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: So turn the fucker off! But Fermi remained silent and still, watching the pen, and such was his authority that no one challenged him. The chain reaction was happening, but it was under control. He let it run for a minute, then another.

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.

McHugh was jubilant. ‘We proved it!’ he said. ‘The chain reaction is real!’

‘And it’s controllable, more importantly,’ said Greg.’

‘Yes, I suppose that is more important, from the practical point of view.’

Greg smiled. Scientists were like this, he knew from Harvard: for them theory was reality, and the world a rather inaccurate model.

Someone produced a bottle of Italian wine in a straw basket and some paper cups. The scientists all drank a tiny share. This was another reason Greg was not a scientist: they had no idea how to party.

Someone asked Fermi to sign the basket. He did so, then all the others signed it.

The technicians shut down the monitors. Everyone began to drift away. Greg stayed, observing. After a while he found himself alone in the gallery with Fermi and Szilard. He watched as the two intellectual giants shook hands. Szilard was a big, round-faced man; Fermi was elfin; and for a moment Greg was inappropriately reminded of Laurel and Hardy.

Then he heard Szilard speak. ‘My friend,’ he said, ‘I think this will go down as a black day in the history of mankind.’

Greg thought: Now what the hell did he mean by that?

(v)

Greg wanted his parents to accept Georgy.

It would not be easy. No doubt it would be unnerving for them to be told they had a grandson who had been concealed from them for six years. They might be angry. On top of that, they might look down on Jacky. They had no right to take a moralistic attitude, he thought wryly: they themselves had an illegitimate child – himself. But people were not rational.