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The father of Feynman had been brought with his immigrant parents from Minsk, Byelorussia, in 1895. Feynman himself was born in New York and educated at the Massachusetts Institute of Technology and at Princeton, where he completed his PhD in 1942 under the supervision of John Wheeler. In 1943 Feynman moved to Los Alamos to work on the Manhattan Project in the theoretical division under Hans Bethe. He was soon recognized to be, in the words of Robert Oppenheimer, “the most brilliant young physicist here.” Feynman's own writings about the period deal less with the bomb than with his wife, Arline who was dying of TB. He had married her in 1942 against much family opposition. She moved into a sanatorium in nearby Albuquerque and died in June 1945, a month before the first atomic bomb was tested.

In 1945 Feynman moved to Cornell as professor of physics, a post he held until 1950 when he was appointed to a similar position at the California Institute of Technology, where he remained for the rest of his career. While at Cornell he began to consider anew some of the outstanding problems in quantum electrodynamics (QED) – an area of physics dealing with the interactions between electrons and photons. The electron was seen as a point charge. As the strength of a charged body diminishes with distance in accordance with the inverse square law, it will vary as 1/r². But what about the strength of the charge at the electron itself where r = 0? At this point the charge (and for a point, density) of the electron must be infinite. To handle this and other similar absurdities physicists developed a number of artificial mathematical techniques which would allow them to ‘renormalize’ their equations so as to remove the infinite terms. Yet the charge on the electron is finite and can be measured accurately. Theoretical calculations, it was felt, should reach the same value without requiring artificial manipulation.

Freeman Dyson has described Feynman at this time as claiming that “he couldn't understand the official version of quantum mechanics,” and that he had to “reinvent quantum mechanics” in a form he could understand. Feynman first presented his new approach in a paper, turned down by the Physical Review, entitled Space-Time Approach to Non-Relativistic Quantum Mechanics (1948) in which he introduced the notion of path integrals, also referred to as “sum over histories.”

In Feynman's approach, the probability of an event that can happen in a number of different ways, such as finding an electron at a certain place, was the sum of the probabilities of all the possible ways the event could happen. When all the probabilities were added, Feynman noted, the result was Schrödinger's wave function.

In a 1949 paper, Space-Time Approach to Quantum Electrodynamics, Feynman showed how to calculate these path integrals using simple sketches which have since become widely known as Feynman diagrams. It was for work in this field that Feynman shared the 1965 Nobel Physics prize with Julian Schwinger and Sin-Itiro Tomonaga. His first reaction had been to decline what he terms “Alfred Nobel's other mistake” on the grounds that he would thereafter become a celebrity and not just someone who wanted to talk about physics. Warned that a refusal would mark him in the media as an even bigger celebrity, Feynman agreed to accept the award.

Feynman also worked on problems connected with superconductivity and with particle physics. In 1955 he devized a new model to represent the structure of liquid helium. During a visit to Stanford in 1968 Feynman began to work on the strong nuclear interaction. He attributed to the proton a set of constituents he named ‘partons’, which were pointlike and did not interact with each other. Their value lay in their ability to explain the inelastic scattering results emerging from the Stanford Linear Accelerator (SLAC).

With the publication in 1963 of the Feynman Lectures in Physics, Feynman began to be known outside the small community of theoretical physicists. However, he gained international celebrity in the 1980s following a number of TV programs and the publication of Surely You're Joking Mr Feynman (1985). The picture of a man of rare seriousness and honesty, with little time for honors, institutions, and formality, yet who clearly enjoyed the life of the flesh as well as the mind, had rarely been presented with such clarity. Despite his reluctance to accept the Nobel award, Feynman seems to have enjoyed his fame, and even to accentuate his unconventional character.

When he was asked to serve in 1986 on the presidential commission to investigate the explosion of the Challenger space shuttle, he assumed that he was being asked to contribute to a genuine scientific investigation. Pointed in the right direction by sympathetic colleagues, Feynman soon realized that the immediate cause of the explosion had been the O-ring seals used in the booster rocket. On the morning of the shuttle's launch the temperature was below freezing and the seals failed to retain their elasticity at low temperatures. Feynman also found out that the NASA officials had been warned about this potential failure. Feynman demonstrated the point, unannounced, at a televised meeting of the commission. He placed the O-rings in a glass of iced water for a few minutes and showed that, for several seconds after their removal, the seals had lost their resilience.

Feynman wrote up his findings as a separate appendix. He was aware that, while the commission would not actually suppress any evidence, much that was critical of NASA could be scattered throughout the report and consequently picked up by only the most careful of readers. Before the commission agreed to publish his report in a form acceptable to Feynman, he first found it necessary to threaten to resign and issue the report elsewhere. Feynman found his Washington experiences genuinely distressing. Much of his life had been spent trying to understand various natural phenomena. The work had been hard, demanding many hours of intense intellectual concentration. He went to Washington intending to put the same effort into the service of the commission. Yet he found himself working with people who, though not crooks, liars, or lazy, were only marginally interested in the truth. It was more important for them to find a story acceptable to a community consisting of the Washington establishment, NASA, and “the American people,” rather than to set out to establish what happened.

By this time, however, Feynman was a seriously ill man. In 1978 a malignant growth had been removed from his abdomen. A second cancer, involving bone marrow, was diagnosed in 1986. The abdominal cancer returned in late 1987 and soon after Feynman died from renal failure.