Permutation City

by Greg Egan

  Maria fell silent. It was good news, a rare opportunity for both of them, but she still couldn’t understand why he was unloading it on her out of the blue. He should have told her everything when he’d applied, however poorly he’d rated his chances.

  She glanced at the stage, at the twelve sweating musicians playing their hearts out, then looked away. There was something disconcertingly voyeuristic about watching them without tuning in: not just the sight of them emoting in silence, but also the realization that none of the bands could see each other, despite the fact that she could see them all.

  Aden said, “There’s no rush to make up your mind. The academic year starts on January ninth. Two months away.”

  “Won’t they need to know, long before then?”

  “They’ll need to know by Monday if I’ve accepted the job – but I don’t think the accommodation will be a big deal. I mean, if I end up alone in an apartment for two, it’ll hardly be the end of the world.” He looked at her innocently, as if daring her to give the time and place he’d ever promised to turn down a chance like this, just because she didn’t want to come along for the ride.

  Maria said, “No, of course not. How stupid of me.”

  #

  Home, Maria couldn’t resist logging on to the QIPS Exchange, just to find out what was going on. Operation Butterfly had vanished from the market. Omniaveritas, her knowledge miner, had picked up no news reports of a typhoon in the region; perhaps the predicted one had failed to eventuate – or perhaps it was yet to appear, but the simulations had already given their verdict. It was strange to think that it could all be over before the storm was a reality … but then, by the time anything newsworthy happened, the actual meteorological data would – hopefully – bear no relationship at all to what would have happened if the weather control rigs had been in use. The only real-world data needed for the simulations was the common starting point, a snapshot of the planet’s weather the moment before intervention would have begun.

  The QIPS rate was still about fifty per cent higher than normal, as ordinary users jostled to get their delayed work done. Maria hesitated; she felt like she needed cheering up, but running the Autoverse now would be stupid; it would make far more sense to wait until morning.

  She logged on to the JSN, slipped on her gloves, activated the workspace. An icon of a man tripping on a banana skin, frozen in mid-fall, represented the snapshot of her interrupted task. She prodded it, and the Petri dishes reappeared in front of her instantly, the A. lamberti feeding, dividing, and dying, as if the past fifteen hours had never happened.

  She could have asked Aden to his face: Do you want to go to Seoul alone? Do you want a year away from me? If that’s it, why don’t you just say so? But he would have denied it, whether or not it was the truth. And she wouldn’t have believed him, whether or not he was lying. Why ask the question, if the answer told you nothing?

  And it hardly seemed to matter, now: Seoul or Sydney, welcome or not. She could reach this place from anywhere – geographically or emotionally. She stared into the workspace, ran a gloved finger around the rim of one of the Petri dishes, and declaimed mockingly, “My name is Maria, and I am an Autoverse addict.”

  As she watched, the culture in the dish she’d touched faded from muddy blue to pure brown, and then began to turn transparent, as the viewing software ceased classifying dead A. lamberti as anything more than chance arrangements of organic molecules.

  As the brown mass dissolved, though, Maria noticed something she’d missed.

  A tiny speck of electric blue.

  She zoomed in on it, refusing to leap to conclusions. The speck was a small cluster of surviving bacteria, growing slowly – but that didn’t prove anything. Some strains always lasted longer than others; in the most pedantic sense, there was always a degree of “natural selection” taking place – but the honor of being the last of the dinosaurs wasn’t the kind of evolutionary triumph she was looking for.

  She summoned up a histogram showing the prevalence of different forms of the epimerase enzymes, the tools she’d been pinning her hopes on to turn mutose back into nutrose … but there was nothing out of the ordinary, just the usual scatter of short-lived, unsuccessful mutations. No hint of how this strain was different from all of its extinct cousins.

  So why was it doing so well?

  Maria “tagged” a portion of the mutose molecules in the culture medium, assigning multiple clones of Maxwell’s Demon to track their movements and render them visible … the Autoverse equivalent of the real-world biochemist’s technique of radioactive labeling – along with something like nuclear magnetic resonance, since the demons would signal any chemical changes, as well as indicating position. She zoomed in on one surviving A. lamberti, rendered neutral gray now, and watched a swarm of phosphorescent green pin-pricks pass through the cell wall, and jostle around the protoplasm in the sway of Brownian motion.

  One by one, a fraction of the tags changed from green to red, marking passage through the first stage of the metabolic pathway: the attachment of an energy-rich cluster of atoms – more or less the Autoverse equivalent of a phosphate group. But there was nothing new in that; for the first three stages of the process, the enzymes which worked with nutrose would squander energy on the impostor as if it were the real thing.

  Strictly speaking, these red specks weren’t mutose anymore, but Maria had instructed the demons to turn an unmistakable violet, not only in the presence of nutrose itself, but also if the molecules under scrutiny were rehabilitated at a later stage – salvaged in mid-digestion. With the epimerase enzymes unchanged, she doubted that this was happening … but the bacteria were thriving, somehow.

  The red-tagged molecules wandered the cell at random, part-digested mixed with raw indiscriminately. Neat process diagrams of metabolism – the real-world Embden-Meyerhof pathway, or the Autoverse’s Lambert pathway – always gave the impression of some orderly molecular conveyor belt, but the truth was, life in either system was powered by nothing at the deepest level but a sequence of chance collisions.

  A few red tags turned orange. Stage two: an enzyme tightening the molecule’s hexagonal ring into a pentagon, transforming the spare vertex into a protruding cluster, more exposed and reactive than before.

  Still nothing new. And still no hint of violet.

  Nothing further seemed to happen for so long that Maria glanced at her watch and said “Globe”, to see if some major population center had just come on-line for the day – but the authentic Earth-from-space view showed dawn well into the Pacific. California would have been busy since before she’d arrived home.

  A few orange tags turned yellow. Stage three of the Lambert pathway, like stage one, consisted of bonding an energy-rich group of atoms to the sugar. With nutrose, there was a pay-off for this, eventually, with twice as many of the molecules which supplied the energy ending up “recharged” as had been “drained.” Stage four, though – the cleaving of the ring into two smaller fragments – was the point where mutose gummed up the works irretrievably…

  Except that one yellow speck had just split into two, before her eyes … and both new tags were colored violet.

  Maria, startled, lost track of the evidence. Then she caught sight of the same thing happening again. And then a third time.

  It took her a minute to think it through, and understand what this meant. The bacterium wasn’t reversing the change she’d made to the sugar, converting mutose back into nutrose – or doing the same to some part-digested metabolite. Instead, it must have modified the enzyme which broke the ring, coming up with a version which worked directly on the metabolite of mutose.

  Maria froze the action, zoomed in, and watched a molecular-scale replay. The enzyme in question was constructed of thousands of atoms, it was impossible to spot the difference at a glance – but there was no doubt about what it was doing. The two-atom blue-red spike she’d repositioned on the sugar was never shifted back into its “proper” place; instead, the enzyme n
ow accommodated the altered geometry perfectly.

  She summoned up old and new versions of the enzyme, highlighted the regions where the tertiary structure was different, and probed them with her fingertips – confirming, palpably, that the cavity in the giant molecule where the reaction took place had changed shape.

  And once the ring was cleaved? The fragments were the same, whether the original sugar had been nutrose or mutose. The rest of the Lambert pathway went on as if nothing had changed.

  Maria was elated, and a little dazed. People had been trying to achieve a spontaneous adaptation like this for sixteen years. She didn’t even know why she’d finally succeeded; for five years she’d been tinkering with the bacterium’s error correction mechanisms, trying to force A. lamberti to mutate, not more rapidly, but more randomly. Every time, she’d ended up with a strain which – like Lambert’s original, like those of other workers – suffered the same handful of predictable, useless mutations again and again … almost as if something deep in the clockwork of the Autoverse itself ruled out the exuberant diversity which came so effortlessly to real-world biology. Calvin and others had suggested that, because Autoverse physics omitted the deep indeterminacy of real-world quantum mechanics – because it lacked this vital inflow of “true unpredictability” – the same richness of phenomena could never be expected, at any level.

  But that had always been absurd – and now she’d proved it was absurd.

  For a moment she thought of phoning Aden, or Francesca – but Aden wouldn’t understand enough to do more than nod politely, and her mother didn’t deserve to be woken at this hour.

  She got up and paced the tiny bedroom for a while, too excited to remain still. She’d upload a letter to Autoverse Review (total subscription, seventy-three), with the genome of the strain she’d started out with appended as a footnote, so everyone else could try the experiment…

  She sat down and began composing the letter – popping up a word processor in the foreground of the workspace – then decided that was premature; there was still a lot more to be done to form the basis of even a brief report.

  She cloned a small colony of the mutose-eating strain, and watched it grow steadily in a culture of pure mutose. No surprise, but it was still worth doing.

  Then she did the same, with pure nutrose, and the colony, of course, died out at once. The original ring-cleaving enzyme had been lost; the original roles of nutrose and mutose as food and poison had been swapped.

  Maria pondered this. A. lamberti had adapted – but not in the way she’d expected. Why hadn’t it found a means of consuming both sugars, instead of exchanging one kind of exclusive reliance for another? It would have been a far better strategy. It was what a real-world bacterium would have done.

  She brooded over the question for a while – then started laughing. Sixteen years, people had been hunting for a single, convincing example of natural selection in the Autoverse – and here she was worrying that it wasn’t the best of all possible adaptations. Evolution was a random walk across a minefield, not a pre-ordained trajectory, onward and upward toward “perfection.” A. lamberti had stumbled on a successful way to turn poison into food. It was tough luck if the corollary was: vice versa.

  Maria ran a dozen more experiments. She lost all track of time; when dawn came, the software brightened the images in front of her, keeping the daylight from washing them out. It was only when her concentration faltered, and she looked around the room, that she realized how late it was.

  She started again on the letter. After three drafts of the first paragraph – all eliciting the same response from Camel’s Eye: You’ll hate this when you re-read it later. Trust me. – she finally admitted to herself that she was wasted. She shut down everything and crawled into bed.

  She lay there awhile in a stupor, burying her face in the pillow, waiting for the ghost images of Petri dishes and enzymes to fade. Five years ago, she could have worked all night, and suffered nothing worse than a fit of yawning in the middle of the afternoon. Now, she felt like she’d been hit by a train – and she knew she’d be a wreck for days. Thirty-one is old, old, old.

  Her head throbbed, her whole body ached. She didn’t care. All the time and money she’d squandered on the Autoverse was worth it, now. Every moment she’d spent there had been vindicated.

  Yeah? She rolled onto her back and opened her eyes. What, exactly, had changed? It was still nothing but a self-indulgent hobby, an elaborate computer game. She’d be famous with seventy-two other anal-retentive Autoverse freaks. How many bills would that pay? How many typhoons would it neutralize?

  She wrapped her head in the pillow, feeling crippled, stupid, hopeless – and defiantly happy – until her limbs went numb, her mouth went dry, and the room seemed to rock her to sleep.

  Chapter 5

  (Remit not paucity)

  November 2050

  Peer anchored the soles of both feet and the palm of one hand firmly against the glass, and rested for a while. He tipped his head back to take in, one more time, the silver wall of the skyscraper stretching to infinity above him. Cotton-wool clouds drifted by, higher than any part of the building – even though the building went on forever.

  He freed his right foot, re-anchored it higher up the wall, then turned and looked down at the neat grid of the city below, surrounded by suburbs as orderly as plowed fields. The foreshortened countryside beyond formed a green-brown rim to the hemispherical bowl of the earth; a blue-hazed horizon bisected the view precisely. The features of the landscape, like the clouds, were “infinitely large,” and “infinitely distant”; a finite city, however grand, would have shrunk to invisibility, like the base of the skyscraper. The distance was more than a trick of perspective, though; Peer knew he could keep on approaching the ground for as long as he liked, without ever reaching it. Hours, day, centuries.

  He couldn’t remember beginning the descent, although he understood clearly – cloud-knowledge, cloud-memories – the sense in which there was a beginning, and the sense in which there was none. His memories of the skyscraper, like his view of it, seemed to converge toward a vanishing point; looking back from the present moment all he could recall was the act of descending, punctuated by rest. And although his mind had wandered, he’d never lost consciousness; his past seemed to stretch back seamlessly, forever – yet he could hold it all in his finite gaze, thanks to some law of mental perspective, some calculus of memory limiting the sum of ever diminishing contributions to his state of mind from ever more distant moments in the past. But he had his cloud-memories, too; memories from before the descent. He couldn’t join them to the present, but they existed nonetheless, a backdrop informing everything else. He knew exactly who he’d been, and what he’d done, in that time before the time he now inhabited.

  Peer had been exhausted when he’d stopped, but after a minute’s rest he felt, literally, as energetic and enthusiastic as ever. Back in cloud-time, preparing himself, he’d edited out any need or desire for food, drink, sleep, sex, companionship, or even a change of scenery, and he’d pre-programmed his exoself – the sophisticated, but non-conscious, supervisory software which could reach into the model of his brain and body and fine-tune any part of it as required – to ensure that these conditions remained true. He resumed the descent gladly, a happy Sisyphus. Making his way down the smooth mirrored face of the skyscraper was, still, the purest joy he could imagine; the warmth of the sun reflecting back on him, the sharp cool gusts of wind, the faint creak of steel and concrete. Adrenaline and tranquility. The cycle of exertion and perfect recovery. Perpetual motion. Touching infinity.

  The building, the earth, the sky, and his body vanished. Stripped down to vision and hearing, Peer found himself observing his Bunker: a cluster of display screens floating in a black void. Kate was on one screen; two-dimensional, black-and-white, nothing but her lips moving.

  She said, “You set your threshold pretty damn high. You’d be hearing about this a decade later if I hadn’t called you
in.”

  Peer grunted – disconcerted for a moment by the lack of tactile feedback from the conventional organs of speech – and glanced, by way of eye-movement-intention, at the screen beside her, a graph of the recent history of Bunker time versus real time.

  Observing the Bunker – “being in it” would have been an overstatement – was the most computing-efficient state a Copy could adopt, short of losing consciousness. Peer’s body was no longer being simulated at all; the essential parts of his model-of-a-brain had been mapped into an abstract neural network, a collection of idealized digital gates with no pretensions to physiological verisimilitude. He didn’t enter this state very often, but Bunker time was still a useful standard as a basis for comparisons. At best – on the rare occasions when demand slackened, and he shared a processor cluster with only two or three other users – his Bunker-time slowdown factor dropped to about thirty. At worst? Up until a few minutes ago, the worst had been happening: a section of the graph was perfectly flat. For more than ten hours of real time, he hadn’t been computed at all.

  Kate said, “Operation Butterfly. Weather control simulations. The fuckers bought up everything.”

  She sounded shaken and angry. Peer said calmly, “No great loss. Solipsist Nation means making your own world, on your own terms. Whatever the risks. Real time doesn’t matter. Let them give us one computation per year. What would it change? Nothing.” He glanced at another display, and realized that he’d only been in the skyscraper model for seven subjective minutes. The false memories had meshed perfectly; he would never have believed it had been so short a time. Pre-computing the memories had taken time, of course – but far less than it would have taken to accumulate the same effect by conventional experience.

  Kate said, “You’re wrong. You don’t—”

  “Let them run one moment of model time for one Copy on every processor cluster, the day it’s commissioned – and then dedicate it entirely to other users. Each Copy would thread its way from machine to machine, with a slowdown of a few billion … and it wouldn’t matter. The manufacturers could run us all for free – turn it into a kind of ritual, a blessing of the hardware by the spirits of the dead. Then we could abolish all the trust funds, and stop worrying about money altogether. The cheaper we are, the less vulnerable we are.”