The Clockwork Rocket

by Greg Egan

  “Of course,” Fulvio replied.

  No sooner had they plunged into the crowd than Yalda spied a stall full of artificial flowers, made from some kind of polished, translucent stone. They wouldn’t look like much at night, she guessed, but the way they caught the afternoon sun really did mimic a petal’s glow. How could anyone have fashioned such a thing, so delicate and precise? As she walked past the stall her rear gaze lingered on the sparkling curios, but then she spotted a dye wheel up ahead, the pits arranged around its wooden disk filled with vivid powders of various hues. The stallholder was demonstrating their quality for a customer, raising a series of decorative patterns on the palm of her hand then sprinkling a different dye over each design before pressing it onto a square of paper.

  “What about some groundnuts?” Fulvio asked.

  “What about them?” By the time Yalda had turned to him he had already concluded the transaction, and he passed her a conically wrapped petal full of the expensive delicacies.

  “But—”

  “It’s all right, I got two.” Fulvio showed her his other hand.

  “Thank you.” Yalda was embarrassed by his profligacy, but she didn’t want to be rude. She tried the nuts. The flavor was strong, and strange to her, but after a moment she decided that she liked it.

  She said, “I don’t think they grow around here.”

  Fulvio buzzed amusement. “They bring them from the Shining Valley, three severances away; that’s practically on the other side of the world.”

  “Oh.”

  “By train from Mount Respite to Jade City and Red Towers, then by truck to Shattered Hill and Sunstone and then here.” Fulvio spoke as confidently as if he’d ridden alongside a consignment himself. Yalda’s astonishment must have shown in her eyes, because he added by way of explanation, “I hear the truck drivers talking all the time, when they’re buying fuel.”

  “I’d like to be a truck driver,” Yalda said.

  “Really?” Fulvio sounded surprised by her choice, but his tone wasn’t dismissive.

  “What are you studying for?” she asked.

  “To work in my father’s business.”

  “Can’t he teach you that himself?”

  “He can teach me what he knows,” Fulvio said, “but he wants me to be able to change the business, to do something different if I have to.”

  “Like what?”

  “Who knows?” he replied. “Maybe something no one’s even heard of yet.”

  When they parted, Yalda stared uneasily at the cone of groundnuts Fulvio had given her. It was still half full, and she wondered if she should share what was left with the rest of her family. But with so many people there would barely be a taste for each one, and she felt uncomfortable about showing them the lavish gift. As she cut across the park toward the eastern road, she hastily stuffed the remainder into her mouth and dropped the empty petal onto the ground.

  It was still light when Yalda arrived home. Aurelia was in the clearing, milling grain and making loaves. “Can I help?” Yalda asked her.

  Aurelia said sharply, “I didn’t think you worked here anymore.”

  Yalda knelt beside her and took the mill. The resistance as she cranked the handle sent a welcome surge of vitality through the muscles in her arms, which had grown sluggish after a day spent sitting motionless.

  “You smell peculiar,” Aurelia complained.

  “They gave us something strange for lunch,” Yalda said. “I think there were worms in it.” She handed the mill back to Aurelia, who squeezed a thumb-sized piece of resin from the sweetbush branch she’d cut and started mixing it into the flour.

  That night, as they lay in their beds, Yalda told Aurelia about the lesson she’d received. Every child knew the twelve basic symbols, but it was a revelation to learn that there were ten times more. And just as Clara had shared her lessons with Vita, Yalda had decided that she would pass on everything she learned to Aurelia.

  But after Yalda had described just three of the new symbols, Aurelia said irritably, “Go to sleep. I’m not interested.”

  The next day, Angelo began teaching his class how to write. The students formed pairs and used the same trick that Vito had shown Yalda in the forest: prodding their partners with sharpened fingers to goad them into taking control of the instinctive twitching of their skin. Yalda’s brief introduction to the technique helped a little, but it still took a few days’ practice before she and Fulvio could form even the simplest symbols accurately, and hold them for as long as they wished. Yalda walked to school with shapes flickering over her skin, imagining a time when she’d have something written on her chest worth sprinkling with dye and committing to paper.

  As the class was gathering for what should have been the last day of their third stint, one of the other teachers came to them with a message: Angelo was sick. His illness wasn’t serious and he expected to be back soon, but for today his students should return to their families.

  Yalda was disappointed; she’d grown used to the routine of eleven days of school then one day off, and the prospect of two days’ farm work in a row felt tedious now. As she slouched despondently out of the schoolyard, Fulvio said, “Why don’t you come and see the refinery?”

  Yalda thought it over, and could find no reason to refuse the invitation.

  As they crossed the village to the west, the market stalls, parks and gardens gave way to warehouses and factories. Trucks were coming and going constantly; Yalda had never seen so many at once.

  “How do you sleep?” she asked Fulvio. He looked at her blankly. “Or does the noise stop at night?” It wasn’t just the trucks; most of the factories were emitting some kind of clattering or thumping.

  “It doesn’t stop,” he said. “But I like it. It’s soothing. If there’s silence I wake up; silence means something’s broken.”

  All around them, buildings made from timber or stone rose to twice Yalda’s height or more. Some were sleek, some were shoddy, but apart from the roads there was scarcely a stride of land left bare. Yalda understood that some kinds of manufacturing needed shelter from the dust and the wind, but she would have been hard-pressed to name half a dozen. How little she knew of her own village, she thought, let alone the wider world.

  “There’s the refinery.” Fulvio pointed out a broad stone building ahead of them. A truck was parked some distance away, its winch attached to a complicated system of pulleys that was raising a bin full of brown ore toward a long chute leading into the building.

  “Why make it so complicated?” Yalda wondered. “Why don’t the trucks just tip their load in where it’s needed?” She gestured at the point where the chute entered the refinery.

  “The trucks need to keep their distance,” Fulvio explained. “The liberator they use has to be ground very fine, which means it leaks out of everything. That’s bad enough for the trucks themselves, but if it gets into our production line people can die.”

  “Oh.” Yalda had been striding forward eagerly; now she slowed her pace.

  “Don’t worry, we’re careful,” Fulvio assured her. “And the liberator factory is a long, long way away.”

  As they approached, a rhythmless cacophony rose up over the sounds of traffic and the noises from the other factories. Fulvio led her to an entrance on the other side of the building from the ore chute. Yalda stepped through, peering into the gloom ahead; the air was thick with dust, shimmering in pale columns slanting down from the grubby skylights.

  As her eyes adapted, she made out a long line of shallow trays, joined to each other in a sequence that zigzagged across the cavernous space. People were standing beside the trays, bashing lumps of ore with hammers, scraping smaller rocks over elaborate toothed sieves, sorting fuel from clods of dirt with practiced darting fingers. There must have been four dozen workers in all, laboring amid the noise and dust.

  Yalda let out a faint hum of distress. The harvest wasn’t easy, but it only lasted six days. The work here looked like a kind of never-ending tortur
e.

  Fulvio must have noticed her discomfort. “There are three shifts,” he said, “so it’s really not so bad. I used to help out myself, before I started school. And my brother, my sister and my co all still work here.”

  Yalda waited for him to introduce her to them, but then she realized that he wasn’t prepared to do anything that might interrupt the flow of ore from tray to tray, as it grew ever finer and lost its troublesome impurities.

  “Your co works here?” she asked. “Fulvia?”

  He gestured toward a girl bent over a sieve. “And there’s my brother, Benigno.” The slender boy was sweeping orange dust across the floor into a grate, carefully separating spilt traces of fuel from the general muck; if he knew Fulvio was watching, he gave no sign of it. “Benigna works a later shift; so do my cousins.”

  “Where’s your father?”

  “He’s in the office with my uncle. We shouldn’t disturb them.”

  Yalda retreated into the sunlight. Fulvio followed her. “I don’t know why you’re so upset!” he said. “Your brother and sister still work on the farm, don’t they?”

  “Yes.”

  “Everyone has to do something,” Fulvio declared. “Or they’ll starve.”

  “I know,” Yalda conceded. “But you and I, our lives are so easy now—”

  “You and I are learning to do other kinds of work. Why should we feel bad about that?”

  Yalda didn’t know how to reply. After a while, she said, “Couldn’t they use an engine to smash the rock?”

  “They use engines at the mine,” Fulvio said. “But once the pieces of ore are smaller than a certain size, having any liberator around is too dangerous.”

  “There has to be a better way than people with hammers.”

  Fulvio spread his arms. “Maybe there is. And maybe when I’m educated, I’ll find it.”

  Yalda said, “I should probably get home now.”

  “I’ll walk with you back to the village,” he insisted. “I don’t want you getting lost.”

  Yalda didn’t object. As they walked, she wondered what she’d expected to see in the refinery, if not toiling children. Some dazzling secret of light, revealed? Fulvio and his family didn’t know how fuel turned into light, any more than she knew why wheat-flowers glowed. Half the things that happened right in front of their eyes remained as mysterious as the most distant stars.

  As they approached the village, Fulvio turned to her.

  “Do you have a plan yet?” he said. “For your children?”

  “What?” Yalda stared at him.

  “A plan for them. Who’ll raise them, who’ll feed them?”

  Yalda felt her skin writhing, as if it could sweep his words away like troublesome mites. “That’s a long way into the future,” she said.

  “Of course,” Fulvio agreed. “I just wondered if you had something in mind.”

  Yalda said, “Thank you for the visit. I’ll see you in school.”

  When she reached the empty eastern road, she started humming quietly to herself. She’d thought she was turning into Clara, that mysterious paragon of knowledge and friendship from her father’s stories of her mother’s time. But what exactly had become of Clara? Yalda had never dared ask.

  Giusto had wanted to harness her strength for the farm until she went the way of men—but what kind of escape from that fate was it, to step into a world where would-be co-steads were already sizing up her children as factory fodder?

  When she came to the turn-off leading back to the farm, Yalda kept walking. She found a quiet corner of a neighbor’s field where she knew no one would disturb her.

  She knelt low on the ground beside a sweetbush and let a sharp twig press into her skin, until the muscles all around the point of impingement were sweeping back and forth, desperately trying to dislodge it.

  The third symbol of the third dozen was one of the hardest: a full figure of a person, bipedal, four-armed, standing alone. Composed, self-contained, holding no tools. Maybe the four arms were for balance, or beauty.

  Yalda stayed kneeling against the bush, shouting with frustration at all her stupid failed scrawls. A teacher and a writing partner made it easier; rest and guidance and encouragement made it easier.

  But when the sun had crossed half the sky, the figure from her memory was there on her chest, imperfect but legible, hers to command.

  3

  On the day after her twelfth birthday, Yalda woke before dawn and forced herself to open her eyes before the cool soil lured her back to sleep. The vines that crisscrossed the low ceiling above her were studded with tiny yellow blossoms; thumps and scraping sounds filtered through from the floor of the markets as the stallholders made their preparations.

  Zeugma’s public beds were much in demand, and Yalda preferred to be gone before the night shift workers came down grumbling and prodding for spaces of their own. She rose and threaded her way between her sleeping neighbors, aware of other shapes moving softly nearby. The slender vines gave out just enough light to let her see where she was going, but it took care and practice not to step on a sleeper, or collide with someone else on the way to the exits.

  She bounded up the stairs and ducked into the markets to buy a loaf, then made it out onto the street in time to see the stars before the pale sky extinguished them completely. In Zeugma, only the wealthiest inhabitants with their private, walled gardens had the choice of sleeping in the open air; if you dug an indentation beside the flowers in the parks you were beaten for damaging city property. But Yalda preferred to spend her nights beneath the markets rather than waste money on an apartment in the towers, where your bed was cooled by a thermal conduit of calmstone columns, buried in the ground but stretching up to drain the heat from the highest of those dreary cages.

  She still had five chimes before her appointment with Eusebio, but she wanted to be thoroughly prepared in order to ensure that the session didn’t run over time; there was a mid-morning lecture by a visiting scientist on new developments in optics that she didn’t want to miss. So she paced the grimy streets between the markets and the university, planning her lesson in detail, composing diagrams as she walked. There weren’t many pedestrians about, and in any case the people she passed showed no surprise at the strange shapes forming and shifting on her skin. Some academics went to great pains to conceal their priceless musings, learning to make purely mental sketches or to ensure that anything showing on their body was at least writ small on the palms of their hands, but Yalda had never felt the need to cultivate those furtive habits.

  She had timed her peregrinations perfectly; the university clock made its doleful noise just as she entered the stone tower where Eusebio lived. Yalda took the stairs quickly; to arrive right on the chimes would have been ill-mannered, but a sprint to the fourth floor would be enough to take the edge off her punctuality.

  When she reached the apartment the curtained entrance was already parted to welcome her; she called out “It’s Yalda!” and stepped through. The room smelled of dye and paper; there were dozens of textbooks stacked against the walls, and Eusebio’s own notes rivaled them in bulk. A merchant’s son hoping to break into the railway business, he took his engineering studies seriously. Even the three small clockwork figurines, marching back and forth beside one pile of books, were evidence of a diversion equally concerned with the subject of what a machine could or could not be made to do.

  “Good morning, welcome!” Eusebio was sitting on the floor in the corner, loose pages spread out in front of him. He was bulky for a man, but no less agile for it; Yalda suspected that he’d strived from childhood to match the deftness of smaller peers, much as she had.

  She sat facing him, cross-legged, and got straight to the point. She knew exactly what he would have been told in the lecture he’d had the day before; not one word had changed in the introductory physics course since she’d taken it herself, four years previously.

  “Conservation of energy and momentum,” she said. “How much did you unders
tand?”

  “Maybe half,” he confessed. But Eusebio didn’t claim understanding lightly; Yalda suspected that he’d followed the whole lecture, but longed for a deeper grasp of the subject.

  “Let’s start with something simple,” she suggested. “Suppose an object is free to move, without friction. It starts out at rest, and you apply a constant force to it. After some time has passed, tell me how the force, the time, and the object’s velocity are related.”

  Eusebio said, “Force equals mass times acceleration; acceleration by time gives velocity. So, the product of force and time equals the product of the object’s mass and its velocity—also known as its ‘momentum’.”

  Yalda widened her eyes approvingly. “And in the general situation, where the object need not start from rest? The product of the force and the time for which it’s applied gives…?”

  “The change in the object’s momentum.” Eusebio lifted a sheet of calculations. “I confirmed that.”

  “Good. So, if two objects interact—if a child throws a stone at an approaching train, and it bounces off the front carriage—what happens to their momenta?”

  “The force of the train on the stone is equal and opposite to the force of the stone on the train,” Eusebio replied. “And since both forces act for the same amount of time, they cause equal and opposite changes of momenta: as much as the stone’s momentum rises—measured in the direction of the train’s motion—the train’s will fall.”

  Yalda said, “So the total, the sum of the two, is unchanged. What could be simpler?”

  “Momentum is simple enough,” Eusebio agreed. “But energy—”

  “Energy is almost the same!” Yalda assured him. “It’s just that instead of the product of force and time, you use the product of force and distance traveled. What’s an easy way to turn the first into the second?”

  Eusebio thought for a moment. “Multiply it by distance over time, which is the average velocity. For an object that started from rest and accelerated smoothly, that’s half the final velocity it’s reached. So the product of the force and the distance traveled is the product of momentum and half the velocity… or half the mass times the velocity squared. The kinetic energy.”