Science of Discworld III

think that’s Professor Rincewind, sir?’
    ‘Very well, professor ,’ said Ridcully. ‘Come on, it’s past time for Early Tea.’
    ‘The world’s gone wrong, Archchancellor.’
    As one wizard, everyone looked out at what could be seen of theworld through Archchancellor Sloman Discovering the Special Theory of Slood.
    ‘Don’t be a fool, man,’ said Ridcully. ‘The sun’s shining! It’s a nice day!’
    ‘Not this world, sir,’ said Rincewind. ‘The other one.’
    ‘What other one?’ said the Archchancellor, and then his expression changed.
    ‘Not—’ he began.
    ‘Yes, sir,’ said Rincewind. ‘That one. It’s gone wrong. Again.’
    Every organisation needs someone to do those jobs it doesn’t want to do or secretly thinks don’t need doing. Rincewind had nineteen of them now, including Health and Safety Officer. 1
    It was as Egregious Professor of Cruel and Unusual Geography that he was responsible for the Globe. These days, it was on his desk out in the gloomy cellar passage where he worked, work largely consisting of waiting until people gave him some cruel and unusual geography to profess.
    ‘First question,’ said Ridcully, as the faculty swept along the dank flagstones. ‘Why are you working out here? What’s wrong with your office?’
    ‘It’s too hot in my office, sir,’ said Rincewind.
    ‘You used to complain it was too cold!’
    ‘Yes, sir. In the winter it is. Ice freezes on the walls, sir.’
    ‘We give you plenty of coal, don’t we?’
    ‘Ample, sir. One bucket per day per post held, as per tradition. That’s the trouble, really. I can’t get the porters to understand. They won’t give me less coal, only no coal at all. So the only way to be sure of staying warm in the winter is to keep the fire going allsummer, which means it’s so hot in there that I can’t work in – don’t open the door, sir!’
    Ridcully, who’d just opened the office door, slammed it again, and wiped his face with a handkerchief.
    ‘Snug,’ he said, blinking the sweat out of his eyes. Then he turned to the little globe on the desk behind him.
    It was about a foot across, at least on the outside. Inside, it was infinite; most wizards have no problem with facts of this sort. It contained everything there was, for a given value of ‘contained everything there was’, but in its default state it focused on one tiny part of everything there was, a small planet which was, currently, covered in ice.
    Ponder Stibbons swivelled the omniscope that was attached to the base of the glass dome, and stared down at the little frozen world. ‘Just debris at the equator,’ he reported. ‘They never built the big skyhook thing that allowed them to leave. 2 There must have been something we missed.’
    ‘No, we sorted it all out,’ said Ridcully. ‘Remember? All the people did get away before the planet froze.’
    ‘Yes, Archchancellor,’ said Stibbons. ‘And, then again, no.’
    ‘If I ask you to explain that, would you tell me in words I can understand?’ said Ridcully.
    Ponder stared at the wall for a moment. His lips moved as he tried out sentences. ‘Yes,’ he said at last. ‘We changed the history of the world, sending it towards a future where the people could escape before it froze. It appears that something has happened to change it back since then.’
    ‘Again? Elves did it last time!’ 3
    ‘I doubt if they’ve tried again, sir.’
    ‘But we know the people left before the ice,’ said the Lecturer inRecent Runes. He looked from face to face, and added uncertainly, ‘Don’t we?’
    ‘We thought we knew before,’ said the Dean, gloomily.
    ‘In a way, sir,’ said Ponder. ‘But the Roundworld universe is somewhat … soft and mutable. Even though we can see a future happen, the past can change so that from the point of view of Roundworlders it doesn’t. It’s like … taking out the last page of a book and putting a new one in. You can still read the old page, but from the point of view of the characters, the ending has changed, or … possibly not.’
    Ridcully slapped him on the back. ‘Well done, Mr Stibbons! You didn’t mention quantum even once!’ he said.
    ‘Nevertheless, I suspect it may be involved,’ sighed Ponder.
    1 The N’tuitiv tribe of Howondaland created the post of Health and Safety Officer even before the post of Witch Doctor, and certainly before taming fire or inventing the spear. They hunt by waiting for animals to drop dead, and eat them