1When Boltzmann taught in Vienna, in the last years of his life, there sat on his benches a small dark shy girl named Lise Meitner. She was one of the first women the old university had let in. She said all her life that no one had ever taught as he did: that he gave his pupils the feeling that the search for truth was a thing worth a whole life.
2He went through the Last Door. She took what he had given her and went north to Berlin.
3There she found a partner for her work, a cheerful chemist named Otto Hahn. But the master of the house of chemistry would not have a woman among his students. He said she might work in the cellar, in a room that had been a carpenter's shop, if she promised never to come upstairs. She promised. For two years she went in and out by the cellar door. When she needed a privy she walked down the street to an inn.
4She worked for five years without wages. In time they made her a master, with rooms of her own above ground.
5She and Hahn worked side by side for thirty years. He knew the stuffs and she knew the laws. They were never anything but friends, and neither could have done the work alone.
6She was born of Jewish parents. When the shouting man came to power they took away her right to teach, as they took Emmy Noether's. But she was a subject of Austria and not of Germany, and so for five years his laws could not quite reach her. She kept her rooms and her work. She told herself that the work was what mattered, and that it would pass.
7She said afterward that it had been not only foolish but wrong that she did not leave at once: that by staying she had lent her good name to that house. Remember that she said it. It belongs to the Completion of this book.
8In the thirty-eighth year the shouting man's army marched into Austria. There was no Austria any more. In one morning her passport became a piece of paper, and she became a Jew of the German lands like any other.
9A man in her own house of learning, one who wore the party's badge, began to say in the passages: the Jewess is a danger to this place. She asked for leave to go abroad. Word came down from the chief of the black-coated police himself: it was not wished that well-known Jews should leave the country and speak against it. She was not to go. And she was not to stay in her post. There was a third thing that happened to such people, and everyone knew what it was.
10Her friends outside worked quickly and in secret. In Holland a tall man named Dirk Coster went from door to door among the masters of his country until he had a paper that said she might come in, though she had no passport that any border would honour. Then he took the train to Berlin himself to fetch her.
11She had an hour and a half to pack. She was to take two small cases and no more, as if for a week's holiday. She left thirty years of notes in her desk. On the last night she slept at Hahn's house, so that no one would see a light in hers.
12Before she left in the morning, Hahn put something into her hand. It was a ring with a diamond, that had been his mother's. "For need," he said. A stone can be traded for a border guard's silence, or for bread. She had ten marks in her purse.
13She was fifty-nine years old, and she had never done an unlawful thing in her life.
14The train ran west all day across the flat country. Coster sat near her and they did not speak. She has told how the fear grew in her as the border came nearer, until at one station she wanted to get off and go back to Berlin and wait for whatever would come, only so that the waiting would be over.
15At the last German station the train stopped. A patrol of five men in uniform came through the wagon, taking papers. One of them took her dead passport out of her hand and looked at it, and looked at her, and walked on down the wagon with it.
16She sat with her hands in her lap. She said later that she sat so for ten minutes, and that her heart nearly stopped, and that the ten minutes were like hours.
17Then the man came back down the wagon and gave it into her hand without a word. The train jerked and rolled on. The next station had its name in Dutch.
18Coster sent a wire to Hahn that the baby had arrived safely. She never used the ring.
19But she was a master of her science who had been cut off from it. They found her a corner in a house of learning in Stockholm, in the far north, with no tools, no helpers, and not even a key of her own. She wrote to Hahn often, and he wrote back, for there was a puzzle they had left on the table.
20Here is the puzzle. They had been shooting at the heaviest of all atoms, uranium, with the smallest of bullets, hoping to make it heavier yet. Something was being made; but it would not behave as it should. Hahn, working on without her, was the best chemist in the world at telling stuffs apart, and in December he wrote to her in something near despair.
21What he had found in the dish, after shooting at uranium, was barium. And barium is not a little heavier than uranium. It is hardly more than half as heavy.
22He wrote: you are the one who knows the laws. Perhaps you can think of some fantastic explanation. We know it cannot really burst.
23The letter reached her at the turning of the year, in a small town on the western coast called Kungälv, where a friend had asked her to spend Christmas. Her sister's son had come up to be with her: Otto Frisch, a young master of the same science, driven out as she had been.
24He found her at breakfast, bent over Hahn's letter. He wanted to tell her about his own work. She would not hear it. She made him read the letter.
25"It is a mistake," he said. "It must be."
26"Hahn does not make that kind of mistake," she said.
27So they went out to think. He strapped on his long skis. She said she could go as fast on her own feet, and she did. They went over a frozen river and up among the pines, the old woman walking quickly beside the young man gliding, and all the while she was turning the thing over.
28At length they sat down on the trunk of a fallen tree. She brushed off the snow and found some scraps of paper in her pocket, and a pencil.
29Now hear how it came.
30The Dane, Bohr, had said that the heart of an atom is not like a hard stone. It is more like a drop of water, held together by its own skin. She thought: a drop that is very large trembles. Its skin can barely hold it. And the heart of uranium is the largest there is, and it is full of the kind of force that pushes like from like. It is a drop that is nearly bursting already.
31Strike such a drop, even gently, and it may stretch. It grows a waist, as a drop does before it falls from a tap. And then it does not chip. It parts in two. And the two halves, being alike, fly from one another with great violence.
32How great? She could reckon that in her head, and did. It was a huge number, for so small a thing.
33But from where could so much fire come? Nothing gives what it has not got.
34And then, sitting on the log in the snow, she remembered a lecture she had heard as a young woman, thirty years before, from a young man with a moustache who had lately been a patent clerk. She remembered that it had turned her world over. She knew by heart the weights of all the atoms, as a shepherd knows his sheep. She added up the two halves. Together they weighed a little less than the uranium they came from. A little was missing: about a fifth part of the weight of the smallest atom's heart.
35She took the missing weight, and multiplied it by the speed of light, and by the speed of light again.
36It was the same number. The fire that flung the halves apart was exactly the weight that had been lost. It all fitted.
37They sat still on the tree. The snow lay quiet on the branches. Two people who had been hunted out of their country, with scraps of paper on their knees, were the first on earth to know that the purse could be opened: that the fire in the rooms of the atom, which the woman of Paris had found leaking out grain by grain, could be let out all at once by a tap on the door.
38Frisch gave it a name a few weeks later, borrowing the word that those who study living things use when one cell becomes two. He called it fission.
39When Bohr was told, in Copenhagen, as he was stepping onto a ship for America, he struck his forehead with his hand. He carried the news across the ocean with him.
40For there is one thing more to be told about that parting of the drop, and it is the thing that turns a wonder into a dread. When the heart of uranium splits, it throws off two or three of the same small bullets that split it. Each of those may strike another heart. Each of those gives two or three more. One becomes two, two become four. In less time than it takes to say a word, the count is past all the grains of sand on all the shores.
41A Hungarian exile named Szilard had foreseen such a chain six years before, standing at the kerb of a London street waiting for the light to change. He had kept it secret. He had been afraid ever since that he was right.
42Now mark where the uranium of Europe lay. It lay in the mines of Bohemia: the same mines whose black heap had been carted to the shed in Paris. And the shouting man had just taken Bohemia. Within weeks, no more ore from those mines could be bought by anyone. In Berlin, Hahn and others who had not been driven out were at work in their rooms. Everyone who understood the scraps of paper understood the same thing. If such a fire could be built, the worst hand in the world might be the first to hold it.
43In the summer before the second war, Szilard drove out with a friend from New York to the far end of a long island, where the clerk of Bern was spending the hot months in a borrowed cottage, sailing a small boat. They lost their way among the lanes. At last they asked a sunburnt boy of seven whether he knew where Professor Einstein lived. The boy knew, and pointed.
44The old man received them on the porch in his shirt and rolled-up trousers. Szilard laid out the chain: one, two, four. The old man listened. He had not thought of it, he said. It had not once crossed his mind. He, who had written the line, had never believed that the door would open.
45All his grown life he had spoken against armies. Now two exiles sat on his porch and asked him to put his name, which was the one name every ruler knew, to a letter. The letter would tell the chief of the American people that a bomb of a new kind could be made, far stronger than any before; that the enemy might be making it; and that America should begin.
46It was not a hard thing to understand. It was a hard thing to weigh. On one side lay the certainty of putting such a fire into human hands at all. On the other lay the chance of its coming first, and only, into those hands that had lit the books in the square.
47Some days later Szilard came again, with the letter written out. The old man read it through, and signed. He signed at a wooden table, on an August day, with the sound of the water outside.
48He did no work on the thing itself. The soldiers judged him unsafe to be told of it, for his love of peace. He signed, and went back to his boat and his pencil, and for six years he heard almost nothing. But he never afterward pretended that his hands were clean of what came. He had seen two roads, and each of them ran through fire, and he had chosen one.
49And Lise Meitner? When the makers of the bomb gathered in the desert, the English sent to ask her to come and join them. She was poor, and lonely, and shut out of her science, and this was the greatest work of her science in that age. She refused. She said that she would have nothing to do with a bomb.
50The great prize of the north, for the splitting of the atom, was given at the war's end to Otto Hahn alone. Her name was not read out. She did not quarrel with him over it. She was grieved by something else: that he and the others who had stayed spoke so quickly of their own sufferings, and so slowly of what had been done in their name.
51She lived to be very old. On her gravestone, in an English churchyard, her nephew had these words cut, and they are still to be read there:
52"Lise Meitner: a physicist who never lost her humanity."
53The ring that had been Hahn's mother's she kept for many years, and then gave to her nephew for his bride. It was the one thing in this story, among so many, that was made ready for a dark hour and ended at a wedding.