Timelike Infinity

by Stephen Baxter

  "Jasoft Parz," the Qax said, its voice almost silky now, the relish audible, "you are the only human to return through time with this Qax expedition. Fifteen centuries ago humans were still largely cooped up in the dull star system of their birth. When we have destroyed the home planet — and scoured the neighboring worlds and spaces — you will be the only human left alive. And with the termination of your species's world line, you will also be the last human. How will that feel?"

  Parz felt his lifetime of compromise — of diplomacy — weigh down on him, a freight of age still heavy despite his AS rejuvenation. He tried, as he'd tried before, to comprehend the significance of the Qax's monstrous act. Surely it was his duty, as the last human, to feel the pain of this crime, to suffer on behalf of his race.

  But he couldn't. It was beyond him. And, he thought, he had moved beyond hope.

  He wondered how he'd feel, though, if he had children of his own.

  He nodded, infinitely tired. "So. You've brought me here so you can watch me, as I watch my race die. I've not understood before; I guess I was hoping for — what? nobility? — from the murderer of my species. But it really is as petty as that. My reaction, the grief of one man, will dramatize for you the emotional significance of the event. It will heighten your pleasure. Won't it?"

  "Pleasure? I am not psychopathic, Jasoft Parz," the Qax said. "But the sweetness of my revenge will be great."

  "Revenge for what?"

  "For the destruction of my own world, of the home of the Qax, by the actions of a single human."

  Parz had been told something of the story.

  A few centuries after Parz's era, there would be a human: Jim Bolder, an unremarkable man.

  The Qax would try to employ Bolder, to exploit him for gain. But Bolder would deceive them — somehow trick them into turning starbreakers on their own sun.

  The new Governor came from a future in which the comparatively lenient Occupation of Earth had led, inexorably, to the destruction of the Qax home world, to a diaspora in which dozens of the fragile Qax had perished. In this timeline the Qax were marginalized; humans, freed of the Occupation, grew far stronger.

  The Qax wanted to change all that.

  Ironically, Parz had come to understand, the rebellion of the Friends of Wigner had nothing to do with the ultimate collapse of the Occupation, in this timeline. Whatever the rebels' scheme was it was seen as irrelevant by the Qax — in fact, the sequence of time bridges initiated by the rebellion was actually an opportunity for the Qax to move back into time, far beyond Bolder, and to rectify their earlier leniency.

  Parz, baffled and disturbed by the philosophy of it all, wondered if a multiplicity of variant worlds would be initiated by this series of trips into the past, of closed timelike curves. The original variant, the prime timeline, saw no impact on events from either the rebels' activities or the Qax's actions; the timeline would unfold with relentless logic to the Qax diaspora. The Qax, now, hoped to return through time to crush humanity before such events had a chance to occur; this second variant would see no diaspora and the emergence — presumably — of the Qax as the dominant species in the absence of mankind. The rebels, with their unknown project, must hope to initiate a third variant in which the Occupation would be crushed before the time of Jim Bolder — of whom, of course, the rebels could have no knowledge; to them the Occupation must have looked immense and eternal.

  But even that wasn't the end of it, Parz realized; for presumably the actions of the various groups of time travelers would interact to set off a fourth, fifth, or sixth variant...

  But most human philosophers seemed to agree, now, that only one of these variants could be considered "real"; only one could be collapsed into actuality by the observation of conscious minds.

  Parz pressed his face against the warm lens material; it yielded like thin rubber. The electric blue struts of the Interface portal had almost embraced the Spline now; the nearest face, which already blocked out the stars, the moons of Jupiter, was dark and empty, its blackness relieved only by a hint of autumn gold. Parz twisted his head about. He caught a glimpse of the second Spline he'd seen earlier; it hovered above and behind the Qax's ship, following it toward the portal. "Some armada," he said. "Two ships?"

  "Two are all that is required. The humans of fifteen centuries ago will have no means of defense against the weaponry of the Spline craft. The second craft will destroy the vessel of these rebels from your present — these Friends of Wigner — while my ship will besiege Earth."

  Parz felt his throat tighten. "How?"

  "Starbreaker beams."

  Parz closed his eyes.

  "Maybe your revenge won't be so sweet," he said at random. "What about causality? Maybe I'll pop out of existence as soon as my ancestors are destroyed. Maybe you will too. Have you thought about that? And then the destruction of your world by this human hero will never have happened... and you'll have no reason, or means, to travel through time to assault the Earth." But then, he thought further, if the Qax did not travel back through time, surely humanity would survive to destroy the Qax world after all... "We'll be caught in a causality loop, won't we?"

  "Jasoft Parz, causality does not operate in such a simplistic fashion. In such a circumstance the different outcomes may all exist simultaneously, like the probabilities expressed by a quantum function. But only one of those possibilities will be collapsed to actuality—"

  "Are you sure?" Parz said grimly. "You're talking about destroying a race... about altering history on a cosmic scale, Qax."

  "Yes, we are sure. My intention is to close off all probabilities, all variants of reality in which humanity can survive. After the reduction of your system, you will be the only human left alive."

  "And you and I will disappear into nonexistence," Parz said grimly.

  "No," the Qax said. "But the timeline from which we emerged will no longer exist, as a potentiality. We will be stranded, out of time. But my job will be done."

  Yes, Parz thought, what it's saying is possible. The Qax was plotting not just the destruction of humankind but the destruction of all variant realities in which humanity might have survived. It was more than genocide, he saw; it was a murder of reality.

  The Qax's calculation somehow penetrated Parz's dulled heart more deeply than anything else. How could a sentient being discuss such gruesome events — the destruction of species, of worlds, of timelines — in the language of cold logic, of science?

  Damn it, Parz protested silently, we're talking about the snuffing out of species — of the potential of countless billions of souls as yet unborn...

  But, as always, he realized dully, the Qax were doing nothing that humans had not tried to perpetrate on sections of their own species in the past.

  "Parz, shortly we will be entering the throat of the wormhole. You must be prepared for causality stress."

  "Causality stress?" Parz stared into the blank, gaping mouth of the wormhole portal; the hints of silver-gold were gone now, leaving only a receding darkness that covered the stars. "You know, Qax, you intend to destroy my home world. And yet all I feel now is a personal dread of entering that damn wormhole."

  "You are a limited species, Jasoft Parz."

  "Perhaps we are. Perhaps we're better off that way."

  The Spline trembled; to Jasoft, cushioned as he was by the entoptic matter, the mile-wide animal's shudder was like a mild earth tremor.

  "I'm frightened, Qax."

  "Imagine my concern."

  The Spline's shuddering became continuous; Parz felt it as a high-frequency oscillation of the entoptic fluid — small waves beating against his flesh like insect wings — overlying a bass rumble that must come from resonances in the immense skeleton of the Spline itself. The ship was suffering.

  "Qax. Talk to me."

  "What about?"

  "Anything," Parz muttered. "I don't care. Anything to take my mind off this. Tell me the story of how a human destroyed your planet... Tell me about Jim Bolder."
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  "Will destroy it. Would have destroyed it."

  "Whatever."

  The Qax seemed to consider. "Perhaps. But what an odd question for you to ask, Jasoft Parz. I must consider what you have to gain by acquiring such information. Perhaps you have some vain scheme to use the data to rehabilitate yourself in the eyes of your people... from the race's greatest traitor, to an unsung hero—"

  Parz, surprised, frightened, looked inward. Traitor? A month ago he would have denied the charge.

  But now the Qax had changed the rules.

  Suddenly Parz had found himself transformed from a morally dubious collaborating diplomat into a witness to the destruction of his race...

  The Spline shuddered again, more violently, and through the entoptic medium he seemed to hear a low groan, as if of pain, or terror.

  Could the Qax be right? Was some element of his subconscious still scheming, looking for advantage, even now?

  Did he, he asked himself with wonder, still entertain hope?

  The Qax was silent.

  Now the Spline shuddered so hard that Parz was thrown into a soft collision with the wall of the huge eyeball. It felt as if the Spline had jerked through a few hundred yards, as if hauling itself away from some source of pain.

  Jasoft closed his eyes and, with a subvocalized command, ordered the software in his eyes to call up an external image of the Spline, transmitted from the companion ship.

  His craft was entering the portal face, inching forward as delicately as any docking, the curves of its flanks almost brushing the powder-blue edges of the tetrahedral framework.

  Parz was a hundred hours away from the past.

  The Qax spoke abruptly, its decision evidently made. "The human was — will be — called Jim Bolder. A man of the Occupation era — from not far into your own future, Parz.

  "Bolder was one of the last human pilots. Eventually the Qax interdiction on human operation of spacecraft will become complete, Jasoft Parz. Ships will be impounded on landing. The off-Earth human colonies will become self-sufficient. Or they will be closed, their inhabitants returned to Earth. Or they will die.

  "Men such as Bolder will lose their vocation, Parz. Their reason to be. This made — will make — it possible to recruit Bolder for a special assignment."

  The clean geometries of the Interface framework looked stark, inhuman, against the flesh of the Spline. At one point the Spline came within a few dozen yards of brushing the frame itself. Flesh toughened against the rigors of hyperspatial travel was boiling. As Parz watched, blisters the size of city blocks erupted in that pocked, metal-gray surface; the blisters burst like small volcanoes, emitting sprays of human-looking blood that froze instantly into showers of ice crystals, sparkling in the blue glow of the framework. Acres of the Spline convulsed, trying to pull the damaged area away from the exotic matter.

  "What was Bolder's assignment?" Parz asked.

  "Parz, what do you know of galactic drift?"

  Galaxies — and clusters and superclusters of galaxies, across half a billion light-years — were moving in great, coherent streams through space. It was as if the galaxies were moths, drawn toward some unseen light... Human astronomers had described such drift for centuries, but had never been able satisfactorily to explain it.

  "What does this have to do with Bolder?"

  "We suspected the drift had some connection with the Xeelee," the Qax said.

  Parz snorted. "Come on. The Xeelee are powerful, but they're not gods."

  "We sent Bolder to find out," the Qax said mildly.

  Parz frowned. "How? That's impossible. Even in the fastest of our hyperdrive craft it would take centuries of subjective time—"

  "We had access to a Xeelee ship."

  Parz felt his jaw working. "But that's impossible too."

  "Such details are unimportant. It is sufficient that Bolder survived his journey to the center of the streaming."

  "To the place where all the galaxies go."

  "Yes," said the Qax. "Although, close enough to the center, Bolder found that the structure of all but the most compact ellipticals was shattered; galaxy fragments, stars and worlds, tumbled into the immense gravity well at the center of it all, their blue-shifted light tumbling ahead of them."

  "And at the bottom of the well?"

  The Qax paused.

  To Parz, still studying the Spline from without, it was as if the portal framework were scorching the flesh of the hapless Spline. But it wasn't heat, he knew, but sleeting high-frequency radiation and gravity tides raised by the superdense exotic matter that were damaging the Spline so.

  Parz shuddered in sympathy with the suffering Spline.

  The image winked out. Parz, reduced to sudden artificial blindness, realized with a shock that his ship must now be totally inside the wormhole. With a feeling of claustrophobia and panic he snapped out subvocal commands.

  His vision cleared.

  The eye chamber had been reduced to the darkness within which he had awoken; his faithful globe lamp, floating beside him, cast his own shadow on the fleshy interior of the eyelid.

  So the Spline had shut its eyes. Well, he couldn't entirely blame it.

  The ship shuddered, buffeted; entoptic fluid sloshed within its spherical chamber. Parz half swam to the nearest wall and clung to a ropy nerve channel.

  "Gravitational stress," the Qax murmured in his ear. "This wormhole is a throat in space and time, Parz: a region of stress, immensely high curvature. The throat is lined with exotic matter throughout its length; we are traversing a tube of vacuum that runs along the axis, away from the exotic matter. The minimum width of the throat is about a mile. Our velocity is three miles per second—"

  "Not fast enough," Parz gasped.

  Vibration traveled through Parz's grasping fingers, up through his arms, and to his very core; it felt as if the Spline were being beaten by some immense fist. "Can the ship endure this?"

  "So the simulations tell us," the Qax said complacently. "But the creature is scarcely comfortable."

  "Right." Parz clung to his nerve rope, imagining centuries unraveling around the hurtling Spline. "Tell me what Bolder found," he said through chattering teeth. "At the bottom of the gravity well."

  A Ring, the Qax said. A torus. Composed of some unknown, crystalline substance. A thousand light-years across. Rotating at a respectable fraction of the speed of light.

  It was massive. It had caused a well in spacetime so deep that it was drawing in galaxies, including Earth's Milky Way, from across hundreds of millions of light-years.

  "I don't believe it." Parz said, shaking in sympathy with the Spline.

  "It is an artifact," the Qax said. "A Xeelee construct. Bolder watched the Xeelee build it."

  Xeelee craft — cup-shaped freighters the size of moons, and fighters with night-dark discontinuity wings hundreds of miles wide — patrolled the huge construction site. With cherry-red starbreaker beams they smashed the infalling, blue-shifted galactic fragments; they plated layers over the growing Ring.

  "We believe the Xeelee have already invested billions of years in this project," the Qax said. "But its growth is exponential. The more massive it becomes, the deeper the gravity well grows, and the faster matter falls toward the site, feeding the construction crews further."

  "But why? What's the point of it?"

  "We speculate that the Xeelee are trying to construct a Kerr metric region," the Qax said.

  "A what?"

  The Kerr metric was a human description for a special solution of Einstein's equations of general relativity. When spacetime was distorted by a sufficiently massive, rotating toroid, it could — open.

  "Like a wormhole?" Parz asked.

  "Yes. But the Kerr metric interface would not connect two points in the same spacetime, Parz. It is a throat between spacetimes."

  Parz struggled to understand that. "You're saying that the artifact is a doorway — a way out of our universe?"

  "Crudely, yes. The Xeelee are
trying to build an exit from this cosmos."

  "And to do it they're prepared to wreck a region of space hundreds of millions of lightyears wide..."

  Suddenly Parz was blind again. Hurriedly, panicking, he snapped subvocal commands; but this time his vision would not clear. The darkness in which he was immersed was deeper than the inside of his own eyelids... it was, he realized with a terrifying clarity, the darkness of nothingness, of emptiness. "Qax." His own voice was muffled; it was as if all his senses were failing together. "What's happening to me?"

  The Qax's voice came to him, distant but clear. "This is causality stress, Parz. The severance of the causal lines, of the quantum wave functions in which you are embedded. Causality stress is causing sensory dysfunction—"

  Jasoft felt his body sense softening, drifting away from him; he felt as if he were becoming disembodied, a mote of consciousness without anchor in the external universe.

  The Qax continued to speak. Its words were like distant trumpet notes. "Jasoft Parz. This is as difficult for me, for any sentient being, as it is for you... even for the Spline. But it will pass. Do not let it undermine your sanity. Concentrate on what I am saying to you.

  "Jim Bolder, in his stolen craft, evaded the Xeelee engineers. He returned to the Qax home system, where his journey had begun. Jasoft, the Qax are a trading nation. Bolder had returned with a treasure valuable beyond price: data on the greatest Xeelee artifact. It will not surprise you that the Qax decided to, ah, retain the data.

  "But Bolder tricked us."

  There was a glimmering around Parz now, a ghostly shimmer, a reflection of ripples, like moonlight on a sea.

  "The details have never become clear. Bolder should have emerged from hyperspace into a region surrounded by Spline warships, all bearing gravity-wave starbreaker technology... He failed to do so. Bolder survived, escaped.

  "Starbreakers were used. In the confusion and panic, they brushed the Qax sun. It was enough to cause the sun to become unstable — ultimately, to nova.

  "The Qax were forced to flee. Dozens of individuals died in the exodus. Our power was lost, and the Occupation of Earth crumbled..."