When they reached the third floor, he saw no one coming up from the 120th Street entrance, so he asked, “Was this announced?”
“No time for it. Bohr appeared, surprise visit. Urey got the room, word spread.”
It was a good idea to show up, then. Karl had been working for Urey only a short while, so far on calculations for a paper, “Van Der Waals’ Forces and the Vapor Pressures of Ortho- and Paradeuterium.” Not exactly a pulse-pounding subject. But it was solid science and Harold Urey was pressing him to finish and submit to the Journal of Chemical Physics. “It’ll show my grant guy you can do things. I’ve got to get him to renew the two thousand for another year, and he’s talking cheap. I can’t guarantee your job for much longer.”
Urey had a good sense for these things. He had discovered deuterium, the heavy form of hydrogen, and swiftly won a Nobel Prize for it. But Urey was interested in nuclear physics now and thought that chemists, who were the final authorities on identifying elements in tiny concentrations, could play a part. Here was a chance to get up to speed on the furiously competitive field, so far dominated by the Europeans like Niels Bohr.
Karl checked himself out as they walked. His overall gawkiness called attention to his hands and elbows, which often seemed to have minds of their own. He made himself stand straighter, walk firmly, head up. He didn’t know many people here yet and had not tried to breach the perimeter of the nuclear physics group, small as it was. He spent his time pushing his pencil. Urey expected results quickly, because even Nobelists came under tightening screws when the only source of funding lay in private foundations.
Urey had built up a group finding how to isolate medically useful isotopes like carbon 13. His support came in grants from the Rockefeller Foundation, which was pioneering the new field of radioactivity for medical use. But Urey was growing tired of these utilitarian tasks, so he had turned down the Foundation ’s offer to continue the grants.
Karl normally did theory, using his mathematical talents, but lately, Urey made him move into the lab, where he had to do experiments. How far this would go was a mystery, though Karl feared for his future under the rickety funding of all research, in the gathering recession that now threatened to dip into a new depression.
As chance had it, Urey was the first person he saw as they approached the lecture room, hasty heels ringing in the corridor. He was sturdy and compact, with an air of compressed energy. The man who had discovered heavy hydrogen had a bantam energy, pacing impatiently. He hailed each approaching graduate student or assistant professor with “Hey, ’bout to start. Glad you could make it.”
Urey grinned at Karl and Irving. “You’re gonna like this.”
Karl said, “Hope so,” then added, “Sounds great.”
This was entirely phony, but he owed Urey a lot. He had returned to New York from France in the fall of 1938 looking for a job, since his savings were vanishing and his mother could spare him only a paltry fifty-five dollars a month. Urey had not been on Karl’s thesis committee, but he sympathized with those who suffered from the pervasive bias against Jews. Urey had sought a job for Karl, but the chemical companies didn’t want a mathematical chemist, or a Jew.
Karl had growled at Urey then, saying, “They hire B students but not the best.” Urey had shrugged, chewing gum, his shoes propped on his desk. These little habits had annoyed Karl when he’d looked for a thesis professor in 1933, and he saw now that error had major consequences. His own thesis professor, Miller, had been a classier guy but made no effort on Karl’s behalf beyond the minimum.
Karl had become even more mathematical in Paris, by self-study, his preferred way to learn things. Now he might be facing unemployment within months, even though he would soon be Urey’s last assistant; the others Urey had already let go. It was a good idea to be enthusiastic about whatever tickled Urey’s nose.
He and Irving walked into the lecture room and sat near the front. About two dozen people were in the first few rows and Karl took a moment to look around, getting an idea of who was here. He studied the faces with care, thinking, Kind of like Daniel looking over the lions when he strolled into their den.
Enrico Fermi was talking to Niels Bohr, standing in front of the blackboard. Karl had seen a photo of Fermi arriving on the liner Franconia on the New York Times’s front page. He was the latest Nobel physicist, a fairly short man in a business suit, with an open, friendly Italian face and animated eyes. The Times had played up the intrigue of how Fermi and his family had left Italy to receive the prize in Sweden and then sailed off to New York, while the Italian authorities were readying a big reception for him back in Rome.
The Fermis had managed to get their household goods shipped, as if to a new home in Rome, but in fact to America. Their break with the Mussolini regime was sudden and shocking, making headlines. They were driven out by the new racial laws the Fascist government had instituted against Jews, copying the Germans. Fermi’s wife was a Jew. Those Jews who could were streaming out of Europe, but most had no way to do so.
Karl studied the two. Fermi was frowning, Bohr gesturing, both talking—at the same time—and the seminar had not started. Karl sensed a tension rising: feet shuffling, a fretful murmur. By now there were maybe twenty people, all men, in the rectangular rigidities of the lecture hall, and Karl sniffed in the air a heady sense of something new, fresh, urgent. All without knowing what Bohr was going to say.
Others he knew because Irving had pointed them out before, but Karl had been uneasy about approaching them. The heavyset bearlike man in the front row was Edward Teller—one of the “Hungarian geniuses,” as Urey had once described him. Teller spoke with animation, making his points with bushy black eyebrows that moved like a major feature of his dark face.
Another one sat beside Teller. Karl studied the scowling, animated face with thick lips and flat cheekbones, topped by thick brown hair, and groped for the name. Ah yes, Leo Szilard. Everyone in the front row wore three-piece suits in the European manner, though some were Americans. Urey was not a big “dresser-upper,” as Karl’s mother always put it, meaning people who used clothes to impress others. Urey was still playing host at the doorway, so Karl studied the rest of the crowd—
Then he saw it. Written out on the blackboard in a European hand was the reaction formula.
The formula spread across the blackboard was easy to follow. Slam a neutron into a uranium 235 nucleus—the lighter version of the element, Karl recalled—and you get out a batch of barium plus some krypton, with three more neutrons left over.
In his head Karl worked out the energy implications of the formula—and gasped. People had done this. Broken a huge nucleus into two middle-size ones plus more neutrons. Germans had . . .
The main point was that the collision gave off two hundred million times as much energy as an ordinary atom’s reactions with other atoms. He was used to the low-energy end of science, the province of chemists. Now came this utter surprise, opening doors to—
“Good afternoon,” Harold Urey said, coming to the front. “Thanks for coming on short notice. Professor Niels Bohr”—a nod—“arrived with major news, and I thought you should hear it from him.”
Scattered applause, unusual in a seminar at the beginning of a talk. Bohr got distracted by some slide projector problem.
Karl could see the leading lights of the nuclear physics group lean forward intently—Isidor Rabi’s team, and Eugene Wigner, up from Princeton. These faces he had learned from watching carefully in past seminars, but he had met none of them. They batted in another league.
Leo Szilard, the Hungarian physicist, sat with Edward Teller, who was scowling intently at the board. Karl had seen them in the halls, without ever speaking to them. He was a chemist fresh from his PhD and they were sharp, quick, well-known physicists with much experience. Their field was changing fast and he had picked up on some of it while in Europe, but as a chemist he seldom had anything to do with them.
Bohr made polite introductory remarks as he sl
id a slide into a projector. Urey pulled down a white screen and clicked on the projector. “I have done some calculations, somewhat based upon my own model, which treats a nucleus as a liquid, so the nuclear force is something like a surface tension. Here is a rough outline of that.”
Karl had not seen the nuclear work summed up in such crisp fashion. It was all there, as the label made clear: CURVE OF BINDING ENERGY. The higher up the curve, the tighter a nucleus of an element held together. The curve had a maximum around iron, where the total number of protons and neutrons, the nucleons, was sixty. It fell off sharply for the light elements, and more slowly for the heavy ones, and uranium was highlighted at the far end, U-235. That was the less common isotope, less than a percent of the major one, U-238.
Curve of Binding Energy
Karl had studied nuclear physics at the Sorbonne, but not systematically, and he had never seen this curve before. But he had read about bits of it in papers, while studying by himself in Paris—when he wasn’t distracted by falling in love.
Bohr spoke carefully, slowly, in his Danish-accented English. “Two Germans in Berlin—Otto Hahn, a chemist, and Fritz Strassmann, physical chemist—have been following on Enrico’s work”—a nod to Fermi—“by bombarding uranium with neutrons.”
Karl had seen some uranium once, a dense, purple-black metal that had modest commercial use as a pottery glaze. Otherwise, worthless. But not any longer.
“So they worked away. After some slamming of neutrons into uranium metal, element ninety-two, they noticed something odd in their beaker—barium! They were startled! Like Enrico, they figured a neutron might hit a nucleus and chip off a few protons—make it into thorium, say.” Bohr waved his hands, shrugged. “Thorium is element ninety. But barium!—it’s element fifty-six. And iodine. They split uranium in two!”
And released lots of energy, Karl thought, but he kept quiet. That was what the equation said, but nobody in the room uttered a word.
Bohr slipped into some recent history, bringing the audience slowly toward what this meant. The Berlin experiments came directly from Enrico Fermi’s work with neutrons four years earlier. He had bombarded uranium with neutrons and discovered that it produced dozens of radioactive substances. Fermi thought he had made elements heavier than uranium, and everyone had believed him. But Otto Hahn and Strassmann had now shown that the products were radioactive forms of much simpler elements, barium and iodine.
“So Hahn wrote to Lise Meitner on December 19, 1938—she showed me the letter—‘Perhaps you can put forward some fantastic explanation,’ Hahn wrote.” He paused and faced the audience. “So she did.”
Bohr was something of a dramatist, Karl saw. For this result, justifiably so.
Bohr turned to the blackboard, as if considering launching into the meaning of the equation there, and the curve on his slide—then turned back. “After Hitler took over Austria last March, her situation became desperate.”
Karl thought, Along with hundreds of thousands more left-wingers and Jews.
Bohr shook his head. “Meitner was lucky to escape. Kurt Hess, a Nazi chemist, warned the authorities she was about to flee. Last July she took a train under cover to the Dutch border and some physicists argued her way across. She left Germany forever with ten marks in her purse. Before she got out, Otto Hahn gave her a diamond ring to bribe the frontier guards, if needed. Shortly afterward, the Gestapo killed a Jew who had worked with her. Apparently in a fit of rage.”
A murmur from the audience. There were more stories like this all the time now.
Bohr spread his hands in apology. “I could not land her an appointment; there was no money. But she went instead to Stockholm, where she took up a post at a laboratory, despite the prejudice against women in science. There she established a working relationship with her nephew, Otto Frisch. They cracked the problem.”
Karl thought, So the Nazis drove out the Jew who really understands this. And those left behind . . .
Bohr said, “Therefore, quite rightly, Lise Meitner and Otto Frisch ran an experiment over the holidays to test their idea—that the fragments would move very fast, spraying electrons and losing energy they could see with a Geiger counter. There it was!”
He turned to the equation and gestured to the curve of binding energy. “The energy yield they found fits the model too. They came to Copenhagen to tell me about it. Frisch calls it ‘fission’—from the biologists’ term for the division of cells.” A final wave of his hand to the audience, coming to a stop when he pointed to Fermi. “And so I’ve come to tell you.”
Fermi seemed to be calculating something in his head. Edward Teller’s voice boomed from the front row. “Does it release enough neutrons to start a chain reaction?”
“We do not know,” Leo Szilard answered in his quick, darting English, before Bohr could. “Never mind, Edward, I already gave the patent on this idea, of the chain reaction, to the British Admiralty.” A decisive nod of his head. “Years ago.”
“Why?” Fermi asked.
“To keep the idea secret, unpublished.”
A silence fell as everyone thought this through. Fermi had been silent so far, his calm face showing no reaction. Karl knew something of what Fermi had done and saw a collision coming. Fermi rose and wrote some equations on the blackboard, musing. “In Rome we screened very carefully, looking only for alpha particles. . . .”
Bohr said, “The really energetic barium and iodine, they would stop very fast in a screen.”
“So we missed them.” Fermi sighed. “The screen we used, it stopped the barium and iodine from getting into the residues we checked.”
Fermi turned to Bohr with weary eyes and a slanted smile, and shrugged. “So we thought we had discovered new elements. We even named them—hesperium, ausonium. Wrong! Mythical! They were ordinary old barium and iodine. We were careful—too careful.” He grew more emotional as he said this, losing his mild manner. Now, there’s the Italian in him, Karl thought.
Harold Urey said, “Recall Ida Noddack? She’s a chemist—German, right?—wrote a paper, ‘On Element 93.’ About your experiments, Enrico. She suggested you’d failed to chemically eliminate all elements lighter than uranium, rather than only working down to lead. Barium, iodine—you missed those.”
“We did not think it possible to make light elements from heavy,” Fermi said.
“She didn’t just point out the flaw in your chemical proof, though.” Urey stood, walked to the blackboard, picked up chalk, thought better of it, and put it down. Karl had worked for the man a year now and he could see the slight jumpy energy in his gestures. “She suggested that the nucleus breaks up into several large fragments. All the way back in 1934.”
Fermi said softly, “Noddack offered no experimental proof or theoretical basis for this possibility.”
“So she was generally ignored.” Urey’s eyes danced with mirth. “Maybe because she was just a chemist—or a woman?”
Karl knew many chemists felt all the glory had gone to the physicists in the twentieth century. They had profoundly wrenched all conceptions of the world around them. Quantum mechanics undermined the small world of atoms, and relativity shook the larger cosmos, with its weird mechanics and models of the universe as a whole. But here in nuclear physics the chemists were essential, because they could tell what elements emerged from the disruptive experiments, which could now change one element to others.
There were a few chuckles, but otherwise the room was silent. The drama of Bohr’s revelation could be seen on Fermi’s face. His words came out cautiously, his features stern and still grappling with these ideas. Karl watched closely and saw a small tic in Fermi’s left eye, as though the man was under pressures he did not want to show. His lips moved silently; he was deep in thought.
The others could see this reaction too. Fermi had just won the Nobel Prize for demonstrating the existence of new radioactive elements, brought about by slow neutrons. Quietly he said, “We entirely missed the big effect. The heavy elements, the
y split. The Latin is, they fission.”
Karl already knew from corridor gossip that Teller was moody, tireless, given to fits of quick laughter and bursts of anger. But now he leaned back and said lightly, “Suppose Enrico had paid attention to Noddack, eh?”
Bohr frowned. “Looked for the lighter elements?”
Teller nodded energetically. “Maybe removed his shielding, too. Found this fission, could have.”
“He would’ve gotten the Nobel even sooner,” Bohr said. “So?”
“No, think.” Teller wagged a scolding finger. “Germany, the Soviets—they take the military application of science far more seriously than these Americans. They would have started work on the obvious.”
So there it was, out in the open. The obvious was a device beyond comprehension, a superweapon.
“Making a chain reaction go out of control?” Szilard nodded. “I thought of this in 1932, while walking to my office at Imperial College, London. To thus make a . . . bomb.”
“They would be very far ahead, Germans, the Soviets. So Fermi’s mistake was perhaps fortunate.”
Another long silence in the room. “But not for long, not now,” Urey said.
Urey’s American speech style was more clipped, more direct than that of the formal Europeans. Karl thought about this through another long silence. American speech felt sawed off, forceful but less precise than the long, languid sentences of the Hungarians—Teller and Szilard, particularly. Karl was a mere twenty-six years old and these Europeans seemed vastly more mature, seasoned by millennia of war and trouble. It seemed impossible for him to imagine calling them colleagues.
Karl saw that for Fermi, the news came as a profound embarrassment. His somber eyes searched the floor, mouth turned down in a puzzled scowl. The elements beyond uranium he had partly been awarded the Nobel Prize for discovering had not been more massive than uranium; they came from fission.
The Berlin Project Page 2