Incandescence

by Greg Egan

  Rakesh said, «No, we're not sure yet, but thank you for asking.»

  Parantham said, «Travel how? By what method? How long will it take?» The map remained silent. She re-invoked the option and the map asked again if she was sure, but it remained unresponsive to her requests for details.

  Rakesh said, «Try some more stars, see if the option's always present.» They worked their way through a hundred candidates. In every case, the map claimed to be able to take them there.

  «Does this mean they're all on the network?» Parantham wondered. The eavesdroppers out in the disk had only succeeded in mapping a small part of the Aloof's network, near the edge of the bulge. The nodes there weren't closely aligned with particular stars, but the known ones were certainly spread more thinly than the stars themselves. If the Aloof really did have receivers at all of the places where the map said it could take them, then either this was the best-connected region in the galaxy, or they had receivers at every single star in the bulge, period.

  Rakesh said, «I doubt it. More likely they've just automated the ability to add new nodes.» Out in the disk, getting a receiver built at a new location was a major endeavor. First, you needed permission from the custodians of the local material resources. Then you had to organize the logistics of sending spores to construct the receiver itself. The technology had been streamlined over the millennia — with the need for eavesdroppers to chase the spillage of the Aloof's data around the inner disk providing a substantial boost — but it still wasn't something you did casually, just by pointing at an obscure star on a map and leaving the rest to insentient software.

  Parantham said, «I've often wondered if the network we've mapped isn't merely a kind of decoy, which they built to make us think we understood them better than we really do.»

  «You mean, not at all?»

  «We've been telling ourselves that they use the same general communications technology as we do. Gamma rays modulated with data packets. Encryption keys separately distributed. All very cozy and familiar, as if it were the only conceivable way.»

  Rakesh couldn't argue with her skepticism. Convergent technology was one thing, but in the Age of Exploration travelers had been amazed by the myriad ways other civilizations had found to solve identical problems, at least as often as they'd been startled to find their own culture's inventions eerily mirrored. «You think they were the ones who eavesdropped on our network first, and then they decided to build an imitation of it, as a sop to our curiosity?»

  «As a sop to our curiosity. As a honey pot to lure us in. I don't know about their motives. But it wouldn't surprise me if all the 'traffic' we've been seeing over the last three hundred millennia has just been gibberish, and the Aloof's real highways are completely invisible to us.»

  Rakesh said, «I don't know if that's good news or bad. Do you think they're going to let us ride the real highway?» He was past the point of feeling vulnerable, but he couldn't decide if it was somehow demeaning, or simply exhilarating, to imagine being whisked across the light years by a process he didn't even understand.

  Parantham summoned up the first of their candidates on the chemistry-based list, a main-sequence star about four billion years old, two hundred and seventy-nine light years away. While it lay further from the crowded galactic center than their present location, the Amalgam's eye-view of it was still compromised by distance and obstacles. The presence of at least three gas giants had been deduced from the star's slight periodic motion, but no further details could be resolved from afar.

  She said, «There's only one way to find out.»

  8

  Roi immersed herself in study, determined to reach the point where she could understand every detail of Zak's ideas. Excited as she was by the simplicity and grandeur of his vision, until she could test the fine points for herself she knew that her instinctive sense that he was on the right track needed to be treated with caution. Anyone could thump their carapace and invent a story so big that it seemed to swallow the world. The one thing that made Zak's account of weight and motion different was that anyone willing to make the effort could investigate the logic of his claims firsthand. On that, the whole thing would stand or fall.

  Zak helped her to revise and extend her mathematical skills, starting with multiplication, then continuing all the way to something he called «template calculations»: manipulating abstract symbols as well as actual numbers, allowing her to perform a generic version of a sequence of computations without specifying all the quantities involved. After a while, it struck Roi that this was far more than a method for saving labor when she wished to repeat the same calculation many times on different sets of numbers. Just contemplating the template for the answer to a problem — without substituting any particular values for the symbols — could illuminate the relationship between all the quantities involved in a way that staring at endless lists of figures never would.

  Zak was a patient teacher. Before she'd met him, Roi had thought of the unrecruited as pitiful creatures, lonely failures on the verge of death. Zak's time at the Null Line had certainly damaged his health, but in his own way he had worked far harder than anyone she'd ever known. Roi had rarely been so confident that the respect she felt for someone was deserved, and not just a product of the haze of camaraderie.

  Between their lessons, Roi managed to extract some of his story. Like every hatchling, Zak had found tutors to provide him with a rudimentary education, but when the time came to join a work team, he'd drifted from one recruitment to the next. He'd felt the buzz of cooperation every time, but it had never been strong enough to hold him for long.

  One shift, while working as a courier, he'd stumbled upon a library out in the sardside. The cargo he was carrying had had nothing to do with the place, but an accidental detour had been enough to capture his interest, and on the return leg of his journey he'd gone back for a closer look.

  The library was full of maps, work notes, diagrams of strange machines, fragments of calculations, and scrawls in languages nobody understood. The librarians painstakingly copied the sheets of skin to preserve their contents from loss or damage, and constructed catalogs and lists of cross-references, trying to piece together a larger picture from these bewilderingly disparate parts. Every now and then, they explained to Zak, someone would bring in a new find, a page or even a bundle of pages that had never been seen before.

  Wandering through the collection, overwhelmed by the aroma of long-dead susk, Zak had suffered a giddying shift in perspective. People had been thinking and writing for an unimaginable time, and here, right in front of him, lay countless samples of their labors. A whirlwind tour of history, a million tantalizing snatches of overheard conversations, had been etched into these skins. Zak felt the presence of the thousands of generations that had come before him, and understood that it might be possible to join them in a vast endeavor, a project spanning the ages that he could as yet only glimpse.

  He'd begged the librarians to recruit him on the spot, and once they'd recovered from their surprise they had agreed, but they were not the ones who had truly captured his loyalty.

  «I was recruited by the dead,» Zak said. «Not in any rush to join them in their silence, but from the urgent need to understand what they might have thought and done that could survive them, that could speak across the ages, that could be continued even now.»

  There was no coherent history of the Splinter, no account of one time following another, but everywhere Zak looked he found evidence of change. The language he understood, the language of his contemporaries, accumulated curious additions and alterations as he moved from page to page into the past. Other pages were written in scripts that, so far as his fellow librarians knew, no living person could decipher.

  There were stories of the birth of the Splinter, of the old world being torn apart, but like the stories that spread through the work teams they did not agree on the details, and they all had the sound of having been retold over and over, accumulating embellishments and omissi
ons, before being put into writing. Some even spoke of the calamity recurring many times, stretching back into the unimaginably distant past. How vast, how grand, the mythical First World must have been, if after thirty-six divisions even one of the crumbs that remained was inhabitable!

  Hard as it was to believe these stories, let alone know which ones to trust, for anyone who'd so much as crossed the Calm the undeniable fact remained that the weight in the garmside tugged the opposite way to that in the sardside, and the further one went in both directions the stronger this discord became. If the Splinter had suddenly been doubled in size, it was not at all preposterous to imagine that the weight might have been enough to tear rock from rock.

  The trouble was, this raised the question of how the old world could have held itself together for more than an instant. The most reasonable answer, it seemed to Zak, was that it must have been born under a different regime of weights, which had only later become so powerful.

  During shift after shift in the library, he came across fragments of speculation on these matters, but there was nothing whole, and nothing convincing. The thinkers of the past had left many hints and guesses, but if they had ever fully understood the truth about these mysteries, it had not survived. In the end, Zak decided that he couldn't spend his life merely sifting through these skins, searching for one more inconclusive sign that his reasoning was not completely misguided. If weight had dictated the history of the Splinter, and however many worlds that had come before it, then weight was what he needed to understand.

  Armed with the Map of Weights, some plans for ancient instruments, and copies of the few surviving notes on his predecessors' methods and philosophies, he'd walked out of the library and headed for the Null Line, ready to begin uncovering the secrets of weight and motion, and to search for something simple that had torn the world apart.

  Roi still didn't understand the wind.

  On one level, Zak's idea of natural motion seemed to explain it perfectly. If things moved in circles around the distant point in the Incandescence that she and Zak had come to call the Hub, and if the smaller the circle the faster they moved, then everything about the wind made sense. On the garmside — closer to the Hub — the wind was moving faster than the Splinter, and so it overtook the rock, blowing in from the sharq ever faster the further garm you went. On the sardside — further from the Hub — the wind was orbiting more slowly so the Splinter overtook it, ploughing through it, making it seem to blow in from the rarb when in truth it was merely failing to flee with sufficient haste in the opposite direction. And between them, in the Calm, wind and rock moved together at exactly the same pace, leaving not so much as a breeze to be felt.

  The trouble was, while Zak's theory gave a simple, persuasive account of the phenomenon, Roi couldn't reconcile it with the mundane reality of weights. If weight was determined by natural motion, why didn't the wind follow the weights? If she stood anywhere in the garmside, and a crack opened up in the rock beneath her, surely she would fall away from the Splinter, garmwards. Notwithstanding the wind's speed in the cross-direction, which might make such motion harder to spot, and the way the rock and the tunnels worked to divert and complicate its flow, Roi's time among the crops left her thoroughly convinced that the wind wasn't falling at all.

  Shift after shift she struggled with this problem, hoping she might solve it by her own efforts. Finally, she had to admit that the resolution was beyond her. The next time she met Zak, she asked him to defer their scheduled lesson in template mathematics, and she begged him to make sense of the wind before she lost her mind.

  Zak was both amused and chastened. «This is my fault, Roi; I should have explained this much sooner. The weights on the map are fine — give or take the question of three versus two and a quarter — but they're not the whole story.»

  «There's something missing?»

  «Yes. There is a kind of weight that the map doesn't show at all.»

  Roi was baffled. «How can that be? Weight is weight. I've felt it, I've measured it. It's not something you can hide.»

  «No, but the map only shows weights for objects that are fixed firmly to one place in the Splinter.»

  «I've moved from place to place in the Splinter,» Roi protested, «and the map described correctly how my weight changed.»

  «That's not what I'm talking about,» Zak said patiently. «You moved at a walking pace to a new location, you didn't race the wind. The wind feels something extra, everywhere, compared to the fixed weights on the map, simply because it's in motion, not because those fixed weights change from place to place.»

  If this was true it had the potential to resolve the paradox, but the idea still struck Roi as very strange. «Why should it feel something extra just because it's moving?»

  «Because the Splinter is spinning,» Zak said. «Now, I know the map already takes account of that, in part. An object fixed to the Splinter is really turning in a circle — a small one, much smaller than its orbit — which frustrates its natural motion and contributes to its weight. There's one further twist, though. Imagine a stone that's moving in a straight line, as seen from outside the Splinter. Because the Splinter is constantly turning, as the stone moves, we're moving too. If we try to trace the path of the stone against our surroundings — against the rocks and tunnels we think of as fixed, but which in truth are turning — the line we see it following won't be a straight line, because of the way our motion adds to the stone's. Its path will seem bent, as if there were a weight constantly pushing it sideways. And the faster the stone moves, the greater the apparent weight bending its path.»

  «The faster it moves in reality, or the faster we think it's moving?»

  «The faster we think it's moving.»

  Roi struggled to visualize it. If a stone moved in a straight line away from the axis of spin, then the rotation of the Splinter would make it seem to follow a spiral path, forever turning. And if the stone was sitting completely still? Then the motion of the Splinter meant that it would appear to be moving in a circle, again with its path constantly veering sideways.

  «I think I understand,» she said. «But the wind doesn't wrap itself into a spiral. On the garmside, it blows straight from sharq to rarb.»

  Zak said nothing.

  Roi struck her carapace. «Of course, that's the whole point! I've been wondering why the weights from the map don't push the wind garmwards, in some kind of curve plunging back out into the Incandescence. But the extra weight from its motion must push it in the other direction, balancing the ordinary weight exactly.»

  «That's right,» Zak said. «The further garm you go, the stronger the garmwards weight, but because the wind is also blowing more strongly, the weight from its motion keeps perfect step, and the two of them always cancel.»

  Roi was pleased that she'd finally grasped what she'd been missing, but there was still something frustrating about the whole matter. The Splinter was turning, Zak claimed, and this claim turned out to be absolutely vital in order to make sense of the rest of his vision. Without the strange distortions in weight and motion brought about by the spin, it would have been impossible to reconcile a simple concept such as circular orbits for the wind with the ordinary realities of the Splinter.

  However, everything about the Splinter's rotation seemed to involve a kind of conspiracy of self-effacement. It contributed to the garm-sard weights on the map, but who was to say exactly how much it added? It balanced a hypothetical rarb-sharq weight exactly, but that perfect balance left nothing behind to be felt or measured. And now it conspired with the garm-sard weights again. in order not to bend the wind.

  Roi understood that at least some of this was a logical necessity, not a matter of coincidence. The two points of view, one tied to the rock of the Splinter, the other taking a grand cosmic perspective, were describing exactly the same reality, so of course they had to agree with each other, once you knew how to translate between them. Nonetheless, she couldn't accept that the fact of the Splinter's rotation
could be both crucial and completely invisible, impalpable, and immeasurable.

  She said, «When I throw a stone in the Null Chamber, why can't I see its path being bent?»

  «It's a subtle effect,» Zak said. «I've made some crude measurements of it, but it's hard to detect just by looking.»

  «You've measured the Splinter's rotation!» Roi was astonished. «Why didn't you tell me that before?»

  «I wouldn't say I'd measured the rotation. My measurements show that the rotation exists, but I haven't come close to quantifying the rate of spin.»

  «But you've seen the effect itself?»

  «Absolutely,» Zak said.

  «Can you show me?»

  They went to the Null Chamber, and Zak fished out a device he called a spring-shot from one of the storage clefts. It was a tube fitted with a spring-loaded plunger that could be cocked to varying degrees of compression and then released, propelling a stone from the tube. The projectile emerged in a reasonably predictable direction, with a choice of velocities.

  He attached the spring-shot to the wire that marked the Null Line. Then he prepared a «target board», a flat sheet of cuticle that he coated first with resin, then with a kind of powder. If you pushed a stone against the surface of the target, however gently, the powder sank into the resin, changing the way the two of them scattered the light, leaving a visible record of the point of contact.

  He fixed the target board to the Null Line with a bracket, six spans or so rarb of the spring-shot.

  «We're sending this stone straight down the Null Line, so according to the map it should feel no weight at all,» Zak said. «First I'll make it move as fast as possible, and we'll see what happens.»

  He squeezed the plunger as tightly as it would go, then released it. The stone flew out rapidly, more or less following the wire that marked the Null Line, and struck the target. When they went to examine the board, it was, unsurprisingly, marked at the edge, just beside the wire.