The Clockwork Rocket

by Greg Egan

  “We don’t know the details for every kind of matter, but in the case of free light the basic building blocks are just cyclic waves. When you make a full circuit of the cosmos in any direction, these waves undergo a whole number of cycles, so they return smoothly to their starting values. That’s it, that’s destiny fulfilled already… because anything constructed from waves like that will automatically share the same property. However complex a pattern of light you build up, it can’t contradict itself when it comes full circle. That’s guaranteed by the lowest-level physics; it doesn’t have to be orchestrated, or scripted, or contrived.”

  Benedetta considered this. “So where are we in this picture? If the matter we’re made from works the same way, where are our choices?”

  “In our biology,” Yalda said. “I think there’s a degree of consistency between our desires and our actions grounded in the structure of our brains and bodies. What you want, what you do, who you are… these things might not be in perfect harmony, but we’re not prisoners trapped in our bodies while they follow some plan that has nothing to do with us.” At least not until fission took over and split you in four, but Yalda didn’t want to get into that.

  Benedetta fell silent as they started across the Great Bridge. Yalda didn’t expect to change her mind on this; the important thing was for her to understand that she could raise anything with her colleagues in the project. When you planned to send a mountain flying through the void at an infinite velocity, there was no such thing as too abstruse a concern.

  Finally she said, “I’ll have to think on this more deeply. I can certainly see some force in your arguments.”

  Yalda could hear the reservation in her voice. “But?”

  Benedetta said, “It’s one thing to argue an abstract case that the future being fixed changes nothing: that there’s really no freedom lost, because our actions are determined in the same way, regardless. The fact remains, though, that we’re accustomed to seeing the future as open. That’s how our lives appear to us, that’s how we usually feel.”

  Yalda stopped walking. They were halfway across the bridge, supported by a slender arch of stonework over the blackness of the crevasse. She felt a shudder pass through the skin of her back; she’d just had an eerie sense of knowing what her shy, intense new colleague would say next.

  “When our descendants turn around and travel back in time,” Benedetta wondered, “will they still have the luxury we have, of debating this in the abstract? Once past and future are no longer so clear, will they still have the choice to go on seeing things the old way?”

  Eusebio counted, “Three. Two. One.”

  A distant line of light split the sky, wavering in the heat haze. A pause later the bunker trembled; as the timber boards holding back the sand flexed and rattled, the air filled with fine dust. Yalda and her companions were lying flat on their backs, a stride beneath the ground, but the tilted mirror above let them watch the ascending rocket as if they were upright in the desert, while the tinted clearstone pane protected them from the glare.

  Yalda was prepared for the hiss when it came, but not the crack that abruptly bisected the pane along a jagged diagonal. She reached up to support the two pieces before they could slip from the frame and decapitate someone.

  Amando cursed quietly and raised his own hands to help; Eusebio did the same, exchanging a glance with Yalda expressing relief that it hadn’t been worse. They’d isolated both the mirror and the pane from ground vibrations, but the shock wave in the air had still been enough to do damage. Nereo didn’t flinch; he was still tracking the rocket with his theodolite, and probably hadn’t even noticed the crack.

  Giulio, the journalist from Red Towers, turned to Eusebio chirping with excitement. “To be honest with you, I thought it would just explode on the ground. But it’s really up there!” He was too overwhelmed by the spectacle of the launch to care that he’d narrowly avoided being sliced in two by a giant stone blade.

  “That’s what rockets do,” Eusebio replied modestly. “Ascend.”

  “When does it fall down again?” Giulio asked.

  “This one won’t,” Eusebio predicted.

  Yalda wasn’t so sure. Through the protective filter the rocket had almost dimmed to invisibility; Eusebio would have gauged its progress by eye, but it would take the precise measurements of their independent observer to confirm its ultimate destination.

  Giulio raised his head so he could peer over the intervening bodies and see what Nereo was up to. Nereo was propped up on a special bench that Amando had constructed; this allowed him to watch a clock with his rear gaze at the same time as he followed the rocket through the theodolite. Yalda could see a list of pairs of times and angles written along the length of Nereo’s right arm; as she watched, he added one more pair then looked away from the theodolite and began producing further columns of numbers. The rocket would still be burning fuel—so there was still a chance that it could lose stability and drive itself back toward the ground—but on the assumption that it would do no worse, now, than if it had simply cut off its engines at the last clear observation, Nereo could give a tentative verdict on its fate.

  “It’s escaped the world’s gravity,” Nereo declared. “I suspect it’s heading for an eccentric orbit around the sun with a period of several dozen years.”

  “How can it have escaped?” Giulio asked. “Are you saying it’s already reached a height where gravity’s negligible?”

  His tone of incredulity was appropriate, but he’d missed the point. Nereo said, “At the altitude it had reached on my last observation, gravity is barely diminished—but it was already moving rapidly enough to guarantee that it would never be brought to a halt. Not by the world—though the sun still had hold of it.”

  Yalda looked to Amando, and together they managed to slide the tinted pane aside without the pieces falling on them. The bunker’s five occupants climbed to their feet and scrambled up onto the sand, slipping between the ground and the mirror.

  Yalda searched the sky, high to the east. There weren’t many Hurtlers today to confuse the view, and she could see a faint gray speck that could only be Eusebio’s house-sized pillar of rock—engines still blazing, still gaining speed. The escape velocity for the sun itself was only three times greater than the world’s. Given the results from earlier yield experiments, if the rocket burned all its fuel without mishap it could actually end up leaving the solar system.

  Giulio addressed Eusebio. “You should come to Red Towers and talk about your plans. Nereo’s already given public lectures on rotational physics, so the ideas aren’t completely new to people, but I can run some articles in the Report beforehand to help your audiences prepare.”

  Yalda wondered what was in the crops around Red Towers that was missing from Zeugma’s diet.

  Eusebio said, “I’d be delighted.”

  Yalda thanked Nereo for his participation. “It’s a pleasure,” he said. “I don’t know if your guess about the Hurtlers is right, but I’m glad someone’s thinking about these possibilities.”

  “I can’t interest you in a place on the rocket?”

  Nereo buzzed with mirth. “I’d rather stay safe on the ground, and wait for your dozen-fold-great-grandchildren to tell me all the marvelous science they’ve discovered.”

  Yalda said, “I get that answer a lot.”

  She wished she could have spent longer with Nereo, but he and Giulio needed to get back to Red Towers. Amando brought one of the trucks out of the shed and sped off across the desert with their guests.

  Eusebio turned to Yalda. “Will you come to Red Towers with me? Tour the show?”

  “If I can get leave from the university.” Yalda hesitated. “Do you think you could pay me a small fee for that?”

  “Of course.” Eusebio had invited her several times to become an employee, but so far she’d resisted; she’d wanted to retain her independence, in order to be able to speak her mind to him freely.

  She added apologetically, “If I
’m not teaching I won’t get paid, and it’s not fair on Lidia and Daria to be looking after the children with no help.”

  “Hmm.” Eusebio had already made it clear that he disapproved of what the three of them were doing: women—however capable they could be in other spheres—had not been shaped by nature for the raising of children. There were plenty of widowers in Zeugma desperate for heirs, and prepared to treat them like the flesh of their own co.

  But he had more important things to think about than the flaws in Yalda’s domestic life. “Beyond spreading the news to the citizenry of Red Towers,” he said, “I’m hoping your colleague Nereo can arrange a meeting for me with his patron.”

  “You can’t get an introduction to Paolo yourself?” Yalda was amused. “Whatever happened to the plutocrats’ network?”

  “Networks, plural. They’re not all joined together.”

  “Why do you want to meet Paolo?”

  “Money,” Eusebio replied bluntly. “My father’s set a ceiling on my investment in the rocket. If I’m going to have to build the whole structure myself—mining and transporting all the sunstone, incorporating it into an artificial shell… if I tried to match the scale of Mount Peerless the costs would be greater by a factor of several gross, but even the smallest viable alternative is far beyond what I can afford on my own.”

  “Have you thought of bribing all the people who are entitled to vote on the observatory?” Yalda suggested. “Not just with a shiny new telescope—with money they can put in their own pockets?”

  Eusebio was insulted. “I’m not a fool; that was my very first plan. But Acilio has the Council scrutinizing the University’s business very closely, and he has so many spies in the University himself that I doubt I could get away with that kind of thing.”

  Yalda joked, “I’m always willing to kill Ludovico, for a nominal fee.”

  Eusebio regarded her with a neutral expression for an uncomfortably long moment.

  “Don’t tempt me,” he said.

  As the train approached Red Towers, Yalda was surprised to discover that the city still lived up to its name. She’d read that the local calmstone deposit with the eponymous hue had been mined out long ago, but now she could see with her own eyes that the skyline still bore an unmistakable red tint. Perhaps the original buildings had been lovingly preserved. Either that, or they’d all been recycled as decorative veneer.

  Nereo met her at the station—along with all four of his children, who fought with each other for the thrill of carrying her luggage. Seeing how young they were, Yalda guessed that his co must have lived almost as long as her own grandfather. Nereo was still healthy, though—and no doubt he’d made arrangements for the children to be cared for even if some tragedy struck him down.

  “Your friend Eusebio’s already at the house,” Nereo said.

  “He had some business in Shattered Hill,” Yalda explained. “We’ve come in from opposite directions.”

  Nereo lived within his patron’s walled compound. Yalda’s skin crawled as they walked past the sentries with their knife belts, but the children took the sight for granted. “It’s just a tradition,” Nereo told her, noticing her discomfort. “Paolo has no enemies; those weapons have never been used.”

  “Don’t the guards get bored, then?”

  Nereo said, “There are worse jobs.”

  Eusebio was sitting on the floor in the guest room, reading a copy of The Red Towers Report. He greeted Yalda, then added in a tone of disbelief, “This man Giulio actually read and understood every word in the briefings I sent him. He raises some objections and concerns, but… they’re all entirely sensible.”

  “Let’s just strap the whole city to a rocket and get it over with,” Yalda suggested. “Let Red Towers flourish in splendid isolation in the void for an age or two, then they can come back and teach the world how to live.”

  They only had a couple of bells before the show, so they went to the hall to familiarise themselves with the layout. Yalda hadn’t been able to bring the equipment to produce the projected backdrops they’d used in Zeugma, but Giulio had organized printed sheets bearing the same material, which would be handed to the audience as they entered. That meant keeping the general lighting on during the performance.

  “Seeing all those faces is going to make me anxious,” she told Eusebio, standing on the stage at the front of the empty hall.

  “Don’t worry, you’re a professional now.” He squeezed her shoulder reassuringly.

  The solution only came to her when she finally stepped out in front of the crowd: she delivered exactly the same message as in Zeugma, but she shifted her attention to her rear gaze and focused on the blank wall behind her, allowing herself to imagine that all the people in the hall were staring, not at her, but at the same soothing whiteness.

  After Eusebio had done his part—with a few changes from the original version in which he’d boasted of a rocket the size of a mountain—it was time for questions. Everyone they’d spoken to in Red Towers had told them that they’d have to take questions from the floor; it was the custom here, and if they defied it they would not be forgiven. Giulio—whose employers had paid half the cost of renting the hall, in exchange for the right to display the paper’s name prominently throughout the venue—joined Yalda and Eusebio on stage to moderate.

  Yalda braced herself for the predictable “Why can’t I walk to yesterday?” jokes, or perhaps even the perennial “Where’s your co?”

  The first questioner Giulio selected, an elderly man, called out, “How will you keep the machinery repaired?”

  Eusebio said, “There’ll be workshops within the rocket, equipped for every eventuality.”

  The man was unimpressed. “And factories? Mines? Forests?”

  “There’ll be stocks of minerals,” Eusebio said, “and gardens for raw materials as well as for food.”

  “Stocks to last an age? Soil to last an age? All inside one tower? I don’t think so.”

  Giulio chose another questioner.

  “How will you control the population?” the woman asked.

  “At the moment we have more of a shortage of travelers than an excess,” Eusebio replied.

  “Double that number a few dozen times,” she suggested, “then tell me where you’ll put them, and how you’ll feed them.”

  Eusebio was beginning to look flustered. Yalda said, “There’ll be the same mortality rates on the rocket as we experience anywhere else. No city’s population actually doubles in a generation.”

  “So there’ll be no progress in medicine, then? For era after era, the only thing these travelers will care about is dealing with the Hurtlers… which no longer even threaten them?”

  Yalda said, “Progress in medicine could end up controlling population growth as much as it lowers mortality.”

  “Could—but what if it doesn’t?”

  The questions continued in this fashion: tough but undeniably pertinent. It felt like an eternity before Giulio called a halt; Yalda was so exhausted that it took her a moment to realize that the audience was now cheering enthusiastically.

  “That went well,” Giulio whispered to her.

  “Really?”

  “They took you seriously,” he said. “What more did you want?”

  In the foyer, they recruited more than three dozen ground crew volunteers, but no passengers. People here were far more willing than their cousins in Zeugma to accept Yalda’s premise about the Hurtlers, and even the abstract principle behind Eusebio’s solution—but no one was confident that he could build the kind of habitation in which they’d want their own grandchildren to spend their entire lives.

  The servant ushered Yalda, Nereo and Eusebio into the dining room, then withdrew.

  Paolo was standing at the far end of the room, flipping through a thick stack of papers. He looked younger than Yalda had expected, perhaps a bit more than two dozen years old. He put the papers down on a shelf and approached, gesturing at a wide circle of cushions on the floor. �
�Welcome to my home! Sit, please!”

  Nereo introduced Yalda and Eusebio. Yalda tried not to be intimidated by the opulence of the room; the walls were decorated with an abstract mosaic, and there was a bewildering array of food spread out in front of them, almost none of it familiar to her. To her eye, there was enough to feed at least a dozen people—and when six young men entered the room, the quantity began to seem almost reasonable—but it turned out that Paolo’s sons were just passing through to greet his guests, and would not be joining them.

  Six sons! Had he adopted some of them, or taken two co-steads? Either way, if it was a family tradition the house would be overflowing with grandchildren.

  The formalities over, Paolo sat with them and urged them to start eating. Yalda made a conscious decision not to hesitate—not to stare at the dishes and try to guess their origins. She was confident that nothing here would be too repellent, let alone dangerous, so it didn’t really matter that she had no idea what she was putting in her mouth. The first few flavors were strange, but not unpleasant. She decided to adopt a fixed expression of mild enjoyment and maintain it throughout the meal, regardless.

  Paolo addressed Eusebio. “I’ve heard about your rockets; an extraordinary venture.”

  “It’s only just beginning,” Eusebio replied. “To send people safely into the void will take many more years of work.”

  “I admire the audacity of your vision,” Paolo said, “and I appreciate that the Hurtlers might well become dangerous. But what exactly do you think your travelers will bring back from a trip into empty space?”

  “That’s difficult to predict,” Eusebio admitted. “Imagine, though, how wondrous our cities would appear to a visitor from the eleventh age. They had no engines, no trucks, no trains. Only the crudest lenses. No reliable clocks.”

  “But what comes next?” Paolo wondered. “An engine that runs a little more smoothly? A clock that loses no time in a year? Undoubtedly civilized refinements, but how would they safeguard us against the Hurtlers?”