Salt by Adam Roberts

infinite dust, settling all around us, now, tomorrow, onwards.’
    ‘I read in Lucretius,’ said Csooris, suddenly, ‘that this is the nature of the universe.’ Csooris had a passion for Old and New Latin. ‘So the ancients believed: an endless rain of dust through the universe, falling from nowhere and falling towards nowhere. Lucretius says that this is all reality is, except that something has introduced the slightest of swerves into the falling, so that the atoms begin to move about, come together, move apart.’
    ‘He didn’t mean radiation though,’ said the more literal-minded Sipos. ‘He was one of the ancients; they surely had no such conceptions.’
    ‘It was a poet’s conceit, I think,’ I said.
    Csooris seemed angered by this. ‘What do you know of it?’ she snapped.
    ‘I have read the thing,’ I countered, bridling a little myself. ‘ The Nature of Things . I read it in my mother’s dormitory.’
    ‘But in translation,’ she insisted. ‘Not in the Old Latin.’
    ‘Latin!’ I scoffed.
    ‘I can read a bit of New Latin,’ said Sipos, trying to defuse the situation. She had travelled amongst the Vaticano Republics when she was a young woman, I think.
    But Csooris was not impressed. She spat. ‘Kindergarten tongue!’ she scoffed. ‘You can learn it in a day.’
    Hamar was harumming, clearing his throat. He was being made uncomfortable by the sparring. Sipos didn’t like it either; she was a straightforward woman, more comfortable with facts than fancies.
    ‘The big question,’ she said, her voice a little too loud, to try andbully the other conversation out of the way, ‘remains. What are we going to do long-term about the levels of radiation? We need more than domes and holes in the ground.’
    Hamar was nodding. ‘We need two things. We need an ozone layer, and we need a magnetosphere.’
    ‘In that order?’
    ‘Other way round,’ said Csooris.
    I confess I was a little heated by the occasion, and perhaps angry with Csooris. ‘Of all the stupid things to say! And how do you intend to create a magnetosphere?’ I said, sneery.
    The situation (but I am sure you know it): Salt possesses a very weak magnetosphere. Our world has a nickel-iron core, molten, and a granite mantle, mostly quartz. The core revolves at a different rate from the rest of the world, and this differential generates a magnetic field, as it does on Earth. But the differential on Salt is not great, and the field generated is not strong. There were many theories, but the most likely explanation was that our world is a very old world. That its core has been slowing down for billennia. This would also explain certain other features. Maybe the surface of our world was once covered with a salty sea, but the water has been lost over many years. Maybe life once crowned our world, maybe even intelligence. There were people who boasted that they intended to dig out fossils of our Saltian foremothers; others who insisted that there had never been backbones on our world before, let alone intelligence. Other still refused to believe that our world was a dying one: and indeed, there were other possible explanations for the state of things.
    A magnetosphere is a very effective protection against the rigours of solar radiation. But ours was not strong enough, and there were no ways to increase it, short of reaching into the heart of the world with a god’s hand and giving the core a great spin.
    ‘We must work at pumping ozone, or similar screening gases, into the stratosphere,’ said Sipos. The conventional response.
    ‘I’m in a dorm group,’ said Hamar, ‘and we have a plan. After all, we don’t need to shield the whole world, just ourselves. Why notbuild a filter, a huge filter kilometres across, and position it in geosync orbit over Als?’
    The rest of us laughed and scoffed at this, of course; but Hamar seemed quite genuine, and tried for a while to flesh out his conception. It could be constructed out of crystals,