Richard Feynman

by John Gribbin

  The uranium for the bomb was actually being separated at Oak Ridge, Tennessee. Again, the industry workers in the plant where the work was being done didn’t know what the work was for. And, again, progress was slow and difficult. Emilio Segre, one of the Los Alamos team, was eventually sent to Oak Ridge to identify some of the problems, and while carrying out a preliminary inspection of the plant he was horrified to find large amounts of unpurified uranium nitrate being kept in solution in large tanks. If the pure uranium-235 were to be stored in the same way, it would explode. The military people in charge at Oak Ridge knew that a certain amount of pure uranium-235 (the so-called critical mass) was needed to cause an explosion, but they hadn’t realized that when neutrons are slowed down by passing through water they are much more effective at causing fission. Considerably less uranium-235 in a solution of this kind would still be a hazard.

  Segre brought back all the information he could glean about how uranium was being refined and stored at Oak Ridge. The Los Alamos scientists studied the information and worked out appropriate safety procedures. Then, somebody had to go and explain it all to the workers at Oak Ridge. Who else but Dick Feynman? Before he left, Oppenheimer told him how to make sure he was given a hearing. If there were any objections on grounds of security, he had to say, ‘Los Alamos cannot accept the responsibility for the safety of the Oak Ridge plant unless …’ The mantra worked like a charm. He explained everything, about fission, the role of neutrons, how they behave when they pass through different substances and so on. The plant was redesigned to avoid the possibility of too much purified uranium-235 piling up in one place, and as a side effect the workforce became much more enthusiastic about the project and worked much more efficiently. Many of the people involved felt that Feynman, on behalf of the Los Alamos team, had prevented a disastrous accident and saved their lives.

  Not that the Los Alamos team themselves weren’t, by modern standards, horrifyingly careless of their own safety when handling radioactive material. To be sure, they took care to avoid the buildup of a critical mass of either uranium-235 or plutonium as the material became available. But as the first atomic bombs were being assembled, these highly radioactive materials were handled with few of the safety precautions that would now be de rigueur. Of course, it was wartime, and at that time the risks of radiation poisoning were poorly understood. But apart from the, perhaps necessary, risks involved in handling the radioactive material, the team kept, in one of the rooms at Los Alamos, a small silver-plated ball mounted on a pedestal, something to impress visitors with. The ball was made of plutonium, today regarded as one of the most toxic substances on Earth. It was warm to the touch, because of its radioactivity – warmer, at the high altitude of Los Alamos, than it would have been at sea level, because cosmic rays striking the nuclei inside the ball triggered additional fission reactions. With hindsight, it would have been surprising if some members of the team had not eventually died of cancer.

  With the benefit of modern knowledge, perhaps Feynman and his colleagues could have taken precautions that would have extended their own lives. But they didn’t have that knowledge, and their situation was, in his own words, ‘just an accident of life’. Equally, there was nothing he could do to save Arline’s life. By the beginning of 1945, many factors in Feynman’s life were coming to a head. The Manhattan Project itself was nearing completion. Meanwhile, the cost of keeping Arline in hospital was beginning to be a problem. In a letter to ‘Dearest Putzie’ dated 24 April 1945, Richard spelled out their financial situation. His income was $300 a month; after meeting his own modest expenses and her hospital bills, they needed another $300 a month, which was coming from Arline’s dwindling savings, now down to $3,300. They could keep going at this rate for another ten months, but Richard asked whether it might be ‘necessary to sell the ring and piano now’.8 He also offered to go back to eating in the mess hall, saving $15 a month. But Arline was wasting away, and realistically Feynman cannot have expected her to last long enough for them to run out of money.

  Against this background, they at last, at Arline’s instigation, made love. It was a last stand against the inevitable, perhaps Arline’s desperate attempt to leave Richard with the child that they both yearned for, even if she could not stay with him herself. She missed her next period, and was overjoyed at the prospect of being pregnant. But she was not; it was just another symptom of her illness.

  Her condition continued to deteriorate, so much so that she asked Richard not to visit her on some weekends. In May, her father made the long and difficult wartime journey from New York to see her for the last time. One day in June he called Feynman at Los Alamos, and told him the end was near. Borrowing a car from Klaus Fuchs, Richard made it to Albuquerque in time to be with her when she died. The next day, he returned to Los Alamos and buried himself in his work, not grieving properly until, months later, he was in Oak Ridge and noticed a pretty dress in a shop window: ‘I thought, “Arline would like that,” and then it hit me.’9

  Soon after Arline’s death, Feynman was able to take a short break in Far Rockaway as the project neared completion. He was there when he received a message from Bethe, saying, ‘The baby is expected.’ He flew back to New Mexico just in time to be present at the Trinity test, where he was part of the group of observers twenty miles from ground zero. Everyone had been issued with dark glasses to protect their eyes from the ultraviolet radiation produced in the explosion; Feynman, still his own man, knew that even ordinary glass stops ultraviolet light, and calculated that the ordinary light from the explosion wouldn’t be bright enough to damage his eyes. So he watched the explosion through the windshield of a truck – the only person to watch the first nuclear explosion on Earth with his naked eyes.

  The immediate reaction among the team was euphoria that their work had been successful. Only much later did people start to ask the questions which now concern historians, about the morality of proceeding with the Manhattan Project once it was clear that Germany was being defeated and it was known that there was no nuclear threat from Japan, and whether the Hiroshima and Nagasaki bombs should ever have been dropped. Feynman’s own counter-reaction was both more immediate, and more personal. By the end of the year, when he was still just 27 years old, he was teaching at Cornell University, in Ithaca, New York; he recalls sitting in a restaurant in New York City around that time, working out how much of the city would be destroyed by a bomb the size of the one dropped on Hiroshima:

  I would go along and I would see people building a bridge, or they’d be making a new road, and I thought, they’re crazy, they just don’t understand, they don’t understand. Why are they making new things? It’s so useless.10

  Happily, Feynman’s assumption of the inevitability of nuclear war has, so far, proved wrong. But the story gives a good idea of his state of mind in his early years as a ‘real professor’ at Cornell.

  He had chosen Cornell because that was where Bethe worked. By 1945, Feynman’s reputation was such that he could have had his pick of several posts (although he didn’t seem to be fully aware of his ‘market value’); but he had got on well with Bethe at Los Alamos, and had been impressed by Bethe’s skills both as a physicist and as a mathematician who knew even more mathematical tricks and short cuts than Feynman did. Technically, Feynman’s first academic position was with the University of Wisconsin – after completing his PhD, while still working in Princeton on the bomb project, he had accepted the offer of a job there, without pay, suspended until the war work was finished. But he never took up the post. By the end of October 1943, Bethe was already urging Cornell to sign Feynman up, and this led to the offer of an appointment from the autumn of 1944, with a leave of absence (again, unpaid) granted for the duration of the war. Feynman was happy to accept, and later said that he didn’t consider the other offers he received, because he wanted to be with Bethe.

  But that didn’t stop the other offers coming in. One of the most frustrated players in the story was Oppenheimer, who wanted t
o lure Feynman to his own home base, at the University of California, Berkeley. His correspondence11 shows how strongly he felt about this. In a letter to Raymond Birge, the head of Berkeley’s physics department, dated 4 November 1943, Oppenheimer describes Feynman as:

  The most brilliant young physicist here, and everyone knows this. He is a man of thoroughly engaging character and personality, extremely clear, extremely normal in all respects, and an excellent teacher with a warm feeling for physics in all its aspects … Bethe has said that he would rather lose any two other men than Feynman from this present job, and Wigner said, ‘He is a second Dirac, only this time human.’

  It wasn’t enough to persuade Berkeley to make an immediate offer to Feynman, and six months later, on 26 May 1944, Oppenheimer was still banging his head against their bureaucratic brick wall:

  It is not an unusual thing for Universities to make commitments to young men whom they wish to have after the war … [Feynman] is not only an extremely brilliant theorist, but a man of the greatest robustness, responsibility and warmth, a brilliant and lucid teacher, and an untiring worker. He would come to the teaching of physics with both a rare talent and a rare enthusiasm … he is just such a man as we have long needed in Berkeley to contribute to the unity of the department and to give it technical strength where it has been lacking in the past.

  Eventually, Berkeley did make Feynman an offer, but he turned it down, happy to be going to Cornell. The authorities at Cornell, though, didn’t know that Feynman had no intention of going anywhere else, and kept hearing, via Bethe, rumours about the offers he was getting from other universities, including Berkeley. As a result, from time to time, while he was still at Los Alamos, Feynman received notification that he had been awarded a raise in his notional salary. By the time he actually arrived there, and started drawing the salary, it had been increased to $3,900 a year, a very healthy rate for the job in 1945, with every prospect of reaching the $5,000 per annum that the young Feynman had always hoped for.12

  Feynman’s efforts to settle down as a ‘dignified professor’ were doomed to failure, as he recounts in Surely You’re Joking. He left Los Alamos earlier than most of the physicists, and arrived in Cornell to take up his appointment at the beginning of November 1945, having worked out on the train an outline of the course he was to teach. He had no trouble with the teaching side of being a professor; it was the ‘dignified’ bit that somehow never seemed to work. For a start, without Arline and the home they had both longed for, he preferred the community life on campus to a solitary apartment. He lived much the same kind of life as he had as a graduate student at Princeton and undergraduate at MIT, only now he had a fund of anecdotes about his wartime experiences with which to regale people at dinner, beginning the development of the ‘colourful character’ persona. Still young, and looking younger, he tried to make a new social life without Arline by going to student dances, where he was puzzled by his initial lack of success with the ladies. It turned out that they regarded his matter of fact claims to be a professor of physics who had worked on the atomic bomb project as an outrageous line-shooting exercise, and he got on much better when he said nothing about his war work and allowed them to think he was a freshman on the GI Bill, for soldiers returning from the war.

  Underneath it all though, Feynman was, by his own standards, lonely and depressed. Nobody noticed. Many years later, Bethe explained – ‘Feynman depressed is just a little more cheerful than any other person when he is exuberant.’13 His depression was understandable – the death of Arline, and the end of the stressful years of war work were beginning to catch up with him. On top of that, after a few months at Cornell Feynman began to worry that he was burned out. He thought he wouldn’t be able to think about fundamental physics any more. Then, on 7 October 1946, Melville (who had long suffered from high blood pressure) had a stroke; he died the next day. Shortly after the funeral, Feynman wrote a last letter to Arline, which he never showed to anyone and which was found among his papers after his own death. It told her how much he loved her, and how empty his life still seemed without her. He ended with a poignant P.S.: ‘Please excuse my not mailing this – but I don’t know your new address.’14

  Against this background of inner turmoil and the conviction that he was burned out, Feynman continued to receive offers of posts at other universities and to get raises in salary as a result. A few months after writing his last letter to Arline, early in 1947, he received the offer to end all offers. It was from the Institute for Advanced Study in Princeton. Knowing that Feynman felt that the Institute was too ‘theoretical’, an ivory tower cut off from the hurly-burly of a normal university, they offered to create a special post just for him, so that he could spend half his time at the Institute and half at Princeton University. It was a dream position, a position, in Feynman’s words, ‘better than Einstein’s’. And the salary was impressive, too. All in all, he wrote in Surely You’re Joking, ‘it was ideal; it was perfect; it was absurd!’

  On the spot, he decided that the whole business was ridiculous. Nobody could live up to the expectations others had of him. He certainly couldn’t, so he wasn’t going to try any more.

  The very same day, perhaps because he had overheard Feynman talking along these lines to his colleagues, Robert Wilson, who was by now head of the Nuclear Research Laboratory at Cornell, called Feynman into his office, and told him not to worry about research. As Feynman later paraphrased it, he said,

  You’re teaching your classes well; you’re doing a good job, and we’re satisfied. Any other expectations we might have are a matter of luck. When we hire a professor, we’re taking all the risks. If it comes out good, all right. If it doesn’t, too bad. But you shouldn’t worry about what you’re doing or not doing.15

  So Feynman was officially freed from the responsibility of coming up with any brilliant new ideas. He had said farewell to his father, and written his last letter to Arline. In the spring of 1947, he remembered how he used to enjoy doing physics – how it used to be fun, not a chore. He decided that he had a cushy job, secure for life, teaching classes that he rather enjoyed. He wouldn’t look for any more big problems to solve; instead he would play with physics, for fun, the way he used to.

  A few days later he was in the cafeteria when one of the students, fooling around, threw a plate into the air, spinning it like a modern frisbee. Like all the plates, it had the red medallion of Cornell on it, and Feynman noticed that as the plate wobbled and spun the medallion went round at a different rate from the wobble. Intrigued, and just for fun, he set out to calculate the relationship between the wobble and the spin, and found that there is a precise ratio, 2:1, which comes out of a complicated equation.* He told Bethe the news. Bethe asked why he had done the work. For fun, Feynman replied; there’s no importance in it at all.

  But he was wrong. As his subconscious may have been well aware all along, the big problem that he was stuck with in developing his thesis work was how to include the effects of the spin of the electron in these calculations. The equations that Feynman had played with in calculating the wobble of a spinning plate were directly relevant to that problem. As he realized this, he slipped easily into fresh work on the old problem. ‘It was’, he said in Surely You’re Joking, ‘like uncorking a bottle. Everything flowed out effortlessly.’ Physics was fun again, and ‘The whole business I got the Nobel Prize for came from that piddling around with the wobbling plate.’

  Well, it wasn’t really quite that easy, or quite that quick. Feynman’s route to the work that won him the Nobel Prize, from the spring of 1947 onwards, can actually be marked out by the events associated with three select gatherings of scientists, each organized by Oppenheimer on behalf of the National Academy of Sciences, in 1947 and the next two years.

  The first of these meetings took place from 2 to 4 June 1947, at the Ram’s Head Inn on Shelter Island, right at the tip of Long Island. The official theme of the meeting was ‘Problems of Quantum Mechanics and the Electron’, but it has go
ne down in scientific history simply as ‘the Shelter Island Conference’. It was Feynman’s first opportunity to participate in a scientific gathering with some of the top physicists in peacetime, and, with just 24 participants in all, the gathering was small enough to get real work done, in a manner reminiscent of some of the brainstorming sessions of the Manhattan Project. Apart from Feynman, the other bright young man at this gathering of the great was Julian Schwinger, a professor at Harvard University. Schwinger was an almost exact contemporary of Feynman (he had been born three months earlier, on 12 February 1918, also in New York City), and a renowned prodigy, already with a string of papers to his name. He had actually completed the work that became his PhD thesis before he graduated (from Columbia University) in 1936, at the age of eighteen.

  The big talking point at the Shelter Island Conference was an experimental discovery that had been made a few weeks before, at the end of April, by Willis Lamb and his colleague Robert Retherford at Columbia University. They had been probing hydrogen atoms using beams of microwaves – a technique developed directly from Lamb’s own war work, on radar – to measure the energy levels of the electrons in those atoms. In effect, they were measuring the spacing between the rungs on the energy level ladder. According to the Dirac theory, the electron in a hydrogen atom could exist in either of two quantum states which had precisely the same energy, as if there were a double rung on the ladder. But Lamb found that one of these states had slightly more energy than the Dirac theory predicted, so that there was a tiny separation between the two energy levels. One of the energy levels was shifted slightly – one rung of the pair on the ladder was slightly higher than its companion. This became known as the ‘Lamb shift’. The Shelter Island Conference got all this from the horse’s mouth, because Lamb was one of the participants. An almost equally dramatic discovery, a precise measurement of the magnetic moment of the electron, was reported to the meeting by Isidor Rabi, but was overshadowed by Lamb’s work; soon, though, (as we shall see in Chapter 6) it also played a major part in the development of quantum electrodynamics.