Diaspora

by Greg Egan

  Paolo willed the polis library to brief him; it promptly rewired the declarative memory of his simulated traditional brain with all the information he was likely to need to satisfy his immediate curiosity. This clone of C-Z had arrived at Vega, the second closest of the thousand target stars, twenty-seven light years from Earth. Theirs was the first ship to reach its destination; the ship aimed at Fomalhaut had been struck by debris and annihilated en route. Paolo found it hard to grieve for the ninety-two citizens who’d been awake; he hadn’t been close to any of them prior to the cloning, and the particular versions who’d willfully perished two centuries ago in interstellar space seemed as remote as the victims of Lacerta.

  He examined his new home star through the cameras of one of the scout probes — and the strange filters of the ancestral visual system. In traditional colors, Vega was a fierce blue-white disk, laced with prominences. Three times the mass of the sun, twice the size and twice as hot, sixty times as luminous. Burning hydrogen fast, and already halfway through its allotted five hundred million years on the main sequence.

  Vega’s sole planet, Orpheus, had been a featureless blip to the best interferometers in the solar system; now Paolo gazed down on its blue-green crescent, ten thousand kilometers below Carter-Zimmerman itself. Orpheus was terrestrial, a nickel-iron-silicate world; slightly larger than Earth, slightly warmer — a billion kilometers took the edge off Vega’s heat — and almost drowning in liquid water. Paolo rushed at a thousand times flesher, allowing C-Z to orbit the planet in twenty subjective tau; daylight unshrouded a broad new swath with each pass. Two slender ocher-colored continents with mountainous spines bracketed hemispheric oceans, and dazzling expanses of pack ice covered both poles — far more so in the north, where jagged white peninsulas radiated out from the midwinter arctic darkness.

  The Orphean atmosphere was mostly nitrogen — six times as much as on Earth — with traces of water vapor and carbon dioxide, but not enough of either for a runaway greenhouse effect. The high atmospheric pressure meant reduced evaporation — Paolo saw not a wisp of cloud — and the large, warm oceans in turn helped lock up carbon dioxide. The gamma-ray burst from Lacerta had been even stronger here than on Earth, but with no ozone layer to destroy, and an atmosphere routinely ionized by Vega’s own intense ultraviolet, any change in the chemical environment or the radiation levels at low altitudes would have been relatively minor.

  The whole system was young by Earth standards, still thick with primordial dust. But Vega’s greater mass, and a denser protostellar cloud, would have meant swifter passage through most of the traumas of birth: nuclear ignition and early luminosity fluctuations; planetary coalescence and the age of bombardments. The library estimated that Orpheus had enjoyed a relatively stable climate, and freedom from major impacts, for at least the past hundred million years.

  Long enough for primitive life to appear —

  A hand seized Paolo firmly by the ankle and tugged him beneath the water. He offered no resistance, and let the vision of the planet slip away. Only two other people in C-Z had free access to this scape — and his father didn’t play games with his now-twelve-hundred-year-old son.

  Elena dragged him all the way to the bottom of the pool, before releasing his foot and hovering above him, a triumphant silhouette against the bright surface. She was flesher-shaped but obviously cheating; she spoke with perfect clarity, and no air bubbles at all.

  “Late sleeper! I’ve been waiting five megatau for this!”

  Paolo feigned indifference, but he was fast running out of breath. He had his exoself convert him into an amphibious exuberant — biologically and historically authentic, though none of his own ancestors had taken this form. Water flooded into his modified lungs, and his modified brain welcomed it.

  He said, “Why would I want to waste consciousness, sitting around waiting for the scout probes to refine their observations? 1 woke as soon as the data was unambiguous.”

  She pummeled his chest; he reached up and pulled her down, instinctively reducing his buoyancy to compensate, and they rolled across the bottom of the pool, kissing.

  Elena said, “You know we’re the first C-Z to arrive, anywhere? The Fomalhaut ship was destroyed. So there’s only one other pair of us. Back on Earth.”

  “So?” Then he remembered. Elena had chosen not to wake if any other version of her had already encountered life. Whatever fate befell each of the remaining ships, every other version of him would have to live without her.

  He nodded soberly, and kissed her again. “What am I meant to say? You’re a thousand times more precious to me, now?”

  “Yes.”

  “Ah, but what about the you-and-I on Earth? Five hundred times would be closer to the truth.”

  “There’s no poetry in five hundred.”

  “Don’t be so defeatist. Rewire your language centers.”

  She ran her hands along the sides of his ribcage, down to his hips. They made love with their almost-traditional bodies — and brains; Paolo was amused to the point of distraction when his limbic system went into overdrive, but he remembered enough from the last occasion to bury his self-consciousness and surrender to the strange hijacker. It wasn’t like making love in any civilized fashion — the rate of information exchange between them was minuscule, for a start — but it had the raw insistent quality of most ancestral pleasures.

  Then they drifted up to the surface of the pool and lay beneath the radiant sunless sky.

  Paolo thought: I’ve crossed twenty-seven light years in an instant. I’m orbiting the first planet ever found to hold alien life. And I’ve sacrificed nothing — left nothing I truly value behind. This is too good, too good. He felt a pang of regret for his other selves — it was hard to imagine them faring as well, without Elena, without Orpheus — but there was nothing he could do about that, now. Although there’d be time to confer with Earth before any more ships reached their destinations, he’d decided prior to the cloning not to allow the unfolding of his manifold future to be swayed by any change of heart. Whether or not his Earth-self agreed, the two of them were powerless to alter the criteria for waking. The self with the right to choose for the thousand had passed away.

  No matter, Paolo decided. The others would find — or construct — their own reasons for happiness. And there was still the chance that one of them would wake to the sound of four chimes.

  Elena said, “If you’d slept much longer, you would have missed the vote.”

  The vote? The scouts in low orbit had gathered what data they could about Orphean biology. To proceed any further, it would be necessary to send microprobes into the ocean itself — an escalation of contact which required the approval of two thirds of the polis. There was no compelling reason to believe that the presence of a few million tiny robots could do any harm; all they’d leave behind in the water was a few kilojoules of waste heat. Nevertheless, a faction had arisen that advocated caution. The citizens of Carter-Zimmerman, they argued, could continue to observe from a distance for another decade, or another millennium, refining their observations and hypotheses before intruding ... and those who disagreed could always sleep away the time, or find other interests to pursue.

  Paolo delved into his library-fresh knowledge of the “carpets,” the sole Orphean lifeform detected so far. They were free-floating creatures living in the equatorial ocean depths — apparently destroyed by UV if they drifted too close to the surface, but sufficiently well-shielded in their normal habitat to have been completely oblivious to Lacerta. They grew to a size of hundreds of meters, then fissioned into dozens of fragments, each of which continued to grow. It was tempting to assume that they were colonies of single-celled organisms, something like giant kelp, but there was no real evidence yet to back that up. It was difficult enough for the scout probes to discern the carpets’ gross appearance and behavior through a kilometer of water, even with Vega’s copious neutrinos lighting the way; remote observations on a microscopic scale, let alone biochemical analyses,
were out of the question. Spectroscopy revealed that the surface water was full of intriguing molecular debris, but guessing the relationship of any of it to the living carpets was like trying to reconstruct flesher biochemistry by studying their ashes.

  Paolo turned to Elena. “What do you think?”

  She moaned theatrically; the topic must have been argued to death while he slept. “The microprobes are harmless. They could tell us exactly what the carpets are made of, without removing a single molecule. What’s the risk? Culture shock?”

  Paolo flicked water onto her face, affectionately; the impulse seemed to come with the amphibian body. “You can’t be sure that they’re not intelligent.”

  “Do you know what was living on Earth, two hundred million years after it was formed?”

  “Maybe cyanobacteria. Maybe nothing. This isn’t Earth, though.”

  “True. But even in the unlikely event that the carpets are intelligent, do you think they’d notice the presence of robots a millionth their size? If they’re unified organisms, they don’t appear to react to anything in their environment — they have no predators, they don’t pursue food, they just drift with the currents — so there’s no reason for them to possess elaborate sense organs at all, let alone anything working on a sub-millimeter scale. And if they’re colonies of single-celled creatures, one of which happens to collide with a microprobe and register its presence with surface receptors ... what conceivable harm could that do?”

  Paolo shrugged. “I have no idea. But my ignorance is no guarantee of safety.”

  Elena splashed him back. “The only way to deal with your ignorance is to vote to send down the microprobes. We have to be cautious, I agree, but there’s no point being here if we don’t find out what’s happening in the oceans, right now. I don’t want to wait for this planet to evolve something smart enough to broadcast biochemistry lessons into space. If we’re not willing to take a few infinitesimal risks, Vega will turn red giant before we learn anything.”

  It was a throwaway line, but Paolo tried to imagine witnessing the event. In a quarter of a billion years, would the citizens of Carter-Zimmerman be debating the ethics of intervening to rescue the Orpheans — or would they have lost interest and departed for other stars, or modified themselves into beings entirely devoid of nostalgic compassion for organic life?

  Grandiose visions for a twelve-hundred-year-old. The Fomalhaut clone had been obliterated by one tiny piece of rock. There was far more junk in the Vegan system than in interstellar space; even ringed by defenses, its data backed up to all the far-flung scout probes, this C-Z was not invulnerable just because it had arrived intact. Elena was right; they had to seize the moment — or they might as well retreat into their own hermetic worlds and forget that they’d ever made the journey.

  “We can’t lie here forever; the gang’s all waiting to see you.”

  “Where?” Paolo felt his first pang of homesickness; on Earth, his circle of friends had always met in a real-time image of the Mount Pinatubo crater, plucked straight from the observation satellites. A recording wouldn’t be the same.

  “I’ll show you.”

  Paolo reached over and took her hand, then followed her as she jumped. The pool, the sky, the courtyard vanished — and he found himself gazing down on Orpheus again ... nightside, but far from dark, with his full mental palette now encoding everything from the pale wash of ground-current long-wave radio to the multicolored shimmer of isotopic gamma rays and back-scattered cosmic-ray bremsstrahlung. Half the abstract knowledge the library had fed him about the planet was obvious at a glance, now. The ocean’s smoothly tapered thermal glow spelled three-hundred Kelvin instantly — as well as back-lighting the atmosphere’s tell-tale infrared silhouette.

  He was standing on a long, metallic-looking girder, one edge of a vast geodesic sphere, open to the blazing cathedral of space. He glanced up and saw the star-rich dust-clogged band of the Milky Way, encircling him from zenith to nadir; aware of the glow of every gas cloud, discerning each absorption and emission line, Paolo could almost feel the plane of the galactic disk transect him. Some constellations were distorted, but the view was more familiar than strange, and he recognized most of the old signposts by color. Once he had his bearings, the direction they’d taken became clear from the way the nearer stars had gained or lost brightness. The once-dazzling Sirius was the most strikingly diminished, so Paolo searched the sky around it. Five degrees away — south, by parochial Earth reckoning — faint but unmistakable: the sun.

  Elena was beside him, superficially unchanged, although they’d both shrugged off the constraints of biology. The conventions of this scape mimicked the physics of real macroscopic objects in free-fall and vacuum, but it wasn’t set up to model any kind of chemistry, let alone that of flesh and blood. Their bodies were now just ordinary C-Z icons, solid and tangible but devoid of elaborate microstructure — and their minds weren’t embedded in the scape at all, but were running as pure Shaper in their respective exoselves.

  Paolo was relieved to be back to normal. Ceremonial regression to the ancestral form every now and then kept his father happy — and being a flesher was largely self-affirming, while it lasted — but every time he emerged from the experience he felt like he’d broken free of billion-year-old shackles. There were polises where the citizens would have found his present structure almost as archaic, but the balance seemed right to Paolo; he enjoyed the sense of embodiment that came from a tactile surface and proprioceptive feedback, but only a fanatic could persist in simulating kilograms of pointless viscera, perceiving every scape through crippled sense organs, and subjugating vis mind to all the unpleasant quirks of flesher neurobiology.

  Their friends gathered round, showing off their effortless free-fall acrobatics, greeting Paolo and chiding him for not arranging to wake sooner; he was the last of the gang to emerge from hibernation.

  “Do you like our humble new meeting place?” Hermann floated by Paolo’s shoulder, a chimeric cluster of limbs and sense-organs, speaking through the vacuum in modulated infrared. “We call it Satellite Pinatubo. It’s desolate up here, I know — but we were afraid it might violate the spirit of caution if we dared pretend to walk the Orphean surface.”

  Paolo glanced mentally at a scout probe’s close-up of a typical stretch of dry land, an expanse of barren red rock. “More desolate down there, I think.” He was tempted to touch the ground — to let the private vision become tactile — but he resisted. Being elsewhere in the middle of a conversation was bad etiquette.

  “Ignore Hermann. He wants to flood Orpheus with our alien machinery before we have any idea what the effects might be.” Liesl was a green-and-turquoise butterfly, with a stylized face stippled in gold on each wing.

  Paolo was surprised; from the way Elena had spoken he’d assumed that his friends must have come to a consensus in favor of the microprobes, and only a late sleeper, new to the issues, would bother to argue the point. “What effects? The carpets —”

  “Forget the carpets! Even if the carpets are as simple as they look, we don’t know what else is down there.” As Liesl’s wings fluttered, her mirror-image faces seemed to glance at each other for support. “With neutrino imaging, we barely achieve spatial resolution in meters, time resolution in seconds. We don’t know anything about smaller lifeforms.”

  “And we never will, if you have your way.” Karpal — an ex-gleisner, flesher-shaped as ever — had been Liesl’s lover, last time Paolo was awake.

  “We’ve only been here for a fraction of an Orphean year! There’s still a wealth of data we could gather non-intrusively, with a little patience. There might be rare beachings of ocean life —”

  Elena said dryly, “Rare indeed. Orpheus has negligible tides, shallow waves, very few storms. And anything beached would be fried by UV before we glimpsed anything more instructive than we’re already seeing in the surface water.”

  “Not necessarily. The carpets seem to be vulnerable, but other species might be be
tter protected if they live nearer to the surface. And Orpheus is seismically active; we should at least wait for a tsunami to dump a few cubic kilometers of ocean onto a shoreline, and see what it reveals.”

  Paolo smiled; he hadn’t thought of that. A tsunami might be worth waiting for.

  Liesl continued, “What is there to lose, by waiting a few hundred Orphean years? At the very least, we could gather baseline data on seasonal climate patterns — and we could watch for anomalies, storms, and quakes, hoping for some revelatory glimpses.”

  A few hundred Orphean years? A few terrestrial millennia? Paolo’s ambivalence waned. If he’d wanted to inhabit geological time he would have migrated to the Lokhande polis, where the Order of Contemplative Observers rushed fast enough to watch Earth’s mountains erode in kilotau. Orpheus hung in the sky beneath them, a beautiful puzzle waiting to be decoded, demanding to be understood.

  He said, “But what if there are no ‘revelatory glimpses’? How long do we wait? We don’t know how rare life is — in time, or in space. If this planet is precious, so is the epoch it’s passing through. We don’t know how rapidly Orphean biology is evolving; species might appear and vanish while we agonize over the risks of gathering better data. The carpets — and whatever else — could die out before we’d learned the first thing about them. What a waste that would be!”

  Liesl stood her ground.

  “And if we damage the Orphean ecology — or culture — by rushing in? That wouldn’t be a waste. It would be a tragedy.”

  Paolo assimilated all the stored transmissions from his Earth-self — almost three hundred years’ worth — before composing a reply. The early communications included detailed mind grafts, and it was good to share the excitement of the Diaspora’s launch; to watch — very nearly firsthand — the thousand ships, nanomachine-carved from asteroids, depart in a blaze of annihilation gamma rays. Then things settled down to the usual prosaic matters: Elena, the gang, shameless gossip, Carter-Zimmerman’s ongoing research projects, the buzz of inter-polis cultural tensions, the not-quite-cyclic convulsions of the arts (the perceptual aesthetic overthrows the emotional, again ... although Valladas in Konishi polis claims to have constructed a new synthesis of the two).