The Clockwork Rocket

by Greg Egan

“What am I doing here?” she muttered, trying to decide how low to squat for safety without completely obscuring her view.

  “Watching history being made,” Eusebio replied, not entirely seriously. Yalda glanced at Amando, but his face gave nothing away.

  “Three, two, one,” Eusebio counted.

  The barrier concealed the flash of ignition, but by the time Yalda felt the ground tremble a dazzling line of white light had risen into view. A moment later a deafening hiss arrived through the air.

  Yalda shielded her eyes and sought the rocket at the top of the afterimage, but something wasn’t right; the line seared on her vision had been joined by an arc, a circle, a widening helix. Then the point of radiance that had been inscribing these curves dropped below the barrier, and the ground shuddered. She stiffened her tympanum protectively, deafening herself to the sound of the impact, then tensed for a larger explosion.

  Nothing followed. Either the fuel had all been consumed, or the liberator had ended up scattered.

  Yalda turned to Eusebio. He looked shaken, but he recovered his composure rapidly.

  “It reached a good height,” he said. “Maybe ten strolls.”

  It took them more than a bell riding around the desert before they found the remains of the rocket. If it had stayed in one piece it might have made a spectacular crater, but the fragments of hardstone casing and mirrorstone cogs strewn across the ground had barely gouged the surface, and some were already half-buried in the dust. If Yalda had stumbled upon them unawares, she would have called for an archaeologist.

  “Attitude control,” Eusebio said. “It just needs some refinement.”

  He left the others sorting through the debris and gave Yalda a ride back to the city.

  “What does your family think about all this?” she asked him. Yalda had said nothing to Lidia and Daria, or any of her colleagues; Eusebio had asked her to hold off mentioning the project to anyone until he’d tied up various “administrative loose ends”.

  “I’ve managed to convince my father that it’s worth risking the money,” he said. “Even if the world’s in no danger from the Hurtlers, anything that the travelers invent on their journey could easily double our fortune.”

  “What about your co?”

  “She thinks I’m crazy. But I’ve told her—and my father—that I can’t countenance bringing children into the world until this rocket’s been launched to vouchsafe their future… which seems to have made both of them happy.”

  “Why?”

  Eusebio buzzed amusement. “She’s glad the day’s so far away. He’s glad it’s going to be so soon.”

  Yalda said nothing. Eusebio turned to her and added, “Just to be clear, she can actually wait as long as she wishes.”

  Yalda fought down the urge to reply sarcastically: How generous of you. If Eusebio really was supporting his co against their father’s nagging, it wasn’t worth starting a fight with him just because he sounded smug about it.

  “Are you sure this isn’t going to lose you your fortune?” she asked. “What’s the going price for a mountain these days?”

  Eusebio said, “I’ve already bought mining licenses from all the Councils that claim jurisdiction. It wasn’t cheap, but it didn’t ruin me.”

  Mount Peerless was almost equidistant from five different cities; the only way to ensure an undisputed title would be to pay them all off. Yalda said, “Doesn’t a mining license include some deal about a share of the profits?”

  “Of course. And if I do make any money from the project, I’ll give the Councils their cut.”

  “But they all think you’re planning to dig out the sunstone and sell it?”

  “I haven’t disabused them of that assumption.” The truck shuddered on the stony track. “But do you really want me to try lecturing my fellow Councilors on rotational physics? My father was willing to take my word for it—having paid so much for my education—but I can’t see Acilio and his cronies patiently following the trail of evidence from the velocity-wavelength formula to the passage of time for fast-moving travelers.”

  “No.” The mention of Acilio reminded Yalda of someone else she’d been trying not to think about. “How do things stand with the university?”

  “I’m negotiating a payment for them to relocate the observatory,” Eusebio said. “It’s not finalized, but given the amount we’ve been discussing they’ll be able to build a new telescope twice the size.”

  “But not at the same altitude.”

  “You can’t have everything. Don’t you think this is more important?”

  “It’s not me you’ll have to convince,” Yalda warned him. “Have you ever heard of a man called Meconio?”

  “Meconio? I thought he was long dead.”

  “Not in spirit.” Perhaps the university would take Eusebio’s money and accept the deal before Ludovico discovered the connection between this “mining project” and the loathsome subject of the new physics.

  “How much of the mountain do you think is sunstone?” she asked.

  “Maybe two-thirds, by mass.”

  Yalda did some quick calculations on her back. “That might be enough for one quarter-turn in four-space, but there’s no chance at all that it will cover the whole voyage.”

  Eusebio glanced at her, surprised. “You expect the yield to stay the same, after half an age working on improvements?”

  “Maybe not, but if there’s barely any sunstone left over from the acceleration stage… what kind of yield are you hoping for?”

  “I don’t expect the travelers to burn sunstone for the later stages,” Eusebio replied.

  Yalda was startled. “You want them to turn hardstone and calmstone into fuel?”

  “Either that,” he said, “or move beyond the need for fuel entirely.”

  Yalda waited for a sign that he was joking; none came. “So you’re counting on this rocket riding the Eternal Flame? Is that what you told your father to expect?”

  Eusebio hunched his shoulders defensively. “Just because Ninth Age charlatans wrote a lot of nonsense about a similar idea doesn’t mean it’s actually impossible.”

  “A flame that consumes no fuel?”

  “Tell me why it can’t exist!” he demanded. “Not the version the philosophers imagined: some magic stone that would sit on your shelf, creating light and nothing else—that would violate conservation of energy. But if light and kinetic energy are created together there’s no reason they couldn’t balance each other precisely, without any change in chemical energy to plug the gap. Fuel doesn’t need to be consumed; that’s just the way it works with the kinds of fuel we have right now.”

  Yalda had no argument about the energy balance, and while she couldn’t calculate the relevant entropies on the spot, creating light generally meant an increase. In conventional flames the hot gas formed by the spent fuel also contributed to the rise in entropy, but there was no reason to think it was essential. On the face of it, then, a slab of rock could create a beam of light—balancing the energy and momentum of the beam by recoiling in the opposite direction, but suffering no other change—without violating any principle she could name.

  Accepting that statement of theory was one thing. Being stranded in the void with an infinite velocity, exiled from your home until you conjured the Eternal Flame into existence, was a different proposition.

  “I can’t tell you it’s impossible,” Yalda conceded, “but you still need to ensure that there’s a useful amount of sunstone left after the acceleration—even if you have to throw away half the rest of the mountain to eliminate some dead weight. Give them something they can make more efficient, not a choice between bringing a Ninth Age myth to life, or never coming back!”

  “Let’s see what the detailed surveys tell us,” Eusebio said, trying to sound conciliatory. “Two thirds was just a conservative guess.”

  Yalda stared out across the desert. Who was going to volunteer to ride on this folly if it looked harder to survive than the Hurtlers?

>   She said, “Please tell me you’re not expecting the travelers to invent their own means of dealing with waste heat.”

  “Of course not.”

  “So…?”

  “I’m planning to divert some of the exhaust gas,” Eusebio said. “Letting it expand and drive a piston while it’s thermally isolated will cool it down and supply some useful energy—then decompressing it further while it’s circulating around the habitation will draw in heat. Most of it will then be released into the void, but some will be used to maintain the pressure in the habitation, which would otherwise decline over time as the original atmosphere leaks out.”

  “So you’ll be burning some sunstone for these purposes, even when the rocket isn’t in use?”

  “Yes—though compared to the amount used for propulsion it won’t be much.”

  Yalda couldn’t fault this scheme, or suggest any obvious refinements, but that wasn’t good enough. “Now that you’ve proved that you have no fear of explosions,” she said, “how about a detour to Amputation Alley?”

  Eusebio regarded her suspiciously. “Why?”

  “There’s a man there called Cornelio who knows more about heat than either of us. You should ask his advice on this.”

  “Can he keep a confidence?”

  “I have no idea,” Yalda replied, irritated. Cornelio had always treated her honourably, but she wasn’t going to vouch for his willingness to go along with Eusebio’s whims.

  “Never mind,” Eusebio said. “I’ll hire him as a consultant, have him sign a contract.”

  Yalda lost patience. “Do you honestly think you can send a whole mountain into the void in secret? Just you, and a few dozen advisers? Maybe you could get that much dead rock off the ground through sheer trial and error, but we’re talking about risking lives! You need the best people in the world to know about this, to think about it—to criticize all your ideas, all your systems, all your strategies. And I do mean the best people, not the best you can afford to put on your payroll and subjugate to a vow of silence.”

  “I have enemies,” Eusebio said pointedly. “People who, if they knew of these plans, would happily spend a good part of their own fortune just to see me fail.”

  “I don’t care,” Yalda replied coolly, resisting the urge to remind him that she’d suffered far more from his enemies’ pique than he had. “If the travelers are to have any hope of surviving, you’re going to need every biologist, agronomist, geologist, chemist, physicist and engineer on the planet as worried about their fate as you are.”

  “And why should they fret about the lives of a few strangers?” Eusebio retorted. “You didn’t seem too eager to spread news of the catastrophe that this trip is intended to forestall.”

  “I was wrong,” Yalda admitted. “First I didn’t take my own reasoning seriously, and then I was vain enough to think that if I could see no remedy myself, there was none. You’ve shown me otherwise, and I’m grateful for that. But it can’t end there.”

  Eusebio said nothing, his gaze fixed ahead.

  “No more silence,” Yalda declared. “I need to make the case for the problem, and you need to make the case for the solution. Let people argue, correct us, support us, tear us down. It’s the only hope we have to get this right.”

  When Yalda arrived home Daria was in the apartment, helping Valeria and Valerio infuse some anatomical realism into their sketches of giant lizards laying waste to Zeugma.

  “Lizards can rearrange their flesh almost any way they like,” Daria explained, “but they have five favorite postures, which are used in different places for different tasks. If they were on the ground, smashing buildings like this, you can bet they’d have a lot of flesh in their rear legs and their tails. It’s no good drawing them the way they’d look running along a slender twig.”

  The children were entranced. Yalda sat and listened, not saying too much, hoping that merely sharing their interest would be read as a sign of affection. When she tried too hard Valeria reacted with scorn, but if she kept her distance she was punished later with accusations of indifference. It was exhausting having to be so calculating about it, but whatever it was that could sometimes make the relationship between a child and their protector almost effortless, it rarely seemed in evidence with Tullia’s children and the three friends who’d agreed to raise them. This was a labor of love, but that didn’t stop it being the hardest thing Yalda had done in her life.

  Lidia had taken Amelia and Amelio to the doctor, but they were expected back soon. When the children were asleep tonight, Yalda decided, she would tell Lidia and Daria everything.

  They had a right to know the truth—but what if they simply doubted her sanity? Watching Valeria chirping happily as she and Valerio re-drew each other’s lizards in a cascade of jokes and refinements, Yalda felt her own conviction about the peril of the Hurtlers faltering yet again. Whenever she immersed herself in domestic life, instead of apprehending the threat to the people around her more acutely she found herself growing numb and disbelieving. It wasn’t hard to imagine a time when everyone in this household would be gone; with the passage of years that was inevitable. But picturing every woman and every girl that lived having gone the way of men, leaving not a single child to survive them, only made her mind rebel and doubt the entire chain of reasoning that could lead to such an absurd conclusion.

  Daria disengaged from the anatomy lesson for a moment to speak to Yalda directly. “There’s a letter for you on the sideboard.”

  “Thanks.” Yalda judged the artists sufficiently engrossed not to care if she briefly left the audience.

  The letter was from Lucia. Yalda had written to her several times since her last visit to the farm, but their correspondence had been intermittent.

  She uncapped the wooden tube, tugged out the rolled-up sheets and smoothed them flat. Some of the symbols were a bit shaky, as if Lucia had been unable to keep the ridges still when she pressed the paper to her skin.

  My dear sister Yalda

  I’m sorry that it’s been so long since I last wrote to you. I’m sorry, too, that you haven’t been able to visit us yet and see the new farm, but I understand that you must be busy, taking care of your friend Tullia’s children as well as continuing your work at the university. (You won’t be surprised to hear that when I finally told Giusto about the children he denied that such a thing was possible, and said you needed to hunt down the derelict co or co-stead responsible!)

  Claudio and his children joined us on the new farm a couple of stints ago. It’s lovely to have so many people around after all these years on our own. We never stopped visiting the old place, of course, but since tradition demands that the two farms are more than a separation apart, it hasn’t been too often.

  The main reason I’m writing to you now is to tell you that this will be my last letter. I remember how hurt and saddened you were that you had no news or warning about Aurelia and Claudia, and I wanted it to be different for us. So: tomorrow I will become a mother.

  I would be lying if I told you that I wasn’t afraid, but I’m also filled with great hope and happiness, knowing that Lucio and I have done our best to prepare for the children’s future. The farm is very well established, and we have plenty of money saved, so while the young cousins work under their father’s watchful eye, Lucio will mostly be free to take care of the children. (And please don’t be angry with him, this is my decision as much as it is his.)

  Do you have the same beautiful shooting stars there in Zeugma that we have here? I know you’re studying these things, so it must be an exciting time for you. I can’t believe how glorious they look, even during the day, and it’s rather strange and wonderful to think of my children growing up to take such sights for granted. They’ll be amazed to hear from their father that there was once a time when the sky was so much emptier!

  Your sister Lucia

  11

  The morning after her first appearance with Eusebio in the Variety Hall, Yalda woke early and went out to see what
the papers had made of it.

  A boy on a nearby corner was selling City Skin, so she bought a copy, but after flicking through the sheets three times it was clear that the end of the world didn’t rate a mention here. She went back to ask the boy for Talk; he’d sold out, so she waited while he dusted his chest with dye and made a fresh one for her.

  “I’ll pay you the same for just the news and entertainment sections,” she offered impatiently.

  “We’re not allowed to do that,” he said, summoning the memory of another sheet onto his chest.

  “Why not?”

  “The advertisers don’t like it.”

  When he’d finished, Yalda took the whole bundle from him and walked around the corner before discarding the financial advice, restaurant reviews and railway timetables. She had to search the remainder twice before she found what she was looking for.

  Last night our spies were at the Variety Hall, where the preternaturally plump Professor Yalda regaled a non-paying (!) audience with news of civilization’s impending demise. In a performance mixing the illusionist’s art with the terrors of geometry, the bountifully bulky Professor attempted to tie fleet-footed Mother Time in knots, leaving many observers wondering at her motives.

  If the audience was unpersuaded by her message of doom, the attempt that followed by Councilor Eusebio to attract supporters (or even volunteers!) for his Ride Beyond the Sky was greeted by a veritable uproar of disbelief and derision. To anyone willing to back this venture: we have a design for Mechanical Wings gathering dust in our cupboard, awaiting only the life-giving touch of a gullible investor.

  In the interests of sanity, Talk consulted Professor Ludovico of Zeugma University, who explained that the Hurtlers bringing such angst to last night’s double act are in fact nothing more than Spontaneous Excitations of the Solar Miasma. Despite its alarming appearance this phenomenon can do no harm to anyone, given that said Miasma is unable to interpenetrate our own plentiful atmosphere.