Landfall: Tales From the Flood/Ark Universe by Stephen Baxter Page A

to Earth II – and soon, given Stanndish’s integration of a series of astronomical observations dating back to the Founders themselves. Probably not this year, maybe not this decade – within a century, certainly. It is an excursion that seems to occur once every few tens of thousands of years. Stanndish says there is probably a periodicity to it, but -’
    Thom marched on ever faster, growing angry, not wanting to hear any of this. ‘An excursion? I don’t know what you’re talking about, man. A wobble? How can a planet wobble?’
    The Proctor held his hand level. ‘The rotation axis will tip up, away from the plane of the ecliptic.’ He tilted up his hand. ‘No longer will the summer pole point directly at the sun. We don’t know how far this excursion might be. We do know that everything about the cycle of the seasons will change.’
    Thom tried to imagine it. ‘No coldwinter. No coolsummer. Will it be more as Earth itself was?’
    ‘Perhaps. That might be the end state. But it’s the transition that concerns us, Speaker. For example we know that ice collected at the poles of Earth – huge caps of it, kilometres thick. Sea levels were lowered drastically. That can’t happen on Earth II, not today -’
    ‘Because any ice that forms in coldwinter melts each hotsummer.’
    ‘Yes. But if the axis tips ... And even before then, as the global distributions of ice, water and water vapour adjust we must expect extreme climatic events. Storms. Droughts and floods, failures of rainfall …  
    ‘And, even worse than that, the tipping planet will shudder. There will be earthquakes and volcanoes. Tsunamis, perhaps, triggered by undersea quakes. The crust of our quiescent world is so thick that any volcano, punching through, will be violent, and will hurl billions of tonnes of rock and ash into the air. We can expect acid rain. A darkness, a global shadow perhaps lasting years.’
    Thom stopped pacing at last. He tried to imagine a huge wave washing across the islands of the Scatter. ‘Dear God,’ he said quietly. ‘I never heard of events like this in accounts of Earth.’
    ‘Earth was different, in many ways. Crucially it had a moon, a massive moon. That helped stabilise its spin. We have no moon.’
    ‘Why is it only now that I am learning of this?’
    ‘We try to be responsible. We don’t wish to cause panic. With respect, I have been trying to tell you of this for some months -’
    ‘The Founders themselves must have known this was a danger. They surely knew far more about the dynamics of planets than even your tame genius Jan Stanndish.’
    ‘Yes. We have inferred, from hints in the chronicles, that there was a split among the inhabitants of the Ark when they reached Earth II. Some thought it would be uninhabitable because of the axial tilt. It’s said that our Founders were only a fraction of the crew who chose to stay, rather than go on in the Ark.’
    ‘Go on where? … Never mind.’
    ‘Perhaps they believed there would be plenty of time to deal with any tipping. Perhaps they believed their descendants would be able to stabilise the world. Well, if they thought that, they were wrong; after just four centuries, this is the danger we face. And we have no Ark to escape on.’
    ‘Then what will become of us? Is this the end of mankind on Earth II?’
    ‘Oh, we don’t think so. We’re a pretty resilient species. But we think it may be the end of civilisation. And if we do fall we may be slow to rise again. You know that this world has been emptied of its oil and metal ores by those who went before us.’
    ‘The Dead.’
    ‘Yes. How, then, can our descendants recover? And even if they do, even if there are once more cities and ships and scholars and Speakers, what will they know of where they came from? If the tale of the Founders survives at all, it will seem a legend.’
    And Thom understood. ‘Ah. And this is why you want to build the Library.’
    ‘Yes. So that our memory of our true origin