Terry Pratchett - The Long Mars

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.

But where the Armstrong travelled now, things got weirder. Maggie learned that there had been another milestone mass extinction on Datum Earth more than two hundred million years before humanity had arisen; a community crowded with the first mammals, early dinosaurs and the ancestors of crocodiles had been smashed. Now, millions of steps from the Datum, they found the consequences of different outcomes of that epochal event, jumbled ecologies where mammalian hunters tracked dinosaur-like herbivores, or insectile predators chased crocodilian prey. There were worlds with crocodiles the size of tyrannosaurs, or raptors the size of mice with teeth like needles . . .

Whatever the details, what struck Maggie cumulatively, as these first days of rapid travel wore by, was the sheer, relentless vigour of an elemental life force which seemed to seek expression anywhere it could, any way it could, on any available world – an expression in living things shaped by relentless competition, creatures breathing, breeding, fighting, dying.

It got overwhelming after a while. Maggie retreated into the familiar routine of work.

ON THE NINTH DAY after the inception of the Chinese drive, Maggie, writing up reports in her sea cabin, barely looked up as she sensed the airship come to a stop, once again. Another science halt; she’d be informed if it was necessary for her to know the details, or if it was thought she’d be interested.

And a day later, with the ship still halted, Gerry Hemingway called. ‘Captain, sorry to bother you. You might want to see this one for yourself.’

She checked her earthometer: Earth West 17,297,031. What the hell, she needed some fresh air. ‘I’ll be there. How’s the weather?’

‘We’re near a sea coast here. Kind of crisp, and it’s February. Bring cold-weather gear, and waterproof boots. And Captain—’

‘Yes, Gerry?’

‘Be careful where you step.’

‘See you on the access deck.’ She stood, and glanced down at Shi-mi. ‘You coming?’

Shi-mi sniffed. ‘Will Snowy be there?’

‘Probably.’

‘Bring me back a T-shirt.’

Maggie Kauffman stood on a sandy beach, by a gently lapping sea. She wondered if this was an inland American sea like in the Valhallan Belt, or if such labels as ‘America’ made sense any more, as the continents slid around the face of the Earth like jigsaw pieces on a tipped-up tray.

She was here with Gerry, Snowy the beagle and Midshipman Santorini whom she’d assigned as an informal companion for the beagle. Even Snowy, who generally went barefoot, was wearing heavy, improvised boots, she saw. Further away more of Gerry’s science team were recording, mapping, monitoring, staring at this unremarkable beach, the ocean, the dunes. There were two armed marines assigned by Mike McKibben, their tough-talking, Scrabble-playing sergeant. Nobody from the Navy side was sure if the marines were attached to parties like this to keep an eye on the local dinosaurs or crocodiles, or on the Navy crew, or on the dog that spoke English.

And two of the party were civilians, wearing odd-looking sensor packs on their shoulders. These were employed by Douglas Black, and sent a continuous feed back to him. Black rarely showed his face outside his cabin, but he was endlessly curious about the worlds they travelled, and liked to explore, if only vicariously.

Well, there were no crocodiles or dinosaurs here, that Maggie could see. Plenty of life in the ocean; she glimpsed fish, seaweed, the remains of some kind of shellfish on the tidal wrack. And crabs, she saw: a hell of a lot of the little bastards running around.

Gerry Hemingway was watching her. ‘Captain, we haven’t filed a formal report yet. What’s your first reaction?’

‘That I’m glad you warned me to put my boots on. These damn crabs are everywhere.’

‘OK. Fair enough. We’ve found a whole belt of worlds dominated by crabs and crustaceans. This is the most spectacular so far. Look, if you’ll indulge us, we’ll show you this step by step. It’s a way of checking our conclusions.’

‘Show me what?’