Vacuum Diagrams

by Stephen Baxter

  "The Silver Ghosts think it's important. And what they're interested in, I'm interested in."

  That made me cough on my wine. "How do you know what the Ghosts are up to?"

  His grin was suddenly boyish. "I've got my contacts. And they tell me the Ghosts are sending a ship."

  I choked again. "Across fifteen billion lights? I don't believe it."

  "It's a fast ship."

  "Yeah..." I thought it through further. "And how could such a ship report back?"

  Wyman shrugged. "A quantum-inseparability link?"

  "Wyman, the attenuation over such distances would reduce any data to mush."

  "Maybe," he said cheerfully. "In conversational mode anyway. I hear the Ghosts are planning a high-intensity packet burst device. Would that get through?"

  I shrugged. "Perhaps. You still haven't told me why you're talking to me."

  Abruptly he leaned forward. "Because you've the expertise."

  I flinched from his sudden intensity.

  "You've no family. You're fit. And the youthful idealism that trapped you in research has long worn off — hasn't it? — now that your contemporaries are earning so much more in other fields. You need money, Doctor. I have it."

  Then he sipped coffee.

  "I've the expertise for what?" I whispered.

  "I've got my own ship."

  "But the Ghosts—"

  He grinned again. "My ship's got a secret... a supersymmetry drive. The Susy drive is a human development. A new one, can you believe it? The Ghosts don't have it. So my ship's faster, and we'll beat them."

  "For Lethe's sake, Wyman, I'm an academic. I've never even flown a kite."

  A cheese board floated by; he cut himself precise slices. "The ship will fly itself. I want you to observe."

  I felt as if I were falling. I tried to think it out. "...Tell me this, Wyman. Will there be any penalty clauses in my contract?"

  He looked amused. "Such as?"

  "For not getting there first."

  "What's going to beat the Susy drive?"

  "A Xeelee nightship."

  Expressions chased across his face.

  "All right, Doctor. I accept your point. The Xeelee are one of the parameters we have to work within. There'll be no penalty clauses."

  Above my head the Restaurant's geostationary anchor congealed out of starlight into a mile-wide cuboid.

  "Now the details," Wyman said. "I want you to make a stop on the way, at the home world of the Ghosts..."

  Wyman's "ship" was a man-sized tin can.

  It was stored in an open garage on the space-facing side of the Elevator Anchor. The thing's cylindrical symmetry was broken by strap-on packages: I recognized a compact hyperdrive and an intrasystem drive box. Set in one wall was a fist-sized fusion torus.

  Wyman pointed out a black, suitcase-sized mass clinging to the pod's base. "The Susy drive," he said. "Neat, isn't it?"

  I found half the hull would turn transparent. The interior of the pod was packed with instrument boxes, leaving precious little room for me.

  I studied the pod with mild distaste. "Wyman, you expect me to cross the Universe... in this?"

  He shrugged delicately. "Doctor, this is the best my private capital could fund. I've not had a cent of support from any human authority. Governments, universities, so-called research bodies... in the shadow of the Xeelee mankind is suffering a failure of imagination, Luce. We live in sorry times."

  "Yeah."

  "And that's why I've set up a meeting with the Ghosts on the way out. This flying coffin isn't much, but at least it demonstrates our intent. We're going for the prize. Perhaps it will persuade the Ghosts that we should pool our resources."

  "Ah. So this pod is really a bargaining counter... you don't mean it to make the journey after all?" I felt a mixture of relief — and profound regret.

  "Oh, no," Wyman said. "What I told you is true. I sincerely believe the Susy drive could beat the Ghosts to the prize. If necessary. But why not spread the risk?" He grinned, his teeth white in the gloom of his helmet.

  I left a day later.

  Our Universe is an eleven-dimensional object. All but four of those dimensions are compactified — rolled up to an unimaginable thinness. What we call hyperspace is one of those extra dimensions.

  The hyperdrive module twisted me smoothly through ninety degrees and sent me skimming over the surface of the Universe like a pebble over a pond.

  Of course, I felt nothing. Hyperspace travel is routine. With the pod's window opaqued, it was like riding an elevator. I was left with plenty of time to brood. When I checked the pod's external monitors I could see the Susy-space module clinging to the hull, dormant and mysterious.

  After five days, with a soft impact, the pod dropped back into four-space.

  I turned on my window. I was rotating slowly.

  The sun of the Silver Ghosts is in the constellation of Sagittarius. Now it slid past my window, huge and pale. I could see stars through its smoky limb. Something came crawling close around that limb, a point of unbearable blue. It dragged a misty wave out of the sun.

  I knew the story of the Ghosts. That blue thing was the main sun's twin. It was a pulsar; it sprayed gusts of heavy particles across the sky six hundred times a second. Over a billion years that unending particle torching had boiled away the main star's flesh.

  The intrasystem drive cut in with a dull roar, a kick in the small of my back.

  Then the planet of the Silver Ghosts floated into view.

  I heard myself swearing under my breath. It was a world dipped in chrome, reflecting the Universe.

  I was flying over a pool of stars. Towards the edge of the pool the stars crowded together, some smeared into twinkling arcs, and the blanched sun sprawled across one pole. As I descended my own image was like a second astronaut, drive blazing, rising from the pool to meet me.

  Now I saw what looked like the skeleton of a moon, floating around the limb of the world. I directed monitors toward it. "Wyman. What do you make of that?"

  Wyman's voice crackled out of the inseparability link. "That's where they built their ship to the lithium-7 event. They hollowed out their moon and used its mass to boost them on their way."

  "Wyman... I hate to tell you this, but they've gone already."

  "I know." He sounded smug. "Don't worry about it. I told you, we can beat them. If we need to."

  I continued to fall. The pod began speaking to the Ghosts' landing control systems. At last the perfection of the planet congealed into graininess, and I fell amongst silvered clouds. The landscape under the clouds was dark: I passed like a firefly, lighting up cities and oceans.

  Under the Ghosts' control I landed in a sweep, bumping.

  I rested for a moment in the darkness. Then—

  I heard music. The ground throbbed with a bass harmonization that made the pod walls sing. It was as if I could hear the heart of the frozen planet.

  I lit an omnidirectional lamp.

  Mercury droplets glistened on a black velvet landscape. I felt as if I were brooding over the lights of a tiny city. There were highlights on the horizon: I saw a forest of globes and half-globes anchored by cables. Necklaces swooped between the globes, frosted with frozen air...

  When their sun decayed the only source of heat available to the Ghost biosphere was the planet's geothermal energy. So the Ghosts turned themselves and their fellow creatures into compact, silvered spheres, each body barely begrudging an erg to the cold outside.

  Finally clouds of mirrored life-forms rolled upwards. The treacherous sky was locked out... but every stray photon of the planet's internal heat was trapped.

  "I don't get it, Michael," Wyman said. "If they're so short of heat why aren't they all jet-black?"

  "Because perfect absorbers of heat are perfect emitters as well," I said. "High school physics, Wyman. While perfect reflectors are also the best heat containers. See?"

  "...Yeah. I think so."

  "And anyway, who car
es about the why of it? Wyman, it's... beautiful."

  "I think you've got a visitor."

  A five-foot bauble had separated from the forest and now came flying over the sequined field. In its mirrored epidermis I could see my own spectral face. Taped to that hide was a standard translator box. A similar box was fixed to the pod floor; now it crackled to life. "You are Dr. Michael Luce. I understand you represent a Wyman, of Earth. You are welcome here," said the Silver Ghost. "I work with the Sink Ambassador's office."

  "The Sink?" I whispered.

  "The Heat Sink, Luce. The sky. I am Wyman. Thank you for meeting us. Do you know what I wish to discuss?"

  "Of course. Our respective expeditions to the lithium site." The truncated spheroid bobbed, as if amused. "We can make an educated guess about what you seek to achieve here, Mr. Wyman. What we do not know yet is the price you'll ask."

  Wyman laughed respectfully.

  I felt bewildered. "Sorry to butt in," I said, "but what are you talking about? We're here to discuss a pooling of resources. Aren't we? So that humans and Ghosts end up sharing—"

  The Ghost interrupted gently. "Dr. Luce, your employer is hoping that we will offer to buy him out. You see, Wyman's motivation is the exploitation of human technology for personal profit. If he proceeds with your expedition he has the chance of unknown profit at high risk. However, a sell-out now would give him a fat profit at no further risk."

  Wyman said nothing.

  "But," I said, "a sell-out would give the Ghosts exclusive access to the lithium knowledge. All that creation science you told me about, Wyman... I mean no offense," I said to the Ghost, "but this seems a betrayal of our race."

  "I doubt that is a factor in his calculation, Doctor," said the Ghost.

  I laughed dryly. "Sounds like they know you too well, Wyman."

  "So what's your answer?" Wyman growled.

  "I'm afraid you have nothing to sell, Mr. Wyman. Our vessel will arrive at the lithium-7 site in..." A hiss from the translator box. "Fourteen standard days."

  "See this ship? It will be there in ten."

  The Ghost was swelling and subsiding; highlights moved hypnotically over its flesh. "Powered by your supersymmetry drive. We are not excited by the possibility that it will work—"

  "How can you say that?" I snapped, my pride obscurely wounded. "Have you investigated it?"

  "We have no need to, Doctor. Our ship has a drive based on Xeelee principles. Hence it will work."

  "Oh, I see. If the Xeelee haven't discovered something, it's not there to be discovered. Right? Well, at least this shows mankind isn't alone in suffering a fracture of the imagination, Wyman."

  The Ghost, softly breathing vacuum, said nothing.

  "We humans aren't so complacent," snapped Wyman. "The Xeelee aren't omnipotent. That's why we'll have the edge over the likes of you in the end."

  "A convincing display of patriotism," said the Ghost smoothly.

  "Yeah, that's a bit rich, Wyman."

  "You're so damn holy, Luce. Let me tell you, the Ghost's right. This trip is risky. It's stretched me. Unless you come up with the goods I might have trouble paying your fee. Chew on that, holy man."

  "Dr. Luce, I urge you not to throw away your life on this venture." The Ghost's calm was terrifying.

  There was a moment of silence. Suddenly this world of mirrors seemed a large and strange place, and my own troubled eyes stared out of the Ghost's hide.

  "Come on, Luce," said Wyman. "We've finished our business. Let's waste no more time here."

  My drive splashed light over the chrome-plated landscape. I kept my eyes on the Ghost until it was lost in a blanket of sparkles.

  I soared out of the gravity well of the Ghost world.

  "Strap in."

  "Disappointed, Wyman?"

  "Shut up and do as I say."

  The drive cut out smoothly, leaving me weightless. The control screens flickered as they reconfigured. Thumps and bangs rattled the hull; I watched my intrasystem and hyperdrive packs drift away, straps dangling.

  The pod was metamorphosing around me.

  I locked myself into a webbing of elasticated straps, fumbling at buckles with shaking fingers. There was a taste of copper in my throat.

  "Do you understand what's happening?" Wyman demanded. "I'm stripping down the pod. Every surplus ounce will cost me time."

  "Just get on with it."

  Panels blew out from the black casing fixed to the base of the pod; a monitor showed me the jeweled guts of the Susy drive.

  "Now, listen, Luce. You know the conversational inseparability link will cut out as soon as you go into Susy-space. But I'll be — with you in spirit."

  "How cheering."

  The pod shuddered once — twice — and the stars blurred.

  "It's time," Wyman said. "Godspeed, Michael—"

  The antique expression surprised me.

  Something slammed into the base of the pod; I dangled in my webbing. For as long as I could I kept my eyes fixed on the Ghost world.

  I lit up a hemisphere.

  Then the planet crumpled like tissue paper, and the stars turned to streaks and disappeared.

  Wyman had boasted about his Susy drive. "Hyperspace travel is just a slip sideways into one of the Universe's squashed-up extra dimensions. Whereas with supersymmetry you're getting into the real guts of physics..."

  There are two types of particles: fermions, the building blocks of matter, like quarks and electrons, and force carriers, like photons. Supersymmetry tells us that each building block can be translated into a force carrier, and vice versa.

  "The supersymmetric twins, the s-particles, are no doubt inherently fascinating," said Wyman. "But for the businessman the magic comes when you do two supersymmetric transformations — say, electron to selectron and back again. You end up with an electron, of course — but an electron in a different place..."

  And so Wyman hoped to have me leapfrog through Susy-space to the lithium-7 object. What he wasn't so keen to explain was what it would feel like.

  Susy-space is another Universe, laid over our own. It has its own laws. I was transformed into a supersymmetric copy of myself. I was an s-ghost in Susy-space. And it was... different.

  Things are blurred in Susy-space. The distinction between me, here, and the stars, out there, wasn't nearly as sharp as it is in four-space.

  Can you understand that?

  Susy-space is not a place designed for humans. Man is a small, warm creature, accustomed to the skull's dark cave.

  Susy-space cut through all that.

  I was exposed. I could feel the scale of the journey, as if the arch of the Universe were part of my own being. Distance crushed me. Earth and its cozy Sun were a childhood memory, lost in the grief of curved space.

  Eyes streaming, I opaqued the window.

  I slept for a while. When I woke, things hadn't got any better.

  Trying to ignore the oppressive aura of Susy-space I played with the new monitor configurations, looking for the Susy-drive controls. It took me two hours of growing confusion to work out that there weren't any.

  The Susy drive had been discarded after pushing me on my way, like a throwaway rocket in the earliest human flights.

  I could see the logic of it. Why carry excess baggage?

  There were two problems.

  The trip was one way. And Wyman hadn't told me.

  I'm not a strong man; I don't pretend to be. It took some time to work through my first reaction.

  Then I washed my face and sipped a globe of coffee.

  The translator box lit up. "Luce. What's your status?"

  I crushed the globe; cooling coffee spurted over my wrist. "Wyman, you bastard. You've hijacked me... And I thought the inseparability link wouldn't work over these distances."

  "We have a packet link; but apart from that, it doesn't. This isn't Wyman. I'm a Virtual representation stored in the translator box. I should think you're pleased to hear my voice. You need the illusion
of company, you see. It's all quite practical. And this is a historic trip. I wanted some small part of me to be out there with you..."

  I breathed hard, trying to control my voice. "Why didn't you tell me this trip was no return?"

  "Because you wouldn't have gone," said the Wyman Virtual — mentally I started calling him "sWyman."

  "Of course not. No matter what the fee. — And what about my fee? Have you paid it over yet?"

  sWyman hesitated. "I'd be happy to, Michael. But... do you have an estate? Dependents?"

  "You know I don't. Damn you."

  "Look, Michael, I'm sorry if you feel tricked. But I had to make sure you'd take the trip. We have to put the interests of the race first, don't we?..."

  After that my courage began to fail once more. sWyman had the decency to shut up.

  We popped out of Susy-space, sparkling with selectrons and neutralinos.

  My time in that metal box had seemed a lot longer than ten days. I don't remember a lot of it. I'd been locked inside my head, looking for a place to hide from the oppression of distance, from the burden of looming death.

  Now I breathed deeply; even the canned air of the pod seemed sweet out of Susy-space.

  I checked my status. I'd have four days' life support at the lithium-7 site. It would expire — with me — just when the Ghosts arrived. Wyman had given me the bare bones.

  I de-opaqued my window and looked out. I was spinning lazily in an ordinary sky. There was a powdering of stars, a pale band that marked a galactic plane, smudges that were distant galaxies.

  Earth was impossibly far away, somewhere over the horizon of the Universe. I shivered. Damn it, this place felt old.

  There was something odd about one patch of sky. It looked the size of a dinner plate at arm's length. There were no stars in the patch. And it was growing slowly.

  I set up the monitors. "sWyman — what is it?"

  "All I see is a dull infra-red glow... But that's where the lithium object is hiding, so that's the way we're headed."

  The patch grew until it hid half the sky.

  I started to make out a speckled effect. The speckles spread apart; it was as if we were falling into a swarm of bees. Soon we reached the outskirts of the swarm. A hail of huge objects shot past us and began to hide the stars behind us—