Bomb (18 page)

He found the building where Heisenberg was scheduled to talk, entered, located the correct room, and hung his hat and coat in the hall. He walked into the room holding a notebook in his hand. Tucked in one pocket was a pistol. In another was a cyanide tablet, in case he needed to kill himself before being captured.

Berg looked around the small lecture hall. There were about twenty people in the room, most of them professors or graduate students. The room was freezing, due to wartime fuel shortages. Berg sat in the second row.

Heisenberg opened by explaining the basics of a complex mathematical theory called S-matrix, quickly filling the blackboard with a jumble of symbols and formulas. Berg was instantly lost.

“Don't trouble yourself,” called a professor in the front row. “We all know that.”

So Heisenberg moved on to an even more advanced description of S-matrix theory. Unable to follow Heisenberg's math, Berg focused on the man.

“Thinnish,” Berg wrote in his notebook, “heavy eyebrows … sinister eyes.”

Heisenberg paced as he spoke, a piece of chalk in his right hand, his left hand buried in his jacket pocket for warmth. He noticed the man in the second row staring at him.

“H. likes my interest in his lecture,” Berg jotted.

If he heard anything that led him to believe Heisenberg was close to developing an atomic bomb, Berg's orders were to take the man
hors de combat.
He was prepared to do so. But, as far as Berg could make out, Heisenberg was talking about a completely different subject.

“As I listen, I am uncertain … what to do?” wrote Berg. “If they knew what I'm thinking…”

Heisenberg ended the lecture, and the other professors and students began discussing his theories. Berg's pistol stayed in his pocket.

*   *   *

I
T WAS STILL
there a few days later when Berg showed up at a dinner party at a physics professor's house in Zurich. He spotted Heisenberg inside, surrounded by party guests.

Talk turned from science to the war, and several of the guests started grilling Heisenberg, demanding to know how he could live and work under Hitler, a monster who enslaved countries, murdered Jews.

“I'm not a Nazi,” said Heisenberg defensively, “but a German.”

“Now you have to admit,” one guest challenged, “that the war is lost.”

“Yes,” Heisenberg sighed, “but it would have been so good if we had won.”

Many of the guests were disgusted by this, but Berg was glad to hear it. If the Germans were about to finish an atomic bomb, would Heisenberg really believe the war was lost?

Heisenberg grabbed his coat and headed for the door. Berg followed close behind, catching up to Heisenberg outside. He introduced himself as a Swiss student, and they walked together, chatting in German.

The narrow streets were dark and quiet. There was no one around. It was the perfect moment to kill Heisenberg. But Berg had found no evidence that the man really presented a threat to the Allies.

“Oh, it's so boring here in Switzerland,” Berg said, trying to draw Heisenberg into a political discussion. Berg said he'd rather be in Germany, fighting in the war.

Heisenberg disagreed, politely. He said goodnight and walked into his hotel. The next day he left for Germany.

Berg wrote up his report on the mission and sent it to the OSS. Heisenberg's belief that Germany would lose was another piece of evidence suggesting that Hitler was not about to unleash atomic bombs.

But it was not
conclusive
evidence. Heisenberg and the other German scientists were still in Germany, where fission had been discovered. They were still working—but on what?

“If only we could get hold of a German atomic physicist,” said Samuel Goudsmit, “we could soon find out what the rest of them were up to.”

IMPLOSION

ONE NIGHT IN LATE DECEMBER 1944,
Ted Hall sat alone in his room at Los Alamos, writing a letter. Beside him on the desk lay an open copy of Walt Whitman's famous book of poems
Leaves of Grass
. Hall carefully copied a line of poetry into his letter.

The letter was addressed to Hall's friend Saville Sax, who would take the message to Soviet agents in New York City. Back in New York, Hall and Sax had agreed to set a meeting date using what's known in tradecraft as the “book code.” Each had an identical copy of
Leaves of Grass
. When Hall copied a line of poetry into his letter, Sax would find the line in his book. He'd take careful note of the line number, and then check the table of contents to see how many poems had come before this one. These details gave the date of the meeting. If the passage, for example, was from the twelfth line on the page, Sax would know to meet Hall in December, the twelfth month of the year. If the passage was from the twentieth poem in the book, the meeting would be on the twentieth day of the month. The time of day and location had been agreed upon ahead of time.

Army censors read Hall's letter and passed it on to the post office. They had no reason to suspect its true purpose.

When Sax got the letter, he went to the main branch of the New York Public Library and took out a catalogue listing courses offered at the University of New Mexico. He was thinking of studying there, he told friends, and was preparing for a visit to the campus. With this credible alibi in place, he bought a ticket for the three-day cross-country bus ride.

Sax arrived in Albuquerque and walked to the appointed meeting spot. Hall was just arriving from the opposite direction, and together they turned down a quieter street. Sax reached into his shoe and pulled out a piece of paper—a technical question from Soviet scientists. Hall handed Sax two pages of handwritten pages—everything he'd learned about the plutonium bomb so far.

Back in his hotel room, Sax copied Hall's notes onto a newspaper using milk for ink—milk makes good invisible ink because once it dries it can't be seen unless the paper is heated. He burned Hall's handwritten pages, tucked the newspaper into his travel bag, and got on a bus headed back to New York.

*   *   *

I
N
F
EBRUARY 1945,
American forces crossed the Rhine River and began slicing into Germany. Samuel Goudsmit and the Alsos team followed right behind. In the city of Heidelberg, Goudsmit cornered a physicist named Walther Bothe, a man he'd known before the war.

“I am glad to have someone here to talk physics with,” Bothe said, smiling and shaking Goudsmit's hand. He began telling Goudsmit about some interesting research he'd been doing.

“Tell me,” Goudsmit cut in. “How much did your laboratory contribute to war problems?”

Bothe's expression changed from friendly to nervous.

“We are still at war,” Bothe said. “It must be clear to you that I cannot tell anything which I promised to keep secret.”

“I understand your reluctance to talk,” said Goudsmit. “But I should appreciate it if you will show me whatever secret papers you may have.”

“I have no such papers. I have burned all secret documents. I was ordered to do so.”

Goudsmit didn't buy it. “The fear of a German atom bomb development superior to ours still dominated our thinking,” he said later, “and as we had obtained no real information of their uranium project in all our investigations so far, we were still mighty uneasy.”

The Alsos team learned that Werner Heisenberg, and whatever work he was doing, had recently been moved to a town called Haigerloch.

Goudsmit had only one option. “We had to go farther into Germany.”

*   *   *

A
T
L
OS
A
LAMOS,
Robert Oppenheimer was still losing weight. He hurried around the lab with an anxious, distracted look, sometimes not even noticing when people stopped to greet him.

His scientists were wrestling with the challenge of building a plutonium bomb. Since firing two pieces of plutonium together inside a gun was too slow, the only solution, they reluctantly decided, was to blast the pieces of plutonium together with explosives—a process known as “implosion.” Basically, the idea was to take several pieces of plutonium, about the size of a grapefruit all together. Explosives would be arranged around the plutonium, like a very thick skin around a fruit. The explosives would blast the plutonium together at tremendous speed, creating a critical mass and setting off a chain reaction—and an atomic explosion.

It was a nice theory—but scientists doubted it would actually work. For an implosion bomb to succeed, the inward blast had to be perfectly symmetrical. That is, the force driving the pieces of plutonium together had to be exactly the same from every angle. One scientist suggested a comparison: Imagine surrounding an unopened beer can with explosives and trying to blow the can in on itself without spilling a drop of liquid. That was the challenge of implosion. If the shock waves moving in on the plutonium were not perfectly even, some plutonium would squirt out, instead of being driven in. A critical mass would not be achieved, and the bomb would fizzle.

Oppenheimer reorganized the entire lab, assigning everyone available to various aspects of the implosion puzzle. He gave the hardest job, that of figuring out how to create a perfectly symmetrical explosion, to a chemistry professor named George Kistiakowsky—Kisty for short.

Kisty's first reaction: “Dr. Oppenheimer is mad to think this thing will make a bomb.”

Then he got to work.

*   *   *

K
ISTY QUICKLY REALIZED
that he would need to mold his own plastic explosives. His design called for “a hundred or so pieces,” he explained, “which had to fit together to within a precision of a few thousandths of an inch.” Each piece would have to explode at the exact same time, within one millionth of a second, or the bomb would fizzle.

Getting implosion right required a lot of trial and error. That put Ted Hall at the center of the action.

Hall's new job was to help figure out what happened to a ball of metal when it was surrounded by explosives and blown inward. Working in a small wooden cabin, he assembled test bomb cores that were about the size of a basketball. He hung each heavy core from the ceiling, made a series of measurements, then took the core down.

“Twice I dropped the damn object on my toe,” Hall recalled. “I did it once and everyone was very sympathetic, and then I did it again.”

Hall and a team of scientists took the core to a canyon a couple of miles from the lab. They ringed it with explosives, ducked behind a shelter, and set off the bombs.

Hall then took the bomb core back to his cabin, hung it up again, and performed more tests. The results helped convince Oppenheimer that a plutonium implosion bomb might work. There were hundreds of details to hammer out, but the basic design was set.

“Now we have our bomb,” Oppenheimer told Leslie Groves in late February.

Very few people knew more about it than Ted Hall.

*   *   *

I
N
N
EW
Y
ORK
C
ITY,
Saville Sax delivered Hall's report to his KGB contact, Anatoly Yatzkov. The information was cabled to headquarters in Moscow, which reported that the technical details were of “great interest.”

But Hall's report also caused concern—Soviet spies worried they were being given disinformation. Was Hall really an American double-agent, feeding false data to the Soviets in order to make them waste their time and resources on bomb designs that wouldn't work? This is what Stalin's dreaded head of secret police, Lavrenti Beria, suspected.

“If this is disinformation,” Beria warned KGB chiefs, “I'll put you in the cellar.”

To save their jobs, and probably their lives, Soviet spies needed a second source to corroborate Hall's report. They needed Klaus Fuchs.

On a snowy February morning, Harry Gold was at home in Philadelphia, getting ready for work, when he got a phone call from “John”—the name by which he knew Anatoly Yatzkov. Yatzkov was at a nearby gas station and needed to see Gold right away.

Gold bundled up, left the house, and found Yatzkov at the station, wet and freezing. They hopped on a streetcar and talked just loud enough to hear each other over the car's clanking wheels. Yatzkov's message was short and to the point: Fuchs was in Cambridge. Gold was to go see him right away.

Gold jumped off the streetcar. He traveled to Massachusetts on February 21 and found Fuchs at his sister's home.

“K. welcomed me most warmly,” Gold later reported.

Fuchs led Gold to an upstairs bedroom. He explained that he'd been unable to get away at Christmas as planned; things were just too busy at Los Alamos. Then he gave Gold a packet of papers, “a report,” Fuchs later said, “summarizing the whole problem of making an atomic bomb.” The papers, he said, “included a statement on the special difficulties that would have to be overcome in making a plutonium bomb.”

Fuchs explained that he wouldn't be able to get another leave from Los Alamos—everyone was needed for the final push to finish the bomb. Future meetings would have to be in Santa Fe. He unfolded a street map of the city and showed Gold the Castillo Street Bridge. They would meet there, said Fuchs, on the first Sunday in June, at exactly 4:00 p.m.

On directions from Yatzkov, Gold tried to hand Fuchs an envelope with $1,500 in tens and twenties. Fuchs brushed the money aside.

“It was quite obvious that by even mentioning this, I had offended the man,” Gold reported. “He flatly refused to accept it.”

Gold apologized, picked up the money and papers, and left.

*   *   *

W
HEN
F
UCHS'S REPORT
reached Laboratory Number 2 near Moscow, it was read eagerly by Igor Kurchatov, lead physicist of Stalin's atomic bomb program. Through Hall and Fuchs, Kurchatov learned that a gun assembly bomb with plutonium would not work. This saved the Soviets from going down the same dead end as Oppenheimer's team. Kurchatov also learned that it might be possible to build bombs using the principle of implosion. “Very valuable,” Kurchatov said of the material provided by the KGB. “Exceptional importance.”