by Greg Egan
Ve glanced around the Heart, trying to gauge the mood. People were talking quietly in small groups, edgy and subdued, but far from despairing. Since the neutron data had been released, Yatima had seen as wide a spectrum of responses in Voltaire C-Z as ve’d witnessed among the fleshers when they’d heard about Lacerta. Many citizens had simply refused to accept that the core burst was a real possibility — and a few had succumbed to paranoid fantasies to rival any fleshers, declaring that the Transmuters’ message had been planted in order to induce a state of panic and decay among “rival” civilizations. Others were searching for ways to survive the event. Arranging to be in the shadow of a planet could shield the polises from gamma rays, but the neutrino flux would be unavoidable, and intense enough to damage even the most robust molecular structures. The most plausible scheme Yatima had heard so far involved encoding every polis’s data as a pattern of deep trenches on a planetary surface, and then building a vast army of non-sentient robots on a variety of scales, from nanoware up, so numerous that there was a chance that the relatively few survivors would be capable of reconstructing the polis.
“Suppose this burst really is on its way, and the message is a warning.” Paolo settled back in his chair, and regarded Yatima amiably. “Then having gone to the trouble of creating a whole planet’s worth of coded neutrons out of the goodness of their hearts, why didn’t the Transmuters leave us something more than the unpalatable facts? A few survival tips might have come in handy.”
“Don’t give up on the rest of the data yet; it might contain all kinds of things. Preferably instructions for shortening traversable wormholes. Failing that, a reliable technique for sealing and reopening their mouths; then we could hide inside one as a stream of nanomachines until the burst is over.”
Contemplating that scenario gave Yatima severe claustrophobia, but Gabriel had gone even further and suggested that the undeciphered bulk of the neutron data might be the Transmuters themselves: digital snapshots entombed in the particles in the hope that post-core-burst life, once such a thing evolved, would stumble upon them and obligingly restore them to active existence. If that was the case, they’d left no obvious clues for anyone aspiring to join them in their sanctuary — and if they’d known about the burst a billion years ago, it seemed far more likely that they’d set off for another galaxy, whether by wormhole or by more conventional means.
Paolo said, “So you think they used a straightforward pixel array for the warning, but then switched to some diabolical encryption technique for all the helpful advice? Why? A little winnowing of the species, maybe?”
Yatima shook vis head and answered plainly, ignoring the sarcasm. “Everything they’ve done has seemed bizarre or ambiguous at first — and then obvious and transparent once we’ve made sense of it. I don’t believe any of it’s been willfully obscure. And I don’t believe their minds were so different from ours that we’re in danger of wildly misinterpreting anything that looks like a simple message. So far, the worst mistake we could have made would have been to give up too soon on trying to interpret the isotopes.
“But they couldn’t have avoided making a few assumptions about the way we’d think, and the kind of technology we’d be using — and some of those assumptions are bound to be wrong. I can easily imagine a space-faring civilization that wouldn’t have tried the neutron phase experiment in a million years. So maybe the meaning of the rest of the data will be inaccessible to us ... but if it is, that won’t be out of malice, and it won’t be because their whole conceptual framework was beyond our comprehension. It will just be sheer bad luck.”
Paolo gave up his smirk of tolerant amusement, as if reluctantly conceding that this was an appealing vision of the Transmuters, however naive. Yatima seized the moment.
“And whatever you think about the map yourself, just remember that Orlando can’t dismiss it the way you can. Everything about this drags him back to Lacerta.”
“I know that.” He regarded Yatima irritably. “But the fact that it brings back painful memories doesn’t make him right.”
“No.” Yatima steeled verself, and pressed on. “All I’m saying is, if he asks you to take steps to make yourself safe —”
“I’m not going to humor him.” Paolo laughed indignantly. “And I don’t need some ex-Konishi solipsist to tell me about the traumas of carnevale.”
“No?” Yatima scrutinized his face. “Maybe your mental architecture’s closer to his, but you act like you have no idea what he’s been through.”
Paolo averted his eyes. “I know about Liana. But what could he have done? Forced her to use the Introdus? They both made the same decision. It wasn’t his fault.” He looked up defiantly. “And saving me from the core burst won’t bring her back.”
“No. It might not hurt Orlando, though.”
After a while, Paolo said sullenly, “I could live with wasting a thousand years coding myself into some planet’s topography, while being ridiculed by every sane person in the Diaspora. But if I start giving in to him, where does it end? If he thinks I’m migrating back to the flesh with him afterward —”
Yatima laughed. “Don’t worry, he doesn’t. And once he has lots of little flesher children, he’ll probably disown you altogether. Write you off as an unfortunate mistake. You’ll never hear from him again.”
Paolo looked uncertain, then openly wounded.
Yatima said, “That was a joke.”
Blanca floated in a tranquil ocean made up of distinct layers of pastel-colored fluids, each about a quarter of a delta deep, separated by sheets of opaque blue colloid. The only light seemed to come from a diffuse and all-pervasive bioluminescence. As Yatima swam across the scape toward ver, ve wondered whether ve should ask politely about this strange world’s physics before pressing ver to explain the cryptic invitation.
“Hello Orphan.” As Yatima’s viewpoint moved from layer to layer, the intersections of the colloid sheets with Blanca’s solid black absence looked like a diagram for a method of portraying a surface’s critical points as a sequence of curves. One rough ellipse through vis shoulders spawned two ovals on either side on the plane below; each of these split into five smaller ovals, which vanished just before the trunk’s ellipse fissioned. Unable to see the whole icon at once, Yatima found Blanca’s gestalt almost unreadable. “It’s been a while.”
“More for you than me. How are you?” This clone had become estranged from Gabriel soon after arrival, and as far as Yatima knew, no one else had spoken to ver since vis own last visit.
Blanca ignored the question, or took it as rhetorical. “That was interesting data you sent me.”
“I’m glad you had a look at it. Everyone else is stumped.” Yatima had mailed ver a tag pointing to the neutron sequence, despite vis apparent lack of interest in Swift and the Transmuters; it seemed only right to let every clone of ver know that the Fomalhaut Blanca had been vindicated.
“It reminded me of Earth biochemistry.”
“Really? In what way?” People had tried interpreting the data beyond the pixel array as a Swiftian genome, but Yatima doubted that even the quirkiest old SETI software would have attempted anything as absurd as a reading based on the DNA code.
“Just some rough analogies with protein folding. Both turned out to be specific examples of a much more general problem in N dimensions ... but I won’t bore you with that.” Blanca made a series of holes in the colloid sheets in front of ver, creating a transparent void, a sphere about two delta wide. Ve thrust vis hands into this arena, and a tangled structure appeared between them, like an intricately warped chain of beads. The structure was complex, but somehow not quite organic-looking. More like a nanomachine that someone had been forced to design from a single, linear molecule, shaped by nothing but the angles of the bonds between consecutive atoms.
Blanca said, “There was nothing to decipher, nothing to decode. You’ve read all the messages that were there to be read. The rest of the neutron sequence isn’t data at all; it’s there to co
ntrol the shape of the wormhole.”
“The shape? What difference does the shape make?”
“It enables it to act as a kind of catalyst.”
Yatima was dazed, but part of ver was thinking: How stupid of me. Of course. The neutrons served as an attention-grabbing beacon from a distance, then a warning message close-up; ve should have guessed that there was an entirely separate third function buried in the remaining structure. “What does it do? Make other long neutrons? They built just one, and it replicated itself all over the planet?”
Blanca spun the wormhole, but not in any visible dimension; it flexed oddly as the view rotated into other hyperplanes. “No. Think about it, Yatima. It can’t catalyze anything here. It has no shape in this universe, it’s just another neutron to us.”
Ve extended the wormhole into a Kozuch diagram and began demonstrating some interactions with ordinary, short particles. “If you hit it with a neutrino, an antineutrino, an electron, or a positron, the effect propagates all the way along its length.” Yatima watched, mesmerized; with each collision, even though the wormholes didn’t splice, the structure deformed in a distinctive way, like a protein switching between metastable conformations.
“Okay. We can change its shape. But what does that achieve?”
“It makes certain vacuum wormholes real. It creates a stream of particles.”
“Creates them where?” The long neutron threaded its way through billions of adjacent universes, but since the wormhole didn’t open up into any of them, its presence barely registered. If it couldn’t catalyze anything here, it had even less chance of doing so in any universe it merely passed through.
Blanca sent gestalt instructions to the diagram, and suddenly the catalyst was threaded with dozens of tangled, translucent membranes. As each electron or neutrino struck, and the catalyst changed shape, one of these faintly sketched vacuum wormholes became two real wormhole mouths racing apart through the space in which the catalyst was embedded.
That space was the macrosphere. The long neutrons were machines for creating particles in the macrosphere.
Yatima performed an elated backflip through the layered ocean, and found verself upside down. “Let me kiss your feet. You’re a genius.”
Blanca laughed, a remote sound from a hidden part of vis body. “It was a trivial problem. If you weren’t rushing like a flesher, you would have solved it yourself long ago.”
Yatima shook vis head. “I doubt it.” Ve hesitated. “So do you think the Transmuters could have —?”
“Migrated? Upward? Why not? It’s a closer escape route than heading for Andromeda.”
Yatima tried to imagine it: a Diaspora into the macrosphere. “Wait. If our whole universe, our whole space-time, is the standard fiber for macrosphere physics, then our entire history only corresponds to an instant of macrosphere time. Their equivalent of a Planck moment. So how could the Transmuters create a sequence of particles, spread out in time?”
Blanca gestured at a portion of the catalyst. “Look more closely at this domain. Macrosphere space-time is woven out of vacuum wormholes, just like ours. It’s the same kind of Kozuch-Penrose network, only five-plus-one dimensions instead of three-plus-one.” Yatima righted verself for a better view, and peered at the multilobed knot Blanca was pointing to; it seemed to hook into the ghostly structures of the vacuum like a grapple. “They’ve pinned our time to macrosphere time. What would have been a fleeting Planck moment endures as a kind of singularity. And that singularity can emit and absorb particles in macrosphere time.
Yatima’s mind was reeling. The Transmuters hadn’t indulged in any of the spectacular acts of astrophysical monument-building that a bored and powerful civilization might have gone in for: no planet-sculpting, no Dyson spheres, no black-hole juggling. But by tailoring a few neutrons on this obscure planet, they’d hitched the entire universe into synch with the time stream of an unimaginably larger structure.
“Wait. You said emit ... and absorb? What happens if the singularity absorbs a macrosphere particle?”
“A small proportion of the catalysts change state. Which causes a small proportion of the long neutrons here to undergo beta decay, even if they’re in supposedly stable nuclei. If you monitored a ton of Swift’s atmosphere, you could detect absorption events with an efficiency of about one in ten billion.” Yatima had positioned vis viewpoint in the same layer as Blanca’s head, and ve caught a characteristic tilt of amusement. “So it might be worth trying. The Transmuters’ macrosphere clones could be blasting messages at the singularity even as we speak.”
“After a billion years? I doubt it. But they might still be nearby; the originals would have fled the galaxy, but the clones would have had no special reason to travel far from the singularity. So if we went into the macrosphere ourselves, we might still have a good chance of finding them.”
If they could make contact with the Transmuters, they’d have a chance to learn the reasons for both Lacerta and the core burst, helping to convince the skeptics to protect themselves. And if there was no other choice, anyone who was willing could hide in the macrosphere to escape the burst.
Yatima was beginning to feel a kind of vertigo. The Fomalhaut Blanca’s remote, hypothetical, six-dimensional universe of universes had suddenly become as real as the space of the Diaspora itself. As real, and perhaps as accessible. For a space-faring civilization to step into the macrosphere was like a bacterium in a rain drop finding a way to stride across continents — and there was a vestigial ancestral temptation to respond to the scale and strangeness of this revelation with paralytic awe. Yatima struggled to concentrate on the practicalities.
“If we could work out macrosphere physics in enough detail, do you think we could cause the singularity to emit a stream of particles that coalesced into a functioning C-Z clone? Or maybe we could start with a cloud of raw materials, then create nanomachines to fabricate the polis?”
Blanca said, “You’re going to need something more like femtomachines, I think. Femtomachines larger than the universe. Do you want the laws of macrosphere physics?” Ve moved down through the scape a few layers, then reached into the blue colloid. As Yatima approached, Blanca opened vis dark palm to expose a single blue speck, which was radiating a gestalt tag.
“What is this?”
“Five spatial dimensions, one time. A 4-sphere as the standard fiber. Physics, chemistry, cosmology, the bulk properties of matter, interactions with radiation, some possible biologies... everything.”
“When did you do this?”
“I’ve had a lot of time, Orphan. I’ve explored a lot of worlds.” Ve spread vis arms to encompass the whole scape. “Every point you see is a different set of rules.” Ve ran a hand below the blue sheet from which ve’d plucked the macrosphere rules. “These are six-dimensional space-times. Below is five. Notice how it’s thinner? But seven is thinner too. Even numbers of dimensions have richer possibilities.”
The speck had escaped from Blanca’s hand and was drifting back toward its place in the indexscape, but Yatima had memorized the tag.
“Will you come with me, Blanca? Into the macrosphere?”
Blanca laughed, swimming in worlds, drowning in possibilities.
“I don’t think so, Orphan. What would be the use? I’ve already seen it.”
* * *
Part Six
« ^ »
Yatima said, “Blanca should be with us. Orlando should be with us.”
Paolo laughed. “Orlando would be miserable here.”
“Why? Traveling in any kind of scape he liked, with all the comforts of home ...”
“You don’t know Orlando as well as you think.”
“No? Enlighten me.”
* * *
15
–
5 + 1
« ^ »
Carter-Zimmerman polis, Swift orbit
85 803 052 808 071 CST
3 April 4953, 4:33:25.225 UT
A megatau before the cloning, Pao
lo finally managed to drag Orlando along to the Great Macrosphere Exhibition. A group of physicists had set up the scape, a long hall with an arched roof of leaded glass ribbed with wrought iron, packed with demonstrations of those features of the macrosphere that could be predicted with reasonable confidence. Although Orlando was determined to be part of the expedition, he seemed daunted by the prospect of confronting the exotic reality that the new C-Z clone would inhabit.
Paolo surveyed the hall. Less than a hundred citizens had decided to be cloned, but half the polis had been through the Exhibition. It was almost deserted now, though, and the angle of the light, cued to the number of visitors, gave an impression of late afternoon.
They approached the first exhibit, a comparison of gravity wells in three and five dimensions. The gridded surfaces of two circular tables had been made magically elastic in such a way that placing small spherical weights on them produced funnel-shaped indentations, with the effects of the gradient in each case mimicking the gravitational force around a star or planet in the different universes. The force diminished with distance as if it was being spread out over, respectively, an ever larger two-dimensional surface, producing an inverse-square law, or a four-dimensional hypersurface, yielding a visibly steeper inverse-fourth-power effect. It was a simplified pseudo-Newtonian model, but Paolo wasn’t about to scoff; he’d found Blanca’s rigorous six-dimensional space-time curvature treatment heavy going, and he’d skimmed over the hard parts where the Einstein tensor equation was derived by approximating the interactions between massive particles and virtual gravitons.
