‘No, no.’ Joe started tapping eagerly at screens. ‘It’s a good question. Because we might be able to use this line of thinking to estimate how far Feathers here has come.’

  Meriel looked sceptical. ‘Convince me.’

  ‘I’m trying to dig out some data, such as it is,’ he said, staring at his screens. ‘There used to be a theory about this, you know. Centuries back, when we knew a lot less about life in the universe, or the lack of it, than we do now. It used to be thought that the human body was such a natural winner that the sky was bound to be full of human-like forms: the hands, the brain, the vision equipment on top of an upright frame … Yeah. Here it is. They called it convergence.’ He stressed the word. ‘The idea was that maybe there was only one basic useful design if you wanted to make a planet-builder. That is, the human design.’

  ‘Get to the point sometime today,’ Hild said, not unkindly.

  ‘OK. The point is that not all lines of evolution will yield such a planet-builder.’ He tapped his screen some more.

  Salma saw numbers scrolling.

  ‘Consider this. There are thought to be a trillion species on Earth right now.’ He looked up. ‘Impressive. Even the climate-collapse mass extinctions didn’t make much of a dent in the overall numbers, although most of the glamorous species went, or survived only in zoos … But it’s thought that over time about ninety-nine per cent of all species that arose on Earth have gone extinct. So that’s a total of a hundred trillion species on Earth. I imagine that number gets fuzzy when you work back through the tree of life to the beginning and species merge and split …’

  ‘The point, Joe?’

  ‘Sorry, Hild. Here’s the argument. So one in a hundred trillion species on Earth, us, turned out to be planet-shapers – and we showed up late in Earth’s evolution, a couple of million years ago out of four billion or more.

  ‘Now, what if you take that as a ball-park estimate for the chances of any planet evolving technological life like us? At least one species?’

  ‘One in a hundred trillion,’ Boyd said. ‘OK, I’ll buy that. How many planets in the Galaxy?’

  Joe checked his screen. ‘A lot less than a hundred trillion – more like forty billion habitable. Just an estimate, of course.’

  ‘Umm. OK. So how many galaxies for a hundred trillion planets?’

  A quick on-screen calculation. ‘Twenty-five hundred. Wow. That’s the size of a supercluster. A hundred million light-years across. Maybe more.’

  There was a silence after that.

  ‘So,’ Boyd said, ‘to an order of magnitude, we could have expected Feathers here to have had to travel a journey the scale of a supercluster—’

  ‘Just to find one other tool-wielding, planet-scarring culture like our own. But it’s worse than that,’ said Joe, staring into his screen. ‘I love playing with numbers like this. She hasn’t had to find just another tool-making culture. To make this visceral connection with us, she’s had to find one which is humanoid in body form – like her, more or less.’

  ‘Wow,’ Hild said. ‘And what are the odds of that?’

  Nobody knew.

  Boyd said, ‘Let’s make a wild guess.

  ‘Humour the old guy. Suppose it’s about the same order as the odds of finding such an intelligent culture in the first place. Just suppose for now; the super-brains on Cronus can come up with a better guesstimate when they get here. But for now, if you multiply the culture number times the body plan number—’

  ‘It means another factor of a hundred trillion,’ Joe said. ‘You’d need to search a hundred trillion times a hundred trillion planets … These numbers are absurd. There are thought to be around a billion trillion planets in the universe. Shit. There are too few planets in the entire damn universe to make that a worthwhile bet.’

  ‘Then how many universes?’ Hild snapped.

  ‘How many universes? What does that even mean?’ Joe looked discomfited, but made the calculation on a screen. ‘Ten million, it says here. Ten million universes the size of ours …’

  ‘Or,’ Boyd said quietly, ‘if our universe was ten million times older, it might be a fair bet.’

  That made them think, Salma realised.

  ‘Umm.’ Joe pawed at his screens. ‘Ten million times older … A hundred thousand trillion years? That far in the future, our universe will be a dark place, all the stars burned out …’

  Hild said, ‘You know something – I think we made some kind of breakthrough here. Even if my head’s spinning—’

  ‘Mine isn’t,’ said Boyd. ‘I think we got an answer to the question we started off with – even if these are just guesses, if the actual numbers we’re quoting are speculation. You said that even if Feathers doesn’t have a literal message, something to tell us directly, then maybe her very presence here is the message.’ He looked around. ‘And that message is that we’re dealing with something from outside our universe. From somewhere else. Some other place that’s very big, or very old. Or both. Something, or somebody.’

  The mood was sombre now, Salma realised. Hild muttered something about writing all this down, sending the conclusions back to the Conserver bases …

  Boyd nodded. ‘And what we have to figure out now is what that somebody wants. And what it will cost us.’

  Feathers, evidently sensing the change in atmosphere, wriggled over to Salma.

  Salma held her tight.

  Year 6

  AD 2261

  19

  In the final months and weeks of the six-year flight from Earth, John Smith had intended to spend his time at the windows of the big viewing lounges that occupied much of the equator of the passenger hull of the Cronus. In fact, he’d scheduled to have himself woken out of cryo six months out from the arrival of the Cronus at Saturn, for that very purpose.

  Only to discover that from here Saturn was still no more than a pinprick of light. And then to discover that six months was a hell of a long time if one was confined with little to do, even after a years-long sleep.

  It did occupy a few days, but no more, to catch up with the news, and with downloaded messages and technical papers from his own office on Earth, and from the Conserver home base at the heliopause. Most of the messages concerned the science of Planet Nine, and global curiosity about the creature called ‘Feathers’ – against the background of the quasar’s steadily increasing and malevolent effects on the Earth.

  As the years had passed, the intensity of the heat in which Earth and the rest of the Solar System was bathed had continued to increase. By now the increased heating amounted to an extra day’s sunlight load per year. It still didn’t sound much, but year on year more of that energy had to be absorbed by the planet’s various natural reservoirs: the air, the land, the oceans. Year on year that additional load grew, slowly but exponentially increasing. And the fragile, barely recovered systems of Earth – living, climatic, geological – and political – were increasingly feeling the strain.

  It was a paradox that off-world colonies, including on the Moon, fared better than the home planet; out there all you had to do was throw a few more layers of reflective insulation over your habitat. But, tentatively, slowly, cautiously, the space industries were responding, such as with the floating of huge new reflective sails over the planet to deflect the increased insolation.

  But there was more urgent news. In particular, Smith discovered with faint alarm, a high-performance Lunar Consortium ship, the Aquila – eagle-fast as its name implied, he supposed – had been detected apparently pursuing the Cronus out towards Saturn, following much the same trajectory, and would arrive at about the same time. The Aquila had evidently run silent and dark for most of its six-year mission, shadowing Cronus. Now, evidently, it was out in the open, and it was an unsettling development.

  Nobody on Earth or in the Conserver councils knew what the mission of the Aquila was; despite heavy diplomatic pressure the Consortium refused to say what it was up to. There was nothing to be done about it.

  Yet another watching brief, in what felt like a slow-moving, Solar-System-wide crisis to Smith, despite his own long sleep interval.

  So that was the news. All the updates consumed and absorbed.

  Now what?

  He explored the ship, once again.

  Only to find he didn’t actually know anybody well among the currently non-sleeping passengers. There was a logic to that. Those he met now had mostly been sleeping in his own early period of wakefulness.

  Even Elizabeth Vasta, senior science adviser to the top layer of Earth’s multinational government, was absent. He knew that she had put herself into cryosleep a mere three weeks after launch from Earth high orbit, and, he learned now, intended not to wake until three weeks before the destination. Probably sensible. He even considered asking to be put back in the sleep tanks himself, only to find that the medical advice was against submitting oneself to another dose of cryo so soon after the last.

  So he was stuck here, trying to get some work done – trying to find useful work to do – trying not to feel too guilty about another dose of opulent living, unwanted and unearned.

  Guilty, yes, that was inescapable.

  John Smith was a dedicated Conserver partly because of his own background. He had grown up in the slums of New Los Angeles, a legacy now carefully hidden beneath a layer of education and cultivation. He had come to understand that one result of Earth’s one-time addiction to uncontrolled economic growth had been such wells of impoverished misery.

  Smith had been lucky in the education he had received from various charitable institutions – some Christian groups, battling the general post-climate-crash downturn in religious activity, and he had done a lot of Bible studying because of that – and including, most valuably as it turned out, a mission to Earth from the Conservers themselves. In time, and perhaps as a reaction to all that had gone before, in his own life as well as what he had seen of the world, he had gladly accepted the Conservers’ quiet philosophy, their obvious logic, their teachings, and the practices they preached. The basic message was after all simple. The Solar System looks like a big place to expand into – but so did the Earth, once …

  And so he knew that hurling this big luxury hotel across ten astronomical units was a gross misuse of the common resources of mankind: a waste of materials and energy, as well as of the many, many hours of labour it had taken to design, build and crew this thing.

  But he also believed that the astonishing discoveries at Nine justified the full attention of mankind, including, for once, the expenditure of such huge resources. The moral compromise had to be made; the mission had to be achieved.

  And there was wonder to be cherished. At last, as the long journey of the Cronus drew to a close – even though many of the onboard experts continued to look out at the quasar speck in the deep sky – as Saturn finally loomed ahead, for Smith there was only one show in the heavens.

  John Smith knew the basic orbital geometry of the Saturn system.

  You had the planet itself, a gas giant more than ten times the width of the Earth, turning on its axis in an unreasonable ten hours: it spun so fast it was visibly flattened by rotation away from a pure sphere. The sunlight was dim here, almost autumnal. Saturn was ten times as far as Earth from the Sun, so its sunlight was only one per cent of the intensity of that at Earth – but still the light was better, more useful, than Smith had expected.

  And in this September light you could actually see, via simple telescopes, the elevator hub: a speck shining bravely about the planet’s radius above the clouds, though the thin thread of the elevator cable itself, dipping into those clouds, was invisible as yet.

  That hub was the destination of John Smith and the Cronus.

  The timescale for the final approach was set by the ten-hour spin of the planet itself, which was matched by the hub’s orbital speed. So it took a few hours of manoeuvring for the Cronus to sweep in from interplanetary space, heading for that elevator hub.

  A thrilling few hours, more grand spectacle.

  The first encounter was in fact with Titan, Saturn’s largest moon, where the ship’s drive was squirted to gain a gravity-assist boost – an ‘Oberth manoeuvre’, apparently, stealing a little of Titan’s own orbital energy to slow the ship down and help it lodge in the greater gravity well of the giant planet. And at closest approach to Titan, a world in itself, Smith and his fellow window-watchers peered out.

  Titan was known to be rich in useful resources. Even its air was mostly the super-useful gas methane, relatively cheaply extracted from the moon’s shallow gravity well, and employed as propellant by ships such as the Cronus itself before its helium-3 refit. But, under international law, Titan as yet had been left largely unexploited and unexplored, save for a few automated probes. That was because of Titan’s similarity, as it was perceived, to primeval Earth. Even if it had no life itself, Titan as a model of a prebiotic Earth like world could be hugely scientifically valuable, if only as a comparison: this is how Earth was, once …

  John Smith knew that the Lunar Consortium chafed at such restrictions, and had put forward proposals to mine Titan more extensively, going beyond the scoop-mining of methane from the top of its atmosphere, to taking nitrogen from ammonia layers deeper in the air and on the ground, and eventually digging into the moon’s water-ice core. This would disrupt the moon’s scientific value permanently – and, if some kind of life did linger in Titan’s cold oceans, an early extermination could follow, perhaps even without discovery first. Earth believed in a cautious expansion of industry in such realms. The Conservers meanwhile argued for no industrial expansion into the Solar System.

  In this case the resolution of the conflict had played out well, Smith thought. With the coming of the Saturn space elevator, even the aerial mining of Titan’s methane was to be largely abandoned, in favour of extraction of the gas, and others, from the upper atmosphere of Saturn itself presumed lifeless.

  And for now, after a close encounter lasting just minutes, Smith was pleased to see Titan sail by, barely perturbed by this latest invasion from the bright heart of the Solar System.

  While Cronus descended ever deeper towards Saturn and its rings.

  Titan orbited at some million kilometres from the centre of Saturn – and so was in fact well outside the ring system.

  And, once within Titan’s orbit, John Smith and the rest eagerly peered out of the Cronus windows for a first glimpse of the next great spectacle.

  The rings themselves extended around Saturn’s equatorial plane from an inner edge at a few thousand kilometres above the cloud tops – only a tenth or so of the planet’s own radius – out to around a hundred thousand kilometres.

  Smith had seen the rings from further out, a belt of ice fragments orbiting the planet and shepherded into neat concentric circles by the moons’ gravity – a spectacular arrangement that had looked oddly artificial to Smith. Now the ship was much closer in and tracking Saturn’s equator, which was the plane of the rings too – so all that was visible was a scratch of light, a fine line before the planet. This was the ring system seen edge-on, the individual ring fragments too small and distant to make out.

  But the ship needed to sail no further across the plane of the rings than its outer edge, Smith knew; the orbital mechanics demanded that the hub of any Saturn space elevator had to be in the world’s equatorial plane – and, a hundred thousand kilometres above the clouds, actually outside the inner ring system. And the cable to which it was attached had to be that long, or longer, to reach down from hub through the rings and into the clouds of the planet itself.

  The scale of all this was tremendous. The stately approach went on, another hour passing, and another. Smith may have dozed a while.

  And after his last waking, he found a larger body loomed before the ship – a body that shone bright blue, the blue of an Earth sky, even if the wan sunlight didn’t really do it justice, Smith thought. A human-built body amid this grand natural ballet.

  This was the Saturn elevator hub.

  The hub itself was a rough sphere, dotted with what looked like small rocket clusters – perhaps even missile launchers. That wasn’t necessarily militaristic. The hub spent its life outside the main ice-swarm rings, but a collision with even a small rogue fragment could be lethal. Smith guessed he was seeing a collision-avoidance attitude control system – maybe even some kind of weapons system to break up ice chunks.

  Extending from that central spherical structure, he saw a line of sky blue, the elevator cable itself, arrowing horizontally, from his viewpoint, in through the ice of Saturn’s rings, straight down into the cloud layers of the planet. The cable did not reach down to any solid surface, unlike Earth’s elevator; instead the line terminated in a heavy factory installation, suspended deep in the complex air.

  The whole immense arrangement seemed oddly parasitic, Smith thought. But then humans were indeed draining a little of the lifeblood of this huge world, as if taking a medical sample – or as if sucking out sustenance like some tick on a human skin.

  And it was startling to see this strange human colony, this human gadget, suspended in this extraordinary sky, so far from home. Smith felt a surge of pride in the achievement, a reaction to which his Conserver conscience only mildly objected. If you were going to go dipping into Saturn for its resources, this was about as non-disruptive as you could get.

  And John Smith from the New Los Angeles slums could not help but be thrilled at the sight.

  20

  When the Cronus finally reached the elevator hub, the first step was to anchor together the two massive bodies, hub and ship, with rigid struts. Then transparent tunnels were attached to airlocks, through which passengers and freight could pass in either direction – tunnels through the vacuum.