A novel set in the Culture universe created by Iain M. Banks

Backwards Chaining

Screens and holos flashed up all around the accommodation section of the One Hand Clapping as the ship projected images, many scraped from the Rock's own internal monitoring, judging from the static viewpoints, and others which flickered with bewildering swiftness from one view to another. The views shows trees and dense foliage, sandy beaches, sunlit waves, an isolated hut made with some skill from such raw materials as were available and, here and there, a flash of movement as some blue-skinned, bright-eyed creatures hurried about on errands known only to themselves.

It was a little piece of tropical paradise, Mso thought, all trapped inside a rocky ball. A pocket world, preserved, sealed like a fly in amber.

"It's a hollow world, an artificial habitat," the Hand said, adopting the tones of one delivering an impromptu university tutorial, "A Rock, in the standard nomenclature. Inside the rocky integument - which appears to be the original undisturbed fabric of an asteroid, there is an inner sphere a little under twenty kilometres in diameter. The sphere is split precisely in half. On the lower side, if I can adopt a useful convention, are the environment mechanisms which maintain a liveable space and generators for artificial gravity, all tightly packed into the hemisphere. There are no significant voids or openings anywhere."

The ship paused, giving the appearance of ruminating for a moment. A ship's Mind, entirely embedded in hyperspace and functioning at the speed of HS light, could have performed a thousand, thousand lifetimes of cogitation in that one second. Mso wondered if more than an infinitesimal fraction of that thought was being expended on this conversation; if it was, then there must be some careful balance being prepared. Or maybe the ship was just being wilfully ambiguous.

"Rather wasteful; an object of this size could be spun to provide the same apparent effect, and provide more living space on the inside too. Although that would make it harder to maintain an effective disguise from the outside."

The vast majority of the Culture's thirty-plus trillion citizens lived on, or in, artificial structures of some kind. Its cities, where hundreds of millions of people lived cheek-by-jowl - albeit in beautifully crafted and elegantly compact structures - were its great ships, the General Service Vehicles. GSVs constantly threaded the Greater Galaxy, acting as mobile marshalling points for people and material, spinning off smaller ships and generally representing everything that the Culture was to the other species, civilisations and groupings which shared the incomprehensible vastness of this section of the universe.

Stay-at-home types, those who liked a bit of elbow-room or just more variety in their environment tended to live on Orbitals, the Culture's preferred method of providing the maximum of living space with the minimum use of matter. A Full Orbital was three million kilometres in diameter, a hoop of material a few thousand kilometres wide, spun to provide one standard gravity and a standard day-night cycle, with its own spin providing the apparent gravity which glued the landscape, atmosphere, and everything else to its inner surface. A hundred billion people could live on an Orbital without ever coming into shouting distance of one another.

Of course, some people just preferred planets, liking the sensation of ten thousand kilometres of solidity beneath their feet. Yet others tramped the reaches of space in smaller ships, or lived on smaller worlds, Rocks and other kinds of enclosed habitats. Most people in the Culture regarded this kind of life as an amusing peccadillo or harmless eccentricity, something to be sampled for a while, perhaps, a source of anecdotes and talking-points for parties.

"Above, projectors give the appearance of a blue sky and a mobile sun-source mimicking the effects of sunrise and seasons," the ship intoned casually, "The upper surface is a tropical sea with surprisingly authentic waves. The sea is filled with a mixture of small edible fish, rather larger poisonous creatures and a few really huge predators - bioautomations rather than real living creatures - which are presumably intended to discourage swimming. Just as well, otherwise it would only take a reasonably strong swimmer to reach the edge of the world. Boats wouldn't do any good either, at least of the kind you could make on the island; some of those fish are really big and would easily capsize any raft or dugout you might make."

"The central portion is an island - it is the only surface you would consider habitable - formed from sandy beaches overgrown with a tropical forest encircling a rocky core modelled on an extinct volcano. The mountain is roughly conical, hollow and contains more of the environmental support equipment. There are a couple of fake springs on the upper slopes, so there's plenty of fresh water. The plant life is widespread, grows at a prodigious rate and the forest supports a varied collection of small animals and insects - no birds, though. That's another omission to ensure the veracity of the illusion."

Emshala was growing visibly irritated by this lecture delivered in measured tones, the drip-feed of information most of which could have been gleaned from the screens around them. His animated tattoos swirled; the mobile images on his skin provided much the same function as the aura fields used by drones like Schoma Xantic. This pattern, if Mso interpreted it correctly, expressed his growing displeasure and barely-held-in-check frustration. She could understand his feelings: he was a trained and experienced Contact xenobiologist; there was a whole unexplored world full of exciting new creatures within his reach and he was itching to get a closer look.

"Are there any sentient beings, inside?" he interrupted, "Any people?"

There was another pause before the Hand answered, either purely for effect, or as a result of a truly prodigious amount of analysis undertaken by the ship's Mind.

"There is an intricate and complex society living within the Rock," the ship said carefully, "But you're not going to like it."

The remark instigated a certain amount of consternation amongst most of the crew. Those with a lace, and the two drones, had already assimilated more of the situation than the ship's narrative had so far revealed. The others were puzzled by the enigmatic nature of the ship's remarks, but not really surprised; this was the kind of character typical of a GCU; idiosyncrasy polished to an art form; it was a characteristic which tended to rub off on the human crew.

"Look, there are humanoid beings - people by definition, almost certainly - resident on the island," the Hand said quickly, "They have some, ah, extremely unusual physical characteristics and social mores, which we will need to investigate further. With some urgency, too, I expect."

Mso found her attention was caught elsewhere. She gestured at the impossibly slender waterspout on the one screen which still showed a representation in hyperspace.

"Is that what provides the Rock's motive power?" she asked.

"Huh! This thing's got no engines!" the ship almost squeaked, "No mechanism to change course, decelerate, anything. This thing was built without them. It must have been accelerated by some external mechanism and then left to drift. Whoever built this thing tossed it out at some tiny fraction of light speed, and then abandoned it, with extreme prejudice."

"So what's the hyperspace connection for?" Mso asked.

"Power," the Hand said shortly, "The Rock is powered from the Energy grid - like I am, of course, but this has such delicacy" - the ship almost sounded impressed - "the finest, almost infinitesimal filament in hyperspace, a golden thread of energy whose projection in three-space is smaller than a hydrogen atom. But it's just used to supply the energy needed to maintain the environment. This thing has no weapons, no defences - at least, unless they are very well hidden - nothing which uses much power or would attract much attention. And there's no screening or protection; nothing which attempts to prevent a complete inspection by something such as myself" - now the ship sounded faintly smug - "Not that it could, in any case."

Mso seemed to have taken on the role of Inquisitor-in-Chief as far as the ship was concerned - a role normally played by Emshala, to her persistent amusement and his consequent mild irritation. Now that she was asking the questions herself, she could feel the eyes and other assorted senses of the crew on her, the quizzical amusement, the pose of indifference, the sense that the others were merely patronising her.

Undaunted, she pressed her questions anyway.

"Could you make a Grid link like that?"

Again, that pause. With, worrying, the suggestion that the unimaginably vast mental resources of the Mind were struggling to answer the questions.

"Perhaps," came the ambiguous reply.

Mso knew that the Culture's understanding of the energy grid, and the control over access to hyperspace it implied was - by its own admission - limited, flawed. If the builders of this artefact could do something that the Culture would, at best, find difficult then this was a prize to be coveted, pursued, sought after. There was, she considered, more than met the eye going on here.

"What do you mean, perhaps?"

"I think I can see how it's done. There's a trick to it, a way of finessing the field structures which is beyond my experience," the ship said carefully, "Or of anything in the Culture, as far as I know. I'd want to study it for a while before I'd be prepared to try it myself. It looks like it might be unpredictably unstable."

This merely confirmed Mso's suspicions in general terms. She wondered for a moment whether it was worth pursuing the point further, given the ship's - or any of the Culture's Minds, for that matter - ability to misdirect, misunderstand or evade a direct question, without ever telling an actual untruth.

But it seemed like the One Hand Clapping had something else on its mind, as it were.

"This Rock is on a collision course," it said bluntly, before Mso could speak again, "With a star gone nova about three lights away. It'll take about eighty-five years to get there. If I was being paranoid, I would even say that it has been precisely targeted at the star in question."

There was a collective gasp around the accommodation section, ignored by the ship.

"Oh, it could conceivably miss, or perhaps sling-shot off in another direction without significant damage. But, at the present moment, it's fairly precisely targeted at the star and, short of a hugely improbable collision with another peripatetic piece of stellar debris, it's going to burn up completely."

"Could you deflect it? Save the population," Mso demanded.

"I could, naturally." the ship replied with no detectible hesitation, "But, should I?"

"Of course you should!" Mso started to say, but the words died on her lips.

"Look, the Rock has been carefully crafted to avoid attention," the Hand said, "It's obviously a lifeboat, an ark, a generation ship intended to keep a small number of people alive indefinitely."

"But what are they escaping from? Their own star gone nova, an asteroid collision? Although any species which could build this Rock could certainly deflect any comet nucleus or wandering rock which threatened a planet or habitat or their own. Are they fleeing from some pogrom or environmental disaster area, or are they survivors from a war? Or, is it an escape pod for the remnants of the losers, a refuge for those who started a genocidal war, but lost? Or a prison ship, an eternal punishment for crimes too vile to be forgotten or forgiven? Are they victims, or aggressors? Refugees or criminals?"

There was a moment of stunned silence.

"There's another thing," the ship went on, "There are impact craters on the surface of the Rock; on several occasions in the past, something - another wandering body, probably - collided with it. Or perhaps they represent the result of any of several kinds of weapons systems. But were those impacts before or after the asteroid was converted? I can't tell. Have they been attacked? And, if so, by whom? and why?"

"The chances of randomly being pointed at that level of precision at that star are negligible; this is the result of intelligence, of design and forethought. We have to decide whether they should be saved, whether they are worthy, whether they deserve another chance. We are put in the position of judges: whether it would be a crime to allow these beings to perish, horribly in fire and vacuum or whether it would be criminal to prevent an execution, judged as just and deserved hundreds of generations ago."

Humans have always been notoriously argumentative. Those who survive the rigorous selection procedure and make it into Contact will have had years, perhaps decades, of practice in making their case articulately and persuasively to a jury of their peers. It was therefore, inevitably, suddenly rather noisy in the accommodation section.

Mso felt a heavy weight suddenly descend on her shoulders. In amongst the raised voices of the crew attempting to express a point of view, she tapped the brooch which functioned as a terminal.

"Ship, we need more information," she said, "There are too many unknowns."

"Agreed," the Hand's voice spoke from the device, "But where from? The Rock itself is no help. It's barely even proto-sentient. It has no knowledge of its own history, why it was constructed or where it has come from. If it has a purpose, however dimly perceived it may be, it is to preserve the status quo, to make sure today is just like yesterday and tomorrow is just the same."

"We will, I believe, have to make contact with the inhabitants, directly, to find out what, if anything, they know about their own origins. That may be more difficult that you might imagine. And it may well not be successful anyway.

"So we're going to need to find out where it came from. And, at the moment, I don't know were that was."

Tracing the route that the Rock had taken was no more difficult then predicting the starting-point for any peripatetic asteroid or planetary fragment that had been wandering the galaxy for aeons. That was to say, it was impossibly hard.

The Rock could not have varied its own course, as it seemed to have been built deliberately without manoeuvring capability of any kind; it contained nothing which could change its speed or direction beyond the simple expedient of ejecting portions of its own mass at high velocity, an obsolete technology Mso and the others would learn was technically known as "rocket-powered". Although the Rock contained no detectable mechanisms even for that archaic form of engine, its course would have been deflected by the distant gravitational fields of stars and comets over light-years of travel, the deflecting bodies themselves having subsequently shifted and further altering the trajectory of one another, a complexity beyond even the most capable Mind to predict with any degree of accuracy.

"What do you mean, you don't know where it came from?" Mso demanded, her hands placed petulantly on her hips.

The ship sounded genuinely apologetic.

"Oh, I've got some idea. But there are just too many variables for complete precision. Look, see for yourself."

Another wall-screen flickered into life, showing a starfield, then suddenly went out-holo, filling the accommodation space with dozens of stars. Mso and Emshala stepped back instinctively; some of the others did not, the hologram wrapping itself around them seamlessly and making T'wou appear like some impossibly huge and omniscient universal Creator complete with messianic beard and brooding attitude.

"We're here," the ship continued, a tiny green speck brightening briefly, "And the rock's recent trajectory is clear enough."

A line of green light appeared, terminating at the speck which has lit up earlier.

"And the targeted nova is here."

The green line extended fractionally, terminating in one of the few stars visible. As the line reached its end, the point of collision flickered a dull brooding red.

Then, the entire representation swirled and twisted, pulling back from the open cluster within which they were currently located. Now the accommodation section was packed with thousands of stars, each a distinct point of light. The green line represented the known path of the rock had collapsed to a glowing green point, flashing steadily on and off.

"But this region of space is heavily populated with wandering rocks, planetary fragments, lost comets and ice-balls of every description" - the holo scintillated blue and mauve and amber and red as the ship's disembodied voice classified the cosmological detritus - "leftovers from planetary formation which didn't quite complete, or debris where proto-planets were torn apart shortly after formation by near-collisions between the parent stars."

There was a sound like a sharp intake of breath from Quenlily Sikralis. The ancient drone had been constructed before aura fields had been commonplace and had steadfastly refused to be retrofitted with dedicated projectors. It could use its built-in field manipulation capabilities to produce the same effects, but very rarely did so. The sound was for the benefit of the humans present, to indicate its understanding of the innate complexity and difficultly of the situation. Schoma Xantic more economically expressed much the same sentiment by flashing its fields blue-grey picked out with circulating flecks of magenta and yellow-grey.

"Within the cluster," the Hand continued, "All these little perturbations combine, each adding a little more uncertainty to the Rock's direction of travel when it entered the region. And then, outside the cluster, in the general direction of travel, there's nothing much for tens of millennia."

The green line expanded to form a softly illuminated narrow cone in space, layered in multiple shades of green. A few pinpricks - representing, Mso guessed correctly, individual stellar systems - flickered fitfully like moths in a headlight.

"This section of the Rock’s route traverses a very sparsely-populated region. Just a few systems, but nothing close to the high-probability part of the projection. We'll have to investigate, of course, but none of us should be holding our breath. In any case, they will be more-or-less on our way."

"On our way where?" Mso demanded.


The cone of pale green light shrunk again and spun about, so that most of the humans were looking along the axis. The cone expanded again, the far end suddenly lighting up in a confusion of bright motes, like a swarm of bees caught in the beam of a searchlight.

"The Kaligan Cloud," the ship said, with just a little theatrical portentousness which Mso wondered if only she could detect, "The most densely packed region of the Galaxy outside the Core. Suns of every type - in Binaries or Triples, or even larger groupings - and systems with dozens of planets and hundreds of moons. All packed so close that, standing on any of the planets, the night sky would be a blaze of fireworks and the paired nature of the nearby stars would be obvious even to the naked eye."

Mso gazed with growing trepidation at the star-map the ships was projecting. The Cloud was an irregular volume, hundreds of light-years on a side, and almost all of it was within the cone of green which represented the ship's best guess at the origins of the rock.

"Are we still going to keep all this a secret?" Mso breathed, "Or are we going to call in the cavalry?"

The Culture was notoriously bad at keeping secrets, especially big ones. It was one of the very few areas where most of the Culture's civilizational peers and even many much less advanced societies thoroughly eclipsed it, though, being the Culture, this was regarded as being the legitimate source of a certain perverse pride. That didn't stop it - the "it" in such contexts usually meaning Contact or (even more likely) SC - from trying to keep secrets, every now and then, but it never worked for very long.

Though sometimes, of course, not very long was long enough.

"I've made a report to the Hence, Or Otherwise. I'm sure it will have shared the report with the local Contact management group. But it'd urge you to keep this thing quiet for the present, although I suspect we will be expected to go public very soon."

Mso frowned, but she found herself grudgingly agreeing with the Hand's assessment.

"But, for now, we'll need to take a closer look, at the natives here as well as wherever it is they came from," the Hand said firmly, "And it's going to take quite some time."

[tight beam, M16, tra. @n4.29.177.1405]
  xGCU One Hand Clapping
    oGSV Hence, Or Otherwise
My humans seem very unhappy at the suggestion of withholding information on this mysterious Rock.

[tight beam, M16, tra. @n4.29.177.1406]
  xGSV Hence, Or Otherwise
    oGCU One Hand Clapping
Of course they do. It’s part of their function. Fortunately, I don’t believe we’ll need to hold back much longer. There’s no immediate threat here and we could probably do with all the help we can get on understanding this artefact. So I’ll send out a general summary report in the next hour. We’ll probably be inundated with queries soon after that.

I'll tell them that when they start getting fractious.

That won't take long. Keep the detailed reports coming in the meantime.

Of course. But I think fully understanding this thing is going to take more than a few days.

I agree. And it really is genuinely important. Stick with it.

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