Artifacts

by Greg Egan

  She said, “I want sharp borders, right now. I want to deal with this myself.”

  “I understand.” He let the partial model of her which he’d acquired as they’d made love fade from his mind. It was non-sapient, and no longer linked to her—but to retain it any longer when she felt this way would have seemed like a transgression. Paolo took the responsibilities of intimacy seriously. His lover before Elena had asked him to erase all his knowledge of her, and he’d more or less complied—the only thing he still knew about her was the fact that she’d made the request.

  Hermann announced, “Planetfall!” Paolo glanced at a replay of a scout probe view which showed the first few entry capsules breaking up above the ocean and releasing their microprobes. Nanomachines transformed the ceramic shields (and then themselves) into carbon dioxide and a few simple minerals—nothing the micrometeorites constantly raining down onto Orpheus didn’t contain—before the fragments could strike the water. The microprobes would broadcast nothing; when they’d finished gathering data, they’d float to the surface and modulate their UV reflectivity. It would be up to the scout probes to locate these specks, and read their messages, before they self-destructed as thoroughly as the entry capsules.

  Hermann said, “This calls for a celebration. I’m heading for the Heart. Who’ll join me?”

  Paolo glanced at Elena. She shook her head. “You go.”

  “Are you sure?”

  “Yes! Go on.” Her skin had taken on a mirrored sheen; her expressionless face reflected the planet below. “I’m all right. I just want some time to think things through, on my own.”

  Hermann coiled around the satellite’s frame, stretching his pale body as he went, gaining segments, gaining legs. “Come on, come on! Karpal? Liesl? Come and celebrate!”

  Elena was gone. Liesl made a derisive sound and flapped off into the distance, mocking the environment’s airlessness. Paolo and Karpal watched as Hermann grew longer and faster—and then in a blur of speed and change stretched out to wrap the entire geodesic frame. Paolo demagnetized his feet and moved away, laughing; Karpal did the same.

  Then Hermann constricted like a boa, and snapped the whole satellite apart.

  They floated for a while, two human-shaped machines and a giant worm in a cloud of spinning metal fragments, an absurd collection of imaginary debris, glinting by the light of the true stars.

  The Heart was always crowded, but it was larger than Paolo had seen it—even though Hermann had shrunk back to his original size, so as not to make a scene. The huge muscular chamber arched above them, pulsating wetly in time to the music, as they searched for the perfect location to soak up the atmosphere. Paolo had visited public environments in other polises, back on Earth; many were designed to be nothing more than a perceptual framework for group emotion-sharing. He’d never understood the attraction of becoming intimate with large numbers of strangers. Ancestral social hierarchies might have had their faults—and it was absurd to try to make a virtue of the limitations imposed by minds confined to wetware—but the whole idea of mass telepathy as an end in itself seemed bizarre to Paolo … and even old-fashioned, in a way. Humans, clearly, would have benefited from a good strong dose of each other’s inner life, to keep them from slaughtering each other—but any civilized transhuman could respect and value other citizens without the need to have been them, firsthand.

  They found a good spot and made some furniture, a table and two chairs—Hermann preferred to stand—and the floor expanded to make room. Paolo looked around, shouting greetings at the people he recognized by sight, but not bothering to check for identity broadcasts from the rest. Chances were he’d met everyone here, but he didn’t want to spend the next hour exchanging pleasantries with casual acquaintances.

  Hermann said, “I’ve been monitoring our modest stellar observatory’s data stream—my antidote to Vegan parochialism. Odd things are going on around Sirius. We’re seeing electron-positron annihilation gamma rays, gravity waves … and some unexplained hot spots on Sirius B.” He turned to Karpal and asked innocently, “What do you think those robots are up to? There’s a rumor that they’re planning to drag the white dwarf out of orbit, and use it as part of a giant spaceship.”

  “I never listen to rumors.” Karpal always presented as a faithful reproduction of his old human-shaped Gleisner body—and his mind, Paolo gathered, always took the form of a physiological model, even though he was five generations removed from flesh. Leaving his people and coming into C-Z must have taken considerable courage; they’d never welcome him back.

  Paolo said, “Does it matter what they do? Where they go, how they get there? There’s more than enough room for both of us. Even if they shadowed the diaspora—even if they came to Vega—we could study the Orpheans together, couldn’t we?”

  Hermann’s cartoon insect face showed mock alarm, eyes growing wider, and wider apart. “Not if they dragged along a white dwarf! Next thing they’d want to start building a Dyson sphere.” He turned back to Karpal. “You don’t still suffer the urge, do you, for … astrophysical engineering?”

  “Nothing C-Z’s exploitation of a few megatons of Vegan asteroid material hasn’t satisfied.”

  Paolo tried to change the subject. “Has anyone heard from Earth, lately? I’m beginning to feel unplugged.” His own most recent message was a decade older than the time lag.

  Karpal said, “You’re not missing much; all they’re talking about is Orpheus … ever since the new lunar observations, the signs of water. They seem more excited by the mere possibility of life than we are by the certainty. And they have very high hopes.”

  Paolo laughed. “They do. My Earth-self seems to be counting on the diaspora to find an advanced civilization with the answers to all of transhumanity’s existential problems. I don’t think he’ll get much cosmic guidance from kelp.”

  “You know there was a big rise in emigration from C-Z after the launch? Emigration, and suicides.” Hermann had stopped wriggling and gyrating, becoming almost still, a sign of rare seriousness. “I suspect that’s what triggered the astronomy program in the first place. And it seems to have stanched the flow, at least in the short term. Earth C-Z detected water before any clone in the diaspora—and when they hear that we’ve found life, they’ll feel more like collaborators in the discovery because of it.”

  Paolo felt a stirring of unease. Emigration and suicides? Was that why Orlando had been so gloomy? After three hundred years of waiting, how high had expectations become?

  A buzz of excitement crossed the floor, a sudden shift in the tone of the conversation. Hermann whispered reverently, “First microprobe has surfaced. And the data is coming in now.”

  The non-sapient Heart was intelligent enough to guess its patrons’ wishes. Although everyone could tap the library for results, privately, the music cut out and a giant public image of the summary data appeared, high in the chamber. Paolo had to crane his neck to view it, a novel experience.

  The microprobe had mapped one of the carpets in high resolution. The image showed the expected rough oblong, some hundred meters wide—but the two-or-three-meter-thick slab of the neutrino tomographs was revealed now as a delicate, convoluted surface—fine as a single layer of skin, but folded into an elaborate space-filling curve. Paolo checked the full data: the topology was strictly planar, despite the pathological appearance. No holes, no joins—just a surface which meandered wildly enough to look ten thousand times thicker from a distance than it really was.

  An inset showed the microstructure, at a point which started at the rim of the carpet and then—slowly—moved toward the center. Paolo stared at the flowing molecular diagram for several seconds before he grasped what it meant.

  The carpet was not a colony of single-celled creatures. Nor was it a multi-cellular organism. It was a single molecule, a two-dimensional polymer weighing twenty-five million kilograms. A giant sheet of folded polysaccharide, a complex mesh of interlinked pentose and hexose sugars hung with alkyl and amide side
chains. A bit like a plant cell wall—except that this polymer was far stronger than cellulose, and the surface area was twenty orders of magnitude greater.

  Karpal said, “I hope those entry capsules were perfectly sterile. Earth bacteria would gorge themselves on this. One big floating carbohydrate dinner, with no defenses.”

  Hermann thought it over. “Maybe. If they had enzymes capable of breaking off a piece—which I doubt. No chance we’ll find out, though: even if there’d been bacterial spores lingering in the asteroid belt from early human expeditions, every ship in the diaspora was double-checked for contamination en route. We haven’t brought smallpox to the Americas.”

  Paolo was still dazed. “But how does it assemble? How does it … grow?” Hermann consulted the library and replied, before Paolo could do the same.

  “The edge of the carpet catalyzes its own growth. The polymer is irregular, aperiodic—there’s no single component which simply repeats. But there seem to be about twenty thousand basic structural units—twenty thousand different polysaccharide building blocks.” Paolo saw them: long bundles of cross-linked chains running the whole two-hundred-micron thickness of the carpet, each with a roughly square cross-section, bonded at several thousand points to the four neighboring units. “Even at this depth, the ocean’s full of UV-generated radicals which filter down from the surface. Any structural unit exposed to the water converts those radicals into more polysaccharide—and builds another structural unit.”

  Paolo glanced at the library again, for a simulation of the process. Catalytic sites strewn along the sides of each unit trapped the radicals in place, long enough for new bonds to form between them. Some simple sugars were incorporated straight into the polymer as they were created; others were set free to drift in solution for a microsecond or two, until they were needed. At that level, there were only a few basic chemical tricks being used … but molecular evolution must have worked its way up from a few small autocatalytic fragments, first formed by chance, to this elaborate system of twenty thousand mutually self-replicating structures. If the “structural units” had floated free in the ocean as independent molecules, the “lifeform” they comprised would have been virtually invisible. By bonding together, though, they became twenty thousand colors in a giant mosaic.

  It was astonishing. Paolo hoped Elena was tapping the library, wherever she was. A colony of algae would have been more “advanced”—but this incredible primordial creature revealed infinitely more about the possibilities for the genesis of life. Carbohydrate, here, played every biochemical role: information carrier, enzyme, energy source, structural material. Nothing like it could have survived on Earth, once there were organisms capable of feeding on it—and if there were ever intelligent Orpheans, they’d be unlikely to find any trace of this bizarre ancestor.

  Karpal wore a secretive smile.

  Paolo said, “What?”

  “Wang tiles. The carpets are made out of Wang tiles.”

  Hermann beat him to the library, again.

  “Wang as in twentieth-century flesh mathematician, Hao Wang. Tiles as in any set of shapes which can cover the plane. Wang tiles are squares with various shaped edges, which have to fit complementary shapes on adjacent squares. You can cover the plane with a set of Wang tiles, as long as you choose the right one every step of the way. Or in the case of the carpets, grow the right one.”

  Karpal said, “We should call them Wang’s Carpets, in honor of Hao Wang. After twenty-three hundred years, his mathematics has come to life.”

  Paolo liked the idea, but he was doubtful. “We may have trouble getting a two-thirds majority on that. It’s a bit obscure …”

  Hermann laughed. “Who needs a two-thirds majority? If we want to call them Wang’s Carpets, we can call them Wang’s Carpets. There are ninety-seven languages in current use in C-Z—half of them invented since the polis was founded. I don’t think we’ll be exiled for coining one private name.”

  Paolo concurred, slightly embarrassed. The truth was, he’d completely forgotten that Hermann and Karpal weren’t actually speaking Modern Roman.

  The three of them instructed their exoselves to consider the name adopted: henceforth they’d hear “carpet” as “Wang’s Carpet”—but if they used the term with anyone else, the reverse translation would apply.

  Paolo sat and drank in the image of the giant alien: the first lifeform encountered by human or transhuman which was not a biological cousin. The death, at last, of the possibility that Earth might be unique.

  They hadn’t refuted the anthrocosmologists yet, though. Not quite. If, as the ACs claimed, human consciousness was the seed around which all of space-time had crystallized—if the universe was nothing but the simplest orderly explanation for human thought—then there was, strictly speaking, no need for a single alien to exist, anywhere. But the physics which justified human existence couldn’t help generating a billion other worlds where life could arise. The ACs would be unmoved by Wang’s Carpets; they’d insist that these creatures were physical, if not biological, cousins—merely an unavoidable byproduct of anthropogenic, life-enabling physical laws.

  The real test wouldn’t come until the diaspora—or the Gleisner robots—finally encountered conscious aliens: minds entirely unrelated to humanity, observing and explaining the universe which human thought had supposedly built. Most ACs had come right out and declared such a find impossible; it was the sole falsifiable prediction of their hypothesis. Alien consciousness, as opposed to mere alien life, would always build itself a separate universe—because the chance of two unrelated forms of self-awareness concocting exactly the same physics and the same cosmology was infinitesimal—and any alien biosphere which seemed capable of evolving consciousness would simply never do so.

  Paolo glanced at the map of the diaspora, and took heart. Alien life already—and the search had barely started; there were nine hundred and ninety-eight target systems yet to be explored. And even if every one of them proved no more conclusive than Orpheus … he was prepared to send clones out farther—and prepared to wait. Consciousness had taken far longer to appear on Earth than the quarter-of-a-billion years remaining before Vega left the main sequence—but the whole point of being here, after all, was that Orpheus wasn’t Earth.

  Orlando’s celebration of the microprobe discoveries was a very first-generation affair. The environment was an endless sunlit garden strewn with tables covered in food, and the invitation had politely suggested attendance in fully human form. Paolo politely faked it—simulating most of the physiology, but running the body as a puppet, leaving his mind unshackled.

  Orlando introduced his new lover, Catherine, who presented as a tall, dark-skinned woman. Paolo didn’t recognize her on sight, but checked the identity code she broadcast. It was a small polis, he’d met her once before—as a man called Samuel, one of the physicists who’d worked on the main interstellar fusion drive employed by all the ships of the diaspora. Paolo was amused to think that many of the people here would be seeing his father as a woman. The majority of the citizens of C-Z still practiced the conventions of relative gender which had come into fashion in the twenty-third century—and Orlando had wired them into his own son too deeply for Paolo to wish to abandon them—but whenever the paradoxes were revealed so starkly, he wondered how much longer the conventions would endure. Paolo was same-sex to Orlando, and hence saw his father’s lover as a woman, the two close relationships taking precedence over his casual knowledge of Catherine as Samuel. Orlando perceived himself as being male and heterosexual, as his flesh original had been … while Samuel saw himself the same way … and each perceived the other to be a heterosexual woman. If certain third parties ended up with mixed signals, so be it. It was a typical C-Z compromise: nobody could bear to overturn the old order and do away with gender entirely (as most other polises had done) … but nobody could resist the flexibility which being software, not flesh, provided.

  Paolo drifted from table to table, sampling the food to keep up a
ppearances, wishing Elena had come. There was little conversation about the biology of Wang’s Carpets: most of the people here were simply celebrating their win against the opponents of the microprobes—and the humiliation that faction would suffer, now that it was clearer than ever that the “invasive” observations could have done no harm. Liesl’s fears had proved unfounded; there was no other life in the ocean, just Wang’s Carpets of various sizes. Paolo, feeling perversely even-handed after the fact, kept wanting to remind these smug movers and shakers: There might have been anything down there. Strange creatures, delicate and vulnerable in ways we could never have anticipated. We were lucky, that’s all.

  He ended up alone with Orlando almost by chance; they were both fleeing different groups of appalling guests when their paths crossed on the lawn.

  Paolo asked, “How do you think they’ll take this, back home?”

  “It’s first life, isn’t it? Primitive or not. It should at least maintain interest in the diaspora, until the next alien biosphere is discovered.” Orlando seemed subdued; perhaps he was finally coming to terms with the gulf between their modest discovery, and Earth’s longing for world-shaking results. ‘And at least the chemistry is novel. If it had turned out to be based on DNA and protein, I think half of Earth C-Z would have died of boredom on the spot. Let’s face it, the possibilities of DNA have been simulated to death.”

  Paolo smiled at the heresy. “You think if nature hadn’t managed a little originality, it would have dented people’s faith in the charter? If the solipsist polises had begun to look more inventive than the universe itself …”