Vacuum Diagrams

by Stephen Baxter

  The Qax assault approached its climax.

  The hijacked star was mere minutes away from impact with the workplace of the dark matter photino birds, and its hellish glow brought a million dancing highlights from Bolder's Ring. Now Qax-controlled Spline ships crackled out of hyperspace in the wake of the star, their fleshy hulls sparkling with weapons fire. Paul saw how the photino birds were responding; insubstantial flocks rose from the Ring material, like steam from wet earth, to face the Qax vanguard.

  One photino bird flock got too close to the star. Paul watched raging gravitational radiation tear open the flock's structure. Within seconds the birds had dispersed.

  ...And, just at this crucial instant, a little clump of consciousness knots popped out of hyperspace, emerging just outside the clear space around the Ring.

  The humans had arrived. Paul hurried to them.

  Wings outspread, the Xeelee ship hurtled through a storm of light.

  The panel-window showed blue stars, hundreds of them jammed together, some so close they were joined by umbilici of fire. The villagers stood and stared, transfixed. Children clung to the legs of their parents and cried softly.

  "Turn it off!" Sura buried her face in her hands. "I can't bear to look at it; turn it off!"

  Erwal gripped the gloves grimly. "I can't," she said.

  The Friend was in her head again, his visions a clamor that left her unable to think.

  Onwards, he said. She had to go onwards, deeper into this swarm of insect-stars, using all the skills she had learned to haul the ship through this barrage of stars. Tears leaked out of her eyes, but she dared not rest. Her world narrowed to the feel of the gloves on her stiffening hands, the gritty rain of stars in her eyes.

  With a soundless explosion the ship erupted into clear space.

  Erwal gasped, pulled her hands out of the gloves; the ship seemed to skid to a halt.

  They were in an amphitheater of light. The far wall was a bank of stars, hard and blue; it curved into a floor and ceiling also made of blue-tinged starstuff. And at the center of the vast chamber was a jewel, a Ring that turned, huge and delicate. One point of the Ring was marred by smoke; red and blue light flickered in that cloud.

  Erwal felt Sura touch the crown of her head. The girl's hand seemed to be trembling, and Erwal laid her own hand over Sura's — then realized that the trembling was her own, that her whole body was shaking uncontrollably.

  Sura asked, "Are you all right?"

  "...I think so."

  "Where are we?" Sura pointed. "What's that? It's beautiful. Do you think it's some kind of building? Why, it must be miles wide."

  But Erwal barely heard. Once more the Friend clamored in her thoughts, pressing, demanding; she longed to shut him out —

  Without hesitation she shoved her hands back into the gloves. The Xeelee ship plummeted into hyperspace.

  The weapon-star burned through the ranks of photino birds towards the Ring. Vast as it was the star was lost against that great tangled carcass...

  Until it hit.

  The battered star collapsed as if made of smoke. Sheets of hydrogen, some of it still burning at star-core temperatures, were dug out of the star's gut by writhing cosmic string. The star's mass was reduced from lightspeed to stationary in less than a minute; Paul watched huge shock waves race around the Ring's structure.

  Now the Qax's Spline warships followed up the starstrike; cherry-red beams lanced from their weapon pits, and Paul recalled the Xeelee gravity-wave starbreaker cannons observed by Jim Bolder. Photino birds imploded around the beams, flocks of them turning into transient columns of smoke that shone with exotic radiations and then dispersed.

  For a brief, exhilarating moment, Paul speculated on the possibility of a Qax victory, a defeat for the photino birds after this single, astonishing blitzkrieg; and he felt an unexpected surge of baryonic chauvinism.

  Soundlessly he cheered on the Qax.

  But, within thirty minutes, the debris of the starstrike was cooling and dispersing. The photino bird flocks began to regroup, gliding unimpeded through the glowing wreckage of the star. Grimly the Qax fought on; but now, from all around the Ring, photino birds were flicking through hyperspace to join the battle, and soon the marauding Qax were surrounded. The Spline armada, with foe in all directions, became a brief, short-blossoming flower of cherry-red light.

  Soon the end was beyond question. Ghostly photino birds penetrated the Spline fleet and overlaid the battered Qax ships, and the Spline, their effective masses increased enormously, began to implode, to melt inwards one by one.

  Perhaps if the Qax had taken more time, Paul mused; perhaps if they had organized a barrage of the starstrikes...

  Perhaps, perhaps.

  Soon it was evident that the assault had been no more than a temporary inconvenience for the photino birds, and the shadowy flocks were swooping once more into the Ring's crumbling threads.

  Dropping out of hyperspace was like falling through ice.

  The panel-window filled with light, but Erwal, disoriented, could make no sense of the image: of the threads of crystal-blue light that crossed the picture, of the sea of milky, muddled stars below her. Were those threads the Ring? Then they must be very close to it, poised over its very center. And what was the meaning of the crushed, twisted starlight below?

  The Friend returned, screaming visions at her. She cried out, but she grasped the gloves.

  Night-dark Xeelee wings stretched across space for the last time. Ignored by the warring fleets the ship dived towards the Kerr-metric Interface.

  As Erwal entered the sea of light there was a moment of farewell, an instant of almost unbearable pain... and then the Friend was gone.

  She dropped into strangeness.

  The ghost-gray photino birds slid through the Ring's pale flesh and its bruiselike discoloration spread.

  Paul, somber, reflected that the destruction of the Ring had in the end provided the key racial goal for the human race. But now that the end was close the last human — Paul — felt nothing but a cultured sadness, an aesthetic pain at the loss of such power and beauty.

  The surviving Qax, too, were, at last, no more than impotent observers, ignored by the photino birds.

  After about half a year the photino birds withdrew. The fruit of their labor was a slice through the Ring perhaps a light year thick. Around this darkling slice the substance of the Ring was crumbling, turning to sparkling threads that drifted away from the structure.

  The Kerr-metric Interface wavered, dissolved; and the Universe was sealed.

  Paul moved his attention foci closer to the gap. The broken threads of cosmic string shriveled from the wound, so that the gap in the Ring widened at near lightspeed.

  Photino birds swooped around the wound as if in a huge triumphant dance.

  The vast structure had no mechanism to recover from such a wound. Now there was only its long, slow death to play out; and the photino birds, evidently incurious, began to depart, returning their attention to their own mysterious projects.

  Like sea waves from the wreck of some immense ship gravity radiation surged out of the Ring's gravitational well, and at last the vast pit in spacetime began to close.

  The observers — the Qax, the last photino bird flocks — began to leave the scene. Paul grasped his quantum threads and slipped into the gathering darkness.

  The Xeelee ship emerged from the Kerr-metric Interface. It furled its wings, slid to a halt, and sent its sensors probing into the new Universe.

  Erwal stared at a screen that had become suddenly a blank pane of silver, reflecting only her own tired face.

  Sura asked, "What does it mean?"

  Erwal frowned. "I don't know." She tried to move the focus of the screen, but there was no response. And the gloves around her hands were like dead things, inert.

  The ship no longer responded to her touch. She withdrew her hands.

  "I don't understand," Sura said. "Did we pass through the Ring? What should we
do?"

  "How could I know?" Erwal snapped. "We wait, I suppose."

  Sura stepped away, uncertain.

  After some hours, Erwal climbed out of her chair and stretched painfully.

  Trying to overcome her enormous sense of anticlimax she established a routine. After each of the next few sleeps she crossed to the control table and slipped her hands into the gloves. But the ship remained inert, sealed off.

  Gradually her routine broke down.

  She was tired, and she had had enough mystery. She tried to settle into life inside this odd ship-village and forget the strangeness outside.

  The function of the Xeelee ship was to optimize the chances of survival of its human occupants.

  It studied the purposeless emptiness stretching around it and considered how this might be achieved.

  Gas clouds, dark and cooling, reached to the limits of this expanding Universe. There were no stars. There was no evidence of intelligence, or life.

  The ratio of helium to hydrogen here was about twenty-five percent. This, and various other cosmological relics, told the Xeelee ship that this Universe had emerged from its singularity in a broadly similar fashion to that of the Universe of its origin, with comparable ratios between the fundamental forces.

  This, of course, was good.

  The semisentient ship was capable of independent speculation. Perhaps some property of the Ring had guided them to an inhabitable environment, the ship wondered.

  It did not spend much processing time on such theorizing. After all, speculation was not its primary function; and even if it were, there was no one to report back to.

  So the Universe was broadly similar to that once shared by humans and Xeelee. With one important difference.

  It was much younger.

  Less than a billion years had passed since the singularity here. No stars yet burned. There was virtually no iron, no carbon, no silicon — no oxygen. Save for the helium and a few traces of more complex elements which had emerged from the singularity, there was only hydrogen. All the heavy elements would become abundant much later, when true stars began to shine and complex fusion processes in their cores got underway.

  There were no Earths to land the humans on, no air for them to breathe, no metals for them to dig.

  The ship unfurled its night-dark wings and dived into the hydrogen clouds. Cherry-red starbreaker beams blasted ahead of the ship; the gravity waves lanced through convection cells billions of miles wide, and a cylinder of roiling hydrogen-helium gathered. Within the cylinder temperatures rose by millions of degrees and complex fusion chains, comparable to those in the cores of the stars yet to form, were initiated.

  A cascade of heavy elements emerged from the fires, and at last even a few atoms of iron were formed.

  For three months the Xeelee ship patrolled the length of its creation; it passed its beautiful wings through the star-core cylinder, filtering out the heavy elements.

  At last the Xeelee ship was ready to construct an Earth.

  The heart of it was a core of iron seven thousand miles wide. Leaving the core at stellar-surface temperatures the ship now laid down a mantle of silicate rocks, constructed from the mineral banks it had built up, and overlaid the whole with a thin crust of oxygen and silicon. Next — compressing billions of years of planetary evolution into weeks — it deposited lodes of iron, bronze, tin, methane at suitably accessible points. There was even uranium. Then riverbeds, ocean floors, fjords were gouged out by the flickering of a cherry-red beam.

  The process was creative; the ship almost enjoyed it.

  After six months the bones of the planet were laid down. The ship landed at various points on the surface and, by firing refrigerating particle beams into the glowing sky, rapidly cooled the crust through thousands of degrees.

  Next, ice asteroids were smashed into the bare surface, as were lodes of frozen oxygen and nitrogen. The ice melted and flowed into the waiting sea beds; gases hissed into a cloak about the planet.

  All this took two more months; but at last the ship's night-dark wings cruised over clear oceans, through crisp blue oxygen.

  The first clouds formed. Rain fell.

  Next it was time to establish an ecosystem.

  The ship had never visited Earth, or even the interior of the box-world its Xeelee designers had built for the humans. But it knew the general principles.

  The ship's clay was the genetic material of its human occupants, and their various parasites and symbiotes. Tiny laboratories embedded in the ship's hull labored for many days.

  The first priority was an oxygenating flora. The ship chose melanin, the tanning agent stored in the humans' melanocyte cells, to serve as the basis for a photosynthetic process. That, combined with extrapolations of the humans' intestinal flora, proved sufficient.

  Rainforests exploded across the new continents, oceans of banyanlike trees force-grown by the ship. And a kind of plankton spread like a brown stain through the seas. Flows of energy and matter were initiated through the new biosphere, with life, climate and geology combining in a single grand organism, turning the infant planet into an autonomous, self-regulating life-support mechanism with a life span of millions of years.

  Now: animals to populate the land and seas; to serve as food for the people? Human genetic material, the ship found, was a remarkably flexible substance; the adjustment of a mere few percent of the DNA strands gave astonishing scope for design.

  This was another creative phase. The ship lingered over it, taking perhaps six months.

  At last the various feedback cycles were established; the ecosystem, powered by sunlight, was established and self-sustaining.

  The ship hovered over its creation, considering.

  The world's sun was artificial, a fusion reactor, a miniature star. It blazed down, hot and red, over its unlikely new satellite. The star would last mere millions of years, but the ship decided that should be enough time for the humans to work out what to do next for themselves.

  The wings of the Xeelee ship curved one last time over the new world.

  It was done. It was good.

  Without ceremony the ship settled to the ground, threw open its ports, and deactivated.

  Enval arose from sleep, aroused by the soft scent of grass. She rose stiffly, rubbed the sleep from her eyes, and made her way over sleeping bodies past the open port to the control table—

  The open port?

  This port had not opened for a year and a half... Now it led to a gentle ramp. The ramp lay in light, and it nestled against soft earth.

  Trembling, Erwal walked down the ramp and into light which warmed her neck. She paused at the ramp's edge, uncertain. Then, deliberately, she pressed her bare feet into the ground. The grass was cool and a little damp, as if dew-sprinkled — and it was a deep, dark brown. A breeze, strange on her skin after months of ship's air, brought goosebumps to her bare arms.

  She was standing on a grass-covered slope. The sun above was a pinkish red; beyond the sky, great billowing clouds were illuminated. The light brought out rich autumnal tones in the grass's dominant brown. The ship was a slim black cylinder, its wings folded away; it rested on the grass, incongruous.

  The slope fell away to a river which slid, gurgling, between tree-lined banks. The leaves of the trees were brown too, a pale russet color; but they flickered convincingly in the breeze. (What was that she saw in the branches of the trees? — The little creature, about a foot long, returned her gaze with startlingly human eyes, and scurried out of sight to the top of a tree.) She looked along the river. As far upstream as she could see there were no ice-floes. In the distance gray mountains shouldered above the plain; snow touched their peaks. And downstream of the river she made out a line of light, right on the horizon. A sea?

  Something came flickering through the sky, out of the Sun: a bird, no larger than her fist, scooting over the grass at about head-height. She reached up towards it, impulsively; the bird swiveled its tiny (human!) head towards her, opened
its mouth in fright, revealing rows of jewel-like teeth, and veered away, rustling into the distance.

  Sura came climbing up from the river. She was singing quietly. When she saw Erwal she smiled, her nose and forehead pink. "Erwal, where are we?"

  Erwal laughed. "Wherever it is, it seems... agreeable."

  Now more villagers came stumbling from the ship, open-mouthed; they seemed to expand as they sucked in the rich air. The children instantly ran off down the slope.

  Erwal turned back to Sura. "What do you think we should do?"

  The girl shrugged. "Get some teepees built, I suppose. Before the snows come."

  Erwal nodded. "But maybe the snows won't be so bad here."

  "No. Maybe not."

  Arm in arm the two women walked down to the river.

  C.A.D. 500,000,000

  Time passed.

  After a certain point measurement of time became meaningless. For Paul this point arrived when there was no hydrogen left to burn anywhere, and the last star flickered and died.

  Already the Universe was a hundred times its age when the Xeelee left.

  Somberly Paul watched the dimmed galaxies subside like the chests of old men.

  At last there was little free baryonic matter outside the vast black holes which gathered in the cores of galaxies. Then, as the long night of the cosmos deepened, even protons collapsed, and the remaining star-corpses began to evaporate.

  Paul wearied of puzzling over the huge, slow projects of the photino birds. He sought out what had once been a neutron star. The carbon-coated sphere floating between the huge black holes was so dense that proton decay was actually warming it, keeping it a few degrees above the near-absolute zero of its surroundings; Paul, as if seeking comfort, clustered his attention foci close to this shadow of baryonic glory.

  After some time he became aware that he was not alone: the last of the Qax had come sliding through the interstices of space and now hovered with him over the frigid surface of the star.