The Long War

deduction.

54
    U NDER 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.
    ‘What the hell happened here?’
    ‘A gamma-ray burster. Well, that’s our best guess. Probably caused by a kind of massive supernova, the collapse of a supermassive star into a black hole. Could have happened anywhere within thousands of light years. A storm of gamma rays would have stripped away the ozone layers and then fried the surface life.’
    ‘ Boundless and bare, the lone and level sands stretch far away .’
    ‘What’s that, Josh?’
    ‘Just a stray memory of Sister Georgina.’
    ‘In the