Xeelee: An Omnibus: Raft, Timelike Infinity, Flux, Ring

by Stephen Baxter

  ‘You’re missing my point,’ Uvarov said silkily. ‘Mark, democracy as a method of human interaction is already millennia old. And we know how easy it is to subvert any democratic process. There are endless examples of people using a democratic system as a games-theory framework of rules to achieve their own ends.

  ‘Use your imagination. Is there truly nothing better? Have we learned nothing about ourselves in all that time?’

  ‘Democracies don’t go to war with each other, Uvarov,’ Mark said coldly. ‘Democracies - however imperfectly - reflect the will of the many, not the few. Or the one.

  ‘As you’ve told me, Uvarov, we remain primitives. Maybe we’re still too primitive to trust ourselves not to operate without a democratic framework.’

  Uvarov bowed his elegant, silvered head - but without conviction or agreement, as if merely conceding a debating point.

  The four scooters rose smoothly past the half-finished Decks.

  7

  She was suspended in a bath of charged particles. It was isotropic, opaque, featureless . . .

  She had entered a new realm of matter.

  Lieserl. Lieserl ! I know you can hear me; I’m monitoring the feedback loops. Just listen to me. Your senses are overloaded; they are going to take time to adapt to this environment. That’s why you’re whited out. You’re not designed for this, damn it. But your processors will soon be able to interpret the neutrino flux, the temperature and density gradients, even some of the g-mode patterns, and construct a sensorium for you. You’ll be able to see again, Lieserl; just wait for the processors to cut in . . .

  The voice continued, buzzing in her ear like some insect. It seemed irrelevant, remote. In this mush of plasma, she couldn’t even see her own body. She was suspended in isotropy and homogeneity - the same everywhere, and in every direction. It was as if this plasma sea, this radiative zone, were some immense sensory-deprivation bath arranged for her benefit.

  But she wasn’t afraid. Her fear was gone now, washed away in the pearl-like light. The silence . . .

  Damn it, Lieserl, I’m not going to lose you now! Listen to my voice. You’ve gone in there to find dark matter, not to lose your soul.

  Lieserl, lost in whiteness, allowed the still, small voice to whisper into her head.

  She dreamed of photinos.

  Dark matter was the best candidate for ageing the Sun.

  Dark matter comprised all but one hundredth of the mass of the Universe; the visible matter - baryonic matter which made up stars, galaxies, people - was a frosting, a thin scattering across a dark sea.

  The effects of dark matter had been obvious long before a single particle of the stuff had been detected by human physicists. The Milky Way galaxy itself was embedded in a flattened disc of dark matter, a hundred times the mass of its visible components. The stars of the Milky Way didn’t orbit its core, as they would in the absence of the dark matter; instead the galaxy turned as if it were a solid disc - the illuminated disc was like an immense toy, embedded in dark glass.

  According to the Standard Model there was a knot of cold, dark matter at the heart of the Sun - perhaps at the heart of every star.

  And so, Lieserl dreamed, perhaps it was dark matter, passing through fusing hydrogen like a dream of winter, which was causing the Sun to die.

  Now, slowly, the isotropy bleached out of the world. There was a hint of colour - a pinkness, a greater warmth, its source lost in the clouds below her. At first she thought this must be some artifact of her own consciousness - an illusion concocted by her starved senses. The shading was smooth, without feature save for its gradual deepening, from the zenith of her sky to its deepest red at the nadir beneath her feet. But it remained in place around her, objectively real, even as she moved her head. It was out there, and it was sufficient to restore structure to the world - to give her a definite up and down.

  She found herself sighing. She almost regretted the return of the external world; she could very quickly have grown accustomed to floating in nothingness.

  Lieserl. Can you see that? What do you see?

  ‘I see elephants playing basketball.’

  Lieserl—

  ‘I’m seeing the temperature gradient, aren’t I?’

  Yes. It’s nice to have you back, girl.

  The soft, cosy glow was the light of the fusion hell of the core, filtered through her babyish Virtual senses.

  There was light here, she knew - or at least, there were photons: packets of X-ray energy working their way out from the core of the Sun, where they were created in billions of fusion flashes. If Lieserl could have followed the path of a single photon, she would see it move in a random, zigzag way, bouncing off charged particles as if in some subatomic game. The steps in the random walk traversed at the speed of light - were, on average, less than an inch long.

  The temperature gradient in this part of the Sun was tiny. But, it was real, and it was just sufficient to encourage a few of the zigzagging photons to work their way outwards to the surface, rather than inwards. But the paths were long - the average photon needed a thousand billion billion steps to reach the outer boundary of the radiative layer. The journey took ten million years - and because the photons moved at the speed of light, the paths themselves were ten million light-years long, wrapped over on themselves like immense lengths of crumpled ribbon.

  Now, as other ‘senses’ cut in, she started to make out more of the environment around her. Pressure and density gradients showed up in shades of blue and green, deepening in intensity towards the centre, closely matching the temperature differentials. It was as if she were suspended inside some huge, three-dimensional diagram of the Sun’s equation of state.

  As if on cue, the predictions of the Standard Model of theoretical physics cut in, overlaying the pressure, temperature and density gradients like a mesh around her face. The divergences from the Standard Model were highlighted in glowing strands of wire.

  There were still divergences from the Model, she saw. There were divergences everywhere. And they were even wider than before.

  Dark matter and baryonic matter attracted each other gravitationally. Dark matter particles could interact with baryonic matter through other forces: but only feebly, and in conditions of the highest density - such as at the heart of stars. In Earthlike conditions, the worlds of baryonic and dark matter slid through and past each other, all but unaware, like colonies of ghosts from different millennia.

  This made dark matter hard to study. But after centuries of research, humans had succeeded in trapping a few of the elusive particles

  Dark matter was made up of sparticles - ghostly mirror- images of the everyday particles of baryonic matter.

  Images in what mirror? Lieserl wondered feebly. As she framed the question the answer assembled itself for her, but - drifting as she was - it was hard to tell if it came from the voice of Kevan Scholes, or from the forced-learning she’d endured as a child, or from the data stores contained within her wormhole.

  Hard to tell, and harder to care.

  The particle mirror was supersymmetry, the grand theory which had at last shown how the diverse forces of physics - gravitational, electromagnetic, strong and weak nuclear - were all aspects of a single, unified superforce. The superforce emerged at extremes of temperature and pressure, shimmering like a blade of some tempered metal in the hearts of supernovas, or during the first instants of the Big Bang itself. Away from these extremes of time and space, the superforce collapsed into its components, and the supersymmetry was broken.

  Supersymmetry predicted that every baryonic particle should have a super-symmetric twin: a sparticle. The electron was paired with a selectron, the photon with the photino - and so on.

  The particular unified-theory variant called Spin (10) had, with time, become the standard. Lieserl rolled that around her tongue, a few times. Spin (10). A suitably absurd name for the secret of the Universe.

  The divergence, of theory from observation, was immense - and increased to
wards the centre of the Sun.

  ‘Kevan, it’s way too hot out here.’

  We see it, Lieserl, he said wryly. For now we’re just logging the data. Just as well you didn’t pack your winter coat.

  She looked within herself, at some of her subsidiary senses. ‘And I’m already picking up some stray photino flux.’

  Already? This far out from the centre? Scholes sounded disturbed. Are you sure?

  As a star like the Sun swept along its path about the centre of the galaxy - through a huge, intangible sea of dark matter - photinos fell into its pinprick gravity well, and clustered around its heart.

  The photinos actually orbited the centre of the Sun, swarming through its core around the geometric centre like tiny, circling carrion-eaters, subatomic planets with orbital ‘years’ lasting mere minutes. The photinos passed through fusing hydrogen as if it were a light mist . . .

  Almost.

  The chances of a photino interacting with particles of the plasma were remote - but not zero. Once every orbit, a photino would scatter off a baryonic particle, perhaps a proton. The photino took some energy away from the proton. The gain in energy boosted the orbital speed of the photino, making it circle a little further out from the heart of the Sun.

  Working this way, passing through the fusing hydrogen with its coagulated mass of trapped photons, the photinos were extremely efficient at transporting heat out from the centre of the Sun.

  According to the Standard Model, the temperature at the centre should have been suppressed by a tenth, and the fusion heat energy smoothed out into the surrounding, cooler regions, making the central regions nearly isothermal - at a uniform temperature. The core would be a little cooler than it should otherwise have been, and the surrounding material a little warmer.

  . . . Just a little. According to the Standard Model.

  Now, Lieserl studied the temperature contours around her and realized how far the reality diverged from the ancient, venerated theoretical image. The isothermal region stretched well beyond the fusion core - far, far beyond the predictions of the Standard Model with its modest little knot of circling photinos.

  ‘Kevan, there is much more heat being sucked out of the core than the Standard Model predicted. You do realize that there’s no way the Model can be made to fit these observations.’

  No. There was a silence, and Lieserl imagined Scholes sighing into his microphone. I guess this means goodbye to an old friend.

  She allowed the contour forms of the Standard Model to lapse from her sensorium, leaving exposed the gradient curves of the physical properties of the medium around her. Without the spurious detail provided by the overlay of Standard-Model contours, the gradient curves seemed too smooth, deceptively featureless; she felt a remnant of her earlier deprived-sensorium tranquillity return to her. There was no sense of motion, and no real sense of scale; it was like being inside overlaid clouds glowing pink and blue from some hidden neon source.

  ‘Kevan. Am I still falling?’

  You’ve reached your nominal depth now.

  ‘Nominal. I hate that word.’

  Sorry. You’re still falling, but a lot more slowly; we want to be sure we can handle the energy gradients.

  But she’d barely breached the surface of the plasma sea; eighty per cent of the Sun’s radius - a full two light-seconds - still lay beneath her.

  And you’re picking up some lateral drift, also. There are currents of some kind in there, Lieserl.

  It was as if her Virtual senses were dark-adapting; now she could see more structure in the waxy temperature-map around her: pockets of higher temperature, slow, drifting currents. ‘Right. I think I see it. Convection cells?’

  Maybe. Or some new phenomenon. Lieserl, you’re picking up data they’ve never seen before, out here. This stuff is only minutes old; it’s a little early to form hypotheses yet, even for the bright guys in Thoth.

  I wish you could see the Interface - out here, at the other end of your heat sink. Deep Solar plasma is just spewing out of it, pumping from every face; it’s as if a small nova has gone off, right at the heart of the System. Lieserl, you may not believe this, but you’re actually illuminating the photosphere. Why, I’ll bet if we looked hard enough we’d find you were casting shadows from prominences.

  She smiled.

  I can hear you smiling, Lieserl. I’m smart like that. You enjoy being the hero, don’t you?

  ‘Maybe just a little.’ She let her smile broaden. I’m casting shadows onto the Sun. Not a bad monument.

  The uppermost level of the Northern’s habitable section was a square mile of rain forest.

  The four air-scooters rose through a cylindrical Lock. Mark found himself rising up, like some ancient god, into the midst of jungle.

  The air was thick, stifling, laden with rich scents and the cries and hoots of birds and animals. He was surrounded by the branchless boles of trees, pillars of hardwood - some extravagantly buttressed - that reached up to a thick canopy of leaves; the boles disappeared into the gloom, rank on rank of them, as if he were inside some nature-born temple of Islam. The floor of the forest, starved of light by the canopy, was surprisingly bare and looked firm underfoot: it was a carpet of leaves, pierced by Lock entrances which offered incongruous glimpses of the cool, huge spaces beneath this sub-world. Fungi proliferated across the floor, spreading filaments through the leaf litter and erecting fruiting bodies in the shape of umbrellas and globes, platforms and spikes hung about by lace skirts.

  On a whim, Mark rose through a hundred feet alongside the rotting carcass of a dead tree. The bark was thick with ferns and mosses which had formed a rich compost in the bark’s crevices. Huge, gaudy orchids and bromeliads had colonized the bark, drawing their sustenance from leaf mould and collecting moisture from the air with their dangling roots.

  He drew alongside a wild banana. Its broad, drooping leaf was marked by a line of holes on either side of the midrib. Mark lifted the leaf, and found suspended from the underside a series of white, fur-coated balls perhaps, two inches across: nomadic bats, sheltering from the rainfall of this artificial forest.

  There was a motion behind him; he turned.

  Uvarov had followed him, and was now watching appraisingly. ‘Each day,’ Uvarov intoned, his face long in the gloom, ‘an artificial sun will ride its chariot across the glass sky of this jungle-world. And machines will pipe rainfall into artificial clouds. We’re living in a high-technology realization of our most ancient visions of the Universe. What does the fact that we’ve built this ship in such a way tell us about ourselves, I wonder?’

  Mark didn’t answer. He pushed himself away from the tree, and they descended to join the others, just above the forest floor.

  Louise slapped the bole of a tree. She grinned. ‘One of the few real objects in the whole damn ship,’ she said. She looked around. ‘This is Deck Zero. I wanted our tour today to end here. I’m proud of this forest. It’s practical - it’s going to be the lungs of the ship, a key part of our ecology - and it has higher purposes too; with this aboard we’ll never be able to forget who we are, and where we came from.’

  She looked from one to the other, in the green gloom. ‘We’ve all come into this project from different directions. I’m interested in the technical challenge. And some of you, with Paradoxa sympathies, have rather more ambitious goals to achieve. But we four, above all others, have the responsibility of making this project work. The forest is a symbol for us all. If these trees survive our ten centuries, then surely our human cargo will too.’

  Serena Milpitas tilted back her head; Mark followed her example, and found himself peering up at the remote stars through a gap in the canopy. Suddenly he had a shift of perspective - a discontinuity of the imagination which abruptly revealed to him the true nature of this toy jungle, with empty, lightless space above it and a complex warren of humans below.

  Garry Uvarov said, ‘But if the Paradoxa projections are correct, who knows what stars will be shining down on these t
rees in a thousand years?’

  Mark reached out and touched a tree bole; he found something comforting about its warm, moist solidity. He heard a shrieking chorus, high above him; in the branches above his head he saw a troupe of birds of paradise - at least a dozen of them - dancing together, their ecstatic golden plumage shimmering against the transPlutonian darkness beyond the skydome.

  A thousand years . . .

  Dark matter could age a star.

  The photino knot at the heart of the Sun lowered the temperature, and thereby suppressed the rate of fusion reaction. Naively, Lieserl supposed, one might think that this would extend the life of the Sun, not diminish it, by slowing the rate at which hydrogen was exhausted.

  But it didn’t work out like that. Taking heat energy out from the core made the Sun more unstable. The delicate balance between gravitational collapse and radiative explosion was upset. The Sun would reach turnoff earlier - that is, it would leave the Main Sequence, the family of stable stars, sooner than otherwise.

  According to the Standard Model, photinos should reduce the life of the Sun only by a billion years.

  Only?

  A billion years was a long time - the Universe itself was only around fourteen billion years out of its Big Bang egg - but the Sun would still be left with many billions of years of stable, Main Sequence existence . . .

  According to the Standard Model. But she already knew the Model was wrong, didn’t she?

  Lieserl.

  ‘Hmm?’

  We have the answer. We think.

  ‘Tell me.’

  The Standard Model predicts the photino cloud should be contained within the fusing core, within ten per cent of the total Solar diameter. Right? But, according to the best fits we’ve made to your data—

  ‘Go on, Kevan.’

  There are actually significant photino densities out to thirty per cent of the diameter. Three times as much as the Model; nearly a third of the—

  ‘Lethe.’ She looked down. The heart of the Sun still glowed peacefully in interleaved shades of pink and blue. ‘That must mean the fusion core is swamped with photinos.’