J. Robert Oppenheimer

J. Robert Oppenheimer was born in New York City on April 22, 1904,[note 1][7] to Julius Oppenheimer, a wealthy Jewish textile importer who had immigrated to the United States from Germany in 1888, and Ella Friedman, a painter. Julius came to the United States with no money, no baccalaureate studies, and no knowledge of the English language. He got a job in a textile company and within a decade was an executive with the company. Ella was from Baltimore.[8] The Oppenheimers were non-observant Ashkenazi Jews.[9] In 1912 the family moved to an apartment on the 11th floor of 155 Riverside Drive, near West 88th Street, Manhattan, an area known for luxurious mansions and townhouses.[7] Their art collection included works by Pablo Picasso and Édouard Vuillard, and at least three original paintings by Vincent van Gogh.[10] Robert had a younger brother, Frank, who also became a physicist.[11]

Oppenheimer was initially educated at Alcuin Preparatory School; in 1911, he entered the Ethical Culture Society School.[12] This had been founded by Felix Adler to promote a form of ethical training based on the Ethical Culture movement, whose motto was "Deed before Creed". His father had been a member of the Society for many years, serving on its board of trustees from 1907 to 1915.[13] Oppenheimer was a versatile scholar, interested in English and French literature, and particularly in mineralogy.[14] He completed the third and fourth grades in one year, and skipped half the eighth grade.[12] During his final year, he became interested in chemistry.[15] He entered Harvard College one year after graduation, at age 18, because he suffered an attack of colitis while prospecting in Joachimstal during a family summer vacation in Europe. To help him recover from the illness, his father enlisted the help of his English teacher Herbert Smith who took him to New Mexico, where Oppenheimer fell in love with horseback riding and the southwestern United States.[16]

Oppenheimer majored in chemistry, but Harvard required science students to also study history, literature, and philosophy or mathematics. He compensated for his late start by taking six courses each term and was admitted to the undergraduate honor society Phi Beta Kappa. In his first year, he was admitted to graduate standing in physics on the basis of independent study, which meant he was not required to take the basic classes and could enroll instead in advanced ones. He was attracted to experimental physics by a course on thermodynamics that was taught by Percy Bridgman. He graduated summa cum laude in three years.[17]

Heike Kamerlingh Onnes' Laboratory in Leiden, Netherlands, 1926. Oppenheimer is in the middle row, second from the left.

In 1924, Oppenheimer was informed that he had been accepted into Christ's College, Cambridge. He wrote to Ernest Rutherford requesting permission to work at the Cavendish Laboratory. Bridgman provided Oppenheimer with a recommendation, which conceded that Oppenheimer's clumsiness in the laboratory made it apparent his forte was not experimental but rather theoretical physics. Rutherford was unimpressed, but Oppenheimer went to Cambridge in the hope of landing another offer.[18] He was ultimately accepted by J. J. Thomson on condition that he complete a basic laboratory course.[19] He developed an antagonistic relationship with his tutor, Patrick Blackett, who was only a few years his senior. While on vacation, as recalled by his friend Francis Fergusson, Oppenheimer once confessed that he had left an apple doused with noxious chemicals on Blackett's desk. While Fergusson's account is the only detailed version of this event, Oppenheimer's parents were alerted by the university authorities who considered placing him on probation, a fate prevented by his parents successfully lobbying the authorities.[20]

Oppenheimer was a tall, thin chain smoker,[21] who often neglected to eat during periods of intense thought and concentration. Many of his friends described him as having self-destructive tendencies. A disturbing event occurred when he took a vacation from his studies in Cambridge to meet up with Fergusson in Paris. Fergusson noticed that Oppenheimer was not well. To help distract him from his depression, Fergusson told Oppenheimer that he (Fergusson) was to marry his girlfriend Frances Keeley. Oppenheimer did not take the news well. He jumped on Fergusson and tried to strangle him. Although Fergusson easily fended off the attack, the episode convinced him of Oppenheimer's deep psychological troubles. Throughout his life, Oppenheimer was plagued by periods of depression,[22][23] and he once told his brother, "I need physics more than friends".[24]

In 1926, Oppenheimer left Cambridge for the University of Göttingen to study under Max Born. Göttingen was one of the world's leading centers for theoretical physics. Oppenheimer made friends who went on to great success, including Werner Heisenberg, Pascual Jordan, Wolfgang Pauli, Paul Dirac, Enrico Fermi and Edward Teller. He was known for being too enthusiastic in discussion, sometimes to the point of taking over seminar sessions.[25] This irritated some of Born's other students so much that Maria Goeppert presented Born with a petition signed by herself and others threatening a boycott of the class unless he made Oppenheimer quiet down. Born left it out on his desk where Oppenheimer could read it, and it was effective without a word being said.[26]

He obtained his Doctor of Philosophy degree in March 1927 at age 23, supervised by Born.[27] After the oral exam, James Franck, the professor administering, reportedly said, "I'm glad that's over. He was on the point of questioning me."[4] Oppenheimer published more than a dozen papers at Göttingen, including many important contributions to the new field of quantum mechanics. He and Born published a famous paper on the Born–Oppenheimer approximation, which separates nuclear motion from electronic motion in the mathematical treatment of molecules, allowing nuclear motion to be neglected to simplify calculations. It remains his most cited work.[28]

Oppenheimer was awarded a United States National Research Council fellowship to the California Institute of Technology (Caltech) in September 1927. Bridgman also wanted him at Harvard, so a compromise was reached whereby he split his fellowship for the 1927–28 academic year between Harvard in 1927 and Caltech in 1928.[29] At Caltech he struck up a close friendship with Linus Pauling, and they planned to mount a joint attack on the nature of the chemical bond, a field in which Pauling was a pioneer, with Oppenheimer supplying the mathematics and Pauling interpreting the results. Both the collaboration and their friendship ended when Pauling began to suspect Oppenheimer of becoming too close to his wife, Ava Helen Pauling. Once, when Pauling was at work, Oppenheimer had arrived at their home and invited Ava Helen to join him on a tryst in Mexico. Though she refused and reported the incident to her husband,[30] the invitation, and her apparent nonchalance about it, disquieted Pauling and he ended his relationship with Oppenheimer. Oppenheimer later invited him to become head of the Chemistry Division of the Manhattan Project, but Pauling refused, saying he was a pacifist.[31]

In the autumn of 1928, Oppenheimer visited Paul Ehrenfest's institute at the University of Leiden, the Netherlands, where he impressed by giving lectures in Dutch, despite having little experience with the language. There he was given the nickname of Opje,[32] later anglicized by his students as "Oppie".[33] From Leiden he continued on to the Swiss Federal Institute of Technology (ETH) in Zurich to work with Wolfgang Pauli on quantum mechanics and the continuous spectrum. Oppenheimer respected and liked Pauli and may have emulated his personal style as well as his critical approach to problems.[34]

The University of California, Berkeley, where Oppenheimer taught from 1929 to 1943

On returning to the United States, Oppenheimer accepted an associate professorship from the University of California, Berkeley, where Raymond T. Birge wanted him so badly that he expressed a willingness to share him with Caltech.[31]

Before he began his Berkeley professorship, Oppenheimer was diagnosed with a mild case of tuberculosis and spent some weeks with his brother Frank at a New Mexico ranch, which he leased and eventually purchased. When he heard the ranch was available for lease, he exclaimed, "Hot dog!", and later called it Perro Caliente, literally "hot dog" in Spanish.[35] Later he used to say that "physics and desert country" were his "two great loves".[36] He recovered from tuberculosis and returned to Berkeley, where he prospered as an advisor and collaborator to a generation of physicists who admired him for his intellectual virtuosity and broad interests. His students and colleagues saw him as mesmerizing: hypnotic in private interaction, but often frigid in more public settings. His associates fell into two camps: one that saw him as an aloof and impressive genius and aesthete, the other that saw him as a pretentious and insecure poseur.[37] His students almost always fell into the former category, adopting his walk, speech, and other mannerisms, and even his inclination for reading entire texts in their original languages.[38] Hans Bethe said of him:

Probably the most important ingredient he brought to his teaching was his exquisite taste. He always knew what were the important problems, as shown by his choice of subjects. He truly lived with those problems, struggling for a solution, and he communicated his concern to the group. In its heyday, there were about eight or ten graduate students in his group and about six Post-doctoral Fellows. He met this group once a day in his office, and discussed with one after another the status of the student's research problem. He was interested in everything, and in one afternoon they might discuss quantum electrodynamics, cosmic rays, electron pair production and nuclear physics.[39]

He worked closely with Nobel Prize-winning experimental physicist Ernest O. Lawrence and his cyclotron pioneers, helping them understand the data their machines were producing at the Lawrence Berkeley National Laboratory.[40] In 1936, Berkeley promoted him to full professor at a salary of $3,300 a year (equivalent to $61,000 in 2019). In return he was asked to curtail his teaching at Caltech, so a compromise was reached whereby Berkeley released him for six weeks each year, enough to teach one term at Caltech.[41]

Oppenheimer did important research in theoretical astronomy (especially as related to general relativity and nuclear theory), nuclear physics, spectroscopy, and quantum field theory, including its extension into quantum electrodynamics. The formal mathematics of relativistic quantum mechanics also attracted his attention, although he doubted its validity. His work predicted many later finds, which include the neutron, meson and neutron star.[42]

Initially, his major interest was the theory of the continuous spectrum and his first published paper, in 1926, concerned the quantum theory of molecular band spectra. He developed a method to carry out calculations of its transition probabilities. He calculated the photoelectric effect for hydrogen and X-rays, obtaining the absorption coefficient at the K-edge. His calculations accorded with observations of the X-ray absorption of the sun, but not helium. Years later it was realized that the sun was largely composed of hydrogen and that his calculations were indeed correct.[43][44]

Physicists Albert Einstein and Oppenheimer conferring circa 1950

Oppenheimer also made important contributions to the theory of cosmic ray showers and started work that eventually led to descriptions of quantum tunneling. In 1931, he co-wrote a paper on the "Relativistic Theory of the Photoelectric Effect" with his student Harvey Hall,[45] in which, based on empirical evidence, he correctly disputed Dirac's assertion that two of the energy levels of the hydrogen atom have the same energy. Subsequently, one of his doctoral students, Willis Lamb, determined that this was a consequence of what became known as the Lamb shift, for which Lamb was awarded the Nobel Prize in physics in 1955.[42]

With his first doctoral student, Melba Phillips, Oppenheimer worked on calculations of artificial radioactivity under bombardment by deuterons. When Ernest Lawrence and Edwin McMillan bombarded nuclei with deuterons they found the results agreed closely with the predictions of George Gamow, but when higher energies and heavier nuclei were involved, the results did not conform to the theory. In 1935, Oppenheimer and Phillips worked out a theory—now known as the Oppenheimer–Phillips process—to explain the results; this theory is still in use today.[46]

As early as 1930, Oppenheimer wrote a paper that essentially predicted the existence of the positron. This was after a paper by Paul Dirac proposed that electrons could have both a positive charge and negative energy. Dirac's paper introduced an equation, known as the Dirac equation, which unified quantum mechanics, special relativity and the then-new concept of electron spin, to explain the Zeeman effect.[47] Oppenheimer, drawing on the body of experimental evidence, rejected the idea that the predicted positively charged electrons were protons. He argued that they would have to have the same mass as an electron, whereas experiments showed that protons were much heavier than electrons. Two years later, Carl David Anderson discovered the positron, for which he received the 1936 Nobel Prize in Physics.[48]

In the late 1930s, Oppenheimer became interested in astrophysics, most likely through his friendship with Richard Tolman, resulting in a series of papers. In the first of these, a 1938 paper co-written with Robert Serber entitled "On the Stability of Stellar Neutron Cores",[49] Oppenheimer explored the properties of white dwarfs. This was followed by a paper co-written with one of his students, George Volkoff, "On Massive Neutron Cores",[50] in which they demonstrated that there was a limit, the so-called Tolman–Oppenheimer–Volkoff limit, to the mass of stars beyond which they would not remain stable as neutron stars and would undergo gravitational collapse. Finally, in 1939, Oppenheimer and another of his students, Hartland Snyder, produced a paper "On Continued Gravitational Attraction",[51] which predicted the existence of what are today known as black holes. After the Born–Oppenheimer approximation paper, these papers remain his most cited, and were key factors in the rejuvenation of astrophysical research in the United States in the 1950s, mainly by John A. Wheeler.[52]

Oppenheimer's papers were considered difficult to understand even by the standards of the abstract topics he was expert in. He was fond of using elegant, if extremely complex, mathematical techniques to demonstrate physical principles, though he was sometimes criticized for making mathematical mistakes, presumably out of haste. "His physics was good", said his student Snyder, "but his arithmetic awful".[42]

After World War II, Oppenheimer published only five scientific papers, one of which was in biophysics, and none after 1950. Murray Gell-Mann, a later Nobelist who, as a visiting scientist, worked with him at the Institute for Advanced Study in 1951, offered this opinion:

He didn't have Sitzfleisch, 'sitting flesh,' when you sit on a chair. As far as I know, he never wrote a long paper or did a long calculation, anything of that kind. He didn't have patience for that; his own work consisted of little aperçus, but quite brilliant ones. But he inspired other people to do things, and his influence was fantastic.[53]

Oppenheimer's diverse interests sometimes interrupted his focus on science. In 1933, he learned Sanskrit and met the Indologist Arthur W. Ryder at Berkeley. He read the Bhagavad Gita in the original Sanskrit, and later he cited it as one of the books that most shaped his philosophy of life.[54] His close confidant and colleague, Nobel Prize winner Isidor Rabi, later gave his own interpretation:

Oppenheimer was overeducated in those fields, which lie outside the scientific tradition, such as his interest in religion, in the Hindu religion in particular, which resulted in a feeling of mystery of the universe that surrounded him like a fog. He saw physics clearly, looking toward what had already been done, but at the border he tended to feel there was much more of the mysterious and novel than there actually was ... [he turned] away from the hard, crude methods of theoretical physics into a mystical realm of broad intuition.[55]

In spite of this, observers such as Nobel Prize-winning physicist Luis Alvarez have suggested that if he had lived long enough to see his predictions substantiated by experiment, Oppenheimer might have won a Nobel Prize for his work on gravitational collapse, concerning neutron stars and black holes.[56][57] In retrospect, some physicists and historians consider this to be his most important contribution, though it was not taken up by other scientists in his own lifetime.[58] The physicist and historian Abraham Pais once asked Oppenheimer what he considered to be his most important scientific contributions; Oppenheimer cited his work on electrons and positrons, not his work on gravitational contraction.[59] Oppenheimer was nominated for the Nobel Prize for physics three times, in 1946, 1951 and 1967, but never won.[60][61]

On October 9, 1941, two months before the United States entered World War II, President Franklin D. Roosevelt approved a crash program to develop an atomic bomb.[90] In May 1942, National Defense Research Committee Chairman James B. Conant, who had been one of Oppenheimer's lecturers at Harvard, invited Oppenheimer to take over work on fast neutron calculations, a task that Oppenheimer threw himself into with full vigor. He was given the title "Coordinator of Rapid Rupture", which specifically referred to the propagation of a fast neutron chain reaction in an atomic bomb. One of his first acts was to host a summer school for bomb theory at his building in Berkeley. The mix of European physicists and his own students—a group including Robert Serber, Emil Konopinski, Felix Bloch, Hans Bethe and Edward Teller—kept themselves busy by calculating what needed to be done, and in what order, to make the bomb.[91]

Presentation of the Army-Navy "E" Award at Los Alamos on October 16, 1945. Oppenheimer (left) gave his farewell speech as director on this occasion. Robert Gordon Sproul right, in suit, accepted the award on behalf of the University of California from Leslie Groves (center).[92]

In June 1942, the US Army established the Manhattan Project to handle its part in the atom bomb project and began the process of transferring responsibility from the Office of Scientific Research and Development to the military.[93] In September, Groves was appointed director of what became known as the Manhattan Project.[94] He selected Oppenheimer to head the project's secret weapons laboratory. This was a choice that surprised many because Oppenheimer had left-wing political views and no record as a leader of large projects. Groves was concerned by the fact that Oppenheimer did not have a Nobel Prize and might not have had the prestige to direct fellow scientists.[95] However, he was impressed by Oppenheimer's singular grasp of the practical aspects of designing and constructing an atomic bomb, and by the breadth of his knowledge. As a military engineer, Groves knew that this would be vital in an interdisciplinary project that would involve not just physics, but chemistry, metallurgy, ordnance and engineering. Groves also detected in Oppenheimer something that many others did not, an "overweening ambition" that Groves reckoned would supply the drive necessary to push the project to a successful conclusion. Isidor Rabi considered the appointment "a real stroke of genius on the part of General Groves, who was not generally considered to be a genius".[96]

Oppenheimer and Groves decided that for security and cohesion they needed a centralized, secret research laboratory in a remote location. Scouting for a site in late 1942, Oppenheimer was drawn to New Mexico, not far from his ranch. On November 16, 1942, Oppenheimer, Groves and others toured a prospective site. Oppenheimer feared that the high cliffs surrounding the site would make his people feel claustrophobic, while the engineers were concerned with the possibility of flooding. He then suggested and championed a site that he knew well: a flat mesa near Santa Fe, New Mexico, which was the site of a private boys' school called the Los Alamos Ranch School. The engineers were concerned about the poor access road and the water supply, but otherwise felt that it was ideal.[97] The Los Alamos Laboratory was built on the site of the school, taking over some of its buildings, while many new buildings were erected in great haste. At the laboratory, Oppenheimer assembled a group of the top physicists of the time, which he referred to as the "luminaries".[98]

Los Alamos was initially supposed to be a military laboratory, and Oppenheimer and other researchers were to be commissioned into the Army. He went so far as to order himself a lieutenant colonel's uniform and take the Army physical test, which he failed. Army doctors considered him underweight at 128 pounds (58 kg), diagnosed his chronic cough as tuberculosis and were concerned about his chronic lumbosacral joint pain.[99] The plan to commission scientists fell through when Robert Bacher and Isidor Rabi balked at the idea. Conant, Groves, and Oppenheimer devised a compromise whereby the laboratory was operated by the University of California under contract to the War Department.[100] It soon turned out that Oppenheimer had hugely underestimated the magnitude of the project; Los Alamos grew from a few hundred people in 1943 to over 6,000 in 1945.[99]

Oppenheimer at first had difficulty with the organizational division of large groups, but rapidly learned the art of large-scale administration after he took up permanent residence on the mesa. He was noted for his mastery of all scientific aspects of the project and for his efforts to control the inevitable cultural conflicts between scientists and the military. He was an iconic figure to his fellow scientists, as much a symbol of what they were working toward as a scientific director. Victor Weisskopf put it thus:

Oppenheimer directed these studies, theoretical and experimental, in the real sense of the words. Here his uncanny speed in grasping the main points of any subject was a decisive factor; he could acquaint himself with the essential details of every part of the work. He did not direct from the head office. He was intellectually and physically present at each decisive step. He was present in the laboratory or in the seminar rooms, when a new effect was measured, when a new idea was conceived. It was not that he contributed so many ideas or suggestions; he did so sometimes, but his main influence came from something else. It was his continuous and intense presence, which produced a sense of direct participation in all of us; it created that unique atmosphere of enthusiasm and challenge that pervaded the place throughout its time.[101]

A group of physicists at the 1946 Los Alamos colloquium on the Super. In the front row are Norris Bradbury, John Manley, Enrico Fermi and J.M.B. Kellogg. Behind Manley is Oppenheimer (wearing jacket and tie), and to his left is Richard Feynman. The army colonel on the far left is Oliver Haywood. In the third row between Haywood and Oppenheimer is Edward Teller.

In 1943 development efforts were directed to a plutonium gun-type fission weapon called "Thin Man". Initial research on the properties of plutonium was done using cyclotron-generated plutonium-239, which was extremely pure but could only be created in tiny amounts. When Los Alamos received the first sample of plutonium from the X-10 Graphite Reactor in April 1944 a problem was discovered: reactor-bred plutonium had a higher concentration of plutonium-240, making it unsuitable for use in a gun-type weapon.[102] In July 1944, Oppenheimer abandoned the gun design in favor of an implosion-type weapon. Using chemical explosive lenses, a sub-critical sphere of fissile material could be squeezed into a smaller and denser form. The metal needed to travel only very short distances, so the critical mass would be assembled in much less time.[103] In August 1944 Oppenheimer implemented a sweeping reorganization of the Los Alamos laboratory to focus on implosion.[104] He concentrated the development efforts on the gun-type device, a simpler design that only had to work with uranium-235, in a single group, and this device became Little Boy in February 1945.[105] After a mammoth research effort, the more complex design of the implosion device, known as the "Christy gadget" after Robert Christy, another student of Oppenheimer's,[106] was finalized in a meeting in Oppenheimer's office on February 28, 1945.[107]

In May 1945 an Interim Committee was created to advise and report on wartime and postwar policies regarding the use of nuclear energy. The Interim Committee in turn established a scientific panel consisting of Arthur Compton, Fermi, Lawrence and Oppenheimer to advise it on scientific issues. In its presentation to the Interim Committee the scientific panel offered its opinion not just on the likely physical effects of an atomic bomb, but on its likely military and political impact.[108] This included opinions on such sensitive issues as whether or not the Soviet Union should be advised of the weapon in advance of its use against Japan.[109]

The Trinity test of the Manhattan Project was the first detonation of a nuclear device.[110]

The joint work of the scientists at Los Alamos resulted in the world's first nuclear explosion, near Alamogordo, New Mexico on July 16, 1945. Oppenheimer had given the site the codename "Trinity" in mid-1944 and said later that it was from one of John Donne's Holy Sonnets. According to the historian Gregg Herken, this naming could have been an allusion to Jean Tatlock, who had committed suicide a few months previously and had in the 1930s introduced Oppenheimer to Donne's work.[111] Oppenheimer later recalled that, while witnessing the explosion, he thought of a verse from the Bhagavad Gita (XI,12): divi sūrya-sahasrasya bhaved yugapad utthitā yadi bhāḥ sadṛṥī sā syād bhāsas tasya mahāḥmanaḥ [112]

If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one ...[5][113]

Years later he would explain that another verse had also entered his head at that time: namely, the famous verse: "kālo'smi lokakṣayakṛtpravṛddho lokānsamāhartumiha pravṛttaḥ" (XI,32),[114] which he translated as "I am become Death, the destroyer of worlds."[note 2]

In 1965, he was persuaded to quote again for a television broadcast:

We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another.[3]

Brigadier General Thomas Farrell, who was present in the control bunker at the site with Oppenheimer, summarized his reaction as follows:

Dr. Oppenheimer, on whom had rested a very heavy burden, grew tenser as the last seconds ticked off. He scarcely breathed. He held on to a post to steady himself. For the last few seconds, he stared directly ahead and then when the announcer shouted "Now!" and there came this tremendous burst of light followed shortly thereafter by the deep growling roar of the explosion, his face relaxed into an expression of tremendous relief.[115]

Physicist Isidor Rabi noticed Oppenheimer's disconcerting triumphalism: "I'll never forget his walk; I'll never forget the way he stepped out of the car ... his walk was like High Noon ... this kind of strut. He had done it."[116] At an assembly at Los Alamos on August 6 (the evening of the atomic bombing of Hiroshima), Oppenheimer took to the stage and clasped his hands together "like a prize-winning boxer" while the crowd cheered. He noted his regret the weapon had not been available in time to use against Nazi Germany.[117] However, he and many of the project staff were very upset about the bombing of Nagasaki, as they did not feel the second bomb was necessary from a military point of view.[118] He traveled to Washington on August 17 to hand-deliver a letter to Secretary of War Henry L. Stimson expressing his revulsion and his wish to see nuclear weapons banned.[119] In October 1945 Oppenheimer was granted an interview with President Harry S. Truman. The meeting, however, went badly, after Oppenheimer remarked he felt he had "blood on my hands". The remark infuriated Truman and put an end to the meeting. Truman later told his Undersecretary of State Dean Acheson "I don't want to see that son-of-a-bitch in this office ever again."[120]

For his services as director of Los Alamos, Oppenheimer was awarded the Medal for Merit from President Harry S Truman in 1946.[121]

In November 1945, Oppenheimer left Los Alamos to return to Caltech,[126] but he soon found that his heart was no longer in teaching.[127] In 1947, he accepted an offer from Lewis Strauss to take up the directorship of the Institute for Advanced Study in Princeton, New Jersey. This meant moving back east and leaving Ruth Tolman, the wife of his friend Richard Tolman, with whom he had begun an affair after leaving Los Alamos.[128] The job came with a salary of $20,000 per annum, plus rent-free accommodation in the director's house, a 17th-century manor with a cook and groundskeeper, surrounded by 265 acres (107 ha) of woodlands.[129] He collected European furniture, and French post-impressionist and Fauvist artworks. His art collection included works by Cézanne, Derain, Despiau, de Vlaminck, Picasso, Rembrandt, Renoir, Van Gogh and Vuillard.[130]

Institute for Advanced Study in Princeton, New Jersey

Oppenheimer brought together intellectuals at the height of their powers and from a variety of disciplines to answer the most pertinent questions of the age. He directed and encouraged the research of many well-known scientists, including Freeman Dyson, and the duo of Chen Ning Yang and Tsung-Dao Lee, who won a Nobel Prize for their discovery of parity non-conservation. He also instituted temporary memberships for scholars from the humanities, such as T. S. Eliot and George F. Kennan. Some of these activities were resented by a few members of the mathematics faculty, who wanted the institute to stay a bastion of pure scientific research. Abraham Pais said that Oppenheimer himself thought that one of his failures at the institute was being unable to bring together scholars from the natural sciences and the humanities.[131]

During a series of conferences in New York from 1947 through 1949, physicists switched back from war work to theoretical issues. Under Oppenheimer's direction, physicists tackled the greatest outstanding problem of the pre-war years: infinite, divergent, and non-sensical expressions in the quantum electrodynamics of elementary particles. Julian Schwinger, Richard Feynman and Shin'ichiro Tomonaga tackled the problem of regularization, and developed techniques which became known as renormalization. Freeman Dyson was able to prove that their procedures gave similar results. The problem of meson absorption and Hideki Yukawa's theory of mesons as the carrier particles of the strong nuclear force were also tackled. Probing questions from Oppenheimer prompted Robert Marshak's innovative two-meson hypothesis: that there were actually two types of mesons, pions and muons. This led to Cecil Frank Powell's breakthrough and subsequent Nobel Prize for the discovery of the pion.[132][note 3]

As a member of the Board of Consultants to a committee appointed by Truman, Oppenheimer strongly influenced the Acheson–Lilienthal Report. In this report, the committee advocated creation of an international Atomic Development Authority, which would own all fissionable material and the means of its production, such as mines and laboratories, and atomic power plants where it could be used for peaceful energy production. Bernard Baruch was appointed to translate this report into a proposal to the United Nations, resulting in the Baruch Plan of 1946. The Baruch Plan introduced many additional provisions regarding enforcement, in particular requiring inspection of the Soviet Union's uranium resources. The Baruch Plan was seen as an attempt to maintain the United States' nuclear monopoly and was rejected by the Soviets. With this, it became clear to Oppenheimer that an arms race was unavoidable, due to the mutual suspicion of the United States and the Soviet Union,[134] which even Oppenheimer was starting to distrust.[135]

Oppenheimer in 1946 with his trademark cigarette

After the Atomic Energy Commission (AEC) came into being in 1947 as a civilian agency in control of nuclear research and weapons issues, Oppenheimer was appointed as the Chairman of its General Advisory Committee (GAC). From this position he advised on a number of nuclear-related issues, including project funding, laboratory construction and even international policy—though the GAC's advice was not always heeded.[136] As Chairman of the GAC, Oppenheimer lobbied vigorously for international arms control and funding for basic science, and attempted to influence policy away from a heated arms race.[137]

The first atomic bomb test by the Soviet Union in August 1949 came earlier than expected by Americans, and over the next several months there was an intense debate within the U.S. government, military, and scientific communities regarding whether to proceed with development of the far more powerful, nuclear fusion-based hydrogen bomb, then known as "the Super".[138] Oppenheimer had been aware of the possibility of a thermonuclear weapon since the days of the Manhattan Project, and had allocated a limited amount of theoretical research work toward the possibility at the time but nothing more than that given the pressing need to develop a fission weapon.[139] Immediately following the end of the war, Oppenheimer argued against continuing work on the Super at that time, due both to lack of need and to the enormous human casualties that would result from its use.[140][141]

Now in October 1949, Oppenheimer and the GAC recommended against development of the Super.[142] He and the other GAC members were motivated partly by ethical concerns, feeling that such a weapon could only be strategically used, resulting in millions of deaths: "Its use therefore carries much further than the atomic bomb itself the policy of exterminating civilian populations."[143] They also had practical qualms, as there was no workable design for a hydrogen bomb at the time.[144] Regarding the possibility of the Soviet Union developing a thermonuclear weapon, the GAC felt that the United States could have an adequate stockpile of atomic weapons to retaliate against any thermonuclear attack.[145] In that connection, Oppenheimer and the others were concerned about the opportunity costs that would be incurred if nuclear reactors were diverted from materials needed for atom bomb production, to the materials such as tritium needed for a thermonuclear weapon.[146][147]

A majority of the AEC subsequently endorsed the GAC recommendation – and Oppenheimer thought that the fight against the Super would triumph – but proponents of the weapon lobbied the White House vigorously.[148] On January 31, 1950, President Truman, who was always predisposed to proceed with development of the weapon anyway, made the formal decision to do so.[149] Oppenheimer and other GAC opponents of the project, especially James Conant, felt disheartened and considered resigning from the committee.[150] They stayed on, though their views on the hydrogen bomb were well known.[151]

In 1951, Edward Teller and mathematician Stanislaw Ulam developed what became known as the Teller-Ulam design for a hydrogen bomb.[152] This new design seemed technically feasible and Oppenheimer officially acceded to the weapon's development,[153] while still looking for ways in which its testing or deployment or use could be questioned.[154] As he later recalled:

The program we had in 1949 was a tortured thing that you could well argue did not make a great deal of technical sense. It was therefore possible to argue also that you did not want it even if you could have it. The program in 1951 was technically so sweet that you could not argue about that. The issues became purely the military, the political and the humane problem of what you were going to do about it once you had it.[155]

Oppenheimer, along with Conant and Lee DuBridge, another member who had opposed the H-bomb decision, left the GAC when their terms expired in August 1952.[156] President Truman had declined to reappoint them, as the president wanted new voices on the committee who were more in support of H-bomb development.[157] In addition, various opponents of Oppenheimer had communicated to Truman their desire that Oppenheimer leave the committee.[158]

Oppenheimer played a role on a number of government panels and study projects during the late 1940s and early 1950s, some of which found him in the middle of controversies and power struggles.[159]

In 1948 Oppenheimer chaired the Department of Defense's Long-Range Objectives Panel, which looked at the military utility of nuclear weapons including how they might be delivered.[160] After a year's worth of study, in spring 1952 Oppenheimer wrote the draft report of Project GABRIEL, which examined the dangers of nuclear fallout.[161] Oppenheimer was also a member of the Science Advisory Committee of the Office of Defense Mobilization.[162]

Oppenheimer participated in Project Charles during 1951, which examined the possibility of creating an effective air defense of the United States against atomic attack, and in the follow-on Project East River in 1952, which, with Oppenheimer's input, recommended building a warning system that would provide one-hour notice to atomic attacks against American cities.[161] Those two projects led to Project Lincoln in 1952, a large effort where Oppenheimer was one of the senior scientists.[161] Undertaken at the MIT Lincoln Laboratory, which had recently been founded to study issues of air defense, this in turn led to the Lincoln Summer Study Group, where Oppenheimer became a key figure.[163] Oppenheimer's and other scientists' urging that resources be allocated to air defense in preference to large retaliatory strike capabilities brought an immediate response of objection from the United States Air Force (USAF),[164] and a debate ensued about whether Oppenheimer and allied scientists, or the Air Force, was embracing an inflexible "Maginot Line" philosophy.[165] In any case, the Summer Study Group's work eventually led to the building of the Distant Early Warning Line.[166]

Edward Teller, who had been so uninterested in work on the atomic bomb at Los Alamos during the war that Oppenheimer had given him time instead to work on his own project of the hydrogen bomb,[167] had eventually left Los Alamos in 1951 to help found, in 1952, a second laboratory at what would become the Lawrence Livermore National Laboratory.[168] Oppenheimer had defended the history of work done at Los Alamos and had opposed creation of the second laboratory.[169]

Project Vista looked at improving U.S. tactical warfare capabilities.[161] Oppenheimer was a late addition to the project in 1951, but wrote a key chapter of the report that challenged the doctrine of strategic bombardment and advocated for smaller tactical nuclear weapons which would be more useful in a limited theater conflict against enemy forces.[170] Strategic thermonuclear weapons delivered by long-range jet bombers would necessarily be under control of the U.S. Air Force, whereas the Vista conclusions recommended an increased role for the U.S. Army and U.S. Navy as well.[171] The Air Force reaction to this was immediately hostile,[172] and they succeeded in getting the Vista report suppressed.[173]

During 1952 Oppenheimer chaired the five-member State Department Panel of Consultants on Disarmament,[174] which first urged that the United States postpone its planned first test of the hydrogen bomb and seek a thermonuclear test ban with the Soviet Union, on the grounds that avoiding a test might forestall development of a catastrophic new weapon and open the way for new arms agreements between the two nations.[175] The panel lacked political allies in Washington, however, and the Ivy Mike shot went ahead as scheduled.[174] The panel then issued a final report in January 1953, which, influenced by many of Oppenheimer's deeply felt beliefs, presented a pessimistic vision of the future in which neither the United States nor the Soviet Union could establish an effective nuclear superiority but both sides could effect terrible damage on the other.[176] One of the panel's recommendations, which Oppenheimer felt was especially important,[177] was that the U.S. government practice less secrecy and more openness towards the American people about the realities of the nuclear balance and the dangers of nuclear warfare.[176] This notion found a receptive audience in the new Eisenhower administration and led to creation of Operation Candor.[178] Oppenheimer subsequently presented his view on the lack of utility of ever-larger nuclear arsenals to the American public with an article in Foreign Affairs in June 1953,[179] and it received attention in major American newspapers.[180]

Thus by 1953, Oppenheimer had reached another peak of influence, being involved in multiple different government posts and projects and having access to crucial strategic plans and force levels.[181] But at the same time Oppenheimer had become the enemy of the proponents of strategic bombardment, who viewed the physicist's opposition to the H-bomb, followed by these accumulated positions and stances, with a combination of bitterness and distrust.[182] This view was paired with their fear that Oppenheimer's fame and powers of persuasion had made him dangerously influential within government, military, and scientific circles.[183]

The FBI under J. Edgar Hoover had been following Oppenheimer since before the war, when he showed Communist sympathies as a professor at Berkeley and had been close to members of the Communist Party, including his wife and brother. He had been under close surveillance since the early 1940s, his home and office bugged, his phone tapped and his mail opened.[184] The FBI furnished Oppenheimer's political enemies with incriminating evidence about his Communist ties. These enemies included Strauss, an AEC commissioner who had long harbored resentment against Oppenheimer both for his activity in opposing the hydrogen bomb and for his humiliation of Strauss before Congress some years earlier; regarding Strauss's opposition to the export of radioactive isotopes to other nations, Oppenheimer had memorably categorized these as "less important than electronic devices but more important than, let us say, vitamins".[185]

President Dwight D. Eisenhower receives a report from Lewis L. Strauss, Chairman of the Atomic Energy Commission, on the Operation Castle hydrogen bomb tests in the Pacific, March 30, 1954. Strauss pressed for Oppenheimer's security clearance to be revoked.

On June 7, 1949, Oppenheimer testified before the House Un-American Activities Committee, where he admitted that he had associations with the Communist Party in the 1930s.[186] He testified that some of his students, including David Bohm, Giovanni Rossi Lomanitz, Philip Morrison, Bernard Peters and Joseph Weinberg, had been Communists at the time they had worked with him at Berkeley. Frank Oppenheimer and his wife Jackie testified before the HUAC and admitted that they had been members of the Communist Party. Frank was subsequently fired from his University of Minnesota position. Unable to find work in physics for many years, he became instead a cattle rancher in Colorado. He later taught high school physics and was the founder of the San Francisco Exploratorium.[76][187]

The triggering event for the security hearing happened on November 7, 1953,[188] when William Liscum Borden, who until earlier in the year had been the executive director of the United States Congress Joint Committee on Atomic Energy, sent a letter to Hoover which said that "more probably than not J. Robert Oppenheimer is an agent of the Soviet Union."[189] Eisenhower never exactly believed the allegations within the letter, but felt compelled to move forward with an investigation,[190] and on December 3 he ordered that a "blank wall" be placed between Oppenheimer and any government or military secrets.[191] On December 21, 1953, Strauss told Oppenheimer that his security clearance had been suspended, pending resolution of a series of charges outlined in a letter, and discussed his resigning by way of requesting termination of his consulting contract with the AEC.[192] Oppenheimer chose not to resign and requested a hearing instead.[193] The charges were outlined in a letter from Kenneth D. Nichols, General Manager of the AEC.[194][195] The hearing that followed in April–May 1954, which was held in secret, focused on Oppenheimer's past Communist ties and his association during the Manhattan Project with suspected disloyal or Communist scientists.[196] It then continued with an examination of Oppenheimer's opposition to the H-bomb and stances in subsequent projects and study groups.[197] A transcript of the hearings was published in June 1954,[198] with some redactions. The US Department of Energy made public the full text of the transcript in October 2014.[199][200]

Oppenheimer's former colleague, physicist Edward Teller, testified on behalf of the government at Oppenheimer's security hearing in 1954.[201]

One of the key elements in this hearing was Oppenheimer's earliest testimony about George Eltenton's approach to various Los Alamos scientists, a story that Oppenheimer confessed he had fabricated to protect his friend Haakon Chevalier. Unknown to Oppenheimer, both versions were recorded during his interrogations of a decade before. He was surprised on the witness stand with transcripts of these, which he had not been given a chance to review. In fact, Oppenheimer had never told Chevalier that he had finally named him, and the testimony had cost Chevalier his job. Both Chevalier and Eltenton confirmed mentioning that they had a way to get information to the Soviets, Eltenton admitting he said this to Chevalier and Chevalier admitting he mentioned it to Oppenheimer, but both put the matter in terms of gossip and denied any thought or suggestion of treason or thoughts of espionage, either in planning or in deed. Neither was ever convicted of any crime.[202]

Teller testified that he considered Oppenheimer loyal, but that:

In a great number of cases, I have seen Dr. Oppenheimer act—I understand that Dr. Oppenheimer acted—in a way which was for me was exceedingly hard to understand. I thoroughly disagreed with him in numerous issues and his actions frankly appeared to me confused and complicated. To this extent I feel that I would like to see the vital interests of this country in hands which I understand better, and therefore trust more. In this very limited sense I would like to express a feeling that I would feel personally more secure if public matters would rest in other hands.[203]

This led to outrage by the scientific community and Teller's virtual expulsion from academic science.[204] Ernest Lawrence refused to testify on the grounds that he was suffering from an attack of ulcerative colitis, but an interview transcript in which he condemned Oppenheimer was presented as evidence in his absence.[205] Groves, threatened by the FBI as having been potentially part of a coverup about the Chevalier contact in 1943, likewise testified against Oppenheimer.[206] Many top scientists, as well as government and military figures, testified on Oppenheimer's behalf. Inconsistencies in his testimony and his erratic behavior on the stand, at one point saying he had given a "cock and bull story" and that this was because he "was an idiot", convinced some that he was unstable, unreliable and a possible security risk. Oppenheimer's clearance was revoked one day before it was due to lapse anyway.[207] Isidor Rabi's comment was that Oppenheimer was merely a government consultant at the time anyway and that if the government "didn't want to consult the guy, then don't consult him".[208]

During his hearing, Oppenheimer testified willingly on the left-wing behavior of many of his scientific colleagues. Had Oppenheimer's clearance not been stripped then he might have been remembered as someone who had "named names" to save his own reputation.[209] As it happened, Oppenheimer was seen by most of the scientific community as a martyr to McCarthyism, an eclectic liberal who was unjustly attacked by warmongering enemies, symbolic of the shift of scientific creativity from academia into the military.[210] Wernher von Braun summed up his opinion about the matter with a quip to a Congressional committee: "In England, Oppenheimer would have been knighted."[211]

In a seminar at the Woodrow Wilson Institute on May 20, 2009, based on an extensive analysis of the Vassiliev notebooks taken from the KGB archives, John Earl Haynes, Harvey Klehr and Alexander Vassiliev confirmed that Oppenheimer never was involved in espionage for the Soviet Union. Soviet intelligence tried repeatedly to recruit him, but was never successful; Oppenheimer did not betray the United States. In addition, he had several persons removed from the Manhattan Project who had sympathies to the Soviet Union.[212] Haynes, Klehr and Vassiliev also state Oppenheimer "was, in fact, a concealed member of the CPUSA in the late 1930s".[213] According to biographer Ray Monk: "He was, in a very practical and real sense, a supporter of the Communist Party. Moreover, in terms of the time, effort and money spent on Party activities, he was a very committed supporter".[214]