‘OK. But I’m here now. And I’m used to relying on myself for my own survival.’

‘Sure. Well, there are plenty of contingencies we couldn’t survive at all. A massive enough meteor strike. A bad enough failure of the propulsion system during the firing phases – we do have nuclear fusion explosions going on back there.’

‘And what is survivable?’

‘Plenty. A smaller meteor puncture. A containable fire. An atmosphere leak, or some other failure of the air supply. A drastic power failure. In most of these situations the automatics will save us. In most of the rest, I’ll be there to deal with it. And failing that, you can talk to the Brick Moon.’

‘And if all those fallbacks fail?’

Frank grinned. ‘I’d say the primary key survival skill for you is going to be learning to put your pressure suit on, in the dark, with the air failing around you, and the emergency horns sounding like the opening bars of Doomsday. Once you’re in your suit you’ll have time to deal with the rest. Takes hours of practice to master that.’

‘Well, I guess we have hours.’

And so they started, with Sally learning every inch of the ship and its equipment and various failure modes to the best of her ability, while Willis locked himself away and pursued his own projects.

That was how it was, pretty much all the way to Mars.

14

IN HER LOG, Maggie Kauffman noted that it was only once they were past Earth West 1,617,524 – past the world of the beagles, and with that final crewmate on board – that her journey truly began.

Harry Ryan finally declared himself happy with what he described as his ‘fusion-cuisine of an engine suite’, with robust American engineering wrapped around a core of Chinese gel-based ingenuity, and he permitted Maggie to order full throttle, at last.

Maggie herself was in the wheelhouse when it began, with a few of her officers, ready for any of the multiplicity of breakdowns and disasters that Harry had predicted. Wu Yue-Sai was making notes as ever. Maggie had a fine view of the outside worlds through big panoramic windows – windows with tough ceramic shutters ready to clang shut in an instant in case of emergency.

And she watched those worlds flip by, one after the other, ever faster as the drive cut in.

At first the view was routine, if you could call anything about the Long Earth routine: just one arid world after the next in this belt of ‘Para-Venuses’, dissolving away at one per second, the rate of her heartbeat. Then the rate increased steadily, up to two Earths a second, faster, and Maggie felt her own heart beat faster in response, her body’s rhythms unconsciously tracking the music of the worlds. But as the rate increased further Maggie began to find the strobing of realities uncomfortable. They should be in no danger. It was routine now to test twain crews and passengers for epilepsy, and Doc Mackenzie had ordered everybody aboard to put themselves through a final automated screening before consenting to this engine test.

And still the worlds swept past, faster and faster. Maggie became aware that the Earths flickering below were greener than before, the sky sporadically bluer. They must already be out of the Venus belt, then. But the worlds were now flying past her vision too fast for her to make out any details, nothing save the basics of sky, horizon, land, and the steely shine of the river beneath them – a remote cousin of the Ohio, if the ships’ geographers were to be believed.

And then the worlds blurred. They reached a certain critical point when the stepping rate was faster than her vision processing system could follow, as if the worlds – each a whole Earth! – were no more than fast refreshes of a digital image. So there was no longer a sense of stepping from Earth to Earth, but more of continuous movement, of flow and evolution. The sun was a constant, hanging in a sky that was a melange of all the weathers, a kind of deep blue blandness. Below, the river spread out across its flood plain like a pale, greater ghost of itself, and forest clumps melded into a greenish mist that lingered over the landscape. It was no longer possible to make out any animals in the individual worlds, any birds; even the mightiest herd in any one world would be there and gone before her eyes had time to see it. Yet there was a sense of continuity, of the connectedness of all these living worlds, these actualized possibilities for Earth. All of this was sporadically illuminated, or darkened, by Jokers, exceptions to the norm, there and gone every few minutes.

And the Cernan hung constant in the sky, a reassuring companion – the work of mankind enduring against the flickering of multiple realities.

Now there was a thrum of mighty engines pushing the ship through the air, and the landscape shifted beneath the prow of the Armstrong. Continental drift was to some extent an affair of chance, and the positions of the landmasses shifted from world to world, mostly by very little, sometimes by a lot, but cumulatively by significant amounts. So the airships had to navigate geographically, trying to stay roughly over the centre of the North American craton, the antique granite mass at the heart of the continent. Again they were following the precedent of the Chinese expedition five years earlier.

Lieutenant Wu Yue-Sai stood by Maggie, and boldly took her hand. ‘It is just as it was for us aboard the Zheng He,’ she said. ‘As if we see these worlds, the whole of the Long Earth all at once, through the eyes of a god.’

Only a few hours later the ships rushed across the Gap, around Earth West 2,000,000, without pausing. Harry Ryan declared himself happy with the resilience of his ships given the test of that dose of vacuum and weightlessness.

The character of the Earths did change somewhat after the Gap, when they paused to sample, image, visit. The worlds became blander, more colourless, with forest clumps dominated by huge ferns. These in turn gave way to more arid landscapes, with the vegetation restricted to the rivers and the fringes of the oceans. The worlds seemed to come in rough bands of similar types, tens or hundreds of thousands of steps wide, analogous to the Belts that had been identified by the first mappers of the Long Earth a couple of decades back.

Hemingway and his scientists tried to label and investigate a representative sample. They stopped to study features of geology, or geomorphology, or climatology – even astronomy, such as unusual features on the moon. They even checked for radio transmissions bouncing around remote ionospheres, and looked for the lights of human-lit fires, for nobody knew how far the colonization wavefront had come in the years since Step Day. The scientists reported that the basic suites of vegetation and animal types were similar either side of the great interruption of the Gap, and that was no great surprise. But they saw no stepping humanoids beyond the Gap: no trolls, no kobolds, none of the species that were common on the lower worlds. Again that was no great surprise, since, Maggie supposed, most steppers would not take the risk of crossing the Gap. But, for a veteran Long Earth traveller, it seemed strange to see worlds where there had never been trolls at all, worlds where the ecology had not been influenced by their massive presence – worlds which had never known the trolls’ long call.

On the ships sailed. Data poured in, a torrent.

But it was always life that snagged the attention. And the life they saw got odder and odder.

Most of these worlds seemed to host complex life – that is, animals and plants, more than just bacteria. But the worlds of the Long Earth differed from each other by chance, by outcomes of random events in the past that varied a little or a lot. And the great extinction events that littered Earth’s history seemed to Maggie to represent the biggest of all rolls of the cosmic dice. Even worlds closer to the Datum than Valhalla appeared to reflect different outcomes of the big impact that had ended the reign of the dinosaurs on the Datum. There, people had found strange assemblages of beasts that were like dinosaurs or not, like mammals or not, like birds or not.