E=mc2 (15 page)

America's Turn
I2

The raid bought time for the Allies, but even that would have been wasted if the wrong person had headed their project to build a bomb. At one point the Berkeley physicist Ernest Lawrence's name had been mooted, but his personnel skills made Heisenberg look considerate. America's own physics establishment had been so weak in the 1920s and 1930s that any bomb would have to be constructed, in large parts, by more highly skilled refugees from Europe. No one could have been worse to lead such a team than the broad-shouldered South Dakotan Lawrence.

In 1938, the Italian refugee Emilio Segre had obtained a position at $300 per month in Lawrence's lab. It was a godsend for Segre, who was Jewish, since if he and his young wife had to go back to Italy, there would be no possibility of working in a university anymore; there was also a good chance that they would be turned over to the Germans, and—as happened to many of their relatives—their children would quite possibly be killed. Segre recalls what Lawrence did:

I was stunned, and even now, so many years afterward, I marvel . . . [that] he did not think for a second of the impression he conveyed.

But Groves also carried a constant personal anger, of a sort more accepted in American public life at the time. He screamed, he threatened; he demeaned his assistants in public; his neck veins popped out with anger a lot. (The fact that he was now dealing with theoretical physicists of an intellectual level that dwarfed the accomplishments he'd been so proud of at West Point did not make him any easier to live with.)

When the secret Los Alamos, New Mexico, research center for the bomb project officially opened, in April 1943, Groves stood up to speak. A young member of the audience, Robert Wilson, later remembered: "He said he appeared not to believe in the eventual success of the project. He emphasized that if—or when—we failed, it could be he who would have to stand before a congressional committee to explain how money had been squandered. He could not have done worse at starting the conference on an upbeat note of enthusiasm."

Many possible projects have collapsed when administrators like this took over. A workable jet prototype, for example, had been up and running in Britain as early as 1941, but incompetent organization kept it from ever being deployed in sufficient numbers to help the RAF. Groves could motivate construction engineers who had to follow blueprints, yet he would almost certainly have failed at inspiring theoreticians who had to trust that they would succeed in unexplored intellectual terrain. But in the autumn of 1942—while Heisenberg was readying further work after his successful Leipzig tests-Groves made an appointment of genius. He selected the exquisitely oversensitive J. Robert Oppenheimer to be in day-to-day control of the scientists at Los Alamos.

It was a job that nearly destroyed Oppenheimer's health; by the time the first explosion took place, Oppenheimer, about six feet one, was down to about 116 pounds. In time his work on the Manhattan Project destroyed his career, making him so much of an outcast in the U.S. that he would have been jailed if he tried to read his own past classified papers. But he got the job done.

Oppenheimer's great strength, curiously enough, came from his underlying lack of confidence. It wasn't something most people could tell on the surface, of course. He had graduated from Harvard in only three years, with perfect grades; had studied at Rutherford's lab; taken his doctorate from Gottingen, and quickly after, still in his twenties, become one of America's top theoretical physicists. He seemed effortlessly good at everything. He once asked a graduate student, Leo Nedelsky, to take over some of his lectures at Berkeley: "'It won't be any trouble,' said Oppenheimer,'. . . it's all in a book.'" Finding that the book was in Dutch, which he could not read, Nedelsky demurred. "'But it's such easy Dutch,' said Oppenheimer."

J. Robert Oppenheimer

BULLETIN OF THE ATOMIC SCIENTISTS,
AIP EMILIO SEGRE VISUAL ARCHIVES

As a result, Oppenheimer was superb at identifying weaknesses or inner doubts in others. When he lashed out at fellow researchers throughout his time as a Berkeley professor, he could unerringly select whatever area they felt weakest about, for he knew very well what it was to have an area to feel weak about. Even in his own physics he was aware of his own weaknesses, and felt a crushing sense of self-loathing at the way he regularly pulled back, ever so slightly, just when he might make a major breakthrough.

And then, at Los Alamos, he switched. The sarcasm was dropped, for the duration of the war. But the ability to detect other people's deepest fears or desires remained, and this meant that he became a superb leader of men.

He knew—instantly—that the young postgraduate physicists he needed in large numbers wouldn't pass up work at MIT's radar lab or other famous wartime projects to head to this unknown New Mexico site, simply on the basis of salaries, or offers of future jobs. They'd come only if they thought the top physicists in America were going there. Oppenheimer, accordingly, recruited the senior physicists first; the postgrads followed fast. He even got the authority-resistant genius Richard Feynman on his side. (Tell Feynman that something was a national emergency and his country needed him, and he'd give his mocking New York snort and tell you to get lost.) But Oppenheimer understood that Feynman was so hostile in large part out of furious anger: his young wife had tuberculosis, and in this era before antibiotics it was likely she would soon die. Oppenheimer obtained a rare-as-gold wartime train pass so she could come to New Mexico; he also arranged a place in a hospital close enough to Los Alamos so that Feynman could visit her regularly. In his later memoirs, Feynman joyously mocked every administrator he worked for—with the exception of the two years at Los Alamos, where he did everything Oppenheimer asked.

Oppenheimer's skills came to the fore in the hardest problem Los Alamos needed to solve. America was building two entirely different sorts of bombs. One team, led by Lawrence in Tennessee, took a blunt approach, and was simply trying to extract the most explosive component in natural uranium. When enough of that was accumulated, there'd be a bomb. The Tennessee factories followed the sort of straightforward engineering that Lawrence and other plain-talking Americans liked. Although there were exceptions,
it
was largely pushed by native-born Americans.

Another team, up in Washington State, was taking a more subtle approach. They were starting with ordinary uranium, and then hoping to transform that to an entirely new element, in a process of transmutation much like the one medieval alchemists and even Newton had struggled with in past centuries. The alchemists had wanted to turn lead into gold. The Washington State team, if they succeeded, would transform ordinary uranium into the wickedly powerful, new plutonium metal. Although again there were exceptions, this abstruse approach had been promoted more by the European refugees, educated in a more theoretical tradition.

The Pentagon liked Lawrence and the blunt Americans down in Tennessee, but it turned out that the foreigners' Washington project did best of all. Despite all of Lawrence's screaming and haranguing and threats, even after months of operation the Tennessee factories—giant factories, over a mile in total length; costing over a billion dollars (even in 1940s currency)—could barely sieve out enough purified uranium to stuff into a single envelope. No one was going to be able to make a bomb with that.

But although the Washington team did manage to create its promised plutonium, pretty soon the Los Alamos staff realized that no one could get it to ignite as a bomb. The problem wasn't that plutonium didn't explode. Rather, this new element exploded too
easily.
To make a simple uranium bomb—if the Tennessee team ever got enough purified uranium together—wouldn't be hard. If the amount that would make an explosion was 50 pounds, then you could make a 40-pound ball, and carve a hole in it, and then get a big gun, aim it at the hole, and fire—fast!—the remaining 10 pounds into it. The threshold would be reached so quickly, and the reaction would take place in such a small concentrated area, that much of the explosive U235 form of uranium would convert into energy before it blew itself apart.

The fragile and new plutonium was different. Fire two segments at each other and the plutonium would start exploding before the two halves completely clanged together. You wouldn't want to stand nearby when this started, of course, for there would be a gush of liquefied or gaseous plutonium where the reaction began. But that would be all. There would be almost no nuclear reaction: most of the raw plutonium, not transformed, would simply spatter away.

This is where Oppenheimer's insight and managerial gift came in. Forget about trying to clang two separate pieces of plutonium together. The way to get the plutonium fuel from Washington State to work, he realized, would be to start with a ball of plutonium that was fairly low density. That wouldn't explode. But then you'd wrap explosives around it, and set them off, all at
precisely
the same instant. Do it right, and the ball would crumple inward, so fast that the cascading sequence of E=mc
²
blasts that started spreading within would have enough time to accumulate before the plutonium flew apart.

The technique was called implosion, but the calculations were so hard—how do you make sure the plutonium ball doesn't crumple unevenly?—that there was a great deal of cynicism about whether it could work. (When Feynman first saw what the implosion theorists were trying, he pronounced simply: "It stinks!") Oppenheimer overcame that. He nurtured the first theorists who proposed implosion; he assembled the right explosives experts; as the project grew to a level that under anyone else's supervision it might have fallen apart in a mess of squabbling egos, he deftly manipulated the participants
so
that all the different groups involved worked together in parallel.

At one point he had the top U.S. explosives expert, and the top UK explosives expert, and the Hungarian John von Neumann—the quickest mathematician anyone had met, who would also help create the computer in his long career—and a host of other nationalities all working on it. He even had Feynman joining in! The one prima donna who might have destroyed the effort was the embarrassingly egocentric Hungarian physicist Edward Teller. Oppenheimer neatly led him away, and granted him his own office and work team, even amid the shortages of skilled manpower, to concentrate on his own prize ideas. Teller was vain enough—as Oppenheimer of course understood—that he simply took it as his due; in his pleasure he no longer bothered everyone else.

Paralleling the whole team was a purely British effort, which touched on these theoretical matters as well as practical isotope separation, at Chalk River, near Ottawa. Groves had been suspicious of this group, but Oppenheimer wanted all the help he could get.

Money didn't count. Everyone knew the level Germany was starting from. At one time, at Los Alamos, calculations suggested that a casing of solid gold might help bounce escaped neutrons back into an exploding bomb. (Its weight would also help keep the exploding plutonium bomb intact.) A little later, Charlotte Serber, who ran the library cum document storage room at Los Alamos, received a small package, about the size of a brown paper lunch bag.