The Eternal Flame

by Greg Egan

  To make light and not be consumed. These were the properties of an Eternal Flame.

  Carla paused, amused by her absurd conclusion, wondering where the mistake lay. As things stood, the photons wouldn’t really be produced all conveniently heading in the same direction, so the device would certainly need some refinements. Perhaps she could merge the recoiling mirror trick with her original design for a coherent source. But this source wouldn’t squander most of the energy from a blazing sunstone lamp; the red-shifted reflection of the IR photons it emitted itself would act as the main pump. After an initial flash to get the process started, it would only need a small amount of ongoing illumination to compensate for its imperfections and inefficiencies—and the beam it produced would far outshine that modest input.

  It would not violate the conservation of energy or momentum. It would not violate any thermodynamic law: creating photons and waste heat amounted to an increase in entropy. But a photon rocket based on this design could run on a tiny fraction of the sunstone needed by any conventional engine. If it worked, it would solve the fuel problem.

  No—more than that. If it worked, the ancestors themselves might flee the home world in a swarm of photon rockets. If it worked, not only would the Peerless have gained the means to return home, it would have the right, it would have the reason. The purpose of its mission would have been fulfilled.

  Carla moved slowly down the empty corridor, listening to the twang of the guide rope, waiting for the flaw she’d missed to reveal itself. When it finally hit her, she could buzz ruefully at her foolishness and drag herself back to bed. What about cooling? This rocket would still need a separate cooling system, burning fuel of its own… but there was no law that required the heat it generated to be as much as a conventional engine produced. And the right choices in the design could help: the faster the ultraviolet photons the device was able to emit, the less kinetic energy the mirror would need to remove from the other photons—which meant less energy ending up as heat.

  Carla didn’t need to search for a clock to know that it was still early, but the only person in the mountain there’d be any point in waking was also the only one who’d understand why she couldn’t wait a few more bells to resolve this.

  She reached the precinct easily enough, but she had to check the names on a dozen doors before she found the right one; she hadn’t paid a visit since Patrizia had started living apart from her co. Carla knocked tentatively, wondering belatedly if her behavior would appear completely deranged. But the door opened before she had a chance to change her mind and retreat.

  “Good morning Carla.” Patrizia looked puzzled, but if she was annoyed at being woken she hid it well. “Come in, please!”

  The apartment smelled of paper and fresh dye. There was a lamp burning in the front room, revealing walls stacked with books and tied bundles of notes. The gravity was very weak here, but Carla clung tightly to the guide rope.

  “I won’t waste your time,” she said. “I’ve had a wild idea, and I need to hear your opinion.”

  She described the basic principle of the mirror trick, then went on to explain how it might be used in a real device. When she’d finished speaking she braced herself for a barrage of objections, but Patrizia remained silent, gazing thoughtfully into the middle distance.

  “So have I lost my mind?” Carla pressed her. She’d gently put Patrizia straight when the girl had fallen prey to her own kind of nonsense; it was time for Patrizia to return the favor.

  “I don’t think so. Why would you even say that?”

  “Because it can’t be this easy! The Eternal Flame—from a few mirrors and a slab of clearstone?”

  Patrizia buzzed softly. “In the sagas, the Eternal Flame doesn’t do anything; it just sits there being cool and inscrutable. Your version would be more like the process plants perform every day: extracting energy from the production of light without incinerating themselves. Nature must have found a trick a lot like yours—shuffling luxagens around a closed cycle—even if it puts it to a very different use. Crossing the void with minimal fuel wasn’t something a flower was ever going to find helpful, but that doesn’t mean it’s impossible.”

  Carla felt no sense of reassurance. If Patrizia had found a glaring flaw in the plan that would have settled the matter, but the fact that the idea had survived her brief scrutiny proved nothing. “And no one else thought of this? Not Yalda? Not Sabino? Not Nereo?”

  “They all thought energy was continuous!” Patrizia protested. “Would this scheme work at all, without discrete energy levels?”

  “I don’t know,” Carla admitted. Certainly the whole idea was easier to grasp when the luxagen could cycle repeatedly between a few fixed states.

  “I think Yalda had hopes that we’d master the creation of light by studying plants,” Patrizia said. “And maybe that will give us the best insights into the process, eventually. But someone had to be the first to spell out the kind of steps that would make this possible. You’re the first, Carla. You’re not losing your mind, I promise you.”

  “Thank you.” Carla did trust her to give an honest opinion, and not to indulge in flattery. “But I won’t believe I’m right until we’ve proved it.”

  “So where do we begin?” Patrizia asked. “We’ll need to find varieties of clearstone with the right energy levels, but we’ll also need to calibrate mirrors for their red shifts.”

  “This is going to be a whole new project,” Carla said. “I’ll have to go to the Council to get their approval for the change of plans.”

  “Hmm.” Patrizia was impatient to get started. “Surely I can reanalyse a few absorption spectra without waiting for the Council? When Romolo and I went through them the last time, we were looking for very different properties.”

  “That’s true.” The search for the perfect clearstone would start all over again, and there was a chance that once again it would succeed. But even the navigators’ modest needs would require the entire inventory of the clearstone Romolo had used in his visible light source. For this new application—

  “It won’t be enough,” Carla realized. “Even if we can make this work in a demonstration rocket, there isn’t the slightest chance that we’ll have enough material to replace the engines.” The mountain’s stocks of exotically tinted minerals weren’t miserly, but the ancestors had only intended them to provide representative samples to be studied for the sake of materials science. They had never anticipated the possibility that one particular variety would become more valuable than sunstone.

  Carla buzzed with grim satisfaction, glad that she’d caught her own mistake before making a fool of herself in front of the Council. “What was I thinking? Anything less than a full replacement for the engines would be worthless. If we can’t accelerate the Peerless at close to one gravity, it will take too much of the ancestors’ time for us to get back to them.” Returning to the home world a few years late—by the ancestors’ clocks—would mean arriving just as collisions with the orthogonal cluster began in earnest.

  Patrizia regarded her with bemusement. “Everything you say is true,” she said.

  “Then why didn’t you tell me? That’s what I came here for!” Carla dragged herself back along the guide rope, confused. “I needed to know where I’d gone wrong.”

  “There’s nothing wrong with your plan,” Patrizia insisted. “Not as far as I can tell. But as you say, the proof will be in the demonstration.”

  “And then what?” Carla hummed with frustration. “If we succeed, we’ll have the satisfaction of knowing that if half the mountain had been made of exactly the right kind of clearstone, that would have solved the fuel problem? And that the ancestors are likely to have all the resources they’d need to evacuate the home world—with the only problem being the lack of any way to tell them how to do it?”

  “If we succeed in making a photon rocket,” Patrizia replied, “then it will be the start of an entirely new endeavor: working with the chemists to learn how to make the right k
ind of clearstone, in the quantities we need, from the materials we actually possess.”

  Carla was incredulous. “You want the chemists to make a mineral on demand, now? You mean the way they solved the fuel problem by transmuting all our spare calmstone into sunstone?”

  Patrizia said, “Now you’re being crazy. First, the quantities we’d need would be much, much smaller: we’re talking about making engines that will run for years, not fuel that will be used up in an instant. Second, I suspect that different kinds of clearstone are chemically and energetically far more similar than calmstone is to sunstone. And third… if we can make your idea work, even on a modest scale, that will give us a new energy source. Burning sunstone to provide the energy to make sunstone would have been a losing proposition. But whether it’s heat or photons the chemists need to nudge one kind of clearstone into another, if we can pull off your trick and make an Eternal Flame on our own—even once—then we ought to be able to supply that energy without consuming anything.”

  36

  “Talk to your co!” Silvano pleaded. “I don’t know what’s got into her, but if she starts backing away from our plans to exploit the Object she’ll lose all credibility with the Council.”

  Carlo had been puzzled when Silvano had invited him to visit without Carla, but he hadn’t objected; he understood that there were matters that the two of them would be more comfortable discussing alone. It hadn’t occurred to him, though, that Carla herself might be one of them.

  “She’s had an idea for something better,” he said. “I’m not an expert in any of this, and I gather that the other physicists’ opinions are divided. But what do you expect me to do? I can’t tell her to ignore her own judgment.”

  “Wasn’t the whole point of these new light sources to manipulate orthogonal matter?” Silvano seemed to think that everything came down to that: Carla had gained his support for her project on that basis, and any attempt to change course now made her guilty of acting under false pretences.

  “The research has opened up another possibility,” Carlo replied. “Why is that so terrible? The Object isn’t going anywhere. If this new idea turns out to be a dead end, you’ll still be able to resume the original project.”

  “Resume?” Silvano was appalled. “We won’t get anywhere if we allow ourselves to be distracted every time someone’s mind goes off on a tangent. We need to finish what we’ve started!”

  “Finish it how?” Carlo shifted uncomfortably on the rope, then decided to be blunt. “Do you want to see people annihilated, before we even consider the alternatives?”

  “You’re saying the Object is so dangerous that we should forget about it completely? That wasn’t Carla’s attitude before.”

  “And it’s probably not her attitude now,” Carlo admitted. “I’m sure she still believes that the dangers could be managed, given enough time and effort. But if there’s a chance to avoid those dangers altogether, why not look into that first?”

  “Because it’s a fantasy!” Silvano proclaimed derisively. “Believe me, I admire the courage Carla showed in what she did to capture the Object—and I don’t blame her at all if she’s reluctant to go back. She doesn’t need to fly into the void again; she’s already a hero to everyone on the Peerless. But that’s no reason to sabotage the whole project, just to save face!”

  Carlo said, “I have work to do.” He stretched out an arm, pushing himself away from the rope so he could peer into the playroom. “Bye, Flavia! Bye, Flavio!” The children didn’t turn away from the tent they were building, but they glanced toward him with their rear gazes and nodded in farewell.

  Silvano tried to adopt a more conciliatory tone. “Look, if it were something easily settled then I’d be happy to support her. But it isn’t that simple, Carlo. Even if her demonstration project works—and my advisers all tell me that’s unlikely—there’s this whole separate business about mass-producing new clearstone to order. Let the chemists loose on that, and orthogonal matter will start to look benign in comparison.”

  “So let them experiment out in the void,” Carlo suggested. “Build a new workshop for the chemists and put it a severance or two away from the Peerless. That would deal with the safety issues, it would give the navigators another chance to exercise their skills—and if the clearstone thing doesn’t work out, the same facility would be perfect for experiments with orthogonal matter.” He tipped his head and began backing away along the rope.

  “All I could do was warn you!” Silvano called after him. “It’s up to you whether you listen.”

  In the corridor Carlo sped along the guide rope, trying to work off his agitation. Why had Silvano had to drag him into this dispute? It was possible that Carla was fooling herself and her scheme was too good to be true. It was possible, too, that Silvano was just clinging to his vision of the Object as the gift from fate that would solve all their problems.

  Mercifully, there was no need for him to decide who he believed was right. He was neither a Councilor nor a physicist; no one would care about his opinion on these matters.

  No one but Carla and Silvano themselves.

  Carlo had transformed the storeroom beside the arborine cages into an office, so he wouldn’t have to travel back and forth from the workshop Tosco had allocated for the original influence study. The room was cramped and it stank of the lizards awaiting their death as arborine food, but once he was in the harness beside the tape viewer he soon forgot his surroundings. The six reels sitting inert in their rack did not look like anything special, but in the viewer, illuminated and in motion, the strips’ rhythmic shifts between translucence and opacity became something close to a recitation of the body instructing itself to reproduce.

  A recitation and a transcript. He wound the sequence from Zosima’s lower left probe past the lamp again slowly, pausing every few spans to glance down at his chest and check his notes. He had catalogued almost ten dozen recurring motifs in the recordings, and even those patterns were subject to further small variations—like words repeated with different inflections. Here it was, right in front of him: the language of life.

  Now that they’d fed Benigna and Benigno to the point where quadraparity was all but assured, Macaria was pushing him to let them breed without any further interventions, in the hope that a comparison between the recordings of the two fissions would be illuminating. Carlo couldn’t fault the idea in principle, but he was still reluctant to proceed. Going on the surveys, there were probably less than three dozen arborines on the Peerless in total—counting Zosimo and his children. Aside from any qualms he had about the cruelty of confining and manipulating still more of them, there simply weren’t enough of the animals to grind through any exhaustive set of protocols, the way they’d all been trained to do with voles and lizards. If it was possible to learn more from Benigna than they could by conducting the single most obvious experiment—and losing another female of breeding age in the process—he owed it to all of them to find a way to do that.

  Carlo worked on the tapes until his concentration began to falter. He checked the clock; it had been almost three bells. He pulled himself out of the room and went to check on the infrared recorders. A stack of four machines were monitoring Zosimo and his children, to see if they had acquired any of the influences the team had captured from sick people and played back into the cage. Carlo removed two exposed reels, then reloaded and reset the machines.

  In the tape viewer, the reels were blank. The arborines appeared to be utterly unswayed by messages that had proved themselves capable of commandeering a person’s body. Ultimately that might not matter; the goal was to influence people, not arborines. But the lack of a single message that could infect both species would make it much harder to test the whole scheme.

  Carlo took a meal break, but the storeroom wasn’t a pleasant place to spend it. Chewing on a loaf, he wandered back to the arborines’ cages. Zosimo ignored him, but the children leaped to the bars and thrust their hands through, humming plaintively in the hope that
he’d throw them a morsel. “You want me to spoil you?” he chided them. He’d resisted naming the children but that hadn’t stopped him feeling a tug of affection for them, and he’d been weak enough to toss food to them before. “Your father will feed you soon. Be patient.”

  Carlo swallowed the last of the loaf quickly; Amanda sometimes came early for her shift, and it made him uncomfortable if she surprised him eating. He was about to return to the storeroom when a movement in the other cage caught his attention. He turned and pulled himself along the cross rope for a closer look.

  Benigna remained attached to her plinth, but she was holding something in one of her hands. As Carlo approached she tried to conceal it, but it was too large to be hidden from view.

  It was a stick, about half a stride long. One end tapered to a rough wedge; it must have been snapped off a slender branch. But Benigna’s half of the cage had been emptied of branches, and Benigno hadn’t breached the barred partition that separated him from his co. Carlo was stumped, but then he realized that Benigno must have thrown the improvised tool through a gap in the bars.

  Carlo drew himself to the side for a better view. The skin on Benigna’s back was torn, as if she’d been trying to force the stick between the stone surface and her body. “You want to be free?” he said dully. She couldn’t reach her melded flesh with her fingers, however sharp she made the claws, but not only had she conceived of a better plan, she’d managed to communicate what she needed to her co.