Xeelee: An Omnibus: Raft, Timelike Infinity, Flux, Ring (162 page)

‘I didn’t mean to imply—’

‘Yes, you did,’ she said sharply. ‘Well, I’m sorry if I’ve failed your test, Mark. Look, you and I - by hook or by crook - have survived the decline and destruction of our species. I know we’re going to have to fight for survival, and I’ll be fighting right alongside you, as best I can. But that doesn’t remove the
magnificence
of this cosmic engineering - any more than an ant-hill’s destruction to make way for the building of a cathedral would despoil the grandeur of the result.’

Still holding her hand within his stiff fingers, he turned his face to the galaxy-stained sky. His offence at her words was tangible; he must be devoting a great deal of processing power to this sullen rebuke. ‘Sometimes you’re damn cold, Lieserl.’

Lethe
, she thought.
People
. ‘No,’ she said. ‘I just have a longer perspective than you.’ She sighed. ‘Oh, come on, Mark. Show me the Ring,’ she said.

The sculpture of string, driving itself into the heart of the scarred galaxy, was not symmetrical. It was in the form of a rough figure-of-eight; but each lobe of the figure was overlaid with more complex waveforms - a series of ripples, culminating in sharp, pointed cusps.

‘Do you see it, Spinner?’ Mark asked. ‘That is a loop of string nearly a thousand light-years wide.’

Spinner smiled. ‘That’s not a loop. That’s a
knot
.’

‘It’s moving towards the galactic core at over half the speed of light. It’s got the mass of a hundred billion stars . . . Can you believe that? It’s as massive as a medium-size galaxy itself. No wonder it’s cutting this swathe through the stars; the damn thing’s like a scythe, driving across the face of this galaxy.’

Louise laughed. ‘
A knot
. Knot-making is a skill, up there in the forest, isn’t it, Spinner? I’ll bet you’d have been proud to come up with a structure like that.’

‘Actually,’ Mark said, ‘and I hate to be pedantic, but that
isn’t
a knot, topologically speaking. If you could somehow stretch it out - straighten up the cusps and curves - you’d find it would deform into a simple loop. A circle.’

Spinner heard Garry Uvarov’s rasp. ‘And I hate to be a pedant, in my turn, but in fact a simple closed loop
is
a knot - called the trivial knot by topologists.’

‘Thank you, Doctor,’ Louise said dryly.

Spinner frowned, peering at the detailed image of the string loop; in the false colours of her faceplate it was a tracery of blue, frozen against the remote background of the galaxy core. She realized now that she was looking at one projection of a complex three-dimensional object. Subvocally she called for a depth enhancement and change in perspective.

The loop seemed to loom towards her, lifting away from the starry background, and the string was thickened into a three-dimensional tubing, so that she could see shadows where one strand overlaid another.

The image rotated. It was like a sculpture of hosepipe, rolling over on itself. Mark commented, ‘But the string isn’t stationary, of course. I mean, the whole loop is cutting through this galaxy at more than half lightspeed - but in addition the structure is in constant, complex motion. Cosmic string is under enormous tension - a tension that increases with curvature - and so those loops and cusps you see are struggling to straighten themselves out, all the time. Most of the length of the string is moving at close to lightspeed - indeed, the cusps are moving at lightspeed.’

‘Absurd,’ Spinner heard Uvarov growl. ‘Nothing material can reach lightspeed. ’

‘True,’ Mark said patiently, but cosmic string isn’t truly
material
, in that sense, Uvarov. Remember, it’s a defect in spacetime . . . a flaw.’

Spinner watched the beautiful, sparkling construct turn over and over. It was like some intricate piece of jewellery, a filigree of glass, perhaps. How could something as complex, as
real
as this, be made of nothing but spacetime?

‘I can’t see it move,’ she said slowly.

‘What was that, Spinner?’

‘Mark, if the string is moving at close to lightspeed - how come I can’t
see
it? The thing should be writhing like some immense snake . . .’

‘You’re forgetting the scale, Spinner-of-Rope,’ Mark said gently. ‘That loop is over a thousand light-years across. It would take a
millennium
for a strand of string to move across the diameter of the loop. Spinner, it is writhing through space, just as you say, but on timescales far beyond yours or mine . . .

‘But watch this.’

Suddenly the three-dimensional image of the string came to life. It twisted, its curves straightening or bunching into cusps, lengths of the string twisting over and around each other.

Mark said, ‘This is the true motion of the string, projected from the velocity distribution along its length. The motion is actually periodic . . . It resumes the same form every twenty thousand years or so. This graphic is running at billions of times true speed, of course - the twenty-millennia period is being covered in around five minutes.

‘But the graphic is enough to show you an important feature of this motion. It’s
non-intersecting . .
. The string is not cutting itself at any point in the periodic trajectory. If it did, it would bud off smaller sub-loops, which would oscillate and cut themselves up further, and so on . . . the string would rapidly decay, shrivelling through a thousand cuts, and leaking away its energy through gravitational radiation.’

Spinner wished, suddenly, that she wasn’t
human:
that she could watch the motion of this loop unfold, without having to rely on Mark’s gaudy projections. How wonderful it would be to be able to step out of time!

‘What?’

You
can
step out of time, just as you desire. Close your eyes, and imagine you are a god.

. . . And here, in her mind’s eye - so much more dramatic than any Virtual! - came the knot of string, sailing out of space. The knot wriggled like some huge worm, closed on itself as if swallowing its own tail.

The knot struck the rim of this defenceless galaxy and scythed towards the core, battering stars aside like blades of grass.

It was a disturbing, astonishing image. She snapped open her eyes, dispelling the vision; fear flooded her, prickling over her flesh.

She wasn’t normally quite so imaginative, she thought dryly. Maybe her
companion
had had something to do with that brief, vivid vision . . .

She returned her attention to the harmless-looking Virtual display. Now Mark showed Spinner the loop’s induced magnetic field, a yellow glow of energy which sleeved the fake blue of the string itself.

‘As it hauls through the galaxy’s magnetic field, that string is radiating a lot of electromagnetic energy,’ Mark said. ‘I see a
flood
of high-energy photons . . .’

Cosmic string wasn’t actually one-dimensional; it was a Planck length across, a fine tube containing charged particles: quarks, electrons and their antiparticles, gathered into super-heavy clusters. As a result, string acted as a superconducting wire.

The string knot was cutting through this galaxy’s magnetic field. As it did so immense electrical currents - of a hundred billion billion amps or more - were induced in the string. These currents generated strong magnetic fields around the string.

The string’s induced field was stronger than a neutron star’s, and dominated space for tens of light-years around the knot.

Mark said, ‘The string has a maximum current capacity. If it’s overloaded, the string starts to shed energy. It
glows
with gamma radiation: And the lost energy crystallizes into matter: ions and electrons, whispering into existence all along the length of the string.’ Spinner saw representations of particles - out of scale, of course - popping into existence around the string image. ‘So the string is glowing as brightly as a star.’

‘Yes,’ Louise put in. ‘But the distribution of the radiation is odd, Mark. Look at this. The radiation is beamed
forward
of the loop’s motion - parallel to that forward spike of gravitational radiation.’

‘Like a searchlight,’ Morrow said.

Or a spear
. . ..

She heard Morrow saying, ‘Mark, what is
driving
the string? What is impelling it through space, and into this galaxy?’

‘Gravitational radiation,’ Mark said simply.

Louise said, ‘Morrow, gravity waves are emitted whenever large masses are moved through space. Because the loop is asymmetrical it’s pushing out its gravitational radiation in particular directions - in spikes, ahead of and behind it. It is pushing out momentum . . . It is a
gravitational rocket
, using its radiation to drive through space.’

Mark said, ‘Of course the gravitational radiation is carrying away energy - the string is shrinking, slowly. In the end it will collapse to nothing.’

‘But not fast enough to save this galaxy,’ Uvarov growled.

‘No,’ Louise said. ‘Before it has time to decay away, the string is going to reach the core - and devastate the galaxy.’

Spinner-of-Rope shivered. Once again the voice had come from her left - from somewhere outside her suit. She stared at the Virtual image in her faceplate, not daring to look around.

Suddenly she saw it.

‘Mark,’ she said. ‘This is
not
just a gravitational rocket.’

‘What?’

‘Think about it. The string knot must be a
missile
.’

The galaxy images dimmed, leaving Mark and Lieserl suspended in a crimson-tinged darkness. Then, against that background, new forms began to appear: speckles of light, indistinct, making up the ghostly outline of a
torus
, its face tipped open towards her.

‘Of course this is a false colour representation,’ Mark said. ‘The images have been reconstructed from gravity wave and gamma ray emissions . . .’

The torus as a whole reminded her, distantly, of Saturn’s rings; it was a circle which spanned the galaxy-walled cavity.

At first she thought the component speckles were mere points of light: they were like stars, she thought, or diamonds scattered against the velvet backdrop of the faded galaxy light. But as she looked more closely she could see that some of the nearer objects were not simple points, but showed structure of some kind.

So these weren’t stars, she thought, and nor was this some attenuated galaxy: there were only (she estimated quickly) a few thousand of the shining forms, as opposed to the billions of stars in a galaxy . . . And besides, this cavity-spanning torus was immense: she could see how the blood-dark corpses of galaxies sailed
through
its sparse structure.

She knew that the Galaxy of humans had been a disc of stars a hundred thousand light-years in diameter. This torus must be at least
a hundred times as broad -
more than ten million light-years across.

She turned to Mark; he studied her face, a certain kindness showing in his eyes now. ‘I know how you’re feeling. It’s magnificent, isn’t it?’

‘It can’t be the Ring,’ she said slowly. ‘Can it? As far as we know, Jim Bolder reported a solid object - a single, continuous artifact.’

‘Look more closely, Lieserl. Cheat a little; enhance your vision. What do you see?’

She turned her head and issued brisk subvocals. A section of the torus exploded towards her; the fragments, rushing apart, gave her a brief, disorienting impression of sudden velocity.

Her view steadied. Now, it was as if she was within the torus itself, and the sparkling component objects were all around her.

The fragments weren’t simple discs - or ellipses, or any of the shapes into which a star or galaxy might be distorted by the presence of others. She could see darkness
within the heart
of these objects.

The fragments were
knots.

‘Mark—’

‘You’re looking at loops of cosmic string,’ he said calmly. ‘This immense torus is made up of string knots, Lieserl - ten thousand of them, each a thousand light-years across.’

She was aware of her hand convulsing closed around his. ‘I don’t understand. This is - fantastic.
But it isn’t the Ring Bolder described
.’

He looked distant, wistful. ‘But it
must
be. We know we’ve come to the right place, Lieserl. This is undoubtedly the site of the Great Attractor: the loops, together, have sufficient mass to cause the local streaming of galaxies.

‘And we know this assemblage must be artificial. Primeval string loops could have formed during the formation of the Universe, after the singularity. But there should have been no more than a million of them -
in the entire Universe
, Lieserl - spaced tens of millions of light-years apart. It simply isn’t possible for a collection of ten thousand of the damn things to have gathered spontaneously within a cavity a mere ten million light-years across . . .’

‘But,’ Lieserl said patiently, ‘but Bolder said the Ring was solid. If he was right—’

‘If he was right then the Ring has been destroyed, Lieserl. These loops are - rubble. We’re looking at the wreckage of the Ring. The photino birds have won.’ He turned to her, his face a sculpture, expressionless, obviously artificial. ‘We’re too late, Lieserl.’

She felt bewildered. ‘But if that’s true - where are we to go?’

Mark had no answer.

Louise said, ‘What are you talking about, Spinner?’

‘Can’t you see it?’ She closed her eyes and watched, once again, as the string loop punched through the fragile superstructure of the galaxy. ‘Mark - Louise - this string loop was
aimed
, quite precisely. It’s a weapon. It is blasting through this galaxy with its gravitational rockets, destroying all in its path with focused beams of electromagnetic and gravitational energy . . .’