28

Louise Armonk asked Spinner to take the nightfighter to the source of Mark’s anomalous hydrogen-band signal.

She showed Spinner some data on the signal. ‘Here’s a graphic of the main sequence, Spinner-of-Rope.’ A barchart, in gaudy yellow and blue, marched across Spinner’s faceplate. ‘We’re getting pretty excited about this. For one thing it’s periodic - the same pattern recurs every two hours or so. So we’re pretty sure it has to be artificial. And look at this,’ Louise said. A sequence of thirty bars, buried among the rest, was now highlighted with electric blue. ‘Can you see that?’

Spinner looked at the ascending sequence of bars, trying hard to share Louise’s excitement. ‘What am I looking for, Louise?’

She heard Louise growl with impatience. ‘Spinner, the amplitude of these pulses is increasing, in proportion with the first thirty prime numbers.’

The electric-blue bars were split into discrete blocks, now, to help Spinner see the pattern. She counted the blocks: one, two, three, five, seven . . .

She sensed an invisible smile. Just like a child’s puzzle, isn’t it?

‘Oh, shut up,’ she said easily.

‘What was that?’

‘Nothing . . . I’m sorry, Louise. Yes, I see it now.’

‘Look - what’s exciting about finding this sequence of primes is that it means the signal is almost certainly human.’

‘How do you know that, just from this pattern?’

‘We don’t know for sure, of course,’ Louise said impatiently. ‘But it’s a damn good clue, Spinner-of-Rope. We’ve reason to believe the prime numbers are of unique significance to humans.

‘The primes are fundamental structures of arithmetic - at least, of the discrete arithmetic which seems to come naturally to humans. We are compact, discrete creatures: I’m here, you are out there somewhere. One, two. Counting like this seems to be natural to us, and so we tend to think it’s a fundamental facet of the Universe. But it’s possible to imagine other types of mathematics.

‘What of creatures like the Qax, who were diffuse creatures, with no precise boundaries between individuals? What of the Squeem, with their group minds? Why should simple counting be natural to them? Perhaps their earliest forms of mathematics were continuous - or perhaps the study of infinities came naturally to them, as naturally as arithmetic to humans. With us, Cantor’s hierarchy of infinities was quite a late development. And—’

Spinner barely listened. Humans? Here, at the edge of time and space? ‘Louise, have you decoded any of the rest of it?’

‘Well, we can figure some of it out,’ Louise said defensively. ‘We think, anyway. But remember, Spinner, we may be dealing with humans from a culture far removed in time from our own - by millions of years, perhaps. The people of such a distant future could be almost as remote from us as an alien species. Not even Lieserl has been able to help us work this out . . .’

‘But you’ve made some progress. Right?’

Louise hesitated. ‘Yes. We think it’s a distress call.’

‘Oh, great. Well, we’re certainly in a position to help out god-humans from five million years after our birth.’

‘Who knows?’ Louise said dryly. ‘Maybe we are. Anyway, that’s what we’re going to find out.’

. . . There was motion at Spinner’s left. She turned.

Suddenly, the forest-dream man was visible. He was sitting there, quite casually - outside the cage - on the construction-material shoulder of the nightfighter. He wore no environment suit, nothing but a plain grey coverall. His hands were folded in his lap. Light - from some unseen source - caught the lines around his mouth, the marks of tiredness in his eyes.

At last he had emerged. Gently, he nodded to her.

She smiled.

‘ . . . Spinner?’

‘I’m here, Louise.’ She tried to focus her attention on her tasks; she reached for the hyperdrive waldo. ‘Are you ready?’

‘Yes.’

The nightfighter flickered through hyperspace. Travelling at more than a hundred thousand light-years per hour, the Northern edged around the torus of fragmented string loops, like a fly around the rim of a desert.

The journey took ten hours. As it neared its end Spinner-of-Rope took a brief nap; when she woke, she had her suit’s systems freshen her skin, and she emptied her bladder.

She checked a display on her faceplate. Twenty jumps to go. Twenty more seconds, and—

Something vibrant-blue exploded out of space at her, ballooning into her face.

She cried out and buried her faceplate in her arms.

It’s all right, Poole said softly.

‘I’m sorry, Spinner-of-Rope,’ Louise Armonk said. ‘I should have warned you . . .’

Spinner lowered her arms, cautiously.

There was string, everywhere.

A tangle of cosmic string, rendered electric blue by the faceplate’s false colouring, lay directly ahead of the ship. Cusps, moving at lightspeed, glittered along the twisted lengths. She leaned forward and looked up and down, to left and right; the threads of string criss-crossed the sky as far as she could see, a textured wall across space. Looking deeper into the immense structure, Spinner saw how the individual threads blurred together, merging into a soft mist at infinity.

The string loop was a barrier across the sky, dividing the Universe in two. It was quite beautiful, she thought - but deadly. It was a cosmic web, with threads long enough to span the distances between stars: a web, ready to trap her and her ship.

And, she knew, this was just one thousand-light-year fragment, among thousands in the torus . . .

‘Lethe,’ she said. ‘We’re almost inside this damn thing.’

‘Not quite,’ Louise said. Her voice, nevertheless, was tight, betraying her own nervousness. ‘Remember your distance scales, Spinner. The string loops in this toroidal system are around a thousand light-years across. We’re as far from the edge of that loop as the Sun was from the nearest star.’

‘Except,’ Mark Wu cut in, ‘that the loop has no easily definable edge. It’s a tangle. Cosmic string is damn hard to detect; the display you’re looking at, Spinner, is all Virtual reconstruction; it’s just our best guess at what lies out there.’

‘Then are we at risk by being here?’ Spinner asked.

Of course, Michael Poole said.

‘No,’ Louise said.

‘Yes,’ Mark said. ‘Come on, Louise. Spinner, we’re working to minimize the risks. But the danger is there. Spinner, you need to be ready to react - to get us out of here, quickly. We have escape routines laid into the waldoes, for both hyperdrive and discontinuity drive.’

‘I’ll be ready,’ she said calmly. ‘But why are we here? Is the human signal coming from somewhere in there - inside the string?’

‘No,’ Louise said. ‘Thankfully. Spinner, the signal is coming from the system of a neutron star - just a few light-hours away from here. We’ve laid in—’

‘—a discontinuity-drive sequence into the waldoes,’ Spinner said dryly. ‘I know.’ She reached for her controls. ‘Tell me when you’re ready, Louise.’

Poole looked tired, his brown eyes deep in a mesh of wrinkles. You know, I worked with Louise Armonk, he said. He smiled. And here we are, together again. Small world, isn’t it? She was a good engineer. I guess she still is.

‘I know you decided to close your wormhole time bridge,’ Spinner said. ‘Tell me what happened to you.’

Poole sat, apparently relaxed, on the ‘fighter shoulder; his eyes were closed, his head bent forward. I remember the lifedome of my GUTship entering the Interface, he said slowly. There was light - like fire, blue-violet - from all around the lip of the dome. I knew that was the flesh of the Spline, burning up against the Interface’s exotic-matter framework. I remember - a sense of loss, of alienation.

‘Loss?’

I was passing out of my time frame. Spinner-of-Rope, each of us - (he raised translucent hands) - even I - is bound into the world by quantum functions. I was linked non-locally to everything I had touched, seen, tasted . . . Now, all those quantum bonds were broken. I was as alone as any human had ever been.

I engaged the hyperdrive.

Bits of the wormhole seemed to fall away. I remember streams of blue-white light . . . I almost believed I could feel those hard photons, sleeting through the lifedome.

Spacetime is riddled with wormholes: it is like a sheet of flawed glass, crazed by cracks. When Poole set off his hyperdrive inside the wormhole, it was as if someone had smashed at that flawed glass with a hammer. Cracks exploded out from the point of impact and widened; they joined up in a complex, spreading network of cracks, a tributary pattern that continually formed and reformed as spacetime healed and shattered anew.

The spacetime cracks opened up like branching tunnels, leading off to infinity . . . Poole smiled, self-deprecating. I started to wonder if this had been a good plan, after all.

The pod sailed down from the Northern’s lifedome.

Lieserl sat in a Virtual projection of a pod couch beside Mark Wu; ahead of them blind Uvarov was swathed in his blankets, his cavern of a mouth gaping, his breath a rattle. The huge discontinuity-drive wings of the nightfighter spread over the pod like the vaulted roof of some immense church.

Far below the pod revolved the bleak, airless planet to which they were descending. Staring down as the small island of solidity loomed out of the glowing fog, Lieserl had a sudden - and quite absurd - feeling of vertigo. She felt as if she were suspended, in this couch, without protection far above the planet’s surface; she had an impulse, which she suppressed with determination, to grip the sides of her couch.

Vertigo . . . After all her experiences inside the Sun, and despite her perfect knowledge that she couldn’t be harmed even if the pod exploded here and now - since she was little more than a Virtual projection from the Northern’s main processors, with augmentation from the pod’s processor banks - after all that, she had vertigo.

Still, she thought, it was comforting to know that she’d retained enough humanity to be just a little scared. Maybe she should tell Mark; it might make him think a little better of her.

Beyond the pod’s clear hull, the neutron star system was a huge tableau all around them.

The neutron star itself was a tiny, fierce yellow-red ball. It had a companion - a normal star - and it was surrounded by a ring of gas, which glowed softly. And there were several planets, orbiting the neutron star, inside the smoke ring.

In fact, the anomalous signal was coming from one of the planets, the little world towards which Lieserl was now descending.

The nightfighter had dropped them into the ring of smoke which orbited the star. It was like descending into fog. Close to the pod Lieserl could see dense swirls of the ring gas - clumps and eddies of turbulent stuff - and, beyond that, the rest of the ring was a band of pale light bisecting the Universe. She could see the neutron star itself, a small, hard coal glowing yellow-red at the heart of this ring of smoke. Beside it hung its companion star - huge, pale, distorted into a squat egg-shape by the neutron star’s fierce gravitational field. Tendrils of gas led from the carcass of the companion and reached blindly towards the neutron star.

And beyond that, tilted crazily compared to the gas torus, was a starbow.

This neutron star was moving with extraordinary speed: it plummeted across space at close to the speed of light. As a result of this high velocity, the neutron star and its system were the only visible objects in Lieserl’s Universe. All of the rest - the blue-shifted galaxies, the nearby wall of cosmic string - was compressed into that pale starbow, a band of light around the equator of the star’s motion. And away from the starbow, there was only darkness.

Uvarov tilted his head, and the pod’s internal lights cast shadows across his imploded eye-sockets. ‘Tell me what you see,’ he hissed.

‘I see a neutron star,’ Mark said. ‘An unexceptional member of its species. Just ten miles across, but with a mass not much less than Sol’s . . . What has made this one unusual is the fact that it has a companion, which is - was - a normal star.’

Before Mark, a Virtual diorama of the neutron star system glittered into existence; the globes of the neutron star and its companion were criss-crossed by lines of false colour, showing - Lieserl suspected - gravitational gradients, lines of magnetic flux, and other observables. Bits of text and subsidiary graphics drifted in the air beside the glowing objects.

‘Once,’ Mark said, ‘these stars were a binary pair - a spectacular one, since the neutron star must have been a brilliant giant. Somehow, the companion survived the giant’s supernova explosion. But the remnant of that explosion - the neutron star - is killing its companion, just the same.’ He pointed. ‘The neutron star’s gravity well is sucking out material from the companion . . . Look at it, Lieserl; those delicate-looking tendrils of smoke could swallow Jupiter. Some of the companion’s lost matter is falling onto the neutron star itself. And as the mass down there increases, the rotation of the neutron star will glitch - the neutron star must suffer starquakes, quite regularly. The rest of the gas is drifting off to form this ring we’re in, orbiting the neutron star.’

‘Do you think the birds caused the supernova explosion, Mark?’ Lieserl asked.

He shook his head. ‘No. The system is too stable . . . I think the explosion took place long before the birds took an interest.’

‘And the companion?’

He smiled, peering up at the complex sky. ‘Lieserl, that is one star the birds don’t need to kill. The neutron star is doing their work for them.’

The Virtual representation of the neutron star expanded before his face, expelling the companion and the other features from the diorama. Mark peered in to a complex knot of light at what looked like one of the star’s magnetic poles.

Lieserl looked away. The planet wasn’t far below, now; slowly it was turning from a ball of rock, suspended in emptiness, into a landscape - bare, bleak, riven by cracks.

‘What about the planets?’ Lieserl asked. ‘How could they have survived the supernova?’

‘My guess is they didn’t,’ Mark said, still staring at the star’s pole. ‘I think they probably formed after the explosion: coalesced from material in the gas ring, and from debris left over from the explosion itself - maybe from the previous planetary system, if there was one . . . Lieserl. Lethe. Look at this.’

‘What?’

The neutron star Virtual representation swept across the cabin towards her; the little knot of light at the pole was thrust in her face. Lieserl flinched, but stared gamely into the glowing, complex image.

Mark was grinning, his voice animated by excitement. ‘Do you see it?’

‘Yes, Mark,’ she said patiently, ‘but you’re going to have to tell me what I’m seeing.’

‘There’s a major disturbance in the gravitational gradients at that magnetic pole.’ Arrows clustered around the star’s pole, forming themselves into a two-dimensional plane. ‘Can you see it?’

‘What about it?’

Mark sounded impatient. ‘Lieserl, I think there’s a sheet discontinuity down there. A two-dimensional defect. A domain wall, inside the star . . .’

Lieserl frowned. ‘That’s impossible.’

‘Of course it is.’ He grinned. ‘How could a domain-wall defect form within the structure of a neutron star? Impossible . . . unless it’s been put there.’

Uvarov’s ruined mouth stretched into a smile. ‘Put there?’

‘We wondered how come this neutron star was out here on its own - away from any galaxy, and moving so bloody fast. Well, now we know.’

Lieserl found herself laughing. ‘This is outrageous. Are you suggesting—’ ‘Yes,’ he said seriously. ‘I think someone, maybe human, installed a discontinuity drive at the magnetic pole of this neutron star, and used it to hurl the whole system across space at close to lightspeed.’

‘But that’s absurd,’ she said. ‘Why should anyone do such a thing?’

Now Uvarov laughed, at her. ‘Still the rationalist, Lieserl, after all our experiences? Well, perhaps we will soon learn the answer to such questions. But of this I’m sure - that it has some connection to this endless, bloody war in Heaven we’ve wandered into.’

The pod’s descent bottomed out, now, and the little ship sailed over the planet’s battered landscape.

At length, Mark said, ‘We’re over the source of the signals . . . There,’ he said suddenly. ‘Can you see it?’

Uvarov tilted his head on its thin neck.

Lieserl peered down.

‘A structure, Mark said. ‘There on the surface . . . Some kind of building. Come on; I’ll take us down.’

I fell into the future, Spinner-of-Rope, through a network of transient wormholes that collapsed after me. My instruments were smashed, but I knew my lifedome must have been awash with high-energy particles and gravity waves. I was as helpless as a new-born babe.

Poole sat in raw vacuum on the shoulder of the nightfighter with his legs tucked beneath him, lotus-style, his hands resting comfortably, palms-up, on his knees. Spinner could see a grooved pattern, moulded mundanely into the soles of his shoes.

He said, I fell across five million years . . .

Mark Wu - or rather, one of his Virtual consciousness foci, on the Northern - peered at the loop of cosmic string through the hundred eyes of the ship’s sensors. He wasn’t happy: his multifaceted view was muddy, imprecise.

The trouble was, the ship was in orbit around this damn neutron star planet, which was falling through space so fast the observable Universe was relativity-shifted into a skinny, pale starbow. It was like being taken back to the Northern’s thousand-year flight. Mark had to deconvolve out the effects of the near-lightspeed motion: to unsmear the Universe back out of the starbow once more.

Mark had subroutines to achieve this. But it was, he thought uneasily, a little like unscrambling an egg. The resulting images weren’t exactly clear.

Inside his box of processors, Mark Wu worked on nanosecond timescales. He could process data at several millions of times the rate achievable by humans, and it sometimes took an effort of will to come back out of there and return to the glutinous slowness of the human world.

It was seven centuries since his physical death and downloading into the AI banks of the Northern, and he’d steadily got more proficient at non-human operation. Right now, for instance, he was maintaining a conventional human-Virtual on the pod with Lieserl and Uvarov, and another with Louise in the Great Britain, in parallel with his direct interfacing with the Northern’s systems.

Running these multiple consciousness foci felt odd, but he’d grown used to enduring minor discomforts when the need arose.

And there was need now.

Maybe he should have tried to veto this trip to the neutron star, he thought. It had brought the Northern close - too damn close - to this loop-cloud of cosmic string. When dealing with an object a thousand light-years across, he thought sourly, a separation of a mere handful of light-years didn’t seem nearly sufficient.

Mark split off a series of more subordinate foci, and set to scanning overlapping sectors of the sky.

His image of the Universe was a mosaic, constructed of the fragments supplied to him by the sensors; he imagined it was a little like looking out through the multi-faceted eyes of a fly. And the Universe was criss-crossed, everywhere, by string double-image paths - it was as if the sky were some huge dome of glass, he thought, marred by huge cracks.

By studying the double images of stars and galaxies, Mark was able to check on the near-lightspeed velocities of the string segments; he constantly updated the internal model he maintained of the local string dynamics, trying to ensure the ship stayed a safe distance away from—

A watchful subroutine sounded an alarm. It felt to Mark like a prickling of vague unease, a shiver.

. . . There was movement, in the field of view of one sensor bank. He swivelled his consciousness, fixing most of his attention on the anomaly picked up by that sensor bank.

Against a background provided by a beautiful, blue-stained spiral galaxy, he saw a double track of multiple stellar images.

There had to be two lengths of string there, he realized: two arcs of this single, huge loop of string, no more than light-hours apart. And he could see from the melting flow of the star images that the arcs were sliding past each other in opposite directions; maybe eventually they would intersect.

In some places there were three images of single stars. Light from each of those stars was reaching him by three routes - to the left of the string pair, to their right, and straight through the middle of the strings.

The cause of the alert was obvious. All along the double tracks, he saw, star images were sliding, as if slipping across melting spacetime. These strings must be close - maybe even within the two-light-year limit he’d imposed on himself as a rough safety margin.

He ran a quick double-check on the routines he’d set up to monitor the strings’ distance from the ship. He wondered if he ought to tell Louise and Spinner about this . . .

Now, suddenly, alarm routines shrieked warnings into his awareness. It was like being plunged into an instant panic; he felt as if adrenaline were flooding his system.

What in Lethe—

He interrogated his routines, briskly and concisely. It took only nanoseconds to figure out what was wrong.

The pair of string arcs were closer than he’d thought at first. His distance-estimation routines had been thrown by the interaction of the two strings, by the way the pair jointly distorted star images.

So the strings were closer than his monitoring systems had told him. The trouble was, he couldn’t tell how close; maybe they were a lot closer.

Damn, damn. I should have anticipated this. Feverishly he set off a reprogramming routine, ensuring that for the future he wouldn’t be fooled by multiple images from pairs of string lengths like this - or, indeed, from any combination.

But that wasn’t going to help now.

He ran through a quick hack procedure, trying to get a first-cut estimate of the strings’ true distance . . .

He didn’t believe the answer. He modified the procedure and ran it again.

The answer didn’t change.

Well, so much for my two-light-year safety zone.

The string pair was only around ten million miles from the Northern - less than a light-minute.

One of the pair of strings was receding - but the other was heading straight for the ship.

He ran more checks. There was no error.

In fifty seconds, that encroaching string would hit the Northern.

He burst out of the machinery and back into the world of humans. With impatience he waited for pixels to congeal out of the air, for his face to reassemble; he felt his awareness slow down to the crawl of humans.