QI The Book of the Dead

and clarifying the work of others. Quantum Electrodynamics (QED) was the discipline that explained the behaviour of light, magnetism and electricity, but it was irritatingly unreliable. With two other physicists, Feynman fixed the flaws in the theory but his most important contribution was to describe the motions of subatomic particles using a sequence of small, elegant diagrams. He always downplayed the work he did at this period as so much ‘mathematical hocus-pocus’, but he liked his ‘Feynman diagrams’ enough to paint them all over his van. They are still the best way of describing the quantum world.

    The major portion of Feynman’s professional life was spent at the California Institute of Technology (Caltech). It is sometimes said of him that, although he was unquestionably one of the great physicists of any century, he didn’t make a major theoretical breakthrough or give his name to an important new discovery. That may be less to do with him than the nature of physics in the period – few of his contemporaries could claim to have done so either. It also obscures what is Feynman’s greatest achievement: he was the best and most charismatic teacher of his generation. He loved teaching and believed that, if a theory couldn’t be explained to a non-scientist, there was something wrong with the theory. In the introduction to his best-selling collection of lectures he tells his audience:
    What I am going to tell you about is what we teach our physics students in the third or fourth year of graduate school… It is my task to convince you not to turn away because you don’t understand it. You see my physics students don’t understand it. That is because I don’t understand it. Nobody does .
     
    But this, as he explains, is neither demoralising nor defeatist:
    We can imagine that this complicated array of moving things which constitutes ‘the world’ is something like a great chess game being played by the gods, and we are observers of the game. We do not know what the rules of the game are; all we are allowed to do is to watch the playing. Of course, if we watch long enough, we may eventually catch on to a few of the rules. The rules of the game are what we mean by fundamental physics.
     
    Feynman always described his physics as ‘fiddling about’ or ‘a game’. For him, it was play rather than work: just a matter of looking closely, and wondering:

    When someone says, ‘Science teaches such and such,’ he is using the word incorrectly. Science doesn’t teach anything; experience teaches it. If they say to you, ‘Science has shown such and such,’ you might ask, ‘How does science show it? How did the scientists find out? How? What? Where?’
     
    He spent most of the second half of his life trying to supply intelligible answers to these questions. Perhaps the perfect Feynman moment came in the inquiry into the Challenger space-shuttle disaster in 1986. The commission had become mired in evasions and technical obscurantism and was finding it impossible to pinpoint the cause of the accident. One suspect was the rubber O-rings used as seals between the sections of the solid fuel rockets. The failure of these immense but fragile rings – only a quarter of an inch in diameter but 37 feet in circumference – would certainly have caused the disaster, but nobody could (or would) say for certain whether they had or not, or why. Feynman was convinced the O-rings were to blame. Live on camera, in front of the commission and all the witnesses, he cut through the whole tangle of evidence by taking a small section of O-ring and dipping it into a glass of iced water. It was immediately obvious to everyone that the rubber instantly lost its elasticity at cold temperatures, which would have caused the seals to fail and the rocket to break up. On that fateful morning, the temperature had been 24°F lower than the engineers recommended. Case closed. It was science at its simplest and most powerful: Epicurus would have been proud.
    The rest of Feynman’s life can sometimes look like a parody of the groovy 1960s professor. He taught himself to play bongos in the Brazilian manner, held exhibitions of his own paintings,experimented with drugs, learned how to decipher Mayan hieroglyphs and studied comparative religions. He had a ‘second office’ in a topless bar in Pasadena, where he would scribble equations and new Feynman diagrams on the back of his beer mat. But these were more than the affectations