Richard Feynman

Richard Phillips Feynman (; May 11, 1918 – February 15, 1988) was an American theoretical physicist. He shared the 1965 Nobel Prize in Physics with Julian Schwinger and Shin'ichirō Tomonaga "for their fundamental work in quantum electrodynamics (QED), with deep-ploughing consequences for the physics of elementary particles".

He is also known for his work in the path integral formulation of quantum mechanics, the theory of the physics of the superfluidity of supercooled liquid helium, and the parton model. Feynman developed a pictorial representation scheme for the mathematical expressions describing the behavior of subatomic particles, which later became known as Feynman diagrams and remains widely used.

He assisted in the development of the atomic bomb during World War II and became known to the wider public in the 1980s as a member of the Rogers Commission, the panel that investigated the Space Shuttle Challenger disaster. Along with his work in theoretical physics, Feynman has been credited with having pioneered the field of quantum computing and introducing the concept of nanotechnology. He held the Richard C. Tolman professorship in theoretical physics at the California Institute of Technology. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World, he was ranked the seventh-greatest physicist of all time.

Feynman was a keen physics popularizer through books and lectures, including a talk on top-down nanotechnology, "There's Plenty of Room at the Bottom" (1959) and his undergraduate lectures, The Feynman Lectures on Physics (1961–1964). He delivered lectures for lay audiences, recorded in The Character of Physical Law (1965) and QED: The Strange Theory of Light and Matter (1985). Feynman also became known through Ralph Leighton's collections of his anecdotes, Surely You're Joking, Mr. Feynman! (1985) and What Do You Care What Other People Think? (1988). Leighton covered his dream of travelling to Tannu Tuva in Tuva or Bust!. He has been the subject of several biographies, starting with Genius: The Life and Science of Richard Feynman by James Gleick.

Early life

Feynman was born on May 11, 1918, in Queens, New York City, to Lucille (), a homemaker, and Melville Arthur Feynman, a sales manager for uniforms. Feynman's father was born into a Jewish family in Minsk, Russian Empire, and immigrated with his parents to the United States at the age of five. Feynman's mother was born in the United States into a Jewish family. Lucille's father had emigrated from Poland, and her mother also came from a family of Polish immigrants. She trained as a primary school teacher but married Melville in 1917, before taking up a profession. Though their mother thought women lacked the capacity to understand such things, Richard encouraged Joan's interest in astronomy, taking her to see the aurora borealis in Far Rockaway. As an astrophysicist, Joan would help to explain what caused the northern lights. However, by his youth, Feynman described himself as an "avowed atheist". Many years later, in a letter to Tina Levitan, declining a request for information for her book on Jewish Nobel Prize winners, he stated, "To select, for approbation the peculiar elements that come from some supposedly Jewish heredity is to open the door to all kinds of nonsense on racial theory", adding, "at thirteen I was not only converted to other religious views, but I also stopped believing that the Jewish people are in any way 'the chosen people'".

Later in life, during a visit to the Jewish Theological Seminary, Feynman encountered the Talmud for the first time. He saw that it contained the original text in a little square on each page, and surrounding it were commentaries written over time by different people. In this way, the Talmud had evolved, and everything that was discussed was carefully recorded. Despite being impressed, Feynman was disappointed with the lack of interest in nature and the outside world expressed by the rabbis, who cared about only those questions which arise from the Talmud.

Education

Feynman attended Far Rockaway High School, which was also attended by fellow Nobel laureates Burton Richter and Baruch Samuel Blumberg. Upon starting high school, Feynman was quickly promoted to a higher math class. An IQ test administered in high school estimated his IQ at 125—high but "merely respectable", according to biographer James Gleick. His sister Joan, who scored one point higher, later jokingly claimed to an interviewer that she was smarter. Years later he declined to join Mensa International, saying that his IQ was too low.

When Feynman was 15, he taught himself trigonometry, advanced algebra, infinite series, analytic geometry, and both differential and integral calculus. Before entering college, he was experimenting with mathematical topics such as the half-derivative using his own notation. He created special symbols for logarithm, sine, cosine and tangent functions so they did not look like three variables multiplied together, and for the derivative, to remove the temptation of canceling out the <math>d</math>s in <math>d/dx</math>. A member of the Arista Honor Society, in his last year in high school he won the New York University Math Championship. His habit of direct characterization sometimes rattled more conventional thinkers; for example, one of his questions, when learning feline anatomy, was "Do you have a map of the cat?" (referring to an anatomical chart).

Feynman applied to Columbia University but was not accepted because of its quota for the number of Jews admitted. As an undergraduate, he published two papers in the Physical Review. One of these, which was co-written with Manuel Vallarta, was titled "The Scattering of Cosmic Rays by the Stars of a Galaxy".

The other was his senior thesis, on "Forces in Molecules", based on a topic assigned by John C. Slater, who was sufficiently impressed by the paper to have it published. Its main result is known as the Hellmann–Feynman theorem.

thumb|right|upright=0.5|MIT yearbook portrait (1939)

In 1939, Feynman received a bachelor's degree and was named a Putnam Fellow. He attained a perfect score on the graduate school entrance exams to Princeton University in physics—an unprecedented feat—and an outstanding score in mathematics, but did poorly on the history and English portions. The head of the physics department there, Henry D. Smyth, had another concern, writing to Philip M. Morse to ask: "Is Feynman Jewish? We have no definite rule against Jews but have to keep their proportion in our department reasonably small because of the difficulty of placing them." Morse conceded that Feynman was indeed Jewish, but reassured Smyth that Feynman's "physiognomy and manner, however, show no trace of this characteristic".

Attendees at Feynman's first seminar, which was on the classical version of the Wheeler–Feynman absorber theory, included Albert Einstein, Wolfgang Pauli, and John von Neumann. Pauli made the prescient comment that the theory would be extremely difficult to quantize, and Einstein said that one might try to apply this method to gravity in general relativity, which Sir Fred Hoyle and Jayant Narlikar did much later as the Hoyle–Narlikar theory of gravity. Feynman received a PhD from Princeton in 1942; his thesis advisor was John Archibald Wheeler. In his doctoral thesis titled "The Principle of Least Action in Quantum Mechanics", Feynman applied the principle of stationary action to problems of quantum mechanics, inspired by a desire to quantize the Wheeler–Feynman absorber theory of electrodynamics, and laid the groundwork for the path integral formulation and Feynman diagrams. A key insight was that positrons behaved like electrons moving backwards in time. James Gleick wrote:

One of the conditions of Feynman's scholarship to Princeton was that he could not be married; nevertheless, he continued to see his high school sweetheart, Arline Greenbaum, and was determined to marry her once he had been awarded his PhD despite the knowledge that she was seriously ill with tuberculosis. This was an incurable disease at the time, and she was not expected to live more than two years. On June 29, 1942, they took the ferry to Staten Island, where they were married in the city office. The ceremony was attended by neither family nor friends and was witnessed by a pair of strangers. Feynman could kiss Arline only on the cheek. After the ceremony he took her to Deborah Hospital, where he visited her on weekends.

Manhattan Project

thumb|upright|alt=Feynman smiling|Feynman's Los Alamos ID badge

In 1941, with World War II occurring in Europe but the United States not yet at war, Feynman spent the summer working on ballistics problems at the Frankford Arsenal in Pennsylvania. After the attack on Pearl Harbor brought the United States into the war, Feynman was recruited by Robert R. Wilson, who was working on means to produce enriched uranium for use in an atomic bomb, as part of what would become the Manhattan Project. At the time, Feynman had not earned a graduate degree. Wilson's team at Princeton was working on a device called an isotron, intended to electromagnetically separate uranium-235 from uranium-238. This was done in a quite different manner from that used by the calutron that was under development by a team under Wilson's former mentor, Ernest O. Lawrence, at the Radiation Laboratory of the University of California. On paper, the isotron was many times more efficient than the calutron, but Feynman and Paul Olum struggled to determine whether it was practical. Ultimately, on Lawrence's recommendation, the isotron project was abandoned.

At this juncture, in early 1943, Robert Oppenheimer was establishing the Los Alamos Laboratory, a secret laboratory on a mesa in New Mexico where atomic bombs would be designed and built. An offer was made to the Princeton team to be redeployed there. "Like a bunch of professional soldiers," Wilson later recalled, "we signed up, en masse, to go to Los Alamos." Oppenheimer recruited many young physicists, including Feynman, whom he telephoned long distance from Chicago to inform that he had found a Presbyterian sanatorium in Albuquerque, New Mexico for Arline. They were among the first to depart for New Mexico, leaving on a train on March 28, 1943. The railroad supplied Arline with a wheelchair, and Feynman paid extra for a private room for her. There they spent their wedding anniversary.

At Los Alamos, Feynman was assigned to Hans Bethe's Theoretical (T) Division, and impressed Bethe enough to be made a group leader. He and Bethe developed the Bethe–Feynman formula for calculating the yield of a fission bomb, which built upon previous work by Robert Serber. As a junior physicist, he was not central to the project. He administered the computation group of human computers in the theoretical division. With Stanley Frankel and Nicholas Metropolis, he assisted in establishing a system for using IBM punched cards for computation. He invented a new method of computing logarithms that he later used on the Connection Machine. An avid drummer, Feynman figured out how to get the machine to click in musical rhythms. Other work at Los Alamos included calculating neutron equations for the Los Alamos "Water Boiler", a small nuclear reactor, to measure how close an assembly of fissile material was to criticality.

On completing this work, Feynman was sent to the Clinton Engineer Works in Oak Ridge, Tennessee, where the Manhattan Project had its uranium enrichment facilities. He aided the engineers there in devising safety procedures for material storage so that criticality accidents could be avoided, especially when enriched uranium came into contact with water, which acted as a neutron moderator. He insisted on giving the rank and file a lecture on nuclear physics so that they would realize the dangers. He explained that while any amount of unenriched uranium could be safely stored, the enriched uranium had to be carefully handled. He developed a series of safety recommendations for the various grades of enrichments. He was told that if the people at Oak Ridge gave him any difficulty with his proposals, he was to inform them that Los Alamos "could not be responsible for their safety otherwise".

thumb|alt=A crowd seated in folding chairs|left|At the 1946 colloquium on the [[History of the Teller–Ulam design#Teller's "Super"|"Super" at the Los Alamos Laboratory. Feynman is in the second row, fourth from left, next to Oppenheimer.]]

Returning to Los Alamos, Feynman was put in charge of the group responsible for the theoretical work and calculations on the proposed uranium hydride bomb, which ultimately proved to be infeasible. He was sought out by physicist Niels Bohr for one-on-one discussions. He later discovered the reason: most of the other physicists were too much in awe of Bohr to argue with him. Feynman had no such inhibitions, vigorously pointing out anything he considered to be flawed in Bohr's thinking. He said he felt as much respect for Bohr as anyone else, but once anyone got him talking about physics, he would become so focused he forgot about social niceties. Perhaps because of this, Bohr never warmed to Feynman. Feynman impressed Oppenheimer, who wrote in a letter to the University of California's physics department chairman, Raymond T. Birge, in November 1943 that Feynman was "by all odds the most brilliant young physicist here, and everyone knows this."

At Los Alamos, which was isolated for security, Feynman amused himself by investigating the combination locks on the cabinets and desks of physicists. He often found that they left the lock combinations on the factory settings, wrote the combinations down, or used easily guessable combinations like dates. He found one cabinet's combination by trying numbers he thought a physicist might use (it proved to be 27–18–28 after the base of natural logarithms, e = 2.71828 ...), and found that the three filing cabinets where a colleague kept research notes all had the same combination. He left notes in the cabinets as a prank, spooking his colleague, Frederic de Hoffmann, into thinking a spy had gained access to them.

Feynman's monthly salary of $380 () was about half the amount needed for his modest living expenses and Arline's medical bills, and they were forced to dip into her $3,300 () in savings. On weekends he borrowed a car from his friend Klaus Fuchs to drive to Albuquerque to see Arline. Asked who at Los Alamos was most likely to be a spy, Fuchs mentioned Feynman's safe-cracking and frequent trips to Albuquerque; Fuchs himself later confessed to spying for the Soviet Union. The FBI would compile a bulky file on Feynman, particularly in view of Feynman's Q clearance.

alt=The scientists standing in a semi-circle, wearing suits|thumb|Feynman (center) with [[Robert Oppenheimer (immediately right of Feynman) at a Los Alamos Laboratory social function during the Manhattan Project]]

Informed that Arline was dying, Feynman drove to Albuquerque and sat with her for hours until she died on June 16, 1945. He then immersed himself in work on the project and was present at the Trinity nuclear test. Feynman claimed to be the only person to see the explosion without the very dark glasses or welder's lenses provided, reasoning that it was safe to look through a truck windshield, as it would screen out the harmful ultraviolet radiation. The immense brightness of the explosion made him duck to the truck's floor, where he saw a temporary "purple splotch" afterimage.

Cornell (1945–1949)

Feynman nominally held an appointment at the University of Wisconsin–Madison as an assistant professor of physics, but was on unpaid leave during his involvement in the Manhattan Project. In 1945, he received a letter from Dean Mark Ingraham of the College of Letters and Science requesting his return to the university to teach in the coming academic year. His appointment was not extended when he did not commit to returning. In a talk given there several years later, Feynman quipped, "It's great to be back at the only university that ever had the good sense to fire me."

As early as October 30, 1943, Bethe had written to the chairman of the physics department of his university, Cornell, to recommend that Feynman be hired. On February 28, 1944, this was endorsed by Robert Bacher, also from Cornell, and one of the most senior scientists at Los Alamos. This led to an offer being made in August 1944, which Feynman accepted. Oppenheimer had hoped to recruit Feynman to the University of California, but Birge was reluctant. He made Feynman an offer in May 1945, but Feynman turned it down. Cornell matched its salary offer of $3,900 () per annum. Feynman became one of the first of the Los Alamos Laboratory's group leaders to depart, leaving for Ithaca, New York, in October 1945.

Because Feynman was no longer working at the Los Alamos Laboratory, he was no longer exempt from the draft. At his induction physical, Army psychiatrists diagnosed Feynman as suffering from a mental illness and the Army gave him a 4-F exemption on mental grounds. His father died suddenly on October 8, 1946, and Feynman suffered from depression. On October 17, 1946, he wrote a letter to Arline, expressing his deep love and heartbreak. The letter was sealed and only opened after his death. "Please excuse my not mailing this," the letter concluded, "but I don't know your new address." Unable to focus on research problems, Feynman began tackling physics problems, not for utility, but for self-satisfaction. One of these involved analyzing the physics of a twirling, nutating disk as it is moving through the air, inspired by an incident in the cafeteria at Cornell when someone tossed a dinner plate in the air. He read the work of Sir William Rowan Hamilton on quaternions, and tried unsuccessfully to use them to formulate a relativistic theory of electrons. His work during this period, which used equations of rotation to express various spinning speeds, ultimately proved important to his Nobel Prize–winning work, yet because he felt burned out and had turned his attention to less immediately practical problems, he was surprised by the offers of professorships from other renowned universities, including the Institute for Advanced Study, the University of California, Los Angeles, and the University of California, Berkeley.

thumb|left|alt=A diagram displaying two particles colliding and releasing gamma radiation|Feynman diagram of electron/positron annihilation

Feynman was not the only frustrated theoretical physicist in the early post-war years. Quantum electrodynamics suffered from infinite integrals in perturbation theory. These were clear mathematical flaws in the theory, which Feynman and Wheeler had tried, unsuccessfully, to work around. "Theoreticians", noted Murray Gell-Mann, "were in disgrace". In June 1947, leading American physicists met at the Shelter Island Conference. For Feynman, it was his "first big conference with big men ... I had never gone to one like this one in peacetime." The problems plaguing quantum electrodynamics were discussed, but the theoreticians were completely overshadowed by the achievements of the experimentalists, who reported the discovery of the Lamb shift, the measurement of the magnetic moment of the electron, and Robert Marshak's two-meson hypothesis.

Bethe took the lead from the work of Hans Kramers, and derived a renormalized non-relativistic quantum equation for the Lamb shift. The next step was to create a relativistic version. Feynman thought that he could do this, but when he went back to Bethe with his solution, it did not converge. Feynman carefully worked through the problem again, applying the path integral formulation that he had used in his thesis. Like Bethe, he made the integral finite by applying a cut-off term. The result corresponded to Bethe's version. Feynman presented his work to his peers at the Pocono Conference in 1948. It did not go well. Julian Schwinger gave a long presentation of his work in quantum electrodynamics, and Feynman then offered his version, entitled "Alternative Formulation of Quantum Electrodynamics". The unfamiliar Feynman diagrams, used for the first time, puzzled the audience. Feynman failed to get his point across, and Paul Dirac, Edward Teller and Niels Bohr all raised objections.

To Freeman Dyson, one thing at least was clear: Shin'ichirō Tomonaga, Schwinger and Feynman understood what they were talking about even if no one else did, but had not published anything. He was convinced that Feynman's formulation was easier to understand, and ultimately managed to convince Oppenheimer that this was the case. Dyson published a paper in 1949, which added new rules to Feynman's that told how to implement renormalization. Feynman was prompted to publish his ideas in the Physical Review in a series of papers over three years. His 1948 papers on "A Relativistic Cut-Off for Classical Electrodynamics" attempted to explain what he had been unable to get across at Pocono. His 1949 paper on "The Theory of Positrons" addressed the Schrödinger equation and Dirac equation, and introduced what is now called the Feynman propagator. Finally, in papers on the "Mathematical Formulation of the Quantum Theory of Electromagnetic Interaction" in 1950 and "An Operator Calculus Having Applications in Quantum Electrodynamics" in 1951, he developed the mathematical basis of his ideas, derived familiar formulae and advanced new ones.

While papers by others initially cited Schwinger, papers citing Feynman and employing Feynman diagrams appeared in 1950, and soon became prevalent. Students learned and used the powerful new tool that Feynman had created. Computer programs were later written to evaluate Feynman diagrams, enabling physicists to use quantum field theory to make high-precision predictions. Marc Kac adapted Feynman's technique of summing over possible histories of a particle to the study of parabolic partial differential equations, yielding what is now known as the Feynman–Kac formula, the use of which extends beyond physics to many applications of stochastic processes. To Schwinger, however, the Feynman diagram was "pedagogy, not physics".

Looking back on this period, Feynman would reflect fondly on his time at the Telluride House, where he resided for a large period of his Cornell career. In an interview, he described the House as "a group of boys that have been specially selected because of their scholarship, because of their cleverness or whatever it is, to be given free board and lodging and so on, because of their brains". He enjoyed the house's convenience and said that "it's there that I did the fundamental work" for which he won the Nobel Prize.

However, Feynman was also reported to have been restless during his time at Cornell. By 1949, near the end of this period, he had still not settled into a permanent house or apartment, instead moving between guest houses and student residences. He spent some time living with various married friends, but these arrangements reportedly often ended when the "arrangements became sexually volatile".

At 31 years old, he was reported to frequently pursue married female friends and undergraduate students, and to hire sex workers; according to Gleick, this behavior strained many of his friendships. Feynman later wrote that he was not fond of Ithaca's cold winter weather and that he felt he lived in the shadow of Hans Bethe while at Cornell.

Brazil (1949–1952)

Feynman spent several weeks in Rio de Janeiro in July 1949. That year, the Soviet Union detonated its first atomic bomb, generating concerns about espionage. Fuchs was arrested as a Soviet spy in 1950 and the FBI questioned Bethe about Feynman's loyalty. Physicist David Bohm was arrested on December 4, 1950, and immigrated to Brazil in October 1951. Because of the fears of a nuclear war, a girlfriend told Feynman that he should also consider moving to South America. He had a sabbatical coming for 1951–1952, and elected to spend it in Brazil, where he gave courses at the Centro Brasileiro de Pesquisas Físicas.

alt=Feynman seated on the floor with drums around him|thumb|Feynman with drums

In Brazil, Feynman was impressed with samba music, and learned to play the , a metal percussion instrument based on a frying pan. He was an enthusiastic amateur player of bongo and conga drums and often played them in the pit orchestra in musicals. He spent time in Rio with his friend Bohm, but Bohm could not convince Feynman to investigate Bohm's ideas on physics.

Caltech and later years (1952–1978)

thumb|Paul Dirac and Richard Feynman at Jabłonna, Poland. July 1962.

Personal and political life

Feynman did not return to Cornell. Bacher, who had been instrumental in bringing Feynman to Cornell, had lured him to the California Institute of Technology (Caltech). Part of the deal was that he could spend his first year on sabbatical in Brazil. He had become smitten by Mary Louise Bell from Neodesha, Kansas. They had met in a cafeteria in Cornell, where she had studied the history of Mexican art and textiles. She later followed him to Caltech, where he gave a lecture. While he was in Brazil, she taught classes on the history of furniture and interiors at Michigan State University. He proposed to her by mail from Rio de Janeiro, and they married in Boise, Idaho, on June 28, 1952, shortly after he returned. They frequently quarreled and she was frightened by what she described as "a violent temper". Their politics were different; although he registered and voted as a Republican, she was more conservative, and her opinion on the 1954 Oppenheimer security hearing ("Where there's smoke there's fire") offended him. They separated on May 20, 1956. An interlocutory decree of divorce was entered on June 19, 1956, on the grounds of "extreme cruelty". The divorce became final on May 5, 1958.

In the wake of the 1957 Sputnik crisis, the U.S. government's interest in science rose for a time. Feynman was considered for a seat on the President's Science Advisory Committee, but was not appointed. At this time, the FBI interviewed a woman close to Feynman, possibly his ex-wife Bell, who sent a written statement to J. Edgar Hoover on August 8, 1958: