Terry Pratchett - The Long War

Roberta had learned not to say things like It’s too beautiful a theory not to be true . Once Jacques Montecute, overstressed, had told her that she should have the slogan “Nobody Likes a Smart Alec” tattooed to her forehead in reverse, so she could be reminded of it every morning in the bathroom mirror. She contented herself with saying, “It does fit with the likely physiology, and the evidence of the non-uniformity of the tools. But, yes, the theory needs more testing. It would be interesting to know what’s going on nearer the equator in this world.”

Yue-Sai did a double take. “Why so?”

“Because those tortoises that solved the mazes back on the Datum were allowed to do so in warm conditions. Tortoises are cold-blooded; they shut down in the cold, to some extent.”

“Oh. So maybe the behaviour we’re witnessing here, in the cold, is—”

“Limited by temperature. They may be achieving much more in warmer latitudes. Do you think Captain Chen would sanction a journey south, towards the equator?”

“And risk getting shot down by some super-tortoise? I do not think so.” Yue-Sai packed away her equipment. “Time to get back to the ship.”

Before they left, Roberta glanced across the valley, to the far wall where erosion had exposed the strata of the local sedimentary rocks. She could clearly see a marine deposit, a chalky layer embedded with flints, below a bed of gravel, and then above that a few yards of peat, under the mossy ground surface. She could read the geology. This region, now elevated, had once been under the sea. Later, ice had come and gone, leaving behind the gravel, and then the peat had been laid down over millennia of temperate climates… This world, like all other worlds, had a story of its own, a story billions of years deep and probably not quite like any other in the Long Earth ensemble. A story that probably nobody would ever get around to unravelling, and all she would take away from this place was a few snapshots of tortoises.

She could only turn away.

Back at the airship Captain Chen was excited, and not about tortoises. “Finally—finally!—we have the results back from the probes we sent into the Eastern Gap. You remember, more than six million worlds back.”

“Of course I remember.”

“You asked us to inspect the planets, Venus and Mars. And the scientists found—”

“Life.”

He seemed crestfallen. “You knew? Of course you would know…”

On the Mars of the missing Earth East 2,217,643, there was oxygen and methane in the air, chemically unstable gases that must have been injected by the processes of life. There seemed to be some kind of vegetative covering on the lower ground of the northern hemisphere. And in the clouds of that copy of Venus, high, cool, full of water, chlorophyll had been observed. Earth-like plants, drifting in the Venusian sky.

No, Roberta wasn’t surprised. Any Gap that could be reached by a stepping animal, even the most foolish of humanoids, was going to be a place where bacteria and other living organisms were regularly injected into space, if only accidentally, through the hole where Earth should be. Most such reluctant pioneers would die quickly, including the hapless humanoids if they couldn’t step straight back—but some hardy bacterial spores, having hitched a ride on the stepping humanoids, might survive the radiation, the vacuum. And of those spores, some might ultimately drift into the skies of other worlds, and seed them. This was panspermia, the transfer by natural processes of life between the worlds. It was thought to be possible even in the Datum universe. How much easier panspermia must be in a Gap cosmos, with a way for life to reach space so much more easily than being blasted off by an asteroid impact.

No, Roberta wasn’t surprised. She filed the confirmation away in the back of her mind, where a kind of model of the Long Earth, and all its facets, was slowly being assembled, fact by fact, deduction by deduction.

Under the prow of the airship Shillelagh as it ploughed West, the worlds ticked by, one every second, with hypnotic regularity. Bill paused the journey at recognized Jokers: at the anomalous worlds, flaws in the fabric of the Long Earth, where on a conventional journey travellers would hurry past, unseeing, eyes averted.

Even in the relatively generous, relatively settled worlds of the Corn Belt, in which could be found Reboot, Helen’s family’s home, there were Jokers. Early in the journey Bill stopped briefly at Earth West 141,759, where the multi-channel radio receiver he kept running constantly blared out warnings in a multitude of languages and code formats. Quarantine , Joshua gathered through blistered eardrums: because it was the source of some particularly virulent pathogen, this whole world was under a quarantine administered by the UN, along with staff from the US’s Plum Island Animal Disease Center. Any travellers should keep away from designated areas; otherwise they would be arrested, any materials impounded and destroyed, and they would be kept in confinement until decontamination procedures had been completed… It was a relief to move on and leave it behind.

“Are they serious, Bill? Can you really quarantine a whole Earth?”

“You can try. But how serious they are is another question. We have come across a few nasty viruses out in the Long Earth. Populations of birds and pigs, or birdy creatures and piggy creatures, are always reservoirs of bugs likely to be able to cross over and infect humanity, just as it’s always been on the Datum. And you’d expect humans to have no immunity to such a disease coming from a stepwise world. The greatest threat is to the Datum and the Low Earths, of course, with their dense populations and travel networks. But Cowley and his gang of eejits use fears like this to whip up hostility to combers and trolls, like each one of us is a Typhoid Mary. You know, on worlds like this, they get doctors to volunteer to go in there and support trapped travellers, only to have their Stepper boxes confiscated, and they find they’re not allowed out again…”

On they swept, with regular stuttering pauses.

Jokers weren’t a lot of fun. Many were scenes of devastation one way or another: usually a lifeless ground under a sky that might be either obscured by ash or dust, or else glaring and empty, ozone-free, cloudless, a fierce blue. Bill had Just-So back-stories for many of these shattered worlds, pieced together from travellers’ tales, comber legends, and occasionally some actual science field work.

The most common cause of such collapses, Joshua started to learn, was an asteroid impact. On long enough timescales, it was as if Earth drifted around inside a cosmic pinball machine. Bill lingered briefly at one heavily damaged world, West 191,248. The impact, only a couple of years back in this case, in central Asia, had been far from here; life close to ground zero was devastated, but the world as a whole was suffering under an asteroid winter.

But there were other types of calamity waiting to pounce. Earth West 485,671: a world locked in an Ice Age that had turned into a runaway glaciation, perhaps caused by the solar system drifting through a dense interstellar cloud that blocked the sun’s light. Here the oceans were frozen down to the equator; the ice-shrouded landscapes glared brilliant white in sunlight that poured down from a blue sky empty of clouds, save for wisps that Bill said were probably carbon dioxide snow crystals. But the depths of the ocean, warmed by the Earth’s inner heat, would stay liquid, and life would survive in dark underwater refuges until the volcanoes warmed the world again.

Earth West 831,264: here Joshua looked down on a rust-coloured, Mars-like landscape evidently bare of life, save for occasional streaks of purple slime. The air itself was stained red by the dust raised by incessant windstorms.