oppenheimer received a PhD in theoretical physics in 1927.

After receiving his PhD, Oppenheimer remained in Europe until 1929. He spent his time with Paul Ehrenfest in Leiden and Wolfgang Pauli in Zurich. During this time of work and study, he deepened his understanding of quantum mechanics. His research centered on radioactive effects in the continuous spectrum.

Teacher and Researcher

In 1929 he began his teaching career with a joint appointment to both the California Institute of Technology (Caltech) and the University of California at Berkeley. Over the next thirteen years he was busy working with students on their research projects and conducting his own research. These were productive years, and he wrote several important papers in physics. He worked on calculating the photoelectric effect for hydrogen, the radiation in the form of X-rays produced in collision of an electron with a positively charged atomic nucleus, and the capture of electrons by ions of other atoms. He also developed a theory to describe the extraction of electrons from metal surfaces by very strong electric fields. In addition, he explained the multiplicity of electron showers in cosmic radiation. His most important theoretical contribution was the Oppenheimer-Phillips process, where a deuteron (one proton and one neutron) when entering a heavy nucleus is split into one proton and one neutron so that one is retained by the nucleus while the other is reemitted.

At the University of California at Berkeley he established the School for Theoretical Physics, which became an important training school for many of the nation’s top theorists. During the 1930s, the emphasis of the school was on the study of atomic structure and particles, with the recently discovered quantum mechanics. Oppenheimer wrote to his brother Frank in 1932, “There are lots of eager students, and we are busy studying nuclei and neutrons and disintegrations, trying to make some peace between the inadequate theory and the absurd revolutionary experiments.” Oppenheimer was talented at guiding his graduate students to study cutting-edge problems and supervised their work through their graduate career in physics. His influence was enhanced with his students by his perceptive interest in people and his open hospitality to those around him. To honor his contributions as a researcher and teacher, he was elected to the National Academy of Sciences in 1941.

Katherine “Kitty” Puening Oppenheimer

During the 1930s, the outside world began to intrude into Oppenheimer’s academic cocoon. High unemployment brought on by the Great Depression was evident everywhere; Hitler and Mussolini were showing their aggressive stripes; and the Spanish Civil War drug on in Europe. Like many liberal intellectuals of the day, he became interested in left-wing politics. He and his brother, Frank, supported many left-wing groups, some closely associated with the Communist party. Though Robert never openly joined the Communist party, he supported many of their causes financially.

In 1936, Oppenheimer became involved with Jean Tatlock, the daughter of a Berkeley literature professor. Their relationship was tumultuous, and the two parted ways after three years; however, they would maintain an on-again-off-again affair that would last for years. In the fall of 1939, he met Katherine (“Kitty”) Puening at a party. Though already on her third husband, Kitty set her sights on him immediately. Her friend later spoke of that time: “She’d set her hat for him. She did it the old-fashioned way, she got pregnant, and Robert was just innocent enough to go for it.” In the summer of 1940, she asked her husband for a divorce. He refused, so she went to Reno, Nevada, for an instant divorce. Kitty and Robert were married on November 1, 1940. Their first child, Peter, was born the following spring and their daughter, Kathrine, was born in Los Alamos, New Mexico, in the winter of 1944.

The Nuclear Threat from Germany

At the urging of scientists Leo Szilard and Eugene Wigner, Albert Einstein sent a letter to President Franklin Roosevelt in early August 1939 warning him of the impeding threat to the Allied powers if Germany were to develop an atomic bomb. Einstein wrote: “In the course of the last four months it has been made probable—through the work of Joliot in France as well as Fermin and Szilard in America—that it may become possible to set up a nuclear chain reaction in a large mass of uranium by which vast amounts of power and large quantities of new radium-like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future. This phenomenon would also lead to the construction of…extremely powerful bombs of a new type …”

President Roosevelt took Einstein’s waring seriously and set the wheels in motion for research into atomic science and the making of a bomb. Since many of the scientists who had been involved with the discovery of nuclear fission were of German origin, Roosevelt was forced into taking action to beat the Germans in the building of the atomic bomb. Oppenheimer was soon drawn into the mix of science and technical experts trying to unlock the power of nuclear fission.

Diagram illustrating nuclear fission. A neutron is absorbed by a uranium-235 nucleus, turning it briefly into an excited uranium-236 nucleus. The uranium-236, in turn, splits into fast-moving lighter elements (fission products) and energy.

Diagram illustrating nuclear fission. A neutron is absorbed by a uranium-235 nucleus, turning it briefly into an excited uranium-236 nucleus. The uranium-236, in turn, splits into fast-moving lighter elements (fission products) and energy.

Atomic Research Begins

Following the news of the discovery of nuclear fission in Europe in 1938, Oppenheimer, eager to study this exciting new phenomenon, became involved in atomic bomb research in October 1941. It was Ernest Lawrence, Oppenheimer’s friend and director of one of the physics laboratories at Berkeley, who got Oppenheimer into nuclear research to support the war effort. Lawrence arranged for Oppenheimer to be invited to a conference in Schenectady, New York, in October 1941. Fast neutron reactions—the kind that can lead to nuclear explosions—were being discussed at the conference. There, Oppenheimer presented his own estimate of the amount of uranium needed to begin an explosive chain nuclear fission reaction.

America Is Drawn Into World War II

With the attack on Pearl Harbor in Hawaii on December 7, 1941, the United States was thrust into the war that was raging in Europe and the Pacific nations. In 1942, Oppenheimer was recruited by U.S. Army General Leslie R. Groves to be the scientific head of the secret “Manhattan Project,” which was America’s program to develop a nuclear weapon. This was a bold move on Grove’s part, as Oppenheimer was a theorist with little experience with laboratory work or in managing a large team of researchers. Since some of the science necessary for the development of a nuclear weapon had come out of Nazi Germany, this caused much anxiety in the scientific community. Once government officials and military leaders realized the threat, the U.S. government began to invest heavily in the development of the atomic bomb. The race was on to beat the Germans to be the first nation to possess the most lethal weapon in the history of the world.

As head of the project, Oppenheimer chose the location of the laboratory in the remote Pecos Valley of New Mexico at the former Los Alamos Ranch School. He had fallen in love with the American southwest during his youth, and the remoteness of the area would be ideal for the design and construction of the secret bomb.

He recruited over fifty of the top scientists in the country to work on the project, including Enrico Fermi, Hans A. Bethe, and Edward Teller. As much as possible, given the secret nature of the work, Oppenheimer encouraged his researchers to communicate with each other to solve some of the more complex technical problems, delegating responsibility and making his people feel trusted. His quick perception allowed him to keep abreast of all the phases of the work in the various laboratories at Los Alamos. Oppenheimer’s contribution to building the first atomic bomb was that of a hands-on administrator, rather than of a pure scientist. Before the end of the war, the Los Alamos facility would employ over 6,000 workers and become a small city with a school and hospital for the scientists, engineers, technicians, support staff, and their families living in the secret city.

Mushroom cloud seconds after detonation of the first nuclear bomb at the Trinity Test Site, New Mexico, on July 15, 1945.

Mushroom cloud seconds after detonation of the first nuclear bomb at the Trinity Test Site, New Mexico, on July 15, 1945.

Dropping of Atomic Bombs on Japan

Due to the very limited supply of fissionable material, which was produced at a secret site erected in rural Oak Ridge, Tennessee, Oppenheimer’s team had to develop two separate types of bombs, one that used uranium as the nuclear fuel and one that used plutonium. By 1945, enough of the nuclear fuel (fissionable material) was ready for testing one bomb and building one each of the two types of bombs. The uranium bomb was named “Little Boy,” and the bomb made from plutonium was called “Fat Man.” The first atomic bomb was successfully tested in the New Mexico desert in July 1945.

Though the war in Europe was over with the defeat of Adolf Hitler and the Axis powers, the war with Japan still raged in the Pacific. The dropping of the two atomic bombs on the two Japanese cities of Hiroshima and Nagasaki in 1945 quickly brought the war to an end; Japan surrendered unconditionally. Though the bombs killed over two hundred thousand Japanese, they were credited with saving many more lives, as without the bombs the war would have dragged on and caused the deaths of many more.

Oppenheimer later wrote that the creation of the atomic bomb brought to his mind words from the ancient Hindu text the Bhagavad Gita, “Now I am become Death, the destroyer of worlds.” Many years later he commented on the fateful decision to drop the bombs on Japan, “I believe there was very little deliberation…The actual military plans at that time…were clearly much more terrible in every way and for everyone concerned than the use of the bomb. Nevertheless, my own feeling is that if the bombs were to be used there could have been more effective warning and much less wanton killing…” He remained for the rest of his life painfully aware of the responsibility he bore for his part in birthing this most potent force.

Crew of the “Enola Gay” that dropped the “Little Boy” atomic bomb on Hiroshima.

Crew of the “Enola Gay” that dropped the “Little Boy” atomic bomb on Hiroshima.

Atomic Energy Commission

After the completion of the Second World War, Oppenheimer was appointed Chair of the General Advisory Committee of the U.S. Atomic Energy Commission (AEC), a position he held until 1952. The committee included, among others, such noteworthy scientists as Enrico Fermi, I.I. Rabi, and Glenn T. Seaborg. The commission was charged with advising on scientific matters and policy concerning the development of nuclear energy for both the military and peacetime applications. As chairman, Oppenheimer’s role was not to dominate opinion but to clarify the issues and formulate the committee’s responses. In addition to his role as chair of the General Advisory Committee, he served on other committees related to atomic weapons and defense.

The Institute of Advanced Study

The war effort left him exhausted and troubled over the powerful new weapon he helped create. In the fall of 1945, he resigned as the head of Los Alamos and accepted a professorship at Caltech. The following year he rejoined the Berkeley faculty but was constantly called to Washington to act as a nuclear consultant—by now he was a national figure.

Seeking a change from his academic life in California, in 1947 Oppenheimer was named director of the newly formed Institute for Advanced Study at Princeton University. Along with such luminaries as Albert Einstein and mathematician and computer scientist John von Neumann, they developed a world-class program in theoretical physics at Princeton. As director of the Institute, he was also responsible for policy in other fields, including pure mathematics and history. The Oppenheimers entertained frequently; according to one guest, “He served the most delicious and the coldest martinis.”

Oppenheimer’s interests turned from pure physics research to evaluating the impact of science and technology on society. He believed that the world’s entrance into the atomic age demanded a broader public understanding of the implications of recent advances. During his tenure at the Institute, he wrote a number of books, including Science and Common Understanding in 1954 and The Flying Trapeze: Three Crises for Physicists in 1961. He would remain at the Institute for nearly the remainder of his life.

Security Clearance Hearing

For national security reasons, in 1954, Oppenheimer was removed from the AEC. This was during the period when there were investigations of any public figure who may have or had ties to communist organizations. The communist witch hunt was led by the zealous anti-communist Senator Joseph McCarthy. During the 1930s, Oppenheimer had contributed monies to left-wing causes and his wife and brother were members of the Communist Party—this came back to haunt him two decades later.

He was also brought under scrutiny for his 1949 decision not to back the development of the more deadly hydrogen bomb, making him “soft on communism.” Rather than accept the revocation of his security clearance and the clear implications of disloyalty, he chose the option of a secret hearing before the special appeals board. During the nearly two-month long hearings in 1954, numerous distinguished scientists and public servants testified on his behalf. In June, the committee concluded that although Oppenheimer’s loyalty was not in doubt, his left-wing association in the 1930s made him a poor choice to be trusted with the nation’s official secrets.

The eminent physicist Enrico Fermi was among the scientists who testified in support of Oppenheimer.

The eminent physicist Enrico Fermi was among the scientists who testified in support of Oppenheimer.

Final Years

After the 1954 security hearings, Oppenheimer “was like a wounded animal,” recalled his longtime friend Francis Fergusson. “He retreated. And returned to a simpler way of life.” He took his family to St. John in the Virgin Islands. There he built a simple beach cottage, and the family spent many months each year on the beautiful beach. He and Kitty became expert sailors.

As a gesture of goodwill and in an attempt to repair Oppenheimer’s damaged reputation, in December 1963, President Lyndon B. Johnson awarded Oppenheimer the AEC’s most prestigious Enrico Fermi Award. Oppenheimer acknowledged the award with the words, “I think it is just possible, Mr. President, that it has taken some charity and some courage for you to make this award today. That would seem to me a good augury for all our futures.”

J. Robert Oppenheimer retired from the Institute of Advanced Study in 1966 and died on February 19, 1967, from throat cancer. He will long be remembered as the “father of the atomic bomb.”


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© 2022 Doug West