Diaspora

by Greg Egan

  Karpal replied, more bemused than offended, “It’s the only way to see what’s going on. The only sensible way to apprehend it. Don’t you want to know what the carpets are actually like?”

  Paolo felt himself being tempted. Inhabit a sixteen-dimensional slice of a thousand-dimensional frequency space? But it was in the service of understanding a real physical system — not a novel experience for its own sake.

  And nobody had to find out.

  He ran a quick self-predictive model. There was a ninety-three percent chance that he’d give in, after a kilotau spent agonizing over the decision. It hardly seemed fair to keep Karpal waiting that long.

  He said, “You’ll have to loan me your mind-shaping algorithm. My exoself wouldn’t know where to begin.”

  When it was done, he steeled himself, and jumped back into Karpal’s scape. For a moment, there was nothing but the same meaningless blur as before.

  Then everything suddenly crystallized.

  Creatures swam around them, elaborately branched tubes like mobile coral, vividly colored in all the hues of Paolo’s mental palette — Karpal’s attempt to cram in some of the information that a mere sixteen dimensions couldn’t show? Paolo glanced down at his own body; nothing was missing, but he could see around it in all the thirteen dimensions in which it was nothing but a pin-prick. He quickly looked away. The “coral” seemed far more natural to his altered sensory map, occupying 16-space in all directions, and shaded with hints that it occupied much more. Paolo had no doubt that it was “alive”; it looked more organic than the carpets themselves, by far.

  Karpal said, “Every point in this space encodes some kind of quasi-periodic pattern in the tiles. Each dimension represents a different characteristic size — like a wavelength, although the analogy’s not precise. The position in each dimension represents other attributes of the pattern, relating to the particular tiles it employs. So the localized systems you see around you are clusters of a few billion patterns, all with broadly similar attributes at similar wavelengths.”

  They moved away from the swimming coral, into a swarm of something like jellyfish: floppy hyperspheres waving wispy tendrils (each one of them more substantial than Paolo). Tiny jewel-like creatures darted among them. Paolo was just beginning to notice that nothing moved here like a solid object drifting through normal space; motion seemed to entail a shimmering deformation at the leading hypersurface, a visible process of disassembly and reconsttuction.

  Karpal led him on through the secret ocean. There were helical worms, coiled together in groups of indeterminate number — each single creature breaking up into a dozen or more wriggling slivers, and then recombining ... although not always from the same parts. There were dazzling multicolored stemless flowers, intricate hypercones of “gossamer-thin” fifteen-dimensional petals — each one a hypnotic fractal labyrinth of crevices and capillaries. There were clawed monstrosities, writhing knots of sharp insectile parts like an orgy of decapitated scorpions.

  Paolo said, uncertainly, “You could give people a glimpse of this in just three dimensions. Enough to make it clear that there’s ... life in here. This is going to shake them up badly, though.” Life — embedded in the accidental computations of Wang’s Carpets, with no possibility of ever relating to the world outside. This was an affront to Carter-Zimmerman’s whole philosophy: if nature had evolved “organisms” as divorced from reality as the inhabitants of the most inward-looking polis, where was the privileged status of the physical universe, the clear distinction between reality and illusion? And after three hundred years of waiting for good news from the Diaspora, how would they respond to this back on Earth?

  Karpal said, “There’s one more thing I have to show you.”

  He’d named the creatures squid, for obvious reasons. They were prodding each other with their tentacles in a way that looked thoroughly carnal. Karpal explained, “There’s no analogue of light here. We’re viewing all this according to ad hoc rules which have nothing to do with the native physics. All the creatures here gather information about each other by contact alone — which is actually quite a rich means of exchanging data, with so many dimensions. What you’re seeing is communication by touch.”

  “Communication about what?”

  “Just gossip, I expect. Social relationships.”

  Paolo stared at the writhing mass of tentacles.

  “You think they’re conscious?”

  Karpal, point-like, grinned broadly. “They have a central control structure, with more connectivity than a citizen’s brain, which correlates data gathered from the skin. I’ve mapped that organ, and I’ve started to analyze its function.”

  He led Paolo into another scape, a representation of the data structures in the “brain” of one of the squid. It was — mercifully — three-dimensional, and highly stylized, with translucent colored blocks to represent mental symbols, linked by broad lines indicating the major connections between them. Paolo had seen similar diagrams of citizens’ minds; this was far less elaborate, but eerily familiar nonetheless.

  Karpal said, “Here’s the sensory map of its surroundings. Full of other squid’s bodies, and vague data on the last known positions of a few smaller creatures. But you’ll see that the symbols activated by the physical presence of the other squid are linked to these” — he traced the connection with one finger — “representations. Which are crude miniatures of this whole structure here.”

  “This whole structure” was an assembly labeled with gestalt tags for memory retrieval, simple tropisms, short-term goals. The general business of being and doing.

  “The squid has maps, not just of other squid’s bodies, but their minds as well. Right or wrong, it certainly tries to know what the others are thinking about. And” — he pointed out another set of links, leading to another, less crude, miniature squid mind — “it thinks about its own thoughts as well. I’d call that consciousness, wouldn’t you?”

  Paolo said weakly, “You’ve kept all this to yourself? You came this far, without saying a word —?”

  Karpal was chastened. “I know it was selfish, but once I’d decoded the interactions of the tile patterns, I couldn’t tear myself away long enough to start explaining it to anyone else. And I came to you first because I wanted your advice on the best way to break the news.”

  Paolo laughed bitterly. “The best way to break the news that first alien consciousness is hidden deep inside a biological computer? That everything the Diaspora was meant to prove to the rest of the Coalition has been turned on its head? The best way to explain to the citizens of Carter-Zimmerman that after a three-hundred-year journey, they might as well have stayed on Earth running simulations with as little resemblance to the physical universe as possible?”

  Karpal took the outburst in good humor. “I was thinking more along the lines of the best way to point out that if we hadn’t traveled to Orpheus and studied Wang’s Carpets, we’d never have had the chance to tell the solipsists of Ashton-Laval that all their elaborate invented lifeforms and exotic imaginary universes pale into insignificance compared to what’s really out here — and which only the Carter-Zimmerman Diaspora could have found.”

  Paolo and Elena stood together on the edge of Satellite Pinatubo, watching one of the scout probes aim its maser at a distant point in space. Paolo thought he saw a faint scatter of microwaves from the beam as it made its way out through Vega’s halo of iron-rich dust. Elena’s mind being diffracted all over the cosmos? Best not to think about that.

  He said, “When you meet the other versions of me who haven’t experienced Orpheus, I hope you’ll offer them mind grafts so they won’t be jealous.”

  She frowned. “Ah. Will I or won’t I? You should have asked me before I cloned myself. No need for your clones to be jealous, though. There’ll be worlds far stranger than Orpheus.”

  “I doubt it. You really think so?”

  “I wouldn’t be doing this if I didn’t believe that.” Elena had no power to change the fat
e of the frozen clones of her previous self. But everyone had the right to emigrate.

  Paolo took her hand. The beam had been aimed almost at Regulus, UV-hot and bright, but as he looked away, the cool yellow light of the sun caught his eye.

  Vega C-Z was taking the news of the squid surprisingly well, so far. Karpal’s way of putting it had cushioned the blow: it was only by traveling all this distance across the real, physical universe that they could have made such a discovery — and it was amazing how pragmatic even the most doctrinaire citizens had turned out to be. Before the launch, “alien solipsists” would have been the most unpalatable idea imaginable, the most abhorrent thing the Diaspora could have stumbled upon — but now that they were here, and stuck with the fact of it, people were finding ways to view it in a better light. Orlando had even proclaimed, “This will be the perfect hook for the marginal polises. ‘Travel through real space to witness a truly alien virtual reality.’ We can sell it as a synthesis of the two world views.”

  Paolo still feared for Earth, though, where his Earth-self and others were waiting in hope of guidance. Would they take the message of Wang’s Carpets to heart, and retreat into their own hermetic worlds, oblivious to physical reality? Lacerta could be survived, anything could be survived: all you had to do was bury yourself deep enough.

  He said plaintively, “Where are the aliens, Elena? The ones we can meet? The ones we can talk to? The ones we can learn from?”

  “I don’t know.” She laughed suddenly.

  “What?”

  “It just occurred to me. Maybe the squid are asking themselves exactly the same question.”

  * * *

  Part Five

  « ^ »

  Yatima said, “Swift they’ve seen firsthand. Though they might be surprised by some of the changes since they left.”

  Paolo added wryly, “And how long we took to see past the distractions.”

  “No one’s perfect.” Yatima hesitated. “I was in on the technical side more than you, but I’ll still need you to help piece things together.”

  “Why?” Paolo swung restlessly around the girder he was holding.

  “Are we going to tell them what happened on Poincaré?”

  “Of course.”

  “Then they’ll need to know more about Orlando.”

  * * *

  12

  –

  Heavy

  « ^ »

  Carter-Zimmerman polis, interstellar space

  85 274 532 121 904 CST

  4 July 4936, 1:15:19.058 UT

  Orlando Venetti woke for the twelfth time in nine centuries, clearheaded and hopeful, fully expecting to find that Voltaire C-Z had reached its destination. The previous wake-up calls had all been triggered by bulletins from other clones of the polis, but this time he’d fallen asleep knowing that no more arrivals were due before their own. It was Voltaire’s turn to make news — even if that simply meant adding one more set of barren worlds to the catalogue of post-Orphean anticlimaxes.

  He rolled over and checked the bedside clock, its glowing symbols disembodied in the blackness of the cabin. It was seventeen years before arrival. Someone on another C-Z must have made a belated discovery, important enough for his exoself to wake him. Orlando felt cheated; he’d run out of enthusiasm for the revelations of the other polises, light years away and decades ago.

  He lay swearing for a while, then memories of a dream began to surface. Liana and Paolo had been arguing with him in the house in Atlanta, both trying to convince him that Paolo was her son. Liana had even shown him images of the birth. When Orlando had tried to explain about psychogenesis, Paolo had smirked and said, “Try doing that in a test tube!” Orlando had realized then that he had no choice: he was going to have to tell them about Lacerta. And though he’d been imagining that Paolo would escape unharmed, he could see now that this was impossible. Paolo was flesh, too. The robots would find three blackened corpses in the ruins.

  Orlando closed his eyes and waited for the pain to recede. He’d told Paolo that he’d be staying frozen en route, utterly inert; he hadn’t admitted to anyone that he’d chosen to dream instead. A wise omission, given Fomalhaut. That slumbering clone would have formally diverged into a separate individual; random noise in the embodiment software guaranteed that, even without different sensory inputs. But Orlando didn’t think of it as a death; even his waking Earth-self’s suicide didn’t amount to that. He’d always intended to merge with every willing clone at the end of the Diaspora, and the loss of one or two of them along the way seemed no more tragic than losing his memories of one or two days in every thousand.

  He left the cabin and walked barefoot through the cool grass to the edge of the flying island. The scape was dark as any moonless night on Earth, but the ground was even and the route familiar. He had gladly rid himself of the tedious business of defecation, but he was no more willing to give up the pleasure of emptying his bladder than he was willing to give up the possibility of sex. Both acts were entirely arbitrary, now that they were divorced from any biological imperative, but that only brought them closer to other meaningless pleasures, like music. If Beethoven deserved to endure, so did urination. He manipulated the stream into Lissajous figures as it vanished into the starry blackness beneath the jutting rock.

  He’d forced only a little of his own nature onto Paolo — like any good bridger, just enough to let the two of them understand each other — and he’d gladly see subsequent generations embrace all the possibilities of software existence. But redesigning himself in an attempt to do the same in person would have been nothing but self-mutilation. That was why he dreamt the old way: confused, unconvincing, uncontrollable dreams, not the lucid, detailed, wish-fulfillment fantasies or cloyingly therapeutic psychodramas of the assimilated. His faithfully mammalian dreams would never bring Liana back; nor would they drag him down some tortuous path of allegory and catharsis designed to reconcile him to her loss. They revealed nothing, meant nothing, changed nothing. But to excise or disfigure them would have been like taking a knife to his flesh.

  Voltaire lay low in the sky, in the direction Orlando thought of as east. It was a dim reddish speck at this distance, about as bright as Mercury seen from Earth, an ancient K5 star only one sixth as luminous as the sun. Five terrestrial planets, and five gas giants more in Neptune’s league than Jupiter’s, had been observed or inferred long before the Diaspora’s launch, but individual spectra for the inner planets had continued to elude both the colossal instruments back home and the extremely modest equipment carried by the polis itself.

  “What are you offering? Sanctuary?” He gazed at the star. Not likely. Just a few more barren planets. A few more lessons in the fragility of life, and the indifference of the forces that created and destroyed it.

  Back in the cabin, Orlando considered ignoring the call and going straight back to sleep. It would either be bad news — another Fomalhaut, or worse — or evidence of life so subtle that it had taken a century or two of exploration to uncover. Maybe one of the moons of one of the gas giants orbiting 51 Pegasus had yielded a few fossilized microbes in some previously uncharted crevice. Evidence of a third biosphere would be hugely significant, but he was tired of poring over the details of distant worlds in the pre-dawn darkness.

  Then again, maybe the Orphean squid had finally gained an inkling of the nature of their floating universes. Orlando laughed wearily. He was jealous, but he was hooked; the chance of a development in squid culture was enough to puncture his indifference.

  He clapped his hands, and the cabin lit up. He sat on his bed and addressed the wall screen. “Report.” Text appeared, summarizing his exoself’s reasons for waking him. Orlando could not abide non-sentient software that talked back.

  The news was local, though the chain of events behind it had started back on Earth. Someone in Earth C-Z had designed an improved miniature spectroscope, which could be constructed by nanoware modifications to the existing polis-borne model. The local astronomy
software had taken it upon itself to do just that, and thanks to the new instrument the atmospheric chemistry of Voltaire’s ten planets had now been determined.

  The first surprise was that the innermost planet, Swift, possessed an atmosphere rather different than expected: mostly carbon dioxide and nitrogen, at a fifth the total pressure of Earth’s, but there were also significant traces of hydrogen sulphide and water vapor. With only 60 percent of Earth’s gravity, and a surface temperature averaging 70 degrees Celsius, virtually all of Swift’s water should have been lost in the twelve billion years since its formation — broken down by UV into hydrogen and oxygen, with the hydrogen escaping into space.

  The second surprise was that the hydrogen sulphide appeared not to be in thermodynamic equilibrium with the rest of the atmosphere. It was either being outgassed from the planet’s interior — unlikely, after twelve billion years — or it was a by-product of some form of non-equilibrium chemical process driven by the light from Voltaire. Quite possibly life.

  But the third surprise set Orlando’s skin tingling, outweighing any drab visions of boiling lakes full of malodorous bacteria. The spectra also showed that the molecules in Swift’s atmosphere contained no ordinary hydrogen, no carbon-12, no nitrogen-14, no oxygen-16, no sulfur-32. Not a trace of the most cosmically abundant isotopes, though they were present in the normal proportions on Voltaire’s nine other planets. On Swift, there was only deuterium, carbon-13, nitrogen-15, oxygen-18, sulfur-34: the heaviest stable isotope of each element.

  That explained why water vapor was still present; these heavier molecules would stay closer to the surface of the planet, and when they were split the deuterium would have more of a chance to stick around and recombine. But not even the preferential loss of lighter isotopes could explain these impossibly skewed abundances; Swift’s atmosphere contained hundreds of thousands of times more deuterium than it should have possessed when the planet was formed.