1In the days when Shen Kuo was still a minister in the east, a boy named Farrukh watched his father lose a farm because of the moon.
2It happened so. In Persia the tax on the harvest was gathered by the calendar. But the calendar men used for counting was the calendar of the moon, twelve moons to the year, and twelve moons are eleven days short of the sun's full round. So the tax day slid backward through the seasons, a little every year, like a boat that has slipped its rope.
3The year Farrukh was nine, the tax fell due while the wheat was still green. His father had nothing to pay with but the field itself. The tax-gatherer was not a cruel man. He showed them the date on his roll and spread his hands. "It is the day," he said. "I did not make the day."
4They walked to the city of Isfahan with what they could carry. His father died there within the year, of nothing a physician could name. Farrukh swept floors for his bread. And at twelve he was sweeping the floor of a strange new house on a hill outside the walls, which the Sultan had built at great cost, and which had no roof over half of it.
5It was a house for watching the sky. The Sultan, Malik-Shah, was a Turk, the grandson of horse-lords. His vizier was a Persian, the old and wise Nizam al-Mulk, who ruled the ruling of the empire. The vizier had understood what the sliding calendar cost in ruined farms. He had sent for eight men who could reckon, and told them: Find me the true length of the year.
6The youngest of the eight was put over the rest. He was twenty-six, from Nishapur in the east. His name was Omar, and he was called Khayyam, the Tentmaker, for that had been the trade of his fathers.
7He was not an easy master. He was sparing of words, and short with fools, and he did not like to explain a thing twice. But he found the sweeper boy one morning standing in front of the great wall that had been built to catch the noon shadow, staring.
8"What are you looking at?"
9"The shadow has a top," said Farrukh. "Yesterday the top was on that line. Today it is a hair lower. Is it going somewhere?"
10Khayyam looked at him for a moment. "It is going to the bottom of the wall," he said. "That will take until the longest day. Then it will turn and climb again. Can you count?"
11"No."
12"Then you will learn by tonight. I need someone with young eyes who does not get bored."
13So Farrukh became the keeper of the noon mark. Every day that the sun shone, at the moment the shadow stood shortest, he pricked its place on the wall with a bronze point, and a clerk wrote the day beside it. He did this for five years.
14He learned what they were hunting. The year is the time from one spring to the next: from the moment when day and night stand equal, round through summer and winter, to the moment they stand equal again. Everyone knew it was three hundred and sixty-five days and a little more. All the trouble in the world was in the little more.
15Call it a quarter of a day, as the Romans did, and you are wrong by a few minutes. But a few minutes each year is a day in a little over a century, and the spring festival creeps toward summer, and somewhere a tax falls due on green wheat.
16"How close must we come?" Farrukh asked.
17"As close as the sky allows," said Khayyam. "Then we say plainly how close that is, and stop."
18They watched the sun for five years. They pricked the wall and wrote the tables and reckoned on the dust board deep into the night. And at the end the Tentmaker brought the vizier a number for the year, to more places than anyone had ever given, and a rule to go with it: eight long years, it is said, in every thirty-three. By that rule the calendar and the sun would walk together and not drift apart by a single day for thousands of years.
19The Sultan proclaimed it. A new count of years began on the first day of spring, at the very moment when the sun crossed the line. In every village of Persia the new year now came when the buds came, and the tax came after the harvest and not before.
20Farrukh was seventeen. He went up alone to the sun wall that evening and laid his hand flat on the marks. He thought of a man spreading his hands and saying, I did not make the day. Well, now someone had made the day, and made it true.
21Those were the good years. The Tentmaker had another labour besides the sky, and sometimes at night he let Farrukh watch.
22It was the art that al-Khwarizmi had begun, the restoring and balancing, the finding of the unknown thing. Al-Khwarizmi had mastered the questions where the unknown is multiplied by itself once. Khayyam was hunting the harder ones, where it is multiplied by itself twice: the cube. No one had tamed those.
23He sorted them into every kind there could be. And he found a way through each. He could not do it with numbers. He did it with shapes: he drew the curves that are made when a cone is sliced, the old curves of the Greeks, and where two of them crossed, there lay the answer, as a length you could measure.
24"But that is not a number," said Farrukh.
25"No," said Khayyam. "It is a place where two curves cross. I have tried for the number. I and others before me. We could not find the road." He blew the dust from the board. "I have written that down too, in the book. I have written that perhaps one who comes after us will find it."
26"You wrote in your own book that you failed?"
27"I wrote where the road stops. What else should I write? If I pretend it goes on, the next man walks off the edge. If I say nothing, he must find the edge again for himself, and waste ten years. Let him start where I stopped."
28Then, in the eighteenth year of the watching, in the autumn, a young man in the patched robe of a holy beggar came up to the litter of the old vizier Nizam al-Mulk as he was carried from his tent. He held out a paper, as if to ask a favour. Under the paper was a knife.
29The vizier who had held the empire together for thirty years died on the road. Within forty days the Sultan was dead too, of a fever taken while hunting, and he was only thirty-seven.
30After that the sons and the widow and the uncles fell on each other, and the empire came apart like a tent when the pole is pulled. There was no silver for star-watchers. One by one the eight reckoners took their books and went. There were voices in the city saying that men who measured heaven were prying into what God had veiled, and that the vizier's death was a judgment.
31Khayyam was a man who kept the prayers of his faith. But he knew that a crowd does not ask what a man keeps. He closed his door, and guarded his tongue, and when the next season came he set out on the long pilgrimage to Mecca, as every Muslim hopes to do once in his life.
32Before he went he gave Farrukh the keys. "They will come for the bronze," he said. "Let them have the bronze. Do not be killed for a ring of brass. But the tables—" He stopped. It was the only time Farrukh saw him unable to finish a sentence.
33"I know," said Farrukh.
34They came for the bronze within the month: soldiers of one of the princes, who needed coin. They took the great rings and the sighting tubes and the water clock. They threw the dust boards in the yard. They would have burned the chests of papers for warmth, but when they broke the chests open, they were full of straw.
35The tables were down the dry well behind the kitchen, wrapped in a waxed tent-cloth, with Farrukh's own bedding thrown on top. Eighteen years of the sky. He had carried them down the rope in the dark, nine loads, the night his master left.
36After the soldiers there was nothing. Farrukh stayed. He had nowhere to go, and someone must mind the well. He lived in the gatehouse of the empty house on the hill, and grew a few onions, and at noon each day, out of habit, he walked to the sun wall and looked at where the shadow fell. There was no bronze point now. He used a nail.
37It was in the second winter that the stranger came.
38It was a bitter night, with snow on the hills. Farrukh had a small fire of thorn in the gatehouse and a pot of barley. There was a knock, and he took up his stick, for honest people did not come up that hill any more.
39It was an old woman. She had a bundle of firewood on her back, twice as wide as she was, and frost on her shawl. She said nothing about who she was or where she was bound. She only looked at the fire, and he stood aside.
40She put two of her own sticks on his fire, good dry oak, better than his thorn. He gave her half the barley. They ate without talking, as tired people do.
41When she had eaten, she looked through the gatehouse door at the roofless hall, and the bare stone piers where the instruments had stood, and the snow blowing across the floor.
42"What was this place?" she said.
43"A house for measuring the year."
44"And now?"
45"Now it is nothing. The vizier is dead. The Sultan is dead. The master is gone to Mecca and the bronze is melted into coin to pay men to kill each other." He heard how bitter his own voice was and could not help it. "I gave it eighteen years. I am the watchman of a hole in the ground."
46The old woman nodded slowly. She did not tell him he was wrong. Then she asked him a question, mildly, as one asks the way to a well.
47"What have you left open?"
48"Nothing," said Farrukh. "I told you. It is all shut. Look at it."
49She did not answer. She pulled her shawl round her and lay down by his fire with her back to him and slept, or seemed to.
50And he thought, because he could not stop himself: tomorrow is the shortest day. The shadow will stand at the top of the wall. It will turn. It will turn whether there is bronze here or not. And in ninety days it will be the first day of spring, and in every village from here to the Oxus they will light the fires and begin the year on the true day. They do not need this house for that any more. The year is out of the house. It is in the villages. No prince can melt it.
51He thought of a field of green wheat, and a man who would not lose it.
52He thought of the tables down the well. Not burned. Waiting. And of a page in the master's book that said, perhaps one who comes after us will find it. A page that was itself a door, held open with a stone, on purpose.
53He looked at the old woman's back for a long time. He meant to tell her, in the morning, that he had an answer after all.
54But he slept at last, sitting up. And when he woke the fire was ash and it was not yet light, and she was gone. Her tracks went down the hill in the new snow, small and steady, and beside the hearth she had left the rest of her oak.
55In the spring he hauled the tables up out of the well, nine loads, and hired a mule with the last of his onion money. He took them east across Persia to Nishapur, where the Tentmaker had come home from his pilgrimage and was living quietly behind a shut door. Khayyam opened the waxed cloth himself, and saw the noon marks in a boy's hand, and for a long time he said nothing at all.
56The Tentmaker lived on in Nishapur many years, teaching a few. Men say he also made verses of four lines; which of those that bear his name are truly his, no one can now swear, and so none is written here. It is told that when he was very old he sat one day reading in the great book of Ibn Sina, the physician who had fled across Persia. He came to the chapter that treats of the One and the Many. There he stopped, and laid his gold toothpick between the leaves to keep the place, and rose, and made his prayer to God. And he did not eat or drink again, and that night he died.
57A pupil of his wrote that the Tentmaker had once said his grave would be in a place where the trees would shed their blossoms on it. The pupil thought it an idle saying. Years after, he went to Nishapur and asked for the grave, and found it at the foot of a garden wall. Pear trees and peach trees leaned over the wall from the other side, and the stone was so covered with fallen petals that it could not be seen. The pupil wept.
58But the Tentmaker's true monument is not there. Go to Persia on the first day of spring. At the very moment the sun crosses the line, in the cities and the mountain villages, the people set out green shoots of wheat on a cloth, and embrace, and begin the year. It is his year, a little mended since, and still true to the sun.
59And the question he left on the page stood open more than four hundred years. Then men in Italy, who had learned the bone-setter's art from Arabic books, found the road by numbers that he had said someone would find. They started where he had stopped. He had told them where that was.
60Now hear what came after.