The Long Mars by Terry Pratchett, Stephen Baxter Page A

back to the twain. ‘Viruses are a worse threat to me than any physical violence, no matter how many backups I create. Any synching between my iterations at all leaves me open to a potentially lethal attack. I’m thinking of installing at least one entirely non-electronic backup.’
    ‘Such as?’
    ‘Oh, a few hundred monks in a scriptorium somewhere, endlessly copying my thoughts from one bound paper volume to another. A scriptorium on the moon maybe.’
    ‘One thing has definitely changed about you, Lobsang. Your jokes are no better. But at least now I can tell they are jokes.’
    ‘I’ll take that as a compliment.’
    ‘And to think that just as this incident with Cho-je occurred you were about to lecture me on “common sense”.’
    ‘We can continue that discussion in the morning. The twain is relatively spartan but quite comfortable, I think you’ll find.’
    ‘Any good movies?’
    ‘Of course. Your choice. But nothing with singing nuns in, if you don’t mind . . .’

9
    I N THE MORNING they ate breakfast in near silence, and flew on. Rather than make straight for the caldera Lobsang at first skirted it to the west, following the line of what remained of a south-to-north highway. As they edged closer to the caldera, the increasing thickness of ash began to overwhelm the landscape as it had existed before the eruption. They were entering a true volcanic province, Joshua thought, like a fragment of an alien world brought down to the Earth.
    ‘The civilization of Datum Earth will never recover,’ Lobsang murmured, as they peered down at the strange landscape.
    Joshua grunted. ‘That seems a tough conclusion to come to. It’s only been a few years . . .’
    ‘But think about it. We’d already used up all the easily accessible ore, the oil, much of the coal. And the world was already suffering tremendous climate disruption because of all the industrial gases we spewed into the air. When Yellowstone’s effects finally fade, the best guess for the future is widespread instability, as the world seeks a new equilibrium after two massive environmental shocks, one human-induced, one volcanic.’
    ‘Hmm. So is this why there’s talk of rewilding?’
    The idea was, when the winter finally receded from the Datum Earth, why not take the chance to heal the world? All the species that had been driven to extinction on the Datum still prospered in the neighbouring worlds (though once again, Joshua knew, on some of the Low Earths many of those creatures were already in trouble). So, in North America, you could bring back the mammoth and the wild horse and the bison and the musk ox, and the seals in the rivers and the whales in the oceans – just step specimens over, as infants perhaps, to the Datum. Similarly you could let the landscapes and seas recover to their natural state.
    ‘It’s a romantic idea,’ Lobsang said. ‘Of course there’s a great deal of work to do before the Datum is even safe .’
    ‘Such as, decommissioning nuclear power plants?’
    ‘And waiting for dams to fail, for drained wetlands to flood . . . It will take decades, centuries, for pollutants like heavy metals and radioactive waste to be reduced to safe levels. Even then, where we have driven roads or dug mines into the bedrock, the mark of mankind will linger for millions of years.’
    ‘Makes you proud.’
    ‘If you say so, Joshua. However, an effort to heal this world using the riches of its stepwise siblings seems a noble ambition, whatever the limitations in practice.’
    At last, to the north of Yellowstone itself, they paused over what had once been a township. Little remained but a few scattered traces of foundations, the hint of a grid of streets protruding from the ash; much of the rest was buried completely.
    Joshua checked a map display; in cheerful white, green and yellow, with finely drawn state and county lines, it displayed the vanished human landscape as it had once been. ‘This is Bozeman.’
    ‘Yes. Or