Authors: Terry Pratchett
Bowring shrugged. ‘We think the ceramic shell acts as a kind of exoskeleton, to support the weight. And there is a
lot
of weight; that spongy stuff is very high density. We’ve run various scans – MRI, sonar. There is structure in there, but it’s a kind of network with identifiable nodes, not a collection of organs like the human. The same kind of structure extends to the head, which seems to be more a sensor pod than a brain pan.’ He glanced at Abrahams. ‘Which could be significant. The human skull has grown over our evolutionary history, but even so there’s only so much room in there – and cerebral functionality has to share space with extensive areas devoted to sight processing, for instance.’
‘Hmm,’ Abrahams said. ‘Whereas if these creatures have their brains in their stomachs, so to speak—’
‘Room to grow. And if they are potentially very smart, they’re
also very capable. Take a look at this.’ Bowring picked up a tablet, which showed an image of a bug’s manipulator arm. He swiped the image to magnify a section.
Jha saw that the ‘limbs’ terminated with splits, into twig-like appendages like fingers. But the ‘fingers’ bifurcated too, into still finer manipulators.
‘It goes on down to the nano scale,’ Bowring said. ‘We think these creatures could manipulate molecules.’
Abrahams said, ‘You call it a “creature”. We return to the point. Is it a creature, though? Is it biological?’
‘As Commander Jha said, opinion is divided on that. Animal or robot? My own theory, for what it’s worth, is that this is some kind of very advanced cyborg. And a very
old
design, to the point where the technology and the biology have merged, seamlessly. The manipulator substructures certainly look engineered. On the other hand the basic body plan looks like a throwback to some biological origin, to me. I mean, it’s not efficient. Why not have the whole body as a kind of modular robot? That way you could split off substructures, merge whole bodies to form larger structures . . . Certainly the capability to engineer on a molecular scale and upward gives them enormous manipulative power. Dr Abrahams, I think a beetle could make anything from almost any ingredient, given the right elemental composition.’
‘Including a copy of itself?’
‘Yes. We know these things have – reproduced.’
‘Using locally sourced materials – beetles grown from the substance of this world. I found that out myself. This is a von Neumann replicator, then. A machine capable of reproducing.’
‘Among other capabilities, yes. And when they combine they are clearly capable of tremendous feats, like their globe-spanning viaducts.’
‘But these creatures don’t come from Earth at all,’ Abrahams said. ‘I mean, from any of the worlds of the Long Earth.’
‘Right,’ Bowring said grimly. ‘And of course our best evidence for an extraterrestrial origin—’
‘Is the Planetarium.’
And to get there, to travel from the mundanity of New Springfield into the utterly unknown, the highly trained and heavily armed crew of a Navy twain had to submit to being stepped over hand in hand by local children, just as had Lobsang and Agnes from the beginning. Children who had figured out how to do this by themselves years ago.
M
ARGARITA
J
HA HAD
stood beneath this alien sky several times since the twain’s arrival here at New Springfield. She’d never got used to it, and never expected to. The party of marines and scientists who were working here in the Planetarium, at a small base camp of tents and trestle tables – and a gun emplacement – were a welcome dose of the mundane. There was even a place for the local kids, the vital stepping link, with food and drink and books to read, even toys.
Once the party had stepped through, Colonel Jennifer Wang, who was in charge here, approached Jha with a brisk nod. Wang, the commander of the
Cowley
’s small marine detachment, wore body armour and a facemask, though nobody had any proof that the latter was necessary; the Planetarium air was benign. ‘Commander Jha.’
‘All seems quiet.’
‘Yes, ma’am, just another routine day here at Bug Central. Bugs doing their bug stuff and leaving us alone. Step easy, Commander.’
‘Thank you, Colonel.’ As routine an exchange as they’d ever had, Jha thought. She’d known Wang for a long time, in fact, since they’d shipped together as junior officers on the
Benjamin Franklin
under Maggie Kauffman many years ago.
And yet – look where they were! You couldn’t escape the thought: what if the gossamer bridge they had just crossed to get here vanished as suddenly as, presumably, it had appeared? But here were
these marines in this extraordinary place, and the young scientists from the
Cowley
doing their jobs, joshing and complaining about the food as if they were in some training camp in a Low Earth Iowa. Of course the local kids weren’t troubled at all. Jha suppressed her own gloomy speculations. What else could you do?
She went to rejoin Abrahams and Bowring, who were peering up at the crowded sky.
Bowring said, ‘It’s clear this world doesn’t
belong
. Not in this chain of worlds, our Long Earth. We’re a little light on mathematicians in this expedition,’ he said ruefully. ‘Damn brain-boxes tend not to travel well. But those we do have are suggesting we’re seeing some kind of flaw in the Long Earth. I mean, its structure in higher dimensions.’
‘It has to be something like that,’ Abrahams said.
‘I’m afraid we have no kind of handle on that yet, on how this could happen – or how to fix it. We’re going to need somebody a lot smarter than us to figure that out.’
‘Indeed,’ Abrahams said dryly. ‘But there’s no evidence that the beetles can step, is there? I mean, aside from the unique step that takes them from Gallery to Planetarium.’
‘None at all,’ said Jha severely. ‘But we’re keeping an eye on that. The Captain’s posted sentries in neighbouring worlds, stepwise. It seems that a handful of these bugs leaked into New Springfield from – someplace else. Well, from
this
place, wherever this is. The point is, now they’re using the resources of New Springfield’s Earth to breed like rats in a granary. We do not
want
these bugs to step over into another Long Earth world and start all over again. And, worse yet, spreading even further.’
‘A wise precaution.’
Bowring said, ‘But we are making some progress with our observations.’ He pointed at the sky, the crowding discs of the stars. Many of them were too bright to look at directly, like fine needles in the eye if you stared. ‘Evidently this is a world inside a globular cluster,
a dense cloud of stars. The density tails off if you look through the crowd and further out. Clusters are big balls of stars, quite compact, and most of them orbit the centre of the Galaxy, each travelling as one big mass.’
‘But which cluster?’ Jha asked. ‘Have you made any progress with that?’
‘Actually, yes,’ he said with a grin. ‘Clusters differ in their age, their metallicity, their size, and we can measure such parameters. We
think
this is a globular cluster called M15 in our catalogues. Thirty thousand light years from Earth – well, that’s about as far away as the centre of the Galaxy. Very old but pretty big, a hundred thousand stars crammed into a space less than a couple of hundred light years across. The astronomers we have on board are pretty excited, actually. There’s believed to be a big black hole lurking at the centre of this cluster – a mash-up of dead old stars, I guess. They’re thrilled to be up close and personal with such a thing.’
‘But black holes aren’t what we’re here to study,’ Jha said reprovingly. ‘We’re primarily studying the assemblers. Whatever they seem to be doing on this world.’
‘“Doing on this world”,’ Abrahams repeated. ‘They’re clearly not native to Earth. You don’t think they’re native here either?’
Bowring shrugged. ‘Hard to be definitive, we’ve so little evidence. But, those bubbles you see?’ He gestured around the landscape. ‘Sacs of air everywhere. They look biological, like flotation sacs on seaweed – much larger of course—’
‘Yes.’
‘The gaseous contents of the sacs match the contents of the bags you see attached to individual beetles. And they all contain a subtly different suite of gases from the local atmosphere – which itself isn’t far from Earthlike, which is why it’s breathable for us. In the sacs there’s more carbon dioxide, more sulphur compounds and so on. Rather like a dilute industrial smog, from the peak days of the Datum.’
‘Terraforming,’ Jha said. Suddenly she saw it. ‘You think the bugs are manufacturing a different atmosphere. They aren’t native to this world. They’re terraforming it.’
Bowring pursed his lips. ‘Well, that’s the wrong word. Not making it like the Earth, as we would . . . Delivering conditions that suit them, presumably.
Xenoforming
– perhaps that’s a better term. They came to this world to make it like their own.’ He looked around, pulling a face. ‘Look at them swarming everywhere. They take the stuff of this world, and are making it into copies of themselves. How disgusting – what
greed.
’
‘Perhaps,’ Abrahams said. ‘But we aren’t so holy. The European explorers imported their own farm animals, their vermin, even their song birds to the Americas, to Australasia. What have the Europeans done save convert a significant fraction of those continents’ biomass into hundreds of millions of copies of themselves? Just like the beetles. If by a rather low-tech method.’
‘They are disturbingly like us, then,’ Bowring said.
Jha asked, ‘So if they aren’t from this world, then where?’
‘Well, I can only speculate.’
Jha sighed. ‘I have a feeling we don’t have time to get everything peer-reviewed, Dr Bowring. Speculate away.’
‘I think they crossed space, to this world. As opposed to stepping here. They are interstellar travellers. Look up there.’ He pointed to his left, at the sky. ‘It may or may not be visible to your eyes – it isn’t to mine, but the youngsters can see it, and the spectrometers show it clearly. The stars in
that
direction, many of them, have a greenish tinge.’
‘Dyson spheres,’ Abrahams said immediately. ‘Or some kind of clouds, at least. Another of Freeman Dyson’s big ideas: stars surrounded by life-filled artefacts. Silver beetles, spreading across the stars.’
‘Yes. They are expansionist. Colonizers, as humans have always been. That’s what we
see
up there, visible in the very sky, a grand,
expanding wave of them, coming from somewhere in
that
direction, to your left, which is to the periphery of the cluster. I suppose it’s possible they didn’t originate in this cluster at all. But they are certainly spreading through it.
‘This particular world, the local star, must be somewhere close to the wavefront. Because in
that
direction,’ he pointed to his right, ‘we see no green stars.’
‘OK,’ Abrahams said. ‘But they didn’t cross space to get to New Springfield.’
‘No. They stepped there, as we did. I suspect they just stumbled through some kind of warped stepping process into the Gallery, and found themselves on that particular Earth – and they’re treating it quite differently. With the big spin-up, rather than a replacement of the air and what-not, as they’re doing here.’
‘Why the difference?’
‘I do have some ideas about that.’ Bowring pointed directly above his head. ‘Up
there
, at the edge of the colonization wavefront, we see something else, orbiting the stars. Neither the usual cosmic furniture, the planets and the asteroids of a virgin system, nor the green that characterizes the beetles’ colonization push. We see another kind of cloud, orbiting some of those stars. Big chunks, irregularly shaped.’
Abrahams whistled.
‘Purposeful destruction?’ Jha asked, wondering.
‘If I were not a respectable scientist I would be prepared to speculate that there, at least, somebody is fighting back, against the beetles’ expansion. And that may be why we find so much activity by the beetles, just now, in the New Springfield Earth. It’s no coincidence.
It’s because they encountered us
. They have learned to anticipate resistance. And so they accelerated whatever programme of work they had, in order to get it done before we have a chance to fight back, to stop them.
‘As to what that programme is, as I said, at New Springfield they
seem to have adopted a different strategy. They aren’t xenoforming that world. But what?’
‘I think I know,’ Abrahams said. ‘Dyson didn’t conceive of his spin motor as an end in itself. He was thinking of how to build his great spheres, artefacts that could enclose a whole star.’
‘Ah,’ said Bowring. ‘And the only way you can get enough matter to do that—’
‘Is to dismantle a planet.’
‘
Dismantle
.’ That mundane word shocked Jha. ‘How could you do that? . . . Oh.’
Abrahams said grimly, ‘By spinning it up, faster and faster, until—’
‘Yes.’ Jha took a breath. ‘I need to talk to the Captain.’
Abrahams said, ‘And I need to talk to my wife.’
P
ROFESSOR
E
MERITUS
W
OTAN
Ulm, of the University of Oxford East 5, author of the bestselling if controversial memoir
Peer Reviewers and Other Idiots: A Life In Academia
, had consented to give a recorded lecture on von Neumann replicators to be carried as briefing material on the US Navy twain USS
Brian Cowley
.
‘. . . Is this thing on, Jocasta? What do you mean, your name’s not Jocasta? Young lady, I am seventy-eight years old, my childhood home is under ten metres of ice, and I haven’t got time for
your
nonsense. Eh? What green light? Ah . . .
‘Von Neumann replicators, then. Like a super matter printer – a printer that could produce another matter printer. A machine that can make a copy of itself. Much like yourself, Jocasta! What could we do with such a technology?
‘How about colonizing the Galaxy?
‘In the last century, in a more innocent age of happy memory, the physicist Frank Tipler proposed a way we humans could colonize the stars, and cheaply into the bargain. Tipler’s scheme assumed nothing much beyond the slower-than-light transport methods we can easily envisage today. Just as in our exploration of the solar system, we would begin with unmanned probes. The first wave would be slow, no faster than we could afford.
‘But the probes would be self-replicating, you see: capable of constructing anything, given raw materials, including copies of themselves. And that’s the clever bit. Earlier the great physicist John
von Neumann had shown that such machines are theoretically possible – and, after all, human beings are capable of replication with very little training . . . Have I made that joke already, Jocasta? Oh, very well. I’m seventy-eight, you know.
‘Now, when such a probe arrived at its target, it would settle down, look around a bit, perhaps grow a few human colonists from some seed bank – you know the kind of thing – and then, crucially, start to build copies of itself, a new generation of probes that will move on, further and deeper into the Galaxy, in search of homes of their own.
‘We can expect the migration to continue, in all directions outward from the Earth, pretty relentlessly once it has started. And the process would be self-financing, and
that
would have been music to the ears of every money-grubbing university administrator with whom it has been my misfortune to lock horns. That’s because the new colonies would be built from local resources, requiring nothing of Earth.
We
must invest merely in the cost of the initial generation of probes.
‘But there’s a trap.
‘Suppose we start colonizing the stars, after the manner of Tipler. Earth is suddenly the centre of a growing sphere of colonization – a sphere whose volume has to keep increasing, if a constant growth rate is to be achieved. The leading edge, the colonizing wave, has to sweep on faster and faster, eating up worlds and stars and moving on to the next, because of the pressure from behind . . .
‘Imagine then a Tipler wave of replicating robots swarming across the Galaxy, turning fallow star systems into copies of themselves, working feverishly just to keep up with the pace of expansion. Even if such a probe arrived in an inhabited system it must immediately crush any native life, transforming all in its path into more copies of itself. It would have no choice; it would have no time to do otherwise, to maintain the momentum of the expansion.
‘Is this infeasible, technologically? Not at all.
We
could almost build such things.
‘Would it be unethical to unleash such a compound-interest horror on the rest of the universe? Most people would think so, but don’t ask a banker.
‘Is this what the colonists on that godforsaken High Meggers world seem to have discovered in their hole in the ground? A Tipler wavefront? Sounds like it, doesn’t it? . . .
‘What’s that, Jocasta? What should be done about New Springfield? Well, I should build a very, very high wall around these fellows, metaphorically speaking.
‘Now then, is that enough? I am seventy-eight years old, you know . . .’