The Science of Discworld Revised Edition

lot more carbon dioxide and a lot less oxygen, which was reduced to half today’s level. Land species were especially badly affected.
    Another global extinction, though less severe, occurred 55 million years ago: the Palaeocene/Eocene boundary. In cores of sediment drilled from the Antarctic, James Kennett and Lowell Stott discovered evidence of the sudden death of a lot of marine species. It seemed that trillions of tons (tonnes) of methane had burst from the ocean, sending temperatures through the roof, methane being a powerful greenhouse gas. Jenny Dickens suggested that the methane was released from deposits of methane hydrates in permafrost and on the seabed. Methane hydrates are a crystal lattice of water enclosing methane gas: they are created when bacteria in mud release the gas and it becomes trapped.
    Coincidentally, one of the main results of the Palaeocene/Eocene extinction was a burst of evolutionary diversity, leading in particular to the higher primates – and us. Whether something is a disaster depends on your point of view. Rocks may not have a point of view, as Ponder Stibbons pointed out, but we certainly do.
    1 To the best of our knowledge, based on deduction from the available evidence. Certainly it was a
big
extinction – far bigger than the one that killed off (or helped to kill off) the dinosaurs. We remember the dinosaur one because they’ve had such good PR people.

TWENTY-NINE
GOING FOR A PADDLE

    I THINK IT looks more like a Hogswatchnight ornament,’ said the Senior Wrangler later, as the wizards took a pre-dinner drink and stared into the omniscope at the glittering white world. ‘Quite pretty, really.’
    ‘Bang go the blobs,’ said Ponder Stibbons.
    ‘Phut,’ said the Dean, cheerfully. ‘More sherry, Archchancellor?’
    ‘Perhaps some instability in the sun …’ Ponder mused.
    ‘Made by unskilled labour,’ said Archchancellor Ridcully. ‘Bound to happen sooner or later. And then it’s nothing but frozen death, the tea-time of the gods and an eternity of cold.’
    ‘Sniffleheim,’ said the Dean, who’d got to the sherry ahead of everyone else.
    ‘According to H EX , the air of the planet has changed,’ said Ponder.
    ‘A bit academic now, isn’t it?’ said the Senior Wrangler.
    ‘Ah, I’ve got an idea!’ said the Dean, beaming. ‘We can get H EX to reverse the thaumic flow in the cthonic matrix of the optimized bi-direction octagonate, can’t we?’
    ‘Well, that’s the opinion of four glasses of sherry,’ said the Archchancellor briskly, to break the ensuing silence. ‘However, if I may express a preference, something that isn’t complete gibberish would be more welcome next time, please. So, Mister Stibbons, is this the end of the world?’
    ‘And if it is,’ said the Senior Wrangler, ‘are we going to have a lot of heroes turning up?’
    ‘What are you talking about, man?’ said Ridcully.
    ‘Well, the Dean seems to think we’re like gods, and a great many mythologies suggest that when heroes die they go to feast forever in the halls of the gods,’ said the Senior Wrangler. ‘I just need to know if I should alert the kitchens, that’s all.’
    ‘They’re only blobs,’ said Ridcully. ‘What can they do that’s heroic?’
    ‘I don’t know … stealing something from the gods is a very classical way,’ the Senior Wrangler mused.
    ‘Are you saying we should check our pockets?’ said the Archchancellor.
    ‘Well, I haven’t seen my penknife lately,’ said the Senior Wranger. ‘It was just a thought, anyway.’
    Ridcully slapped the despondent Stibbons on the back.
    ‘Chin up, lad!’ he roared. ‘It was a wonderful effort! Admittedly the outcome was a lot of blobs with the intelligence of pea soup, but you shouldn’t let utter hopeless failure get you down.’
    ‘
We
never do,’ said the Dean.
    It was after breakfast next day when Ponder Stibbons wandered into the High Energy Magic building. A scene of desolation met his eye. There were cups and plates everywhere. Paper littered the floor. Forgotten cigarettes had etched their charred trails on the edge of desks. A half-eaten sardine, cheese and blackcurrant pizza, untouched for days, was inching its way to safety.
    Sighing, he picked up a broom, and went over the tray containing H EX ’s overnight write-out.
    It seemed a lot fuller than he would have expected.
    ‘Not just blobs – there’s
all sorts
of stuff! Some of it’s
wiggling
…’
    ‘Is that a plant or is it an