The Science of Discworld II

it couldn’t pretend to be a cowardly wizard if one walked up to it and thumped it on the memory cache. In contrast, we can think ourselves inside the mind of a cowardly wizard with ease, or recognise someone else when they’re acting the part of one, but we’re completely lost when it comes to doing several million simple sums a second. Even though, to someone not of this universe, that might appear to be a simpler task.
    That’s because we run on narrativium, and computers don’t.
    1 PET = Positron Emission Tomography, meaning that the machine picks up tiny particles emitted by the tissues of the brain and reconstructs a map of what’s going on inside it.
    2 And you’d be in the position of the horrible Discworld ‘Auditors’, who are anthropomorphic representations of the rules of the universe, who in Thief of Time reduce paintings and statues to their component atoms in a fruitless search for ‘beauty’.
    3 And many things that there aren’t, such as Dark.
    4 It would have been an exit hole, but he didn’t.
    5 In the simplest picture of an atom, the nucleus is a relatively small central region made from protons and neutrons. Electrons ‘orbit’ the nucleus at a distance. The triple-alpha process takes place in a plasma, where the atoms have been stripped of their electrons, so only their nuclei are involved. Later, as the plasma cools, the nuclei can acquire the necessary electrons.
    6 1 MeV is one million electron-volts. An electron-volt is a unit of energy, obviously, and for our current purposes it doesn’t really matter what that unit is . For the record, it’s the energy of an electron when its potential is raised by one volt, and is equal to 1.6 × 10 -12 ergs. And the energy referred to here is the excess energy compared to the lowest energy state of the atom, its ‘ground state’. What’s an erg? Look it up if you really need to know.
    7 Not hand and glove, the fit isn’t that close.

THREE
JOURNEY INTO L-SPACE
    I T WAS THREE HOURS LATER , in the cool of Unseen University. Not much had changed in the High Energy Magic building, except that a screen had been set up to show the output of Ponder’s iconograph projector.
    â€˜I don’t see why you need it,’ said Rincewind. ‘There’s only the two of us.’
    â€˜Ook,’ agreed the Librarian. He was annoyed at having been woken from a doze in his library. It had been a very gentle awakening, since no one wakes up a 300lb orangutan roughly (twice, at least) but he was still annoyed.
    â€˜The Archchancellor says that we’ve got to be more organised about these things,’ said Ponder. ‘He says it’s no use just shouting out “Hey, I’ve got a great idea!” These things have got to be presented properly. Are you ready?’
    The very small imp that ran the projector raised a tiny thumb.
    â€˜Very well,’ said Ponder. ‘First slide. This is the Roundworld as it currently—’
    â€˜It’s the wrong way up,’ said Rincewind.
    Ponder looked at the image.
    â€˜It’s a ball ,’ he snarled. ‘It’s floating in space . How can it be the wrong way up?’
    â€˜That crinkly continent should be at the top.’
    â€˜Very well!’ snapped Ponder. ‘Imp, turn it around. Right? Satisfied?’
    â€˜It’s the right way up but now it’s the wrong way arou—’ Rincewind began.
    There was a thwack as Ponder’s pointer stick smacked into the screen. ‘This is the Roundworld!’ he snapped. ‘As it exists at present! A world covered in ice! But time on Roundworld is subordinate to time in the real world! All times in Roundworld are accessible to us, in the same way that all pages in a book, though consecutive, are accessible to us! I have ascertained that the Faculty are on Roundworld but not in what appears to be the present time! They are several hundred million years in the past! Which is, from our point of view, perfectly capable of also being the present! I don’t know how they got there! It should not be physically possible! Hex has located them! We have to assume that they can’t get back the way they came! However – next slide please!’
    Click!
    â€˜It’s the same one,’ said Rincewind. ‘But now it’s sideways—’
    â€˜A globe has no sideways!’ said Ponder. There was a tinkle of breaking