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He looked at Jacky, and saw that pleading expression intensified. He realized what was on her mind: she was desperately afraid he was going to reject Georgy.
"I tell you what," Greg said, and he lifted Georgy onto his knees. "Why don't you call me Uncle Greg?"
iv
Greg stood shivering in the spectators' gallery of an unheated squash court. Here, under the west stand of the disused stadium on the edge of the University of Chicago campus, Fermi and Szilard had built their atomic pile. Greg was impressed and scared.
The pile was a cube of gray bricks reaching the ceiling of the court, standing just shy of the end wall, which still bore the polka-dot marks of hundreds of squash balls. The pile had cost a million dollars, and it could blow up the entire city.
Graphite was the material of which pencil leads were made, and it gave off a filthy dust that covered the floor and walls. Everyone who had been in the room awhile was as black-faced as a coal miner. No one had a clean lab coat.
Graphite was not the explosive material--on the contrary, it was there to suppress radioactivity. But some of the bricks in the stack were drilled with narrow holes stuffed with uranium oxide, and this was the material that radiated the neutrons. Running through the pile were ten channels for control rods. These were thirteen-foot strips of cadmium, a metal that absorbed neutrons even more hungrily than graphite. Right now the rods were keeping everything calm. When they were withdrawn from the pile, the fun would start.
The uranium was already throwing off its deadly radiation, but the graphite and the cadmium were soaking it up. Radiation was measured by counters that clicked menacingly and a cylindrical pen recorder that was mercifully silent. The array of controls and meters near Greg in the gallery gave off the only heat in the place.
Greg visited on Wednesday, December 2, a bitterly cold, windy day in Chicago. Today for the first time the pile was supposed to go critical. Greg was there to observe the experiment on behalf of his boss, General Groves. He hinted jovially to anyone who asked that Groves feared an explosion and had deputed Greg to take the risk for him. In fact Greg had a more sinister mission. He was making an initial assessment of the scientists with a view to deciding who might be a security risk.
Security on the Manhattan Project was a nightmare. The top scientists were foreigners. Most of the rest were left-wingers, either Communists themselves or liberals who had Communist friends. If everyone suspicious was fired there would be hardly any scientists left. So Greg was trying to figure out which ones were the worst risks.
Enrico Fermi was about forty. A small, balding man with a long nose, he smiled engagingly while supervising this terrifying experiment. He was smartly dressed in a suit with a waistcoat. It was midmorning when he ordered the trial to begin.
He instructed a technician to withdraw all but one of the control rods from the pile. Greg said: "What, all at once?" It seemed frighteningly precipitate.
The scientist standing next to him, Barney McHugh, said: "We took it this far last night. It worked fine."
"I'm glad to hear it," said Greg.
McHugh, bearded and podgy, was low down on Greg's list of suspects. He was American, with no interest in politics. The only black mark against him was a foreign wife: she was British--never a good sign, but not in itself evidence of treachery.
Greg had assumed there would be some sophisticated mechanism for moving the rods in and out, but it was simpler than that. The technician just put a ladder up against the pile, climbed halfway up it, and pulled out the rods by hand.
Speaking conversationally, McHugh said: "We were originally going to do this in the Argonne Forest."
"Where's that?"
"Twenty miles southwest of Chicago. Pretty isolated. Fewer casualties."
Greg shivered. "So why did you change your minds and decide to do it right here on Fifty-seventh Street?"
"The builders we hired went on strike, so we had to build the damn thing ourselves, and we couldn't be that far away from the laboratories."
"So you took the risk of killing everyone in Chicago."
"We don't think that will happen."
Greg had not thought so, either, but he did not feel so sure now, standing a few feet away from the pile.
Fermi was checking his monitors against a forecast he had prepared of radiation levels at every stage of the experiment. Apparently the initial stage went according to plan, for he now ordered the last rod to be pulled halfway out.
There were some safety measures. A weight
ed rod hung poised to be dropped into the pile automatically if the radiation rose too high. In case that did not work, a similar rod was tied to the gallery railing with a rope, and a young physicist, looking as if he felt a bit silly, stood holding an axe, ready to cut the rope in an emergency. Finally three more scientists called the suicide squad were positioned near the ceiling, standing on the platform of the elevator used during construction, holding large jugs of cadmium sulfate solution, which they would throw onto the pile, as if dousing a bonfire.
Greg knew that neutron generation multiplied in thousandths of a second. However, Fermi argued that some neutrons took longer, perhaps several seconds. If Fermi was right, there would be no problem. But if he was wrong, the squad with the jugs and the physicist with the axe would be vaporized before they could blink.
Greg heard the clicking become more rapid. He looked anxiously at Fermi, who was doing calculations with a slide rule. Fermi looked pleased. Anyway, Greg thought, if things go wrong it will probably happen so fast that we'll never know anything about it.
The rate of clicking leveled off. Fermi smiled and gave the order for the rod to be pulled out another six inches.
