When the five hundred reach their destination, to wake from Longsleep will be a slow and laborious process. The bodies slowly raised from sub-zero temperatures; the oxygenated preservation fluid drained from lungs and airways; the sustaining gel pumped from their digestive system, and so on and so on. The whole method will take a day or more, the waker only fully recovering consciousness some hours after that. Despite the ship’s gravity system and constant bone/muscle stimulation on the sleepers, it will take weeks of recuperation before they can be said to be close to functioning normally.

  The trials back on Earth for Longsleep were messy and dangerous. Only after decades of research into each individual obstacle posed by trying to shut down aging to an absolute minimum was the technique declared ready for purpose.

  Sentinel Sleep, a rival system developed during the same period, is another matter; it is an almost prohibitively expensive technology aboard a ship where every single thing is unimaginably expensive. But waking takes only half an hour or so, during which Bowman tries to hold on to the dreams that slip through his mind, teasing and taunting his memory like sand running through his fingers.

  Once the waking process is over, the lid to Sentinel Bowman’s pod beeps twice as it glides open. Then there is only the need to remove the feeding and excretion tubes from his body before he climbs out.

  Now, waking for the third time, he stands on the gently curving deck, testing his legs against the force of gravity. Even though he designed several of the ship’s systems himself, he still marvels at the elegant simplicity of the gravity system; artificial gravity created by the application of basic physics.

  The ship is a Toroid Class IV; essentially a giant ring, two kilometers wide, spinning; spinning perpendicular to its direction of travel. The Song of Destiny, like all the Toroid IVs, spins at just the right velocity to create a continuous outward momentum almost equal to the force of gravity on Earth.

  It is this ring that forms the living space of the ship, if living is the word that can be applied to the five hundred Longsleep pods and ten sentinel pods that line its walls. On deck, the gravitational effect is almost indistinguishable from Earth. There are a couple of telltale signs that things are different: the gentle concave curve of the floor, and the fact that on the ship, gravity has a supplementary direction. Yes, the ship spins at its constant speed, so gravity pulls down just as it would on Earth, but then there is the rotation to consider; which means that walking one way round the ring of the ship’s deck is more like walking uphill, and walking the other, something like walking down.

  Even though, for the majority of the time, everyone on board the Song is sleeping, gravity is a necessary part of the fight against the long-term effects of space travel. And when the ship finally arrives at its destination and goes into orbit, then, of course, it will truly come into its own. For now, it merely makes the sentinel’s work sessions that much easier than they would be in zero g.

  The ship is completed by the five Bases spaced out equally around the rim, like five stones spread around an eternity ring. Each is a replica of the other: inside are computer terminals where the sentinels work, chlorophyll banks, water recirculation systems, nutrient facilities, control systems for the ship’s motor, and a planet-to-planet ship, or PTP.

  “Yes,” says Bowman, as he wakes for the third time and climbs from his pod. He slides open the drawer from underneath the pod and pulls on his sentinel’s uniform; dark gray, orange trim. Though he is effectively alone on the ship, it wouldn’t seem right to go to work naked. Besides, there are CCTV cameras in various key places on deck, and he knows that some of the other sentinels are women.

  “Yes,” he says, “twelve hours are more than enough.”

  He gazes down the length of the deck, as far as he can see until it curves upward out of sight. Every ten meters is a Longsleep pod. After fifty Longsleep pods, there’s the pod of Sentinel Seven; fifty pods the other way would take him to Sentinel Five. Whenever he passes one of his colleagues, he waves a hand in greeting. He’s never met any of them, and never will, not till the journey is over. He saw a couple of them briefly on Venture Day, as they were installed in their pods for real, all practice done, a day or so before the ship left Earth orbit. He doesn’t know them, but they are just like him, he supposes; each chosen for their special skills and aptitude, to be the guardians of five hundred souls through space for a hundred years.

  There is not the slightest sound and not the slightest movement anywhere. Inside each pod rests a just-living human being, each of them invisible.

  Since the ship has a radius of a kilometer it’s over 1,200 meters from one Base to the next; Bowman’s pod is 400 meters from where he has spent twenty-four hours in the last twenty-six years: Base Four.

  The lights are dim but grow brighter as he walks toward the Base. He catches sight of his reflection in one of the small ports in the wall of the ring. It faces forward, in the direction they’re flying, but there is no sense of movement at all; the stars are too far away for them to change position as they travel. It’s hard to be sure in this light, but there is his face, looking back at him; not a day older than when he first climbed into the sentinel pod, twenty-six years ago.

  It doesn’t seem possible, but it is. Yet it is only possible because his waking hours are so limited. There is no option. In eleven-and-a-half hours, he must be refitting himself in his pod, waiting to be taken into Sentinel Sleep again. If he misses just one deadline with the pod, his life expectancy will drop, vastly. The chances are he will not make it to their destination a young man, if alive at all.

  * * *

  That’s when it occurs to him, staring through the narrow porthole, he, like all the others on board the Song of Destiny, is not traveling through space in a straight line. The ship itself is traveling in a straight line, but the ship is spinning; so everyone on board is rotating as they move forward at something close to nine-tenths light speed.

  He is traveling in a spiral, a helix through space.

  * * *

  He ambles into Base Four, shutting the door to the ring, only vaguely wondering why he is bothering to shut the door when there is no operational need to do so. If he’d stopped to think, he might have realized that the sight of pod after pod stretching away round the curve of the ring unnerves him slightly, as if he’s flying a mortuary through space. He knows none of these people—none of them. That’s why he was chosen for his job as a sentinel, in part at least. Along with the other sentinels, it is his job simply to see them, and the ship, safely through space.

  He flops down into the chair in front of Terminal Base Four, and that’s when he sees the series of red lights blinking on the screen in front of him.

  Six of the five hundred are dead.

  1

  Of all the problems that faced the world, there was one that nothing could be done about, because it was caused by the success of eradicating all the other threats to human life: overpopulation.

  It took centuries longer for the world to civilize than anyone ever anticipated. But eventually it did. As artificially grown meat solved the food crises; as the threat of climate change stabilized with the disappearance of fossil fuels and their replacement with renewable power; as even the poorest countries in the world became rich enough to be well off as the driving forces for wars dissipated; as finally people everywhere became comfortable enough that their need for religion waned and dwindled, a truly united world Global-Government faced the last remaining issue: there was no longer enough room for the billions of people living in the thin film of habitable space wrapped around the planet. Deserts had been hydrated, floating cities spawned, even the Antarctic colonized, and yet still the birth rate shot ever-upward.

  As the memory of times of war and conflict began to raise itself in countries’ collective minds, the world clamored for a solution to the problem. In response, birth limits were introduced, and so the population began to slowly level off, but, by now, the question of the long-term prospects
for the human race was high in people’s minds. It was, many people felt, in man’s nature to explore, to expand, in short: to live. The desire to survive and prosper, it was argued, is the very meaning of life itself. It must go on, forever, without limit, and to deny that would be to deny life. Mankind should not live with birth quotas and assent forms and enforced sterilisation.

  Billions of dollars were spent merely researching potential solutions, but they all revolved around the same idea: a new Earth must be found, or made.

  As attempts to seed an atmosphere on Mars repeatedly failed, a new strand of thought emerged, so very unthinkable until all other possibilities had been exhausted: we must move to some distant, and already Earth-like, planet.

  The problems facing such an endeavor were plentiful, but the biggest was also the simplest: the nearest habitable world known was very far away. So far that it would take light around one hundred and seventy years to reach it.

  The planet, orbiting a star in the constellation of Lyca, had been dubbed New Earth centuries before anyone ever thought of going there; all the analysis showed this distant world was as close a cousin to our own as could ever be found anywhere, an Eden, waiting to be colonized. But, ever adaptable, the people of the world began to change their viewpoint. This was a journey of a previously unimaginable kind, and yet there was nothing in theory to prevent it. Each obstacle in the way of such a mission was attacked ruthlessly. Trillions were spent researching matters from zero-waste nutrients to chorophyll-based oxygen generators to the issues of the deleterious effects of space travel on the human body; from muscle and bone wastage issues, to electromagnetic shielding against interstellar radiation. The question of how to achieve near-speed-of-light travel was resolved after thirty years of development on the Clarke Drive, a radiation pressure engine that steadily imparted impulse to the mass of the ship.

  Eventually, each and every problem was defeated.

  Finally, there only remained the question of who would dare to venture on such a journey. People reminded each other of previous epic journeys made by mankind. History books told of the voyage of the Mayflower, but the comparison was weak. These would not be a hundred souls on board a ship crossing the ocean in a couple of months to colonize another continent; a continent much like the one they’d left, with other ships soon to follow.

  Though New Earth was one hundred and seventy light-years away, the Song’s journey would take only around a hundred years of ship time to complete, one of the advantages of traveling close to light speed being that time dilation would make clocks on board run slower. With its passengers effectively frozen in time until they reached New Earth, and the ten sentinels to each wake just ten times for half a day to monitor the ship’s progress.

  These people would never come back. News of them would never come back.

  Who would go on such a mission?

  The answer, we should not have been surprised, was millions of people. As five Toroid ships were prepared by the Global-Government, one for each continent, the number of people not only willing but desperate to be part of the first wave of colonization grew. Debates raged endlessly; even those who had no interest in going had strong views on who should be allowed to.

  Scientists would be needed, that much everyone agreed. Technicians of all kinds. Doctors. Engineers. But what of the other areas of human life? Should artists be included, and musicians? Wouldn’t a life without such things be pointless to the human animal?

  The arguments continued, but when it was announced that each of the five ships would hold just five hundred passengers. The arguments erupted into disbelief. Of the 45 billion people on the planet, how could just 2,500 be chosen? And what of these guardians, the sentinels? How could there be just ten per ship, fifty in all? Who would ever dare to make such choices? What calculations or formulas could scientists ever derive to neatly give such answers?

  There was one calculation that was indisputable: the minimum number of people per ship should be at least five hundred. Below that number, there would not be a sufficiently diverse gene pool to support the healthy rebirth of the human species on New Earth. Below that number, the possibility of the Founder Effect was too great: the genes of one person could start to dominate the population with, theoretically at least, disastrous results.

  But who would be the five hundred? And who would be the ten?

  Keir Bowman knew he would be among them.

  Yes, he’d worked on the Americas Continent Toroid, developing software for control systems. Yes, he’d been trained as an astronaut. Yes, he had no family ties: no wife, child, or parents living. His psychometric testing had shown him to be a near-perfect candidate for a sentinel. Early experiments in space travel within the Solar System had quickly demonstrated that no matter how high a compatibility score a group of astronauts might achieve, given the timescales involved, factions and politics and even fights would develop eventually in the close confines of the ship. The answer was the loner. The individual who preferred no other company than this own thoughts. Of course, the danger was that such individuals often displayed borderline psychopathic traits. The key was to find just the right person: calm, contained, at peace with their true nature, able to go for long periods in isolation.

  Bowman knew he would be one of them. Partly because he was the near-perfect candidate anyway, and partly because he’d hacked the computers of the Americas’ Selection Committee in order to erase the report of obsessional tendencies in his psychometric test results.

  2

  “Never look back,” was something Bowman remembered his father telling him. It was about the only thing Bowman could remember of him, a man who’d died when his son was a young man. It was certainly the thing that he’d taken most to heart as a boy.

  Bowman had never looked back in his whole life. Not once. Even before he left Earth on the shuttle to the Song of Destiny, he had been floating free. Floating away from people, away from his family, away from his last lover, to whom he had formed only the weakest attachment. He was always looking ahead, desperate to be somewhere else, though he never knew what it was that he wanted.

  So now, staring at a computer screen that tells him that just over 1 percent of the population have died, for reasons unknown, he does not for one minute question his choice to become a sentinel, or regret coming aboard the Song of Destiny.

  The fact that six people have died since the Sentinel Five was on duty a year ago was worrying enough, but there are further complications. Why didn’t the computer wake him earlier, when the first death happened? The ship is programmed to wake the next sentinel in line for duty in the case of any untoward emergency, anything that it cannot sort itself. The fact that it allowed the deaths to continue is strange in itself. Maybe all six had died at once, but then comes the next problem: How did they die?

  He glances at the large bio-clock above Terminal Base Four; the readout of his status displayed for him to see at all times. He has eleven and a quarter hours in which to find the cause of the deaths, work out how to prevent any more from occurring, and reboot the automatic alert systems.

  He begins tapping away at the smooth black keypad. It seems so old-fashioned to interact with the computer in this way when Earth is full of gestural readers and brainwave-synced devices, but the designers of the Toroid ships wanted no room for the errors those devices still sometimes create. With a keypad, if you touch the glass then you touch the glass, and the extra time and physical movement it takes to do that gives everything a much more mechanical certainty. Bowman doesn’t mind, and his fingers are fast.

  He starts to run reports on the six dead pods, and that’s when he starts to feel uneasy, because nothing is wrong. Since the medical history of all 510 people on the ship is recorded constantly while in their pod, any change in health whatsoever should show on the reports.

  He feeds the reports through a medical analyzer, just to be sure he isn’t missing anything, but the result is just as he’d first thought. Nothing was wrong with the peo
ple who’d died, until the moment of death, when their miniscule brain function flat-lined.

  The obvious conclusion; there’s something faulty with the pods themselves. Bowman runs tech read-outs for the six pods, all of which are stationed a way away from him; between Bases One and Two. Over two kilometers away. The results are the same as with the people themselves. There is nothing apparently wrong with the pods either, and yet something is wrong somewhere; and something must be wrong with the alert system itself for the ship not to have woken him.

  He is alone.

  There is no one to help him solve this puzzle, but that’s the way he likes it. He sits back and takes a precious two minutes of his waking time trying to decide what to do.

  First, he reads the last report from Sentinel Five for signs of any issues, anything that might indicate problems were forthcoming. Sentinel Five’s report is so routine as to be boring; everything was fine a year ago, and yet, somewhere in the time that followed, six pods went offline.

  He is alone.

  The ship’s computers can only help him as far as he directs them to. The network of these computers is vast and unbelievably complex, but it is still only a computer network. Long ago it was decided that artificial intelligence systems posed just as great a risk to ultra-long space flight as teams of astronauts do. Suzuki’s Law; that the closer a computer interface gets to seeming truly human, the more humans find it disturbing, holds true in space just as it did on Earth. In fact, given the isolation, having an artificial intelligence, a computer-generated voice, a hologram or other user interface to interact with, slowly eats away at us for some reason; unnerving us, unsettling us, until we feel that we are talking to a ghost, or some spectral god.

  Bowman, therefore, is alone, but that is why he was chosen for the mission; because he is fast, decisive, and doesn’t need support from anyone else to make those decisions.