“The government. Another term has crept about. Uranmaschine—a uranium machine, perhaps a reactor.”
“What agency is behind this?”
“The German Army Ordnance Office.”
“And still we hear nothing from Roosevelt?” Karl asked.
“I will ask again my agent in this, Alexander Sachs.” Szilard eyed them carefully. “I am not encouraged by your government’s speed.”
“Roosevelt is going for a third term, and he needs votes.” Karl described the crowds he and Marthe had seen flocking to the German-American Bund rally. “Plenty of people don’t want to even think about this war, much less jump into it.”
Urey shrugged and sighed. “Our investors move faster than bureaucrats. It’s the American way.”
• • •
Karl used his same methods to work forward in the seminar room when the fission group met. With Fermi and the others in the front row of the regularly scheduled talks, there was plenty of reason to shut up. Generally speaking, you aren’t learning much when your lips are moving. But now he was working on centrifuges and had genuine curiosity about how physicists dealt with the quickly expanding possibilities.
They still had to use chemical means to select out isotopes produced by neutron bombardment. Karl knew the pitfalls of these methods and pointed them out. Some hastily done experiments had missed nuances. The prime example of missing the point of an experiment was, of course, Fermi’s not seeing the uranium fission phenomenon himself, through years of experiments.
Fermi himself recognized this, and in the seminars came to see Karl as a useful collaborator. He was working with two Nobel winners! Rae loved to hear about all this.
The Ureys helped the Fermis buy a home in New Jersey, just down the block from the Ureys’. Karl was delighted to get an invitation to a housewarming dinner party. Though the whole world worsened, Karl’s world improved.
• • •
Harold Urey was studying the yard of the Fermis’ new home as Karl and Marthe approached. He was bent over, frowning at the grass, hands on his knees. Then he sprang up with a grin.
“Karl! Marthe! I offered to help Enrico and Laura free their lawn of intruding crabgrass. They never heard of it.”
“Very generous of you,” Marthe said. “And . . . what is it?”
Urey waved his arms around. “This! Their yard is all crabgrass!”
That got a laugh repeatedly throughout the dinner party that followed. Apparently crabgrass had no foothold in Italy, or, Marthe said, in France. It was an American irritant. So too were the steps the Fermis had to take to become American citizens—bureaucratic snarls. The Fermis felt they could not just get by on visas, as Columbia University had advised. If they were to help the fight for democracy, they had to get rid of their Fascist Italy ties, embrace their new country. This brought applause around the dinner table. “Bureaucracy is the crabgrass of government,” Urey said.
They were enjoying a risotto Laura had prepared. They had not anticipated the ample baked haddock that followed as well, shimmering with fragrant butter and herbs. Yet no one turned it away.
“I hear that you and Leo have found a possible funder,” Laura said to Karl, across the table.
“Possible. Never know until the check comes in.” It seemed best to be guarded in open company.
“I am wondering when we will hear from the Einstein letter,” Urey said, helping himself to a big chunk of haddock.
Laura Fermi considered this, her dark eyes flashing. “The letter your chairman Professor Pegram sent, asking in a weak way, for that admiral to perhaps listen to this man Fermi—recall it?”
Karl did. It had been passed around at the lunch at the King’s Crown Hotel. He savored the delicious fish, had a glass of Chianti. The Fermis did not share his taste and served a red even with fish, but he was polite, too, and maybe Italians differed from the French. He sat back to hear what this smart, quick woman had to say. Laura Fermi shared a lot of qualities with Marthe. “I thought it a bit awkward.”
Laura nodded. “That was, I suspect, the first time you scientists tried to form connections between science and government.” She paused for dramatic effect. “Very American. I am not surprised that it does not seem to have worked.”
“Why?” Urey asked, frowning with puzzled doubt.
“Why not work? Because you are-a new at it.” Laura spread her hands, as if this was obvious.
“New?” Leo Szilard was puzzled as well.
“Europeans are used to the government paying for research, because we have so many authoritarian nations,” Laura said. “Universities are government-controlled—in Germany, Italy, Hungary. That is where the money is! Americans, the money comes from companies.”
Marthe said, “I see. Enrico went to see the admiral. A man just off the boat, who speaks like me with a thick accent, sprinkled with extra vowels—he goes! Those who wrote to Roosevelt to ask for help—Szilard, Einstein, Teller—all Europeans.”
Urey pointed at Karl. “He had a hand.”
“A small one,” Karl said. “Tiny.” He wondered if he was blushing.
Laura conceded, “Enrico has never learned to bang with his fist on a table.” She leaned to her left and kissed him with a loud smack.
“In Italy, no foreigners would have succeeded, of course,” Laura continued. “None! You Americans have not found your way out of your ivory towers.”
Karl saluted her with his glass. “She is right. Americans are at a disadvantage.”
It was embarrassing that he had never seen this. As talk ricocheted around the table, he saw that scientists in democracies had no strings to government at all, or maybe only long strands of red tape. A dictator decrees; a president asks Congress for permission to organize, then for cash. Hitler had the advantage.
3.
December 15, 1939
The next day Urey came into Karl’s office with a letter in his hand. “Roosevelt’s authorized an Advisory Committee on Uranium.”
Karl rose from a desk covered with sheets of calculations. “Wow, great.”
“Its head is a pretty old guy,” Urey said, “must be sixty-five. It’s a secret project too—a result of the Einstein-Szilard letter.”
“Who’s in it?”
“Me, Conant—here—” Urey tossed a sheet across his desk. “The usual crew.”
“Physicists,” Karl said, reading the list.
“I didn’t tell you before because it’s confidential.”
“Uh, when did it happen?”
“October eleventh.”
“That was months ago.”
“Yeah. Really confidential. I just got our first money from it.”
Karl beamed. “How much?”
“Six thousand dollars.”
“What?”
“Roosevelt has to do it out of his hip pocket. No line items in the budget apply.”
Karl slammed his fist on the desk, remembering suddenly Laura Fermi’s remark about Enrico. “Bloody hell!”
Urey nodded sourly. “You’ve got to get back to your rabbi. We should be flying ahead by now, damn it. I’m stalled out, by crabgrass bureaucrats.”
• • •
The meeting turned out to be mostly a bureaucratic kerfuffle. The investors—all bankers in one way or another—wanted Columbia to sign over all patent rights, and Columbia wasn’t quite that dumb.
Urey and Karl did what they could, but the investors wouldn’t budge. Rabbi Kornbluth was solid with them too, his skeptical eye roving the room. Karl could sense they were on the edge, tempted but cautious with a wholly new area of science.
He now had more information leaked out of Europe, so he used it. Detailed letters and stories—of boxcars stuffed with whole families pressed in hard without food or water, whole villages raked clean, bodies tossed into ditches.
“They’re rounding up Jews!” Karl cried to the investors, in a Fifth Avenue restaurant he would never have been able to afford. His audience just looked embarrassed
. Misjudging, he pushed harder still. “They’re taking away even rabbis.”
That didn’t work either. The investors blinked. This was news, but Karl had crossed a line. People didn’t shout at them, no; they had money, after all.
But Szilard saw the thin wedge of an opening.
So days later Szilard brought Einstein into the Plaza—installed in a suite, no less. How Szilard had managed this he would not say. When Einstein came in by cab from the train station, the old man looked a bit tired. He was more than a bit bemused as the investors trooped in, five of them. They wore black business suits and white shirts and solemn ties, looking to Karl like morticians. Einstein had on baggy pants, a wrinkled white shirt, and no socks in brown loafers. But he was Einstein.
Silence in the room. The great man opened by handing around a postcard a friend had sent, “Years ago, when Germans could make fun of Hitler.”
“It’s you, with a glow behind you like a saint,” Szilard noted. “And Hitler as a raving fool. I suppose the makers are now in prison?”
“Ja,” Einstein said, shaking his head. Szilard spoke quickly, reviewing the chances of uranium leading to a bomb. The investors said nothing.
“Ja,” Einstein said, “this could be a veapon of gross power.”
“You believe it could also have industrial uses?” the more courageous of the five asked.
“I know not of this. I rely”—a nod toward Szilard and Urey and Karl—“on who know besser dan I.”
“There is also the argument,” another black-suit said, “that this can stop the Germans from killing so many Jews.”
“By killing many Germans, ja. It may be so.” A long, sour sigh.
To Karl, that seemed to say it all.
4.
April 1940
Harold Urey was as good a diplomat as any around, so Karl asked him to make an overture to Fermi. Karl simply did not have the courage to knock on Fermi’s door and ask the great man to work on the basic centrifuge physics problems with him.
But a day later he did just that, after getting the nod from Harold. Fermi was a mild-mannered man, slightly shorter than Karl. Karl opened by asking about the Fermi team’s experiments to find the number of neutrons emitted by the fissioning uranium. The results of these experiments were just out, published side by side in the April issue of the Physical Review. They showed that a chain reaction might be possible, since the uranium emitted about two more neutrons when it fissioned.
Fermi’s office had tables stacked with scientific papers and bookshelves standing bare. “You did not bring your references from Rome?” Karl said to ease into the conversation.
“I-a have-a about four books, in all. One by my boyhood friend, Enrico Persico. I keep for sentimental. Rest are numerical tables, and your wonderful Rubber Bible.”
This meant the Chemical Rubber Company Handbook of Chemistry and Physics, the CRC bible, which Karl had used since the 1920s. It was clear Fermi didn’t need books. He worked out everything for himself. Just what Karl needed.
He had already seen that Fermi often raised an objection in a seminar and would not allow matters to proceed until the speaker had dealt satisfactorily with the objection. If the speaker couldn’t, the seminar was over. “Fermi is a physicist with a capital F,” Szilard had said, smiling.
Karl described the problem of the centrifuge mechanics and they set to work, calculating. At the rotor’s bottom cap a heater turned uranium hexafluoride into a vapor. That condensed out on the top cap. The fast spinning drove the condensed vapor to the cylinder’s wall. The heavier U-238 stacked up there and flowed down the walls, carrying just a tiny bit less of the U-235. Circulate the fluids thousands of times and the U-238 got richer in one channel, the U-235 richer in another. Slowly, slowly, the isotopes separated out.
Fermi started to calculate on his own, saying nothing, and in a direct, simple way found the essential point. The ability of a centrifuge to separate U-235 from U-238 was proportional to its length and to the fourth power of the peripheral speed of its rotor.
Karl went through all this, fearing that Fermi would find an error. But he just nodded. Fermi squinted at the blackboard and said, “So double the speed, we get sixteen times the U-235. But rotor energy, it goes only as square of speed. So is more energy efficient than I expected.”
Karl had taken a week to be sure this was true. Fermi had found his way through in ten minutes, a startling example of deft thinking. Karl saw that this stemmed as much from Fermi’s appraisal of the art of the possible, as from his innate skill and intelligence. He simply saw into the physics and selected what he pleased.
Yet as he watched Fermi work at the blackboard, the equations marching on with no step skipped, he recalled that Fermi was modest to his core. He had heard many stories about the man’s self-effacing nature, his dislike of pomp. When Mussolini had appointed him to the Italian Royal Academy, with the title Eccellenza, Fermi drove himself to the first meeting. Since Mussolini was to address the academy, the other Excellences had arrived in big limousines. Guards stopped Fermi in his old Fiat, their weapons drawn. Without pause Fermi said, “I am the driver of His Excellency Signore Enrico Fermi.” The guards said, “Drive in, park, await your master.” Fermi had waved to the guards as he left later, still alone in the Fiat.
Fermi came to a conclusion and reached for the CRC book. In a moment he jotted down some numbers and said, “A plausible rotation rate means . . . ah . . . a linear speed at the end of the rotor of about three hundred meters per second. Steel or aluminum can handle that.”
“Nearly the speed of sound in air,” Karl said.
Fermi nodded, brushing chalk from his suit jacket. “And nearly the speed of a low-caliber bullet.”
In an hour Fermi had redone what Karl had taken weeks to figure out. Karl burned with silent embarrassment. This was what genius looked like, up close—a casual speed and grasp, obliviously enjoying the work. But his quickly jotted equations had told Fermi one more point. “Ah, I see. The major difficulty with a centrifuge is that as the top speed of its rotor increases, it passes through various critical rotation frequencies.”
Karl nodded. “That makes it vibrate like a thin rod. This clearly puts serious engineering demands on its bearings and damping mechanisms.”
“Ah, so. Si. So let us attack that.” Fermi’s hands flew across the blackboard, the chalk clicking. He never talked while calculating, letting his hands speak for him.
It took two more hours, with Karl catching some small errors and adding a term to one equation. The windows darkened, lights came on. Otherwise this was Fermi’s show, and he brightened as results came into clear view, fresh problems arose, got worked around, and they devised together some rule-of-thumb solutions.
“We have to speed up the rotor when it gets to those resonances,” Karl said. “Just zoom through them so they can’t rattle the rotor to pieces.”
Fermi nodded. “Will take a lot of control. Very fast. You know, Pauli called this sort of thing schmutz physics. Dirt physics.” They both chuckled. Pauli was one of the founders of quantum mechanics and a notoriously nasty critic.
A knock at the door, then Urey burst in without waiting. “I just got off the phone with that rabbi, Kornbluth. The investors, they’re in for seventy-five thousand dollars.”
5.
February 8, 1940
The program’s first act was to get Columbia University to sign a contract with Westinghouse Research Laboratories. It paid them tens of thousands of dollars to develop a rotor of about eight inches in diameter, to be spun at five hundred revolutions per second. That rate limited the rotor’s length to about forty-two inches, set by the expected vibration waves in a steel or aluminum rotor. The electromagnetic bearing had to be built to exact specifications, down to a hundredth of a millimeter.
Fermi devised a way to strengthen the magnetic field, too. Karl had not even thought of that element. The man was a quiet miracle.
They all pitched in, working with some Columbia
and Westinghouse engineers. Fermi was at ease with these more practical men too. The design of the first major Columbia machine was finished in January 1940. Before Fermi, Karl had thought it would take far longer.
• • •
Soon enough, the arguments came.
“So this may well be the way to go,” John Dunning ended with a flourish, a sweeping hand gesture at his projected slide. It showed all the methods for separating U-235 from U-238, as proposed by groups around the country.
Electromagnetic mass spectrograph
Liquid thermal diffusion separation
Gaseous diffusion separation
Gas centrifugation
John Dunning
“I’m for number three.”
Dunning was a big, round man with a powerful voice that rolled over the Nuclear Seminar, as it had been innocuously named to seem just another tiny academic field. Yet they were all talking about making a bomb that could kill cities.
Karl kept quiet. He doubted that the diffusion methods would work well. Nobody had built even a prototype.
The first method, flinging uranium nuclei around with magnets to let the heavier U-238 fly outward, and so separate, looked really expensive. The last in Dunning’s list was the centrifuge they already had working. Why list it last?
Harold Urey rose to object. “It’s too early to pick a winner. Your number one, the mass spectrograph, that’s from Lawrence in California. Sure, using his big cyclotron magnetic field to spread out the U-235 from the U-238 is physically clear—but what’s the efficiency?”
Dunning nodded and waved his left hand as if he were batting away a fly. “I kind of agree, Harold. That’s why I think a process I’ve been studying in my lab, number three, can do the job on a mass scale. We know diffusion pretty well. It’s just quicker.”
The crowd was bigger than Karl had ever imagined, in one of Columbia’s biggest rooms. There were nearly a hundred men and a woman nuclear physicist fresh off the boat, too. Fermi had helped her and her husband, a well-known chemist named Joe Mayer, get out of Germany in time. Maria Goeppert Mayer sat just in front of Karl, nodding. She had easily followed it all, taking notes, though much of it had to be new to her. Her questions were clear, direct, and got at interesting parts of the problem Karl had not even thought of, such as flow turbulence.
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