does for sovereign states, the end of national security justified almost any means.
16
Sailing Near the Wind
John von Neumann once told Frangoise Ulam that he had never met anyone with as much self-confidence as her husband — “adding,” writes Stanislaw Ulam puckishly, “that perhaps it was somewhat justified.” Ulam, a handsome, aristocratic Polish mathematician of first rank, had emigrated to the US in the 1930s with von Neumann's encouragement, had been a Junior Fellow at Harvard, had taught at Harvard and the University of Wisconsin (where he and Frangoise married) and had found his way to Los Alamos late in 1943. Theoretical physics was a new field to him then; on his first visit to the Los Alamos Tech Area, when he had encountered von Neumann discussing theory with dark, intense Edward Teller, the “tremendously long formulae on the blackboard” had scared him. “Seeing all these complications of analysis, I was dumbfounded, fearing I would never be able to contribute anything.” But the equations stayed on the board from day to day, which meant to Ulam that the pace of invention was relatively slow, and he soon regained confidence. “I found out that the main ability to have was a visual, and also an almost tactile, way to imagine the physical situations, rather than a merely logical picture of the problems.”
He was soon engaged with Teller, attempting to derive more rigorously a formula Teller had roughed in for the inverse Compton effect that plagued Teller's dreams of a thermonuclear — the effect that cooled the reaction by spilling out radiation and seemed to prevent it from propagating. Ulam appraised the volatile Hungarian perspicaciously:
When I first met Teller, he appeared youthful, always intense, visibly ambitious, and harboring a smoldering passion for achievement in physics. He was a warm person and clearly desired friendship with other physicists. Possessing a very critical mind, he also showed quickness, sense, and great determination and persistence. However, I think he also showed less feeling for true simplicity in the more fundamental levels of theoretical physics. To exaggerate a bit, I would say his talents were more in the direction of engineering, construction, and the surveying of existing methods. But undoubtedly he also had great ingenuity.
George Gamow, the Russian emigre theoretician who had offered Teller the position at George Washington University that brought him to the US before the war, told Ulam later that Teller had been a different person then — “helpful, willing, and able to work on other people's ideas without insisting on everything having to be his own. According to Gamow, something changed in [Teller] after he joined the Los Alamos Project.”
With the war over and Teller and so many others going, the Ulams decided to leave as well. They had both lost family in the Holocaust — Franchise's mother at Auschwitz — and they had both become American citizens, so there was no question of returning to Europe. Ulam accepted an associate professorship at the University of Southern California in Los Angeles, a place the couple found strange — “I used to say that any two points in Los Angeles were at least an hour's drive apart,” Ulam writes. They settled in without quite settling down. Then Ulam was struck with violent illness, a “fantastic headache” that was “the most severe pain I had ever endured.” When Franchise finally roused a doctor and got her husband to the hospital, he was vomiting bile. “The surgeon performed a trepanation not knowing exactly where or what to look for. He did not find a tumor, but did find an acute state of inflammation of the brain. He told Franchise that my brain was bright pink instead of the usual gray. These were the early days of penicillin, which they applied liberally.”
Ulam lapsed into a coma. His wife, his doctors and his friends worried about brain damage. When he awoke a few days later, Ulam worried about it even more. “One morning the surgeon asked me what 13 plus 8 were. The fact that he asked such a question embarrassed me so much that I just shook my head. Then he asked what the square root of twenty was, and I replied: about 4.4. He kept silent, then I asked, ‘Isn't it?’ I remember Dr. Rainey laughing, visibly relieved, and saying, ‘I don't know.’”
Recovery was slow. Ulam spent weeks in the hospital. Nicholas Metropolis, who had set up the ENIAC problem, traveled all the way from Los Alamos to visit him and let slip that “the security people… had been worried that in my unconscious or semi-conscious states I might have revealed some atomic secrets.” The peripatetic mathematician Paul Erdos turned up just as Ulam, still shaky, was leaving the hospital. On the way home they talked mathematics, whereupon Erdos pronounced Ulam “just like before.” When Ulam beat Erdos at chess, he decided he had escaped damage.
On leave from the university, resting at home during his extended recovery, Ulam amused himself playing solitaire. Sensitivity to patterns was part of his gift. He realized that he could estimate how a game would turn out if he laid down a few trial cards and then noted what proportion of his tries were successful, rather than attempting to work out all the possible combinations in his head. “It occurred to me then,” he remembers, “that this could be equally true of all processes involving branching of events.” Fission with its exponential spread of reactions was a branching process; so would the propagation of thermonuclear burning be. “At each stage of the [fission] process, there are many possibilities determining the fate of the neutron. It can scatter at one angle, change its velocity, be absorbed, or produce more neutrons by a fission of the target nucleus, and so on.” Instead of trying to derive the expected outcomes of these processes with complex mathematics, Ulam saw, it should be possible to follow a few thousand individual
Ulam was happy to be invited to the Super Conference in April 1946. Associating Los Angeles with his illness, he was even happier to be invited to return to work at Los Alamos. When he told von Neumann about his solitaire discovery, the Hungarian mathematician was immediately interested in what he called a “statistical approach” that was “very well suited to a digital treatment.” The two friends developed the mathematics together and named the procedure the Monte Carlo method (after the famous gaming casino in Monaco) for the element of chance it incorporated.
Two years after the end of the war, thermonuclear research at Los Alamos was still almost entirely theoretical. The model system on which calculations were based continued to be Teller's Super — a pipe of liquid deuterium with an atomic bomb screwed to one end. The medium that would transfer energy from the atomic bomb to the deuterium would be the copious flood of neutrons that the fission explosion produced. Implosion appeared to be an unsuitable geometry for the Super's fission component, however. Implosion generated neutrons at the center of an imploding mass of hydrogenous material — the chemical explosives that supplied the initial squeeze that assembled the critical mass — and the material interacted with the outward flow of neutrons, soaked up energy and otherwise got in the way. “The radiation just would not get out,” Hans Bethe comments, “because there's all that high explosive around. First the uranium [tamper] and then the high explosive.” Nor was the Mark III implosion bomb hot enough to do the job. Instead of an implosion system they decided they would need a uranium gun — a system that assembled essentially bare critical masses — and a big, powerful uranium gun at that, one that would yield not the nominal 13.5 kilotons of the Hiroshima device but several hundred kilotons. No uranium gun had yet been tested under experimental conditions, on a tower with instrumentation; Little Boy, the Hiroshima bomb, was the only such device so far exploded.
It had also been clear for some time that deuterium alone required too high an ignition temperature to propagate on its own, that some amount of rare and expensive tritium would have to be incorporated into the design, not necessarily mixed with the deuterium throughout the pipe but at least mixed with the deuterium at the end nearer the fission bomb. “The main question,” comments John Manley, who became associate director of Los Alamos in 1947 as well as secretary to the AEC's General Advisory Committee, “… was whether you could under any circumstances get a propagating reaction in a straight deuterium mixture. And the general conclusion I knew: that you couldn't. Then the question [was] how much would you gain from t[ritium] addition… and any other tricks… ”
Teller, doing basic physics with Enrico Fermi at the University of Chicago, kept in touch, meeting travelers passing through Chicago and spending summers on the mesa as a consultant. “One might be going to Washington,” Carson Mark recalls, “and stop off in Chicago and Edward was always interested in what people were doing and
