Manifold: Space

by Stephen Baxter

  "So if there's no zodiacal light –"

  "There are no asteroids here," Ben said.

  "Nemoto. What happened to the asteroids?"

  "You already know, I think," virtual Nemoto hissed.

  Ben nodded. "They were mined out. Probably long ago. This place is old, Madeleine."

  The electromagnetic petals of the flower-ship sparkled hungrily as it chewed through the rich gas pocket at the heart of the system, and the shadows cast by the Sun – now nearby, full and fat, brimming with light – turned like clock hands on the ship's complex surface. But that diffuse gas cloud was now dense enough that it dimmed the farther stars.

  Data slid silently into the FGB module.

  "It's like a fragment of a GMC – a giant molecular cloud," Ben said. "Mostly hydrogen, some dust. It's thick – comparatively. A hundred thousand molecules per cubic centimeter... The Sun was born out of such a cloud, Madeleine."

  "But the heat of the Sun dispersed the remnants of our cloud... didn't it? So why hasn't the same thing happened here?"

  "Or," virtual Nemoto said sourly, "maybe the question should be: How come the gas cloud got put back around this star?"

  They flew around the back of the Sun. Despite elaborate shielding, light seemed to fill every crevice of the FGB module. Madeleine was relieved when they started to pull away and head for the cool of the outer system, and that single mysterious planet.

  It took a day to get there.

  They came at the planet with the Sun behind them, so it showed a nearly full disc. It glared, brilliant white, just a solid mass of cloud from pole to pole, blinding and featureless. And it was surrounded by a pearly glow of interstellar hydrogen, like an immense, misshapen outer atmosphere.

  The flower-ship's petals opened wide, the lasers working vigorously, and it decelerated smoothly into orbit.

  They could see nothing of the surface. Their instruments revealed a world that was indeed like Venus: an atmosphere of carbon dioxide, kilometers thick, scarcely any water.

  There was, of course, no life of any kind.

  The Chaera spun in its tank, volunteering nothing.

  Ben was troubled. "There's no reason for a Venus to form this far from the Sun. This world should be temperate. An Earth."

  "But," Nemoto hissed, "think what this world has that Earth doesn't share."

  "The gas cloud," Madeleine said.

  Ben nodded. "All that interstellar hydrogen. Madeleine, we're so far from the Sun now, and the gas is so thick, that the hydrogen is neutral – not ionized by sunlight."

  "And so –"

  "And so the planet down there has no defense against the gas; its magnetic field could only keep it out if it was charged. Hydrogen has been raining down from the sky, into the upper air."

  "Once there, it will mix with any oxygen present," Nemoto said. "Hydrogen plus oxygen gives –"

  "Water," Madeleine said.

  "Lots of it," Ben told her. "It must have rained like hell, for a million years. The atmosphere was drained of oxygen, and filled up with water vapor. A greenhouse effect took off – "

  "All that from a wisp of gas?"

  "That wisp of gas was a planet killer," Nemoto whispered.

  "But why would anyone kill a planet?"

  "It is the logic of growth," Nemoto said. "This has all the characteristics of an old system, Meacher. Caught behind a wave of colonization – all its usable resources dug out and exploited..."

  Madeleine frowned. "I don't believe it. It would take a hell of a long time to eat up a star system."

  "How long do you think?"

  "I don't know. Millions of years, perhaps."

  Nemoto grunted. "Listen to me. The growth rate of the human population on Earth, historically, was two percent a year. Doesn't sound like much, does it? But it's compound interest, remember. At that rate your population doubles every thirty-five years, an increase by tenfold every century or so. Of course after the twentieth century our growth rates collapsed; we ran out of resources."

  "Ah," Ben said. "What if we'd kept on growing?"

  "How many people could Earth hold?" Nemoto whispered. "Ten, twenty billion? Meacher, the whole of the inner Solar System out to Mars could supply only enough water for maybe fifty billion people. It might have taken us a century to reach those numbers. Of course there is much more water in the asteroids and the outer system than in Earth's oceans, perhaps enough to support ten thousand trillion human beings."

  "A huge number."

  "But not infinite – and only six tenfold jumps away from ten billion."

  "Just six or seven centuries," Ben said.

  "And then what?" Nemoto whispered. "Suppose we start colonizing, like the Gaijin. Earth is suddenly the center of a growing sphere of colonization whose volume must keep increasing at two percent a year, to keep up with the population growth. And that means that the leading edge, the colonizing wave, has to sweep on faster and faster, eating up worlds and stars and moving on to the next, because of the pressure from behind..."

  Ben was doing sums in his head. "That leading edge would have to be moving at light speed within a few centuries, no more."

  "Imagine how it would be," Nemoto said grimly, "to inhabit a world in the path of such a wave. The exploitation would be rapid, ruthless, merciless, burning up worlds and stars like the front of a forest fire, leaving only ruins and lifelessness. And then, as resources are exhausted throughout the light-speed cage, the crash comes, inevitably. Remember Venus. Remember Polynesia."

  "Polynesia?"

  "The nearest analog in our own history to interstellar colonization," Ben said. "The Polynesians spread out among their Pacific islands for over a thousand years, across three thousand kilometers. But by about A.D. 1000 their colonization wave front had reached as far as it could go, and they had inhabited every scrap of land. Isolated, each island surrounded by others already full of people, they had nowhere to go.

  "On Easter Island they destroyed the native ecosystem in a few generations, let the soil erode away, cut down the forests. In the end they didn't even have enough wood to build more canoes. Then they went to war over whatever was left. By the time the Europeans arrived the Polynesians had just about wiped themselves out."

  "Think about it, Meacher," Nemoto said. "The light-speed cage. Imagine this system fully populated, a long way behind the local colonization wave front, and surrounded by systems just as heavily populated – and armed – as they were. And they were running out of resources. There surely were a lot more space dwellers than planet dwellers, but they'd already used up the asteroids and the comets. So the space dwellers turned on the planet. The inhabitants were choked, drowned, baked."

  "I don't believe it," Madeleine said. "Any intelligent society would figure out the dangers long before breeding itself to extinction."

  "The Polynesians didn't," Ben said dryly.

  The petals of the flower-ship opened once more, and they receded from the corpselike planet into the calm of the outer darkness.

  It was time to talk to the icosahedral God again. The second X-ray punch laser was launched.

  After studying the records of the last encounter, Ben had learned how the configuration of the icosahedral artifact anticipated the direction of the resulting beam. Now Madeleine watched the core squint into focus. The killer beam would again lance through the accretion disc – and, this time, right into one of the largest of the Chaera worldlets.

  Millions of Chaera were going to die. Madeleine could see them, infesting their accretion disc, swarming and living and loving.

  In its tank, their Chaera passenger drifted like a Dali watch.

  "Nemoto," Madeleine said, "we can't go ahead with the second firing."

  "But they understand the consequences," virtual Nemoto said blandly. "The Chaera have disturbed the artifact a few times in the past, with their mirrors and smoke signals. Every time it's killed some of them. But they need the X-ray nourishment... Meacher," she warned, "don't meddle as you did
at the burster. If you meddle, the Gaijin may not allow human passengers on future missions. And we won't learn about systems like this. We'll have no information; we won't be able to plan... Besides, the laser is already deployed. There's nothing you can do about it."

  "It is the Chaera's choice, Madeleine," Ben said gently. "Their culture. It seems they're prepared to die to attain what they believe is perfection."

  Nemoto quoted the Chaera. "It knows we're arguing here. 'Where there are prophecies, they will cease. Where there are tongues, they will be stilled; where there is knowledge, it will pass away. For we know in part and we prophesy in part, but when perfection comes, the imperfect disappears.' "

  "Who's the philosopher?" Madeleine asked sourly. "Some great Chaera mind of the past?"

  Ben smiled. "Actually, it was quoting Saint Paul."

  Nemoto looked startled, as Madeleine felt.

  "But there remain mysteries," Ben said. "The Chaera look too primitive to have constructed that artifact. After all, it manipulates a black hole's gravity well. Perhaps their ancestors built this thing. Or some previous wave of colonists, who passed through this system."

  "You aren't thinking it through," virtual Nemoto whispered. "The Chaera have eyes filled with salty water. They must have evolved on a world with oceans. They can't have evolved here."

  "Then," Madeleine snapped, "why are they here?"

  "Because they had no place else to go," Nemoto said. "They fled here – even modified themselves, perhaps. They huddled around an artifact left by an earlier wave of colonization. They knew that nobody would follow them to such a dangerous, unstable slum area as this."

  "They are refugees."

  "Yes. As, perhaps, we will become in the future."

  "Refugees from what?"

  "From the resource wars," Nemoto said. "From the hydrogen suffocation of their world. Like Polynesia."

  The core artifact trembled.

  And Nemoto kept talking, talking. "This universe of ours is a place of limits, of cruel equations. The Galaxy must be full of light-speed cages like this, at most a few hundred light-years wide, traps for their exponentially growing populations. And then, after the ripped-up worlds have lain fallow, after recovery through the slow processes of geology and biology, it all begins again, a cycle of slash and burn, slash and burn... This is our future, Meacher: our future and our past. It is after all a peculiar kind of equilibrium: the contact, the ruinous exploitation, the crash, the multiple extinctions – over and over. And it is happening again, to us. The Gaijin are already eating their way through our asteroid belt. Now do you see what I'm fighting against?"

  Madeleine remembered the burster, the slaughter of the star lichen fourteen times a second. She remembered Venus and Australia, the evidence of ancient wars even in the Solar System – the relics of a previous, long-burned-out colonization bubble.

  Must it be like this?

  Something in her rebelled. To hell with theories. The Chaera were real, and millions of them were about to die.

  And there was – she realized, thinking quickly – something she could do about it.

  "Oh, damn it... Ben. Help me. Go down to the FGB module. Get everything out of there you think we have to save."

  For long seconds, Ben thought it over. Then he nodded. "I'll trust your instincts, Madeleine."

  "Good," she said. "Now I have a little figuring to do." She rushed to the instrument consoles.

  Ben gathered their research materials: the biological and medical samples they'd taken from their bodies, data cassettes and diskettes, film cartridges, notebooks, results of the astrophysical experiments they had run in the neighborhood of the black hole. There was little personal gear in here, as their sleeping compartments were in the Service Module. He pulled everything together in a spare sleeping bag, and hauled it all up into the Service Module.

  Madeleine glanced down for the last time through the FGB module's picture window, at smoky accretion-disc light. The flower-ship skimmed past the flank of "God"; the netting structure swarmed around the pulsing core.

  The Chaera thrashed in its tank.

  Ben pulled down the heavy hatch between the modules – it hadn't been closed since the flower-ship had swept them up from the surface of Earth's Moon – and dogged it tight.

  Madeleine was running a hasty computer program. "Remember the drill for a pressure-hull breach?" she called.

  "Of course. But –"

  "Three, two, one."

  There was a clatter of pyrotechnic bolts, an abrupt jolt.

  "I just severed the FGB," she said. "The explosive decompression should fire it in the right direction. I hope. I didn't have time to check my figures, or verify my aim –"

  Bits of radiation spat out like javelins as the core began to open.

  "What have you done, Meacher?" Nemoto thundered.

  She saw the FGB module for one last instant, its battered, patched-up form silhouetted against the gigantic cheek of "God." In its way it was a magnificent sight, she thought: a stubby twentieth-century human artifact orbiting a black hole, fifty-four light-years from Earth.

  And then the core opened.

  The FGB Module got the X-ray pulse right in the rear end. Droplets of metal splashed across space... But the massive Russian construction lasted, long enough to shield the Chaera worldlets.

  Just as Madeleine had intended.

  The core closed; the surface of the net smoothed over. The slowly cooling stump of the FGB module drifted around the curve of the hole. Madeleine saluted it silently.

  "The journey back is going to be cramped," Ben said dryly.

  The Saddle Point gateway hung before them, anonymous, eternal, indistinguishable from its copies in the Solar System, visible only by the reflected light of the accretion disc.

  "You saved a world, Madeleine," Ben said.

  "But nobody asked you to," virtual Nemoto said, her voice tinny. "You're a meddler. Sentimental. You always were. The Chaera are still protesting. 'Why did you hide God from us?'..."

  Ben shrugged. "God is still there. I think all Madeleine has done is provide the Chaera with a little more time to consider how much perfection they really want to achieve."

  "Meacher, you're such a fool," Nemoto said.

  Perhaps she was. But she knew that what she was learning – the dismal, stupid secret of the universe – would not leave her. And she wondered what she would find, when she reached home this time.

  The blue glow of transition flooded over them, and there was an instant of searing, welcoming pain.

  Chapter 17

  Lessons

  World after world after world.

  He saw worlds something like Earth, but with oceans of ammonia or sulphuric acid or hydrocarbons, airs of neon or nitrogen or carbon monoxide. All of them alive, of course, one way or another.

  But such relatively Earthlike planets turned out to be the exception.

  He was shown a giant world closely orbiting a star called 70 Virginis. This world was a cloudy ball six times the mass of Jupiter. The Gaijin believed there were creatures living in those clouds: immense, whale-like beings feeding off the organics created in the air by the central star's radiation. But colonists had visited here, long ago. At one pole of the planet there was what appeared to be an immense mining installation, perhaps there to extract organics or some other valuable volatile like helium-3. The installation was desolate, apparently scarred by battle.

  Close to a star called Upsilon Andromedae, forty-nine light-years from Earth, he found a planet with Jupiter's mass orbiting closer than Mercury to its Sun. It had been stripped of its cloud decks by the Sun's heat, leaving an immense rocky ball with canyons deep enough to swallow Earth's Moon. Malenfant saw creatures crawling through those deep shadows, immense beetlelike beings. They were protected from the Sun's heat by tough carapaces and had legs like tree trunks strong enough to lift them against the ferocious gravity. Perhaps they fed off volatiles trapped in the eternal shadows, or seeping from the pl
anet's deep interior. Here the battles seemed to have been fought out over the higher ground; Malenfant saw a plain littered with the wreckage of starships.

  Not far from the star Procyon there was a nomadic world, a world without a Sun, hurled by some random gravitational accident away from its parent star. It was in utter darkness, of course: a black ball swimming alone through space. But it was a big planet with a hydrogen-rich atmosphere; it warmed itself with the dwindling heat of the radioactive elements in its core, with volcanoes and earthquakes and tectonic shifts. Thus, under a lightless sky, there were oceans of liquid water – and in their depths life swarmed, feeding off minerals from the deeper hot rocks, not unlike the deep-sea animals that clustered around volcanic vents in Earth's seas. Here, though, life was doomed, for the world's core was inexorably cooling as the heat of its formation was lost.

  But even this lonely planet had been subject to destructive exploitation by colonists; there were signs, Malenfant learned, of giant strip-mine gouges in the ocean floors, huge machines now abandoned, perhaps deliberately wrecked.

  Everywhere, he had learned, life had emerged. But every world, every system, had been overrun by waves of colonization, followed by collapse or destructive wars – not once, but many times. Everywhere the sky was full of engineering, of ruins.

  And the bad news continued. The universe itself could prove a deadly place. He was taken through a region a hundred light years-wide where world after world was dead, land and oceans littered with the diverse remains of separately evolved life.

  There had been a gamma-ray burster explosion here, the Gaijin told him: the collision of two neutron stars, causing a three-dimensional shower of high-energy electromagnetic radiation and heavy particles that had wiped clean the worlds for light-years around. It had been a random cosmic accident that had cared nothing for culture and ambition, hope and love and dreams. Some life survived – on Earth, the deep-ocean forms, perhaps pond life, some insects would have endured the lethal showers. But nothing advanced made it through, and certainly nothing approaching sentience; after the accident, its effects over in weeks or months, it would require a hundred million years of patient evolution to fix the rent in life's fabric suffered in this place.