Diaspora

Yatima liked the way the concentric 3-spheres of color pricked out in the sky by stars of equal Doppler-shift converged on their destination; it seemed so much more emphatic than an ordinary star born of circular bands. Wrapping the image of Weyl so tightly, it seemed to promise that, this time, the Transmuters would not have slipped away.

Paolo said, “End of story, I suppose. From that point on, they’ll know the territory better than we do.”

“Maybe.” Yatima hesitated. “They might still be curious about one thing, though.”

“What?”

“You, Paolo. You had all the information you needed. You’d made the whole Diaspora worthwhile. So why did you choose to keep traveling?”

19. PURSUIT

Carter-Zimmerman polis, U**

The polis returned to the singularity in order to cut communications time lags to a minimum. There was some talk in Poincare C-Z of quarantining themselves from the “infected” second-macrosphere clone, though this made no sense to Paolo; the Contingency Handler had infiltrated the polis by physical manipulation of the hardware on a molecular level, and no mere software sent back through the singularity would be capable of any such feat. But Paolo was happy enough to let the faction reason their way out of paranoia in their own good time; he could interact with Poincare C-Z as easily as if he was there in person, so he felt no great desire to cross back.

The message itself had passed through; he wasn’t needed. The moment an independent check of the Handler’s infinite-dimensional Kozuch Theory (carried out in the uncorrupted Poincare polis) had confirmed its perfect fit to the Lac G-1 data and generated the same dire predictions for the core, Orlando had left by maser to spread the news in person, merging with his Swift self along the way. The entire Diaspora, gleisners included, lay within 250 light years of Swift, so unless they were very unlucky with the timing of another singularity slip, everyone would have the chance to escape. If they didn’t trust the near-omnipotent Star Striders, as the Handler’s creators had come to he called, they could always remain in the first macrosphere. Paolo had no doubt that between Orlando and the Swift versions of Yatima and Karpal, the case would he put forcefully enough to persuade anyone who hadn’t lost touch with the physical world entirely. Even the sequence of the Orphean carpets could be brought through, and re-seeded on another world.

It was the best they could have hoped for, but Paolo felt frustrated, ashamed, superfluous. He knew he’d willfully denied the meaning of the Transmuters’ map because of Lacerta—because he’d been tired of measuring everything against Orlando’s suffering and Orlando’s loss. Even on Poincare, it was Orlando who’d made the sacrifice that opened the way to the second macrosphere; Paolo had merely stepped through the singularity, and the truth had fallen into his hands without cost. And now he faced spending the next five hundred years waiting for Orlando to return in triumph, leading the whole Coalition to safety.

The Handler told Paolo about the galaxy’s six thousand civilizations. There were organic creatures of various biochemistries and body plans, as well as software running in polises and robots, and a spectrum of unclassifiable hybrids. Some were natives of the second macrosphere, some were from as far away as the Star Striders. Twelve had been born in the Milky Way, and either read the Transmuters’ message and followed their path, or reached the same conclusions and invented the same technology themselves.

So there was an abundance of possibilities to contemplate, here, as models for the Coalition’s future evolution. If the right protocols were followed, most of these cultures would he open to some form of contact with the newcomers, hopelessly backward as they were.

But the Transmuters had not stayed. They’d entered this universe after the Star Striders, spoken with them briefly, then moved on.

When Paolo heard of Yatima’s plan, he went straight to Elena. Her current homescape was a verdant jungle on a tide-locked moon of an imaginary gas giant. The banded planet filled a third of the sky.

She said, “Why? Why follow them? There are people with the same technology here. People with as long a history. Out of six thousand cultures, what’s so special about the Transmuters?”

“They weren’t just fleeing the core burst. They wanted to do more than escape.”

Elena gave him a try-harder look. “Most of the people here have nothing to do with the core burst. There are more than a thousand cultures native to this galaxy.”

“And they’ll all be here when I get back. Will you come with me?” Paolo met her eyes, imploringly.

She laughed. “Why should I go with you? You don’t even know why you’re going yourself.”

They argued for kilotau. They made love, but it changed nothing. Paolo felt her tolerant bemusement firsthand, and she understood his restlessness. But it did not draw them closer.

Paolo brushed the dew from his skin. “Can I hold you in my mind? Just below sentience? Just to keep me sane?”

Elena sighed with mock wistfulness. “Of course, my love! Take a lock of my mind on your journey, and I’ll carry a lock of yours on mine.”

“Your journey?”

“There are six thousand cultures here, Paolo. I’m not going to hang around the singularity for five hundred years, waiting for the rest of the Diaspora to catch up.”

“Then be careful.”

Six thousand cultures. And he wouldn’t have to lose her. For an instant, Paolo almost changed his mind.

Elena replied placidly, self-contained. “I will.”

20 INVARIANCE

Yatima-Venetti polis, UN*

Yatima found the sight of the sky in the second macrosphere disturbing; ve kept wondering which combinations of stars were the images of different individual Striders. If the Handler was to he believed, the local computing nodes in each star system were only millimeters wide, and they communicated with the others, light years away, with pulses so weak, so tightly aimed, so unpredictable in wavelength, and so ingeniously encoded that a thousand interstellar civilizations had come and gone without noticing their presence. The Handler had refused to disclose the nature of its own physical infrastructure, but it must have been operating below the femtomachine level to have penetrated the polis defenses. One line of speculation had it that the Striders had woven a computing device into the virtual wormholes of the vacuum throughout the galaxy, and the Contingency Handlers ran on empty space, permeating everything.

Paolo said, “I’m dropping the seeds.”

“Okay.”

He braced himself between two girders of the satellite, and pitched a handful of entry capsules in a counterorbital direction. Yatima smiled. It was very theatrical. The real capsules were launched in response to the mime, and Yatima couldn’t tell when the scape stopped showing Paolo’s fictitious ones and switched to the genuine external image.

Kozuch, the planet beneath them, was Mercury-sized and almost as hot. Like Swift, it stood out for hundreds of light years, branded by heavy isotopes; this step of the route, at least, was clear. The capsules’ nanomachines would build a neutron-manipulation system, and then construct a polis in the third macrosphere. The whole procedure was simpler than interstellar flight, once you knew what to do.

Yatima said, “I hope they repeat the marker they used on Poincare. If we have to find someone in every six-dimensional universe who remembers them passing, this could be a very slow process.”

Paolo replied with studied nonchalance, “I’ll bridge with anyone. I’m willing to do that.”

“That’s nice to know.”

He said, “We can’t be sure that the Transmuters came from our universe. They left a map of the core burst for the locals to find, but they might have been passing through from a lower level, not fleeing it themselves.”

“So they could be more at home in six dimensions?”

Paolo shrugged. “I’m just saying we shouldn’t make any assumptions.”

“No.”

A point on the surface of planet Kozuch beneath them was beginning to sprout a giant black disk, a purely metaphorical gate into the next macrosphere. Yatima could remember when no one in C-Z would have dared taint a realistic scape with abstractionism like this. They could see sparse stars in the disk’s blackness, a two-dimensional projection of the new polis observatory’s view.

Ve stared down into the expanding well. “I’m doing this because of some badly-chosen fields in my mind seed. What’s your excuse?”

Paolo didn’t reply.

Yatima looked up. “Well, you should be good company.”

Ve tugged symbolically downward on a girder of the satellite, and it went plummeting toward the gate.

The nearest star to the singularity in the third macrosphere held more life than Poincare, but there was no marker, and no obviously intelligent species to ask for directions.

The next was barren, or at least too hot and too turbulent for life to have evolved on its thin, fleetingly solid continents. If anything lived in the magma oceans, it was beyond their powers to identify.

The third star was much older and cooler, with a completely solid crust. It was girded by a system of giant causeways, easily visible from orbit. This hypersurface crisscrossed with roads was like some galactic Roman empire out of ancient fantasy, with all the intervening vacuum removed.

Yatima said, “This is it. The Transmuters.”

As they approached, there was no signal from the ground. No imitations of long-lost friends appeared in their scapes to welcome them; no invisible defenses woven into the vacuum burned them from the sky.

The second wave of probes revealed that whatever cities or structures the causeways had linked were buried deep beneath an almost uniform, star-wide layer of rubble. It looked as if the crust had suddenly contracted, as some nuclear/chemical pathway had switched on or off deep within the star. That the causeways were visible at all was astounding. Nothing else had survived.

The fourth star showed traces of primitive life, but they didn’t stop to examine the evidence closely. There was a marker slab, the same pure mineral as Poincare, and this time it was much closer to the polar sphere.

They named the fourth star Yang-Mills. The Diaspora’s rule in the past had been one person only per astronomical body, but it didn’t seem right to split the famous pair between universes, or to give one the gateway star and the other a less significant memorial.

Waiting for the long-nucleon facility to he completed, Yatima viewed images, relayed through two singularities, of the first wave of core-burst refugees arriving in U-star C-Z. Blanca was there, and Gabriel twice; some versions of him must have declined to merge. Yatima searched for Inoshiro, but the refugees were all from the Diaspora. No one had yet arrived from Earth.

In the fourth macrosphere, they carried out remote spectroscopy on the hundred nearest star systems. There was a planet labeled with heavy isotopes, 270 light years away. They named it Blanca. By the time they reached it, the core burst would have annihilated Swift, and the whole migration out of the home universe would he ancient history.

Yatima had vis exoself freeze ver for the journey.

When ve woke, and jumped from vis homescape Satellite Pinatubo, Paolo said flatly, “We’ve lost contact.”

“How? Where?”

“The polis orbiting Yang-Mills can’t communicate with the singularity station. The beacon seems to have vanished from the sky.”

Yatima’s first response was relief. A malfunction in the station’s communications hardware wasn’t as bad as one of the singularities slipping or decaying. They’d receive no more news from the lower levels, but there was nothing to stop them physically returning, repairing the fallible hardware along the way.

Unless the station had not only lost contact with the distant polis, it had also lost track of the Planck-sized singularity right beside it. The entire second macrosphere could vanish like a fiber in a haystack.

Yatima tried to read Paolo’s gestalt. He’d clearly had time to think of the same scenario. “Are you okay?”

Paolo shrugged. “I knew the risks.”

“We can turn back anytime you want to.”

“If the station’s been seriously damaged, we’re already too late. The singularity’s either been lost by now, or it hasn’t; a few thousand years either way before we return won’t make the slightest difference.”

“Except that we’ll know our fate sooner.”

Paolo shook his head, with a determined smile.

“What if we go back, and find that everything’s working perfectly except for the communications link? We’ll feel like complete idiots. We’ll have wasted centuries fur nothing.”

“We could keep going here, but send clones of our selves back into the third macrosphere, to ride the polis to the station and check it out.”

Paolo looked down impatiently at planet Blanca’s cratered surface. “I don’t want to do that. I don’t want to split myself again, just to half turn back. Do you?”

Yatima said, “No.”

“Then let’s drop the seeds, and move on.”

Paolo had spent some time awake in the fourth macrosphere, immersing himself in five-plus-one-dimensional physics, and he’d managed to design a vastly improved spectroscope. With this, they located the Transmuters’ marker from the vicinity of the fifth macrosphere’s singularity, on the second-closest star, which they dubbed Weyl.

The marker was still covering the rotational pole.

Yatima had vis exoself bring ver out of hibernation at the mid-point of the journey. Ve stood on the 5-space version of Satellite Pinatubo, feeling verself dissolving into the sparse sky. It was meaningless to ask how many universes each handful of vacuum here contained. The Handler’s revelations meant that even in the home universe, there were an infinite number of levels below them.

Maybe there was life and civilization, star-farers and long-particle engineers in every universe. But even the Striders, even the Transmuters, could only ascend a finite distance. There could be a Diaspora slowly working its way up from a hundred thousand levels below the home universe, which no one horn in the Milky Way would ever know about.

But their own Diaspora had already overlapped with the Transmuters'. The space around them was infinite, but if they clung to the trail they’d never lose them. It was only a matter of time and persistence before they caught up.

Later, Paolo woke and joined ver. They sat on a girder, planning their meeting with the Transmuters. And the more they talked about it, the more confident Yatima felt that they didn’t have far to go.

In the sixth macrosphere, there was an artifact drifting freely in space, a billion kilometers from the singularity.

It was an irregular shape, roughly spheroidal, two hundred and forty kilometers wide—the size of a large asteroid. It was not greatly pitted, but they were a long way from any star system full of debris. The surface was probably one or two million years old.

It was hard to obtain a spectrum in the faint starlight, and after waiting passively for a megatau for any signs of life, and then as long again for a response to a wide spectrum of radio and infrared signals, they agreed to risk brushing the surface gently with a laser.

They were not incinerated in retaliation.

Apart from contamination with interstellar gas and dust, the surface was pure quartz, silicon dioxide. Silicon-30, oxygen-18, the heaviest stable isotopes of each. The artifact appeared to be in thermal equilibrium with its surroundings, but that didn’t prove that it was dead. Waste heat, entropy, could be poured into a hidden internal sink for a finite amount of time.

They landed microprobes on the artifact, and tomographed it with faint seismic waves. It was exactly the same density throughout, uniform solid quartz, but the technique only had a resolution of about a millimeter. Smaller structures would not show up.

Paolo suggested, “It might he a working polis. They could be getting energy in and out through a traversable wormhole.”

“If you’re right, are they deliberately ignoring us? Or are they oblivious to the outside world?” Even Ashton-Laval’s citizens would have known about it, immediately, if someone had stroked their polis hull with a laser. “And if they’re ignoring us now, what happens if we do something intrusive enough to get their attention?”

Paolo said, “We could wait a thousand years and see if they deign to make contact.”

They sent a small swarm of femtomachines burrowing below the surface. A few meters down, they found structure: a pattern of tiny defects in the quartz. Statistical analysis showed that the defects were not random; the probability of certain spatial correlations arising by chance was infinitesimal. But the whole crystal was static, completely unchanging.

It was not a polis. It was a store of data.

The sheer scale of it was overwhelming. The data was packed almost as densely as their own molecular storage, but the artifact was five hundred trillion times the volume of the polis. They ran pattern-analysis software, trying to make sense of slivers and fragments, but nothing emerged. They rushed for a century while the femtomachines went deeper, and software ground away at the problem.

They rushed for a millennium. The femtomachines found a copy of the old galactic map written in the defects, surrounded by undecipherable material. Taking heart at this, they rushed for another thousand years, but the software could not decode the storage protocol of any other data. And though they’d barely begun to sample it, Yatima suspected that they could read it all and still fail to understand anything more.

Out of the blue, Paolo said numbly, “Orlando will be dead. There’ll be nothing left of him but flesher great-great-grandchildren, living on some obscure planet in the second macrosphere.”

“Your other selves will have visited him. Met his children. Said goodbye.”

Paolo took ancestral form, and wept. Yatima said, “He was a bridger. He created you to touch other cultures. He wanted you to reach as far as you could.”

The surface of the artifact was full of long neutrons, hearing the same catalyst as always. And the core-burst map was encoded in the wormhole sequence, too—though the tiniest fluctuation of the vacuum, here, was an unimaginably greater event than any cataclysm devouring the Milky Way.

They took a sample of the neutrons, built a new polis in the seventh macrosphere, and moved through.

There was another artifact floating freely near the singularity, made out of the marker mineral they’d first seen on Poincare.

It was cold and inert, and full of the same kind of microscopic defects as the first. It was impossible to say whether or not the data was identical; they could only compare tiny samples of each. The software found some matching sequences, bit strings that recurred relatively often in both crystals. The storage protocol remained opaque, but it was probably the same.

Yatima said, “We can turn back anytime.”

“Stop saying that! You know it’s not true.” Paolo laughed, more resigned than bitter. “We’ve burned six thousand years. We’ve turned our own people into strangers.”

“That’s a matter of degree. The sooner we return, the easier it will he to fit in again.”

Paolo was unswayed. “It’s past the point of going back empty-handed. If we cut our losses and give up now, it will mean the search was never worth it in the first place.”

There was a third artifact in the eighth macrosphere, and a fourth in the next. The shapes and sizes could be meaningfully compared between the same-dimensional pairs, and, random microcraters aside, the difference was barely measurable. When they sampled the artifacts at matching positions, lining up the femtomachines’ paths as best they could then hunting for correlations, they found large tracts of data the same. But not all of it.

The pattern continued in the tenth macrosphere, the eleventh, the twelfth. The artifacts changed shape, slightly. Ten or twenty percent of the bits in all the exabytes they sampled at corresponding positions were different.

Paolo said, “They’re like rows of tiles from the Orphean carpets. Only we don’t know the dynamics, we don’t know the rules to get from frame to frame.”

Yatima contemplated the prospect of trying to work it all out by inspection. “This is hopeless. We should stop poring over every artifact, trying to deduce the nature of the Transmuters from their technology.”

Paolo nodded soberly. “I agree. The quickest way to understand what these things are for will be to ask their makers.”

They automated the process, and had their exoselves rush, freeze, and clone them as necessary. They granted themselves eight-dimensional senses, and sat on the girders of an 8-scaped Satellite Pinatubo, watching perpendicular pairs of slender three- and five- dimensional artifacts rotate in and out of view. It was like whirling around a spiral staircase running from macrosphere to macrosphere, dimension to dimension.

As they reached the ninety-third level, contact was lost between the polis and the singularity on the twelfth.

On the two-hundred-and-seventh level, the twenty-sixth singularity slipped ten thousand years.

Yatima felt a surge of panic. “We’re fools. This will go on forever. They’re one step ahead of us, making these things as fast as we can jump.

“You don’t believe that. Didn’t you tell me, back at Swift, that you were sure they weren’t malicious?”

“I’ve changed my mind.”

They agreed to silence the software that reported breaks in the chain; if they had no intention of turning hack, there was no point being distracted by had news.

The artifacts mutated, slowly.

Then, past the trillionth level, there were suddenly two in every universe. Locked rigid in relative position, despite being separated by hundreds of kilometers of vacuum.

Yatima asked Paolo, “Do you want to stop and find out how that’s done?”

“No.”

They couldn’t change the real time it took to complete each link, but they rushed ever faster, until they were perceiving only every tenth, every hundredth, every thousandth level.

A third artifact appeared, then a fourth.

Then they all drifted together, level by level, and merged.

One by one, three new artifacts appeared, all drawing closer to the large central one. Just as they began to fuse with it, a fourth budded off. The large artifact changed shape, becoming more spheroidal. It shrank, grew, shrank, vanished. The fourth of the second set of smaller artifacts—roughly the size of the very first, back in the sixth macrosphere was all that remained.

It persisted for ten trillion more levels, changing only slightly, then abruptly shrank to a tenth, a hundredth its original size.

Then it vanished.

Their ascent halted.

The last singularity—267,904,176,383,054 levels from the home universe—was in empty interstellar space.

They converted the scape and themselves back to three-dimensional versions, and looked around. They were in the plane of a spiral galaxy, and a band of stars wrapped the sky like the lost Milky Way. Paolo swayed on a girder, laughing.

Yatima checked with the observatory. There were no new Swifts in sight, no new long-neutron gateways leading upward. If the Transmuters were anywhere, they were here.

“What now? Where do we look for them?”

Paolo swung around the girder he was holding, then launched himself into space. He tumbled drunkenly away from the satellite, then violated the physics and came spinning back.

He said, “We look right in front of us.”

“There’s nothing in front of us.”

“Not now. Because it’s over. We’ve seen it all.”

“I don’t understand.”

Paolo closed his eyes and forced out the words. The artifacts were polises. What else could they have been? But instead of changing the data in one fixed polis… they kept building new ones, level after level.”

Yatima absorbed this. “Then why did they stop?”

“Because there was nothing more to do.” Paolo’s gestalt seemed to hover between comic agony over the failure of their search, and sheer exaltation at its completion. “They’d seen everything they wanted to see in the outside world—they’d risen through at least six universes—and then they’d spent two hundred trillion clock ticks thinking about it. Building abstract scapes, making art, reviewing their history. I don’t know. We’ll never decipher it; we’ll never know for sure what event on. But we don’t need to. Do you want to ransack the data, hunting for secrets? Do you want to rob their graves?

Yatima shook vis head.

Paolo said, “I don’t understand the shapes, though. The changes in size, and number.”

“I think I do.”

Taken together, the artifacts comprised a giant sculpture, spanning more than a quadrillion dimensions. The Transmuters had built a structure that dwarfed universes, but touched each one only lightly. They hadn’t turned whole worlds to rubble, they hadn’t reshaped galaxies in their image. Having evolved on some distant, finite world, they’d inherited the most valuable survival trait of all.

Restraint.

Yatima played with a model of the sculpture until ve found the right way to assemble it. He converted the scape to five dimensions, then held the figure out to Paolo.

It was a four-legged, four-armed creature, with one arm stretched high above its head. No fingers; perhaps this was a stylized, post-Introdus version of the ancestral form. The tip of one foot was in the sixth macrosphere. The highest point of the Transmuter’s raised arm was in the level just beneath them, reaching up.

To the infinite number of levels above. To all the worlds it would never see, never touch, never understand.

They examined the record of communications failures. There’d been more than seven million broken links, and over ninety billion years of identified slippage in total. Statistically, by now it was beyond belief that at least one of the hundreds of trillions of singularities in the chain hadn’t been lost by the machinery. And even if they could return to the second macrosphere—or some level above, if that universe had been deserted as its stars ran out of fuel—there’d be nothing for them. The Earth culture they’d known would either have merged with others from the second macrosphere, or simply evolved beyond recognition.

Yatima shut off the flow of gestalt from the log book and looked around the star-filled scape. “What now?”

Paolo said, “The other versions of me would have done everything I’m capable of doing. And lived better lives than any I could make for myself, here.”

“We could keep traveling. Search for local civilizations.”

“That could he a long, lonely voyage.”

“If you want more company, we can always make some.”

Paolo laughed. “You do have a beautiful icon, Yatima, but I can’t see us making psychoblasts together,

“No.” After a while Yatima said, “I’m not ready to stop. Not yet. Are you afraid to die alone?”

“It won’t be death.” Paolo seemed calm now, perfectly resolved. “The Transmuters didn’t die; they played out every possibility within themselves. And I believe I’ve done the same, back in U-double-star… or maybe I’m still doing it, somewhere. But I’ve found what I came to find, here. There’s nothing more for me. That’s not death. It’s completion.”

“I understand.”

Paolo took ancestral form, and immediately started trembling and perspiring. “Ah. Flesher instincts. Bad idea.” He changed back, then laughed with relief. “That’s better.” He hesitated. “What will you do?”

“Go exploring, I think.”

He touched Yatima’s shoulder. “Good luck, then.”

Paolo closed his eyes, and followed the Transmuters.

Yatima felt a wave of grief wash over ver, but Paolo was right; other versions had lived for him, nothing had been lost.

And as the grief decayed into loneliness, Yatima was tempted to apply the same logic. Vis’ own clones must have done everything ve was contemplating, and more, long ago.

That wasn’t enough, though. There were still some discoveries ve needed to make for verself.

Yatima surveyed the sky of this universe one last time, then jumped to the copy of the Truth Mines ve’d carried all the way from Konishi.

To play out everything ve was, to be complete, ve had to find the invariants of consciousness: the parameters of vis mind that had remained unchanged all the way from orphan psychoblast to stranded explorer.

Yatima looked around the jewel-studded tunnel, and sensed the gestalt tags of axioms and definitions radiating from the walls. Everything else from vis life in the home universe had been diluted into insignificance by the scale of their journey, but this timeless world still made perfect sense. In the end, there was only mathematics.

Ve began to review the simple concepts nearby—open sets, connectedness, continuity—waking old memories, resurrecting ossified symbols. It would be a long, hard journey to the coal face, but this time there’d he no distractions.