They were not long in coming. His rejection of uniform velocity threw everything into disarray, and he had to begin all over again. He was not discouraged. Here was real work, after all, fully worthy of him. Where before, in the Mysterium, there had been abstract speculation, was now reality itself. These were precise observations of a visible planet, coordinates fixed in time and space. They were events. It was not by chance he had been assigned the study of Mars. Christian Longberg, that jealous fool, had insisted on keeping the lunar orbit; Kepler laughed, glimpsing there too the quivering tips of angelic wings, the uplifted finger. For he knew now that Mars was the key to the secret of the workings of the world. He felt himself suspended in tensed bright air, a celestial swimmer. And seven months were becoming seventeen.
Tycho told him he was mad: uniform velocity was a principle beyond question. Next he would be claiming that the planets do not move in perfect circles! Kepler shrugged. It was the Dane's own observations that had shown the principle to be false. No no no, and Tycho shook his great bald head, there must be some other explanation. But Kepler was puzzled. Why should he seek another answer, when he had the correct one? There stood at the hatch of his mind an invoice clerk with a pencil and slate and a bad liver, who would allow no second thoughts. Tycho Brahe turned away; what little chance there had been that this Swabian lunatic would solve Mars for him was gone now. Kepler plucked at him, wait, look-where is my compass, I have lost my compass-the thing was as good as done! Even assuming a variable rate of speed, to define the orbit he had only to determine the radius of its circle, the direction relative to the fixed stars of the axis connecting aphelion and perihelion, and the position on that axis of the sun, the orbital centre, and the punctum equans, which for the moment he would retain, as a calculating device. Of course all this could only be done by a process of trial and error, but… but wait! And Tycho swept away, muttering.
He made seventy attempts. At the end, out of nine hundred pages of closely-written calculations, came a set of values which gave, with an error of only two minutes of arc, the correct position of Mars according to the Tychonic readings. He clambered up out of dreadful depths and announced his success to anyone who would listen. He wrote to Longberg in Denmark, demanding settlement of their wager. The fever which he had held at bay with promises and prayers took hold of him now like a demented lover. When it had spent itself, he returned to his calculations to make a final test. It was only play, really, a kind of revelling in his triumph. He chose another handful of observations and applied them to his model. They did not fit. Arrange matters as he would, there was always an error of eight minutes of arc. He plodded away from his desk, thinking of daggers, the poison cup, a launching into empty air from a high wall of the Hradcany. And yet, in a secret recess of his heart, a crazy happiness was stirring at the prospect of throwing away all he had done so far and starting over again. It was the joy of the zealot* in his cell, the scourge clasped in his hand. And seventeen months were to become seven years before the thing was done.
His overloaded brain began to throw off sparks of surplus energy, and he conceived all kinds of quaint ingenious enterprises. He developed a method of measuring the volume of wine casks by conic section. The keeper of the Emperor's cellars was charmed. He tested his own eyesight and made for himself an elaborate pair of spectacles from lenses ground in Linz by his old friend Wincklemann. The prosaic miracle of water had always fascinated him; he set up water clocks, and designed a new kind of pump which impressed the imperial engineers. Others of his projects caused much hilarity among the Brahes. There was his design for an automatic floor-sweeper, worked by suction power from a double-valved bellows attached to the implement's ratcheted wheels. He consulted the scullery maids on a plan for a laundry machine, a huge tub with paddles operated by a treadle. They ran away from him, giggling. These were amusing pastimes, but at the end of the day always there was the old problem of Mars waiting for him.
He liked to work at night, savouring the silence and the candleglow and the somehow attentive darkness, and then the dawn that always surprised him with that sense of being given a glimpse of the still new and unsullied other end of things. In the Curtius house he had burrowed into a little room on the top floor where he could lock himself away. The summer passed. Early one October morning he heard a step outside his door, and peering out spied Tycho Brahe standing in the corridor, his arms folded, gazing down pensively at his large bare feet. He was in his nightshirt, with a cloak thrown over his shoulders. Behind him, by the far wall, Jeppe the dwarf was creeping. They had the air of weary and discouraged searchers after some hopelessly lost small thing. Tycho looked up at Kepler without surprise.
"Sleep, " said the Dane, "I do not sleep. "
As if at a signal, there arose in the sky outside a vehement clanging. Kepler turned an ear to it and smiled. "Bells," he said. Tycho frowned.
Kepler's room was a cramped brown box with a pallet and a stool, and a rickety table aswarm with his papers. Tycho sat down heavily, fussing at his cloak; Jeppe scuttled under the table. Rain spoke suddenly at the window: the sky was coming apart and falling on the city in undulant swathes. Kepler scratched his head and absently inspected his fingernails. He had lice again.
"You progress?" said Tycho, nodding at thejumbled papers by his elbow.
"O yes, a little."
"And you still hold to the Copernican system?"
"It is a useful basis of computation…" But that was not it. "Yes," he said grimly, "I follow Copernicus."
The Dane might not have heard. He was looking away, toward the door, where on a hook there hung a mildewed court uniform, complete with sash and feathered hat, a limp ghost of the previous householder, the late vice chancellor. Under the table Jeppe stirred, muttering. "I came to speak to you, "Tycho said. Kepler waited, but there was nothing more. He looked at the Dane's big yellow feet clinging to the floorboards like a pair of purblind animals. In his time Tycho Brahe had determined the position of a thousand stars, and had devised a system of the world more elegant than Ptolemy's. His book on the new star of 1572 had made him famous throughout Europe.
"I have made," said Kepler, picking up his pen and looking at it with a frown, "I have made a small discovery regarding orbital motion."
"That it is invariable, after all?" Tycho suddenly laughed.
"No," Kepler said. "But the radius vector of any planet, it seems, will sweep out equal areas in equal times. " He glanced at Tycho. "I regard this as a law."
"Moses Mathematicus, " said Jeppe, and sniggered.
The rain was still coming down, but the clouds to the east had developed a luminous rip. There was a sudden beating of wings at the window. Kepler's steelpen, not to be outdone by the deluge outside, deposited with a parturient squeak upon his papers a fat black blot.
"Bells," said Tycho softly.
That night he was brought home drunk from dinner at the house of Baron Rosenberg in the city, and relieved himself in the fireplace of the main hall, waking everyone with his yelling and the stench of boiled piss. He kicked the dwarf and staggered away upstairs to his bed, from which Mistress Christine, gibbering in rage, had already fled. The household was no sooner settled back to sleep than the master reared up again roaring for lights and his fool and a meal of quails' eggs and brandy. At noon next day he summoned Kepler to his bedside. "I am ill. He had a mug of ale in his hand, and the bed was strewn with pastry scraps.