Free Strata by Terry Pratchett

seas fuzzed with moonlit cloud. There was what, for want of a better term – how many people had mapped flat planets? – a polar cap, hugging one side of the disc.
    Moonlit? There was a moon, apparently a few thousand miles above the disc, and it
shone
. It couldn’t be reflected light. There was nothing to reflect. And there were stars – between the ship and the disc, there were stars.
    The shadowy oval lay inside a hazy globe. Marco translated what the machines were emotionlessly telling him. The disc was inside a transparent sphere sixteen thousand miles across, and the stars were – ‘that’s what I said, Kin’ – were fixed to this.
    One edge of the disc glowed brighter. It flashed green fire, which ran around the rim until they were looking at a hole in space surrounded by green and silver flames. Then the ring grew a gem, and died as suddenly as it had come. The sun had risen. A tiny sun.
    One machine said it was an external fusion reactor. It looked like a sun.
    This is what I’ll remember, thought Kin. The green fire at sunrise, because all around the disc there’s a sea, and it flows over the edge ina waterfall thirty-five thousand miles long and the sun shines through the falling water – no wonder Jalo was mad.
    Dawn rushed across the disc. Silver was the first to react. She giggled.
    ‘He did call it a flat Earth, didn’t he?’ she asked. ‘It was the truth, wasn’t it?’
    Kin looked. The continents had moved, it was true, and there didn’t appear to be a New World at all. It was Earth down there – she recognized Europe. Earth. And it was flat.
    Marco put them into a fast orbit, and no one left the cabin for three hours. Even Silver let a mealtime go past, and fed on curiosity instead.
    They watched the waterfall slide past under high magnification. There were rocky islands, some tree-lined, overhanging the drop. It was a long drop – five hundred miles into a turmoil of steam. But the disc itself was only five miles thick. As the ship passed under the disc there was nothing but a space-black plain on the underside.
    ‘Some humans used to believe the world was flat and rested on the backs of four elephants,’ said Silver.
    ‘Yeah?’ said Kin. ‘What did the elephants stand on?’
    ‘A giant turtle, swimming endlessly through space.’
    Kin tasted the idea. ‘Stupid,’ she said. ‘What did the turtle breathe?’
    ‘Search me. It’s your racial myth.’
    ‘I’d give a lot to know how the seas can keep on spilling over the edge.’
    ‘Probably a molecule sieve, down there in the steam,’ said Marco without looking up from the shouter screens. ‘The plumbing is a minor matter, however. Where are the inhabitants? This thing is obviously an artefact, a created thing.’
    ‘No one’s trying to contact us?’
    ‘Just listen to my excitement.’
    ‘I suppose you mean no. Perhaps it’s as well. I keep thinking of all those weapons in the hold.’
    ‘The thought seldom leaves my mind. Perhaps Jalo meant to hunt sea-serpents, but I think not. I cannot help thinking that anyone capable of building the artefact would hardly be bothered by any weaponry this ship could carry.’
    ‘Perhaps the inhabitants are dead,’ suggested Silver. Kin and Marco looked at each other blankly.
    ‘Unlikely,’ said Marco. ‘More likely they’ve passed beyond the stage of gross physical existence. Maybe even at this moment they are screwing the inscrutable.’
    ‘They’re due for a big shock one of these days, then,’ said Kin. ‘This set-up must take vast amounts of power just to keep it going. The sun’s orbit is all wrong. What keeps the seas from emptying? Why have they got their own private stars when there’s real ones out here—’
    ‘I can answer that one,’ said Marco. ‘It looks as though the big sphere is only transparent from the outside. We can see in, they can’t see out. Don’t ask me why.’
    ‘Do we land?’ said Silver.
    ‘How could we get in?’ said Kin. Marco