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 weighted 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 sulphate solution, which they would throw on to 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 levelled off. Fermi smiled and gave the order for the rod to be pulled out another six inches.
More scientists were arriving, climbing the stairs to the gallery in their heavyweight Chicago-winter clothing, coats and hats and scarves and gloves. Greg was appalled at the lack of security. No one was checking credentials: any one of these men could have been a spy for the Japanese.
Among them Greg recognized the great Szilard, tall and heavy, with a round face and thick curly hair. Leo Szilard was an idealist who had imagined nuclear power liberating the human race from toil. It was with a heavy heart that he had joined the team designing the atom bomb.
Another six inches, another increase in the pace of the clicking.
Greg looked at his watch. It was eleven-thirty.
Suddenly there was a loud crash. Everyone jumped. McHugh said: ‘Fuck.’
Greg said: ‘What happened?’
‘Oh, I see,’ said McHugh. ‘The radiation level activated the safety mechanism and released the emergency control rod, that’s all.’
Fermi announced: ‘I’m hungry. Let’s go to lunch.’ In his Italian accent it came out: ‘I’m hungary. Les go to luncha.’
How could they think about food? But no one argued. ‘You never know how long an experiment is going to take,’ said McHugh. ‘Could be all day. Best to eat when you can.’ Greg could have screamed.
All the control rods were re-inserted into the pile and locked into position, and everyone left.
Most of them went to a campus canteen. Greg got a grilled-cheese sandwich and sat next to a solemn physicist called Wilhelm Frunze. Most scientists were badly dressed but Frunze was notably so, in a green suit with tan suede trimmings: buttonholes, collar lining, elbow patches, pocket flaps. This guy was high on Greg’s suspect list. He was German, though he had left in the mid-1930s and gone to London. He was an anti-Nazi but not a Communist: his politics were social-democrat. He was married to an American girl, an artist. Talking to him over lunch, Greg found no reason for suspicion: he seemed to love living in America and to be interested in little but his work. But with foreigners you could never be quite sure where their ultimate loyalty lay.
After lunch he stood in the derelict stadium, looking at thousands of empty stands, and thought about Georgy. He had told no one he had a son – not even Margaret Cowdry, with whom he was now enjoying delightfully carnal relations – but he longed to tell his mother. He felt proud, for no reason – he had made no contribution to bringing Georgy into the world apart from making love to Jacky, probably about the easiest thing he had ever done. Most of all he felt excited. He was at the beginning of some kind of adventure. Georgy was going to grow, and learn, and change, and one day become a man; and Greg would be there, watching and marvelling.
The scientists reassembled at two o’clock. Now there were about forty people crowded into the gallery with the monitoring equipment. The experiment was carefully reset in the position at which they had left off, Fermi checking his instruments constantly.
Then he said: ‘This time, withdraw the rod twelve inches.’
The clicks became rapid. Greg waited for the increase to level off, as it had before, but it did not. Instead the clicking became faster and faster until it was continuous roar.
The radiation level was above the maximum of the counters, Greg realized when he noticed that everyone’s attention had switched to the pen recorder. Its scale was adjustable. As the level rose the scale was changed, then changed again, and again.
Fermi raised a hand. They all went silent. ‘The pile has gone critical,’ he said. He smiled – and did nothing.
Greg wanted to scream:
McHugh muttered: ‘Jesus Christ.’
Greg did not want to die. He wanted to be a senator. He wanted to sleep with Margaret Cowdry again. He wanted to see Georgy go to college. I haven’t had half a life yet, he thought.
At last Fermi ordered the control rods to be pushed in.
The noise of the counters reverted to a clicking that gradually slowed and stopped.
Greg breathed normally.
