The Science of Discworld Revised Edition by Terry Pratchett

running back into his room.
    Beyond the window, on the other side of the gardens, the air wavered over the High Energy Magic building. As the Archchancellor watched, the two huge bronze globes on its roof became covered in crawling, zig-zagging purple lines –
    He hit the floor rolling, as wizards are wont to do, just before the shock of the discharge blew the windows in.
    Melted snow was pouring off the rooftops. Every icicle was a streaming finger of water.
    A large door bumped and scraped its way across the steaming lawns.
    ‘For goodness’ sake, Dean, handle your end, can’t you?’
    The door skidded a little further.
    ‘It’s no good, Ridcully, it’s solid oak!’
    ‘And I’m very glad of it!’
    Behind Ridcully and the Dean, who were inching the door forward largely by arguing with each other, the rest of the faculty crept forward.
    The bronze globes were humming now, in the rapidly decreasing intervals between discharges. They had been installed, to general scoffing, as a crude method of releasing the occasional erratic build-up of disorganized magic in the building. Now they were outlined in unhealthy-looking light.
    ‘And we know what that means, don’t we, Mister Stibbons?’ said Ridcully, as they reached the entrance to the High Energy Magic building.
    ‘The fabric of reality being unravelled and leaving us prey to creatures from the Dungeon Dimensions, sir?’ mumbled Stibbons, who was trailing behind.
    ‘That’s
right
, Mister Stibbons! And we don’t want that, do we, Stibbons?’
    ‘No, sir.’
    ‘No, sir! We don’t, sir!’ Ridcully roared. ‘It’ll be tentacles all over the place again. And none of us wants tentacles all over the place, do we?’
    ‘No, sir.’
    ‘No, sir! So switch the damned thing
off
, sir!’
    ‘But it’d be certain death to go into –’ Ponder stopped, swallowed and restarted. ‘In fact it would be
uncertain
death to go into the squash court at the moment, Archchancellor. There must be million of thaums of random magic in there! Anything could happen!’
    Inside the HEM the ceiling was vibrating. The whole building seemed to be dancing.
    ‘They certainly knew how to build, didn’t they, when they built the old squash court,’ said the Lecturer in Recent Runes, in an admiring tone of voice. ‘Of course, it
was built
to contain large amounts of magic …’
    ‘Even if we
could
switch it off, I don’t think that’d be such a good idea,’ said Ponder.
    ‘Sounds a lot better than what’s happening now,’ said the Dean.
    ‘But is falling through the air better than hitting the ground?’ said Ponder.
    Ridcully sucked in his breath between his teeth.
    ‘That’s a point,’ he said. ‘Could be something of an implosion, I suppose. You can’t just
stop
something like this. Something bad would happen.’
    ‘The end of the world?’ quavered the Senior Wrangler.
    ‘Probably just this part of it,’ said Ponder.
    ‘Are we talking here about a sort of huge valley about twenty miles across with mountains all round it?’ said Ridcully, staring at the ceiling. Cracks were zig-zagging across it.
    ‘Yes, sir, I’m wondering if whoever tried this at Loko actually
did
manage to switch it off …’
    The walls groaned. There was a rattling noise behind Ponder. He recognized it, even above the din. It was the sound of H EX resetting its writing device. Ponder always thought of it as a kind of mechanical throat-clearing.
    The pen jerked in its complex network of threads and springs, and then wrote:
    +++ This May Be Time For The Roundworld Project +++
    ‘What are you talking about, man?’ snapped Ridcully, who’d never quite understood what H EX was.
    ‘Oh,
that
? That’s been around for
ages
,’ said the Dean. ‘No one’s ever taken it seriously. It’s just a thought experiment. You couldn’t do it. It’s completely absurd. It needs far too much magic.’
    ‘Well, we’ve
got
far too much magic,’ said Ridcully. ‘Right now we need to use it