The Science of Discworld Revised Edition

by Terry Pratchett

  There is another element of the first moments of our universe that is even more difficult to think about. Where did the Laws come from? Why are there such things as protons and electrons, quarks and gluons? We usually separate processes into two conceptually distinct causal chunks: the initial conditions, and the rules by which they are transformed as time passes. For the solar system, for instance, the initial conditions are the positions and speeds of the planets at some chosen instant of time; the rules are the laws of gravitation and motion, which tell us how those positions and speeds will change thereafter. But for the beginning of the universe, the initial conditions seem not to be there at all. Even there isn’t there! So it seems that it’s all done by rules. Where did the rules come from? Did they have to be invented? Or were they just sitting in some unimaginable timeless pseudo-existence, waiting to be called up? Or did they uncurl in the early moments of the universe, as Something appeared – so that the universe invented its own rules along with space and time?

  Two recent books by top-ranking scientists explore how rules could be ‘invented’. The most recent is Stuart Kauffman’s 2000 Investigations. This is mainly aimed at biology and economics, but it begins with rules of physics. In a new answer to the old question ‘what is life?’, Kauffman defines a lifeform to be an ‘autonomous agent’—any entity or system that can redirect energy and reproduce. ‘Autonomous’ here means that such a system makes up its own rules, determines its own behaviour. Such lifeforms need not be at all conventional. For example, the quantum-mechanical vacuum is a seething mass of particles and antiparticles, being created and annihilated in amazingly complicated ways. A vacuum has more than enough complexity to organise itself into an autonomous agent. If it did, then quantum mechanics would be able to make up its own rules.

  The other noteworthy book on this topic is Lee Smolin’s 1997 The Life of the Cosmos, which asks: can universes evolve? A remarkable feature of our universe is the presence of Black Holes. These are regions of space-time that contain so much mass that light (and matter) cannot get out; they are formed by the collapse of massive stars. It used to be thought that Black Holes are rare, but now they seem to be showing up all over the place, in particular at the cores of most galaxies. Theoretical work shows that the constants of our universe are unusually good for making Black Holes.

  Why? Smolin argues that each Black Hole in our universe is in effect a doorway to an adjacent universe, but because nothing can come out of a Black Hole we cannot know what its on the far side of that door. In particular, the adjacent universe might have different fundamental constants compared to ours. So universes could ‘breed’ by budding off baby universes through Black Holes, and natural selection would favour those that had the most offspring – whose constants would automatically be unusually good for making Black Holes. So maybe we live in one of those babies.

  There are some difficulties with this theory. In particular, how would selection work? How can universes compete? But it’s an interesting, if rather wild, idea. And it offers a concrete proposal about how a universe can ‘make up’ its laws: some, at least, could be imposed upon it at birth.

  The Big Bang, then, may have done more than just bringing space and time into being. It may also have brought ‘the’ rules of physics – the ones that now apply to our world – into being. During the becoming of its first moments, our universe kept changing its state, changing the rules it accessed. In this respect it was rather like a flame, which changes its composition according to its own dynamics and the things that it is burning. Flames are all more or less the same shape, but they don’t inherit that shape from a ‘parent’. When you set light to a piece of paper, the flame builds itself from scratch using the rules of the outside universe.

  In the opening instants of the universe, it wasn’t just substances, temperatures and sizes that changed. The rules by which they changed also changed. We don’t like to think this way: we want immutable laws, the same always. So we look for ‘deeper’ laws to govern how the rules changed. Possibly the universe is ‘really’ governed by these deeper laws. But perhaps it just makes up its own rules as it goes along.

  1 Not while these are still in the polar bear.

  2 This figure replaces the previously favoured value of about 20 billion years. Recently lots of scientists collectively decided it should be 15 billion instead. (For a while some stars seemed to be older than the universe, but the age of those stars has also been downsized.) In other circumstances they might well have settled for 20 billion. If this worries you, substitute the term ‘a very long time’.

  3 Indeed, impeccable Discworld thinking is that no matter how big the universe grows, it’s always the same size.

  SEVEN

  BEYOND THE FIFTH ELEMENT

  IN THE QUIET of the night, Hex computed. Along its myriad glass tubes, the ants scurried. Crude magic sparkled along cobwebs of fine bronze wire, changing colour as it changed logic states.1 In the special room next door the beehives, long-term storage, buzzed. The thing that went ‘parp’ did so occasionally. Huge wheels turned, stopped, turned back. And still it wasn’t enough.

  The light of the Project fell across HEX’s keyboard. Things were happening in there, and HEX did not understand them. And that was taxing, because there was something there to understand.

  HEX was largely self-designed, which was why it worked better than most things in the University. It generally tried to develop a responsive way of coming to grips with any new task; the bees had been a particularly good idea, because although the memory retrieval was slow, the total memory increased with time and good apiary practice.

  Now it reasoned thus:

  One day it would find a way of increasing its conceptual capacity to understand what was happening in the Project;

  If this could ever happen, then – according to Stryme’s Directionless Law – there was already a shape in happening-space, where time did not exist, caused by the fact of that happening; all that was required was a virtual collapse of the wave form;

  … and, although this was in a very strict sense garbage, it was not complete garbage. Any answer that would exist somewhere in the future must, inevitably, be available in potentia now.

  The ants went faster. Magic flashed. HEX could be said to be concentrating.

  Then silvery, shimmering lines appeared in the air around it, outlining towers of unimaginable cogitation.

  Ah. That was acceptable.

  Once-and-future computing was now in operation. Of course, it always had been.

  HEX wondered how much he should tell the wizards. He felt it would not be a good idea to burden them with too much input.

  HEX always thought of his reports as Lies-to-People.

  It was the second day …

  The Project was nudged gently under a glass dome to prevent any more interference. A variety of spells had been installed around it.

  ‘So that’s a universe, is it?’ said the Archchancellor.

  ‘Yes, sir. HEX says that …’ Ponder hesitated. You had to think hard before trying to explain things to Mustrum Ridcully. ‘… HEX seems to suggest that complete and utter nothing is automatically a universe waiting to happen.’

  ‘You mean nothing becomes everything?’

  ‘Why, yes, sir. Er … in a way, it has to, sir.’

  ‘And the Dean here swirled it all around and that started it off?’

  ‘It could have been anything at all, sir. Even a stray thought. Absolute nothing is very unstable. It’s so desperate to be something.’

  ‘I thought you had to have creators and gods,’ mumbled the Senior Wrangler.

  ‘I should jolly well think so,’ said Ridcully, who was examining the Project with a thaumic omniscope. ‘It’s been here since last night and there’s nothing to be seen except elements, if you could call them that. Bloody stupid elements, too. Half of them fall to bits as soon as you look at them.’

  ‘Well, what do you expect?’ said the Lecturer in Recent Runes. ‘They’
re made out of nothing, right? Even a really bad creator would at least have started with Earth, Air, Fire, Water and Surprise.’

  ‘Proper worlds are out of the question here, too,’ said Ridcully, peering into the omniscope again. ‘There’s no sign of chelonium and elephantigen. What kind of worlds can you build without them?’

  Ridcully turned to Ponder.

  ‘Not much of a universe, then,’ he said. ‘It must have gone wrong, Mister Stibbons. It’s a dud. By now the first human should be looking for his trousers.’

  ‘Perhaps we could give him a hand,’ said the Senior Wrangler.

  ‘What are you suggesting?’

  ‘Well, it’s our universe, isn’t it?’

  Ponder was shocked. ‘We can’t own a universe, Senior Wrangler!’

  ‘It’s a very small one.’

  ‘Only on the outside, sir. HEX says it’s a lot bigger on the inside.’

  ‘And the Dean stirred it up,’ the Senior Wrangler went on.

  ‘That’s right!’ said the Dean. ‘That means I’m a sort of god.’

  ‘Waggling your fingers around and saying “oo, it prickles” is not godliness,’ said Ridcully severely.

  ‘Well, I’m the next best thing,’ said the Dean, reluctant to let go of anything that placed him socially higher than the Archchancellor.

  ‘My grandmother always said that cleanliness was next to godliness,’ mused the Lecturer in Recent Runes.

  ‘Ah, that’s more like it,’ said Ridcully cheerfully. ‘You’re more like a janitor, Dean.’

  ‘I was really just suggesting that we give the thing a few shoves in the right direction,’ said the Senior Wrangler. ‘We are, after all, learned men. And we know what a proper universe ought to be like, don’t we?’

  ‘I imagine we have a better idea than the average god with a dog’s head and nineteen arms, certainly,’ said Ridcully. ‘But this is pretty second-rate material. It just wants to spin all the time. What do you expect us to do, bang on the side and shout “Come on, you lot, stop messing about with stupid gases, they’ll never amount to anything”?’

  They compromised, and selected a small area for experimentation. They were, after all, wizards. That meant that if they saw something, they prodded it. If it wobbled, they prodded it some more. If you built a guillotine, and then put a sign on it saying ‘Do Not Put Your Neck On This Block’, many wizards would never have to buy a hat again.

  Moving the matter was simple. As Ponder said, it almost moved under the pressure of thought.

  And spinning it into a disc was easy. The new matter liked to spin. But it was also far too sociable.

  ‘You see?’ said Ridcully, around mid-morning. ‘It seems to get the idea, and then you just end up with a ball of rubbish.’

  ‘Which gets hot in the middle, have you noticed?’ said Ponder.

  ‘Embarrassment, probably,’ said the Archchancellor. ‘We’ve lost half the elements since elevenses. There’s no more cohenium, explodium went ten minutes ago, and I’m beginning to suspect that the detonium is falling to bits. Temporarium didn’t last for any time at all.’

  ‘Any Runium?’ said the Lecturer in Recent Runes.

  HEX wrote: +++ Runium May Or May Not Still Exist. It Was Down To One Atom Ten Minutes Ago, Which I Do Not Seem to Be Able To Find Any More +++

  ‘How’s Wranglium doing?’ said the Senior Wrangler hopefully.

  ‘Exploded after breakfast, according to HEX. Sorry,’ said Ridcully. ‘You can’t build a world out of smoke and mirrors. Damn … there goes Bursarium, too. I mean, I know iron rusts, but these elements collapse for a pastime.’

  ‘My hypothesis, for what it’s worth,’ said the Lecturer in Recent Runes, ‘is that since it was all started off by the Dean, a certain Dean-like tendency may have imparted itself to the ensuing … er … developments.’

  ‘What? You mean we’ve got a huge windy universe with a tendency to sulk?’

  ‘Thank you, Archchancellor,’ said the Dean.

  ‘I was referring to the predilection of matter to … er … accrete into … er … spherical shapes.’

  ‘Like the Dean, you mean,’ said Archchancellor.

  ‘I can see I’m among friends here,’ said the Dean.

  There was a soft chime from the apparatus that had been accumulated around the Project.

  ‘That’ll be etherium vanishing,’ said Ridcully gloomily. ‘I knew that’d be the next to go.’

  ‘Actually … no,’ said Ponder Stibbons, peering into the Project. ‘Er … something has caught fire.’

  Points of light were appearing.

  ‘I knew something like that would happen,’ said the Archchancellor. ‘All those discs are heating up, just like damn compost heaps.’

  ‘Or suns,’ said Ponder.

  ‘Don’t be silly, Stibbons, they’re far too large for that. I’d hate to see one of those floating over the clouds,’ said the Lecturer in Recent Runes.

  ‘I said there was far too much gas,’ the Archchancellor went on. ‘That wraps it up, then.’

  ‘I wonder,’ said the Senior Wrangler.

  ‘What?’ said the Dean.

  ‘Well, at least we’ve got some heat in there … and there nothing like a good furnace for improving matters.’

  ‘Good point,’ said Ridcully. ‘Look at bronze – you can make that out of just about anything. And we could burn off some of the rubbish. All right, you fellows, help me dump more of the stuff in it …’

  Around about teatime, the first of the furnaces exploded, just as happened every day down at the Alchemists’ Guild.

  ‘Ye gods,’ said Ridcully, watching the shapes in the omniscope.

  ‘Yo?’ said the Dean.

  ‘We’ve made new elements!’

  ‘Keep it down, keep it down!’ hissed the Senior Wrangler.

  ‘There’s iron … silicon … we’ve got rocks, even …’

  ‘We’re going to be in serious trouble if the alchemists’ guild finds out,’ said the Lecturer in Recent Runes. ‘You know we’re not supposed to do that stuff.’

  ‘This is a different universe,’ said Ridcully. He sighed. ‘You have to blow things up to get anything useful.’

  ‘I see politicium is still there in large quantities, then,’ said the Senior Wrangler.

  ‘I meant that this is a godless reality, gentlemen.’

  ‘Excuse me –’ the Dean began.

  ‘I shouldn’t look so smug if I was you, Dean,’ said Ridcully. ‘Look at the place. Everything wants to spin, and sooner or later you have balls.’

  ‘And we’re getting the same sort of stuff that we get here, isn’t that strange?’ said the Senior Wrangler, as Mrs Whitlow the housekeeper came in with the tea trolley.

  ‘I don’t see why,’ said the Dean. ‘Iron’s iron.’

  ‘Well, it’s a whole new universe, so you’d expect new things, wouldn’t you? Metals like Noggo, perhaps, or Plinc.’

  ‘What’s your point, Senior Wrangler?’

  ‘I mean, take a look at the thing now … all those burning exploding balls do look a bit like the stars, don’t they? I mean they’re vaguely familiar. Why isn’t it a universe full of tapioca, say, or very large chairs? I mean, if nothing wants to be something, why can’t it be anything?’

  The wizards stirred their tea and thought about this.

  ‘Because,’ said the Archchancellor, after a while.

  ‘That’s a good answer, sir,’ said Ponder, as diplomatically as he could. ‘But it does rather close the door on further questions.’

  ‘Best kind of answer there is, then.’

  The Senior Wrangler watched Mrs Whitlow produce a duster and polish the top of the Project.

  ‘“As Above, So Below”,’ said Ridcully, slowly.

  ‘Pardon?’ said the Senior Wrangler.

  ‘We’re forgetting our kindergarten magic, aren’t we? It’s not even magic, it’s a … a basic rule of everything. The project can’t help being affected by this world. Piles of san
d try to look like mountains. Men try to act like gods. Little things so often appear to look like big things made smaller. Our new universe, gentlemen, will do its crippled best to look like ours. We should not be surprised to see things that look hauntingly familiar. But not as good, obviously.’

  The inner eye of HEX gazed at a vast cloud of mind. HEX couldn’t think of a better word. It didn’t technically exist yet, but HEX could sense the shape. It had hints of many things – of tradition, of libraries, of rumour …

  There had to be a better word. HEX tried again.

  On Discworld, words had real power. They had to be dealt with carefully.

  What lay ahead had the shape of intelligence, but only in the same way that a sun had the shape of something living out its brief life in a puddle of ditchwater.

  Ah … extelligence would do for now.

  HEX decided to devote part of its time to investigating this interesting thing. It wanted to find out how it had developed, what kept it going … and why, particularly, a small but annoying part of it seemed to believe that if everyone sent five dollars to the six names at the top of the list, everyone would become immensely rich.

  1 Of which there were quite a number, given HEX’s unusual construction. In addition to AND, OR and their combinations and variants, HEX could call up MAYBE, PERHAPS, SUPPOSE and WHY. HEX could think the unthinkable quite easily.

  EIGHT

  WE ARE STARDUST

  (or at least we went to Woodstock)

  ‘IRON’S IRON.’ BUT is it? Or is iron made from other things?

  According to Empedocles, an ancient Greek, everything in the universe was a combination of four ingredients: earth, air, fire, and water. Set light to a stick and it burns (showing that it contains fire), gives off smoke (showing that it contains air), exudes bubbly liquids (showing that it contains water), and leaves a dirty heap of ash behind (showing that it contains earth). As a theory, it was a bit too simple-minded to survive for long – a couple of thousand years at best. Things moved more slowly in those days, and Europe, at least, was more interested in making sure that the peasants didn’t get above their station and copying out bits of the Bible by hand in as laborious and colourful a manner as possible.