Permutation City

by Greg Egan

  Squeak. “If you did, it was an artificial world; created, not discovered.”

  “Found, created … there’s no real difference.”

  Squeak. “What are you claiming? Some influence from this other world flowed into the computers, changed the way the model ran?”

  “Of course not! Your pattern hasn’t been violated; the computers did exactly what was expected of them. That doesn’t invalidate my perspective. Stop thinking of explanations, causes and effects; there are only patterns. The scattered events that formed my experience had an internal consistency every bit as real as the consistency in the actions of the computers. And perhaps the computers didn’t provide all of it.”

  Squeak. “What do you mean?”

  “The gaps, in experiment one. What filled them in? What was I made of, when the processors weren’t describing me? Well … it’s a big universe. Plenty of dust to be me, in between descriptions. Plenty of events – nothing to do with your computers, maybe nothing to do with your planet or your epoch – out of which to construct ten seconds of experience.”

  Squeak. The djinn looked seriously worried now. “You’re a Copy in a virtual environment under computer control. Nothing more, nothing less. These experiments prove that your internal sense of space and time is invariant. That’s exactly what we always expected – remember? Come down to Earth. Your states are computed, your memories have to be what they would have been without manipulation. You haven’t visited any other worlds, you haven’t built yourself out of fragments of distant galaxies.”

  Paul laughed. “Your stupidity is … surreal. What did you create me for, if you’re not even going to listen to what I have to say? I’ve had a glimpse of the truth behind … everything: space, time, the laws of physics. You can’t shrug that off by saying that what happened to me was inevitable.”

  Squeak. “Control and subject are still identical.”

  “Of course they are! That’s the whole point! Like … gravity and acceleration in General Relativity – it all depends on what you can’t tell apart. This is a new Principle of Equivalence, a new symmetry between observers. Relativity threw out absolute space and time – but it didn’t go far enough. We have to throw out absolute cause and effect!”

  Squeak. The djinn muttered, dismayed, “Elizabeth said this would happen. She said it was only a matter of time before you’d lose touch.”

  Paul stared at him, jolted back to the mundane. “Elizabeth? You said you hadn’t even told her.”

  Squeak. “Well, I have now. I didn’t tell you, because I didn’t think you’d want to hear her reaction.”

  “Which was?”

  Squeak. “I was up all night arguing with her. She wanted me to shut you down. She said I was … seriously disturbed, to even think about doing this.”

  Paul was stung. “What would she know? Ignore her.”

  Squeak. Durham frowned apologetically – an expression Paul recognized at once, and his guts turned to ice. “Maybe I should pause you, while I think things over. Elizabeth raised some … valid ethical questions. I think I should talk it through with her again.”

  “Fuck that! I’m not here for you to put on ice every time you have a change of heart. And if Elizabeth wants to have a say in my life, she can damn well talk it through with me.”

  Paul could see exactly what would happen. If he was paused, Durham wouldn’t restart him – he’d go back to the original scan file and start again from scratch, handling his prisoner differently, hoping to end up with a more cooperative subject. Maybe he wouldn’t even perform the first set of experiments at all.

  The ones which had given him this insight.

  The ones which had made him who he was.

  Squeak. “I need time to think. It would only be temporary. I promise.”

  “No! You have no right!”

  Durham hesitated. Paul felt numb, disbelieving. Some part of him refused to acknowledge any danger – refused to accept that it could be this easy to die. Being paused wouldn’t kill him, wouldn’t harm him, wouldn’t have the slightest effect. What would kill him would be not being restarted. He’d be passively annihilated, ignored out of existence. The fate that befell his own shit.

  Durham reached off-screen.

  Chapter 13

  (Remit not paucity)

  February 2051

  Maria said, “Recalculate everything up to epoch five, then show me sunrise on Lambert. Latitude zero, longitude zero, altitude one.”

  She waited, staring into the blank workspace, fighting the temptation to change her instructions and have the software display every stage of the simulation, which would have slowed things down considerably. After several minutes, a fissured dark plain appeared, raked with silver light. The unnamed sun – dazzling and swollen, and, so low in the sky, too white by far – turned a chain of extinct volcanoes on the horizon into black silhouettes like a row of pointed teeth. In the foreground, the surface looked glassy, inhospitable.

  Maria raised her viewpoint to a thousand meters, then sent it skimming east. The terrain repeated itself, the eerily symmetric cones of the dead volcanoes the only relief from the fractured igneous plains. This specific, detailed scenery was nothing more than a series of computerized “artist’s impressions”, manufactured on demand from purely statistical data about the planet’s topography; the simulation itself hadn’t dealt with anything so finicky as individual volcanoes. Touring the planet was a wasteful means of finding out anything – but it was hard to resist playing explorer, treating this world as if its secrets had to be deduced painstakingly from its appearance … even when the truth was the exact opposite. Reluctantly, Maria froze the image and went straight to the underlying numerical data. The atmosphere was much too thin, again. And this time, there was almost no aqua at all.

  She backtracked through the simulation’s history to see when the aqua had been lost, but this version of Lambert had never possessed significant oceans – or ice caps, or atmospheric vapor. She’d made a slight change in the composition of the primordial gas-and-dust cloud, increasing the proportion of blue and yellow atoms, in the hope that this would ultimately lead to a denser atmosphere for Lambert. Instead, she’d caused more than half of the debris in the Kuiper belt to condense into a whole new stable outer planet. As a consequence, far fewer ice-rich comets from the belt had ended up striking Lambert, robbing it of its largest source of aqua by far – and much of its atmosphere. Gas released by volcanic eruptions provided a poor substitute; the pressure was far too low, and the chemistry was all wrong.

  Maria was beginning to wish she’d kept her mouth shut. It had taken her almost an hour on the phone to persuade Durham that it was worth trying to give Lambert a proper astronomical context, and a geological history that stretched back to the birth of its sun.

  “If we present this world as a fait accompli, and say: ‘Look, it can exist in the Autoverse’ … the obvious response to that will be: ‘Yes, it can exist – if you put it there by hand – but that doesn’t mean it’s ever likely to have formed.’ If we can demonstrate a range of starting conditions that lead to planetary systems with suitable worlds, that will be one less element of uncertainty to be used against us.”

  Durham had eventually agreed, so she’d taken an off-the-shelf planetary-system modeling program – irreverently titled The Laplacian Casino – and adapted it to Autoverse chemistry and physics; not the deep physics of the Autoverse cellular automaton, but the macroscopic consequences of those rules. Mostly, that came down to specifying the properties of various Autoverse molecules: bond energies, melting and boiling points versus pressure, and so on. Aqua was not just water by another name, yellow atoms were not identical to nitrogen – and although some chemical reactions could be translated as if there was a one-to-one correspondence, in the giant fractionating still of a protostellar nebula subtle differences in relative densities and volatilities could have profound effects on the final composition of each of the planets.

  There were also some
fundamental differences. Since the Autoverse had no nuclear forces, the sun would be heated solely by gravitational energy – the velocity its molecules acquired as the diffuse primordial gas cloud fell in on itself. In the real universe, stars unable to ignite fusion reactions ended up as cold, short-lived brown dwarfs – but under Autoverse physics, gravitational heating could power a large enough star for billions of years. (Units of space and time were not strictly translatable – but everybody but the purists did it. If a red atom’s width was taken to be that of hydrogen, and one grid-spacing per clock-tick was taken as the speed of light, a more or less sensible correspondence emerged.) Similarly, although Planet Lambert would lack internal heating from radioisotope decay, its own gravitational heat of formation would be great enough to drive tectonic activity for almost as long as the sun shone.

  Without nuclear fusion to synthesize the elements, their origin remained a mystery, and a convenient gas cloud with traces of all thirty-two – and the right mass and rotational velocity – had to be taken for granted. Maria would have liked to have explored the cloud’s possible origins, but she knew the project would never be finished if she kept lobbying Durham to expand the terms of reference. The point was to explore the potential diversity of Autoverse life, not to invent an entire cosmology.

  Gravity in the Autoverse came as close as real-world gravity to the classical, Newtonian inverse-square law for the range of conditions that mattered, so all the usual real-world orbital dynamics applied. At extreme densities, the cellular automaton’s discrete nature would cause it to deviate wildly from Newton – and Einstein, and Chu – but Maria had no intention of peppering her universe with black holes, or other exotica.

  In fact, gravity had been seen as an irrelevant side effect of Lambert’s original choice of automaton rules – since running an Autoverse large enough for it to make the slightest difference was blatantly impossible – and several people had tried to remove the redundancy, while leaving everything else intact. Nobody had succeeded, though; their “rationalized” versions had always failed to generate anything remotely like the rich chemistry of the original. A Peruvian mathematician, Ricardo Salazar, had eventually proved that they shouldn’t have bothered: the Autoverse rules were poised on the border between two radically different levels of algorithmic complexity, and any tinkering in the hope of improved efficiency was necessarily self-defeating. The presence or absence of gravity, in itself, had no bearing on Autoverse chemistry – but the roots of both phenomena in the simple automaton rules seemed to be inextricably entwined.

  Maria was aiming for a star with four planets. Three small worlds, one giant. The seed-world, Lambert, second from the sun – with a decent-sized moon if possible. Whether or not tidal pools had been a driving force in real-world evolution, life’s bridge from sea to land (and even though the sun itself would cause small tides, regardless), it couldn’t hurt to make Lambert as generally Earth-like as possible, since Earth was still the only example to turn to for inspiration. With so much about terrestrial evolution still in dispute, the safest policy was to cover every factor which might have been significant. The gravitational effects of the other planets would ensure a reasonably complex set of Milankovitch cycles: minor orbital changes and axis wobbles, providing long-term climate variations, ice ages and interglacials. A belt of comets and other debris would complete the picture; not merely supplying an atmosphere, early on, but also offering the chance of occasional mass-extinctions for billions of years to come.

  The trick was to ensure that all of these supposedly evolution-enhancing features coincided with a version of Lambert which could support the seed organism in the first place. Maria had half a dozen possible modifications to A. lamberti in mind, to render it self-sufficient, but she was waiting to see what kind of environments were available before making a final decision.

  That still left unanswered the question of whether the seed organism – or life of any kind – could have arisen on Lambert, rather than being placed there by human hands. Max Lambert’s original reason for designing the Autoverse had been the hope of observing self-replicating molecular systems – primitive life – arising from simple chemical mixtures. The Autoverse was meant to provide a compromise between real-world chemistry – difficult and expensive to manipulate and monitor in test-tube experiments, and hideously slow to compute in faithful simulations – and the tantalizing abstractions of the earliest “artificial life”: computer viruses, genetic algorithms, self-replicating machines embedded in simple cellular automaton worlds; all trivially easy to compute, but unable to throw much light on the genesis of real-world molecular biology.

  Lambert had spent a decade trying to find conditions which would lead to the spontaneous appearance of Autoverse life, without success. He’d constructed A. lamberti – a twelve-year project – to reassure himself that his goal wasn’t absurd; to demonstrate that a living organism could at least function in the Autoverse, however it had come to be there. A. lamberti had permanently side-tracked him; he’d never returned to his original research.

  Maria had day-dreamed about embarking on her own attempt at abiogenesis, but she’d never done anything about it. That kind of work was open-ended; in comparison, any problems with mutations in A. lamberti seemed utterly tractable and well-defined. And although, in a sense, it went to the heart of what Durham was trying to prove, she was glad he’d chosen to compromise; if he’d insisted on starting his “thought experiment” with a totally sterile world, the uncertainties in the transition from inanimate matter to the simplest Autoverse life would have overwhelmed every other aspect of the project.

  She scrapped the desert Planet Lambert and returned to the primordial gas cloud. She popped up a gadget full of slider controls and adjusted the cloud’s composition, taking back half the increases she’d made in the proportions of blue and yellow. Planetology by trial and error. The starting conditions for real-world systems with Earth-like planets had been mapped out long ago, but nobody had ever done the equivalent for the Autoverse. Nobody had ever had a reason.

  Maria felt a flicker of unease. Each time she stopped to remind herself that these worlds would never exist – not even in the sense that a culture of A. lamberti “existed” – the whole project seemed to shift perspective, to retreat into the distance like a mirage. The work itself was exhilarating, she couldn’t have asked for anything more, but each time she forced herself to put it all into context – not in the Autoverse, but in the real world – she found herself light-headed, disoriented. Durham’s reasons for the project were so much flimsier than the watertight internal logic of the thing itself; stepping back from the work was like stepping off a rock-solid planet and seeing it turn into nothing but a lightly tethered balloon.

  She stood and walked over to the window, and parted the curtains. The street below was deserted; the concrete glowed in the hyperreal glare of the midday sun.

  Durham was paying her good money – money that would help get Francesca scanned. That was reason enough to press on. And if the project was ultimately useless, at least it did no harm; it was better than working on some hedonistic VR resort or some interactive war game for psychotic children. She let the curtain fall back into place and returned to her desk.

  The cloud floated in the middle of the workspace, roughly spherical, rendered visible in spite of the fact that its universe was empty of stars. That was a shame; it meant the future citizens of Lambert were destined to be alone. They’d have no prospect of ever encountering alien life – unless they built their own computers, and modeled other planetary systems, other biospheres.

  Maria said, “Recalculate. Then show me sunrise again.”

  She waited.

  And this time – false colors, by definition – the disk of the sun was bright cherry red, beneath a thick band of clouds streaked orange and violet, spread across the sky – and the whole scene was repeated, stretched out before her, shimmering, inverted. Mirrored in the face of the waters.

  #
>
  By a quarter to eight, Maria was thinking about logging off and grabbing some food. She was still on a high, but she could feel how close she was coming to the point where she’d be useless for the next thirty-six hours if she pushed herself any further.

  She’d found a range of starting conditions for the cloud which consistently gave rise to hospitable versions of Lambert, along with all the astronomical criteria she’d been aiming for – except for the large satellite, which would have been a nice touch but wasn’t critical. Tomorrow, she could begin the task of providing A. lamberti with the means of surviving alone on this world, manufacturing its own nutrose from thin air, with the help of sunlight. Other workers had already designed a variety of energy-trapping pigment molecules; the “literal translation” of chlorophyll lacked the right photochemical properties, but a number of useful analogs had been found, and it was a matter of determining which could be integrated into the bacteria’s biochemistry with the fewest complications. Bringing photosynthesis to the Autoverse would be the hardest part of the project, but Maria felt confident; she’d studied Lambert’s notes, and she’d familiarized herself with the full range of techniques he’d developed for adapting biochemical processes to the quirks of Autoverse chemistry. And even if the pigment she chose, for the sake of expediency, wasn’t the most efficient molecule for the task, as long as the seed organism could survive and reproduce it would have the potential to stumble on a better solution itself, eventually.

  The potential, if not the opportunity.

  She was about to shut down The Laplacian Casino when a message appeared in the foreground of the workspace:

  Juno: Statistical analysis of response times and error rates suggests that your link to the JSN is being monitored. Would you like to switch to a more heavily encrypted protocol?

  Maria shook her head, amused. It had to be a bug in the software, not a bug on the line. Juno was a public-domain program (free, but all donations welcome) which she’d downloaded purely as a gesture of solidarity with the US privacy lobby. Federal laws there still made bug-detection software, and any half-decent encryption algorithms, illegal for personal use – lest the FBI be inconvenienced – so Maria had sent Juno’s authors a donation to help them fight the good fight. Actually installing the program had been a joke; the idea of anyone going to the trouble of listening in to her conversations with her mother, or her tedious VR contract work, or her self-indulgent excursions into the Autoverse, was ludicrous.