by Greg Egan
“Where?” Even the closest star might take too long to reach, if the singularity slipped again. “Are they in the desert? In a polis?”
“No.”
“Which star, then?” Maybe there was still hope, if they used all their fuel for a fast one-way voyage, and relied on signaling back to the station rather than returning physically.
“No star — or none that the Hermits could point to. They’re not in the macrosphere at all.”
“You mean ... they found a way to enter another four-dimensional universe? To break in?” Orlando hardly dared believe it; if it was true, they could bring everyone through to the macrosphere, wait for the radiation to pass, then borrow the Transmuters’ trick to get back to the home universe itself — whether or not any robots survived on Kafka or Swift.
The clone smiled wistfully. “Not quite. But the good news is, the second macrosphere is four-dimensional.”
* * *
Part Seven
« ^ »
Paolo stared into the red-shift, back toward the singularity. “I wish it had been me in his place.”
Yatima said, “Bridging with the Hermits didn’t destroy him. And maybe he was better suited for the task than anyone.”
Paolo shook his head. “It was still too much.”
“Better than just coming along for the ride. Better than being superfluous.”
Paolo turned to ver and said ruefully, “Tell me about it.”
* * *
17
–
Partition of Unity
« ^ »
Carter-Zimmerman polis, U*
Orlando had given up on 5-scapes, so he stood in a shadow-scape of the Long Nucleon Facility, waiting to bid Paolo farewell. The scape was a dense maze of plumbing and wiring, with every pipe and cable in the real, penteractal building squashed together into a crowded cubical space.
There was no such thing as an “isotope” in the macrosphere, but the Transmuters had marked their exit point with a giant slab of implausibly pure refractory minerals, originally covering Poincaré’s rotational “pole” — the two-dimensional sphere on the hypersurface that stayed fixed in space as the star rotated. The entire polar continent had since drifted and broken apart, but the marker had neither melted nor sunk, and once the Hermit ambassador had described its composition it had been easy enough to find. The long nucleons in the rock carried the same map of the Milky Way as Swift’s neutrons, followed by a catalytic sequence designed to interact with the vacuum of the second macrosphere. Bombarding the nucleons with antileptons energetic enough to overcome electrostatic repulsion would cause the singularity in “U-double-star” to emit particles of ordinary matter; conversely, any particles fired back at the singularity would modify the same nucleon-antilepton interaction.
Paolo, Elena, and Karpal were standing beside a metaphoric gateway leading into the second macrosphere, wearing their old 3-bodies, joking with the friends they were leaving behind. Most of the forty-six second-level expeditioners had decided to freeze their Poincaré selves, to be revived only if they failed to return. Orlando approved; he was weary of bifurcations.
Paolo saw him, and approached. “You haven’t changed your mind?”
“No.”
“I don’t understand. This is three-space/one-time, ordinary physics. Galaxies, planets ... everything from the old world. And if it turns out that the core burst can’t be survived —”
“Then I’ll go back to Earth by maser, and put the evidence before the whole Coalition in person. Then I’ll come through. Not before.”
Paolo seemed bemused, but he inclined his head in a gesture of acceptance. Orlando recalled the time when mind grafts had been fashionable, and they’d had to formally compose little packages of emotion to pass to each other; what a nightmare that had been. He embraced his son, briefly, then watched him walk away.
The first of his bridger clones appeared beside him — actually inhabiting the realistic 5-scape, but casting a shadow here, just as Orlando’s own 3-body was rendered visible as a thickened version in the 5-scape.
The clone said, “They’ll find the Transmuters, and come back with the physics of Lacerta and the core burst. People will be persuaded. Lives will be saved. You should be rejoicing.”
“The Transmuters could be a million light years from the singularity by now. And the physics of the core burst will probably turn out to be incomprehensible.”
The clone smiled. “Nothing is incomprehensible.”
Orlando waited for the forty-six to file through the gate. Yatima raised a hand and called out, “I’ll save a planet for you, Orlando! New Atlanta!”
“I don’t want a planet. A small island will do.”
“Fair enough.” Yatima walked into the migration software’s icon and vanished.
Orlando turned to the clone. “What now?” The Hermit ambassador had become uncommunicative; after learning of their plight ve’d been happy enough to tell them everything they needed to know to follow the Transmuters, but once the xenologists, via the bridgers, had started pestering ver for historical and sociological details, ve’d politely suggested that they go away and mind their own business. Idle, many of the bridger clones were growing anxious and depressed.
The clone said, “That depends what you want.”
Orlando replied immediately, “I’ll take back all of you. I’ll merge with all of you.”
“Really?” The clone smiled again, face shimmering. “How much weight can you bear? How much longing for a world you’ll never see again? How much claustrophobia? How much —” He waggled his fingers, like batons. “Frustration at the words you can no longer speak?”
Orlando shook his head. “I don’t care.”
The clone stretched hyperal shoulders; the shadows of his extra pair of arms shrank, then re-grew. “The seventh clone wants to stay on Poincaré. Using the robot for now, until ve can synthesize a proper body.”
Orlando was not surprised; he’d always expected the lowest part of the bridge to fall to the hypersurface. “And the others?”
“The others want to die. The Hermits aren’t interested in a cultural exchange program; there is no role for translators here. And they don’t want to merge.”
“It’s their decision.” Orlando felt a surge of guilty relief; he might have gone mad with his head packed with Hermit symbols, and he would have felt an obligation never to edit them out, never to excise the selves he’d re-absorbed.
The clone said, “But I do. I’ll merge with you. If you really are willing.”
Orlando examined his strange twin’s face, wondering if he was being mocked, or tested. “I’m willing. Are you sure it’s what you want, though? When I merge with the other thousand, what will a few megatau of your experience in 5-scapes amount to?”
“Not much,” the clone conceded. “A tiny wound. A subtle ache. A reminder that you once embraced something larger than you thought you could.”
“You want me to find sanctuary, and still be dissatisfied?”
“Just a bit.”
“You want me to dream in five dimensions?”
“Now and then.”
Orlando spoke to his exoself, preparing the way, then stretched out a hand to the clone.
* * *
18
–
Centers of Creation
« ^ »
Carter-Zimmerman polis, U**
After seventy-nine days in the second macrosphere, Paolo still wanted to shout for joy. The singularity had turned out to lie deep within an elliptical galaxy, and the sky around Satellite Pinatubo was clogged with stars again. Poincaré had possessed a terrible beauty all its own, but seeing the familiar spectral classes scattered into new constellations sent a shudder of pleasant alienness through him that was utterly different from anything he’d felt in the macrosphere.
Elena, sitting beside him, swung her legs from the girder. “What’s the relative volume of galactic to intergalactic space?”
“You
mean here? I’m not sure.”
Karpal said, “First estimate from the observatory data is about one in a thousand, depending on how you define the haloes.”
“So is it just luck that we’re not a million light years from the nearest star?”
“Ah.” Paolo thought it over. “You think the Transmuters chose the singularity’s position? How?”
“Vacuum is vacuum,” Karpal ventured. “Until they created the singularity, it would have been meaningless to ask which point of space-time here was the macrosphere. Until that moment, there was only a set of indistinguishable quantum histories that included every possibility. So it’s not as if they were stuck with any particular, pre-ordained point.”
Elena said, “No, but if they’d collapsed that set of histories at random, the most likely result would have been a singularity out in intergalactic space. So either they were very lucky, or they were able to bias the collapse.”
“I say they biased the collapse. Using the shape of the wormhole. Making it bind preferentially to a certain level of gravitational curvature.”
“Perhaps.” Elena laughed, frustrated. “One more question to ask, if we ever catch up with them.”
Paolo glanced at their destination, Noether, a hot, ultraviolet-tinged star with two waterless terrestrial planets. The Transmuters might well have chosen to settle in this four-dimensional universe in preference to the first macrosphere, but Paolo didn’t have high hopes that they would have picked the Noether system as their new home; when they’d arrived, it wouldn’t even have been the closest star, let alone the most hospitable. If these planets were deserted, it would only take one more singularity slip to eliminate any possibility of finding the Transmuters in time. He’d suggested to Orlando that many citizens would probably be willing to take refuge in the macrosphere, regardless; after all, if the neutron map had been misinterpreted and it was all a false alarm, there’d be nothing to stop them returning. Orlando had not been impressed. “A handful of people isn’t enough. We have to convince everyone.”
A segmented worm with six flesher legs appeared in the scape, winding its way around the girder. Paolo was startled; the icon was exactly like Hermann’s, but Hermann hadn’t even entered the first macrosphere. And the worm wasn’t radiating any signature tag at all.
Paolo turned to Elena. “Is this some kind of joke?”
She looked at Karpal; he shook his head. “Not unless the joke’s on all of us.”
The worm drew nearer, eye-stalks quivering. Elena called out, “Who are you?” Anyone was welcome in Satellite Pinatubo, but appearing without a signature was very poor etiquette.
The worm replied, in Hermann’s voice, “You don’t wish to call me Hermann?”
Karpal asked coolly, “Are you Hermann?”
“No.”
“Then we’d rather not call you Hermann.”
The worm tipped its head from side to side, in a very Hermannesque way. “Then call me Contingency Handler.”
Elena said, “We’d rather not call you that either. Who are you?”
The worm looked dejected. “I don’t know what kind of answer you require.”
Paolo examined the icon carefully, but there was no clue to its true nature. Some very odd programs ran in crevices of the polis, all of them supposedly well-understood and constrained, but over the millennia a few had surfaced in unexpected places. “What kind of software are you? Do you know that much?” If it was not a citizen, they’d be able to invoke operating system utilities to scrutinize it thoroughly, but it seemed only polite to ask it directly, first.
“I’m a Contingency Handler.”
Paolo had never heard of such a thing. “You’re not sentient?”
“No.”
“Why are you using our friend’s icon?”
“Because you know I can’t be him, so that should cause the least confusion.” The worm almost succeeded in making this sound reasonable.
Karpal asked, “Why are you talking to us at all?”
“One of my functions is to greet new arrivals.”
Paolo laughed. “Elena and I are homeborn, and if you’re Karpal’s automatic welcoming party, you’re fifteen hundred years too late.”
Elena took Paolo’s hand and spoke to him privately. “I don’t think it means new arrivals to C-Z.”
Paolo stared at the worm. It waved its eye-stalks endearingly. “Where did you originate? What part of the polis?”
It seemed to have trouble parsing the question. It replied tentatively, “The outside part?”
“I don’t believe you.” He turned to Elena. “Come on! This is a hoax! How could anyone break into the hardware in interstellar space, enter a scape, and imitate Hermann?”
The worm said, “Your data protocols were easy to determine from inspection. The appearance of Hermann was encoded in your minds.”
Paolo felt his certainty wavering. The Transmuters might be able to do it: read and decode the whole polis in mid-flight, laying bare their nature, their language, their secrets. Their Orphean selves had done as much with the carpets, short of actively entering the squid’s world and making contact with them.
Elena asked the worm, “Who created you?”
“Another Contingency Handler.”
“And who created that?”
“Another Contingency Handler.”
“How many Contingency Handlers are there in this chain?”
“Nine thousand and seventeen.”
“And then what?”
The worm pondered the question. “You’re not interested in any level of non-sentient software, are you?”
Elena replied patiently, “We’re interested in everything, but first we’d like to know about the sentient beings who created the system that spawned you.”
The worm waved one leg at the sky. “They evolved on a planet, but they’re more diffuse now, each individual spread out across the space between a million stars. That makes them much slower to act than you, which is why they can’t greet you in person.”
Karpal asked, “A planet in this universe?”
“No. They came here in the same manner as you, but not by the same route.” It created a diagram of nested spheres floating beside the girder, showing a path leading up through a hierarchy of no less than seven universes. A second path, linking just three universes, met the first path at the top level; C-Z’s own route, presumably. The worm’s creators hadn’t arrived via the same macrosphere; they’d never been near Poincaré, let alone Swift. They were not the Transmuters.
Paolo was growing skeptical again. Maybe this was Hermann, disguised as an imitation of himself, an unheralded migrant via the singularity links or a stowaway just out of hiding. Certainly, no one else would attempt such a convoluted prank.
He said sarcastically, “Seven levels? Why so few?”
“That was the length of their journey. They chose to stop here.”
“But there are more levels? They could have gone further?”
“Yes.”
“How can you know that?”
The worm replaced the diagram with another, showing two neutron stars in orbit. “The fate of such a system puzzles you?” It gazed at Paolo earnestly; he nodded, unable to reply. Not even Hermann would joke about Lacerta.
The neutron stars circled each other slowly, confined to a translucent plane representing their universe. The worm added two more planes, above and below, with stars drifting across them at random: adjacent universes, separated by one quantum of distance in the macrospherean dimensions. “The interaction between these universes is very weak, but there are critical values of angular momentum where it reaches a maximum.”
Karpal interjected angrily, “We know that! But it’s too weak to explain Lac G-1! The effect is orders of magnitude less than gravitational radiation. And there’s no chance of a runaway spiral; once the system loses angular momentum and falls below the critical value, the coupling strength plummets and the whole process becomes even slower!”
; The worm said, “With one or two levels, or six or seven, that would be true. A tiny amount of angular momentum would be lost due to random interactions with bodies in adjacent universes, and the effect would be insignificant. But each four-dimensional universe is not surrounded merely in six dimensions by adjacent universes in the same macrosphere. Nor is it surrounded only in ten dimensions, by universes in other macrospheres. There are an infinite number of levels, an infinite number of extra dimensions. So every four-dimensional universe interacts with an infinite number of adjacent universes.”
The two extra planes in the diagram doubled into four, then eight, boxing the orbiting neutron stars in a cube. Then the cube mutated into a series of polyhedrons with an ever-increasing number of faces, each face representing part of an adjacent universe. The polyhedrons blurred into a sphere, swarming with stars passing “nearby” in a continuum of neighboring universes — all of them weakly tugging on the neutron-star binary.
“The system doesn’t lose angular momentum.” The worm placed an arrow at the center of the orbit, pointing up out of the plane. “Which is why the coupling strength doesn’t fall, cutting off the interaction. But with each encounter, the direction of the angular momentum vector is changed slightly.” As stars drifted by, the arrow began to wobble away from the vertical. Its height above the orbital plane represented its component in ordinary 3-space, and as it was jostled further and further from its original direction, the neutron stars began to spiral together. Their angular momentum wasn’t being radiated away, by meson jets or anything else. It was being converted into extra-dimensional spin.
Karpal watched the animation with a dazed expression. Elena touched his arm. “Are you all right?”
He nodded. Paolo knew that this was what he’d joined the Diaspora to find, as much as any carnevale refugee. He’d watched from the moon as Lacerta spiraled down, unable to make sense of the process, while thousands of fleshers died because no one could explain it, no one could convince them it was real.