Terry Pratchett - The Science of Discworld Read online

  Terry Pratchett, Ian Stewart and Jack Cohen The Science of Discworld

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  THE STORY STARTS HERE

  ONCE UPON A TIME, there was Discworld. There still is an adequate supply.

  Discworld is the flat world, carried through space on the back of a giant turtle, which has been the source of - so far - twenty-three novels, four maps, an encylopaedia, two animated series, t-shirts, scarves, models, badges, beer, embroidery, pens, posters, and prob­ably, by the time this is published, talcum power and body splash (if not, it can only be a matter of time).

  It has, in short, become immensely popular.

  And Discworld runs on magic.

  Roundworld - our home planet, and by extension the universe in which it sits runs on rules. In fact, it simply runs. But we have watched the running, and those observations and the ensuing deductions are the very basis of science.

  Magicians and scientists are, on the face of it, poles apart. Certainly, a group of people who often dress strangely, live in a world of their own, speak a specialized language and frequently make statements that appear to be in flagrant breach of common sense have nothing in common with a group of people who often dress strangely, speak a specialized language, live in ... er ...

  Perhaps we should try this another way. Is there a connection between magic and science? Can the magic of Discworld, with its eccentric wizards, down-to-Earth witches, obstinate trolls, fire-breathing dragons, talking dogs, and personified DEATH, shed any useful light on hard, rational, solid, Earthly science?

  We think so.

  We’ll explain why in a moment, but first, let’s make it clear what The Science of Discworld is not. There are several media tie-in The Science of... books at the moment, such as The Science of the X-Files and The Physics of Star Trek. They will tell you about areas of today’s science that may one day lead to the events or devices that the fiction depicts. Did aliens crash-land at Roswell? Could an anti­matter warp drive ever be invented? Could we ever have the ultra long-life batteries that Scully and Mulder must be using in those torches of theirs?

  We could have taken that approach. We could, for example, have pointed out that Darwin’s theory of evolution explains how lower lifeforms can evolve into higher ones, which in turn makes it entirely reasonable that a human should evolve into an orangutan (while remaining a librarian, since there is no higher life form than a librarian). We could have speculated on which DNA sequence might reliably incorporate asbestos linings into the insides of drag­ons. We might even have attempted to explain how you could get a turtle ten thousand miles long.

  We decided not to do these things, for a good reason ... um, two reasons.

  The first is that it would be ... er ... dumb.

  And this because of the second reason. Discworld does not run on scientific lines. Why pretend that it might? Dragons don’t breathe fire because they’ve got asbestos lungs - they breathe fire because everyone knows that’s what dragons do.

  What runs Discworld is deeper than mere magic and more pow­erful than pallid science. It is narrative imperative, the power of story. It plays a role similar to that substance known as phlogiston, once believed to be that principle or substance within inflammable things that enabled them to burn. In the Discworld universe, then, there is narrativium. It is part of the spin of every atom, the drift of every cloud. It is what causes them to be what they are and continue to exist and take part in the ongoing story of the world.

  On Roundworld, things happen because the things want to hap­pen. [1] What people want does not greatly figure in the scheme of things, and the universe isn’t there to tell a story.

  With magic, you can turn a frog into a prince. With science, you can turn a frog into a Ph.D and you still have the frog you started with.

  That’s the conventional view of Roundworld science. It misses a lot of what actually makes science tick. Science doesn’t just exist in the abstract. You could grind the universe into its component par­ticles without finding a single trace of Science. Science is a structure created and maintained by people. And people choose what interests them, and what they consider to be significant and, quite often, they have thought narratively.

  Narrativium is powerful stuff. We have always had a drive to paint stories on to the Universe. When humans first looked at the stars, which are great flaming suns an unimaginable distance away, they saw in amongst them giant bulls, dragons, and local heroes.

  This human trait doesn’t affect what the rules say -not much, anyway - but it does determine which rules we are willing to con­template in the first place. Moreover, the rules of the universe have to be able to produce everything that we humans observe, which introduces a kind of narrative imperative into science too. Humans think in stories. Classically, at least, science itself has been the dis­covery of ’stories’ - think of all those books that had titles like The Story of Mankind, The Descent ofMan, and, if it comes to that, A Brief History of Time.

  Over and above the stories of science, though, Discworld can play an even more important role: What if? We can use Discworld for thought experiments about what science might have looked like if the universe had been different, or if the history of science had followed a different route. We can look at science from the outside.

  To a scientist, a thought experiment is an argument that you can run through in your head, after which you understand what’s going on so well that there’s no need to do a real experiment, which is of course a great saving in time and money and prevents you from get­ting embarrassingly inconvenient results. Discworld takes a more practical view - there, a thought experiment is one that you can’t do and which wouldn’t work if you could. But the kind of thought experiment we have in mind is one that scientists carry out all the time, usually without realizing it; and you don’t need to do it, because the whole point is that it wouldn’t work. Many of the most important questions in science, and about our understanding of it, are not about how the universe actually is. They are about what would happen if the universe were different.

  Someone asks ’why do zebras form herds?’ You could answer this by an analysis of zebra sociology, psychology, and so on ... or you could ask a question of a very different kind: ’What would hap­pen if they didn’t?’ One fairly obvious answer to that is ’They’d be much more likely to get eaten by lions.’ This immediately suggests that zebras form herds for self-protection - and now we’ve got some insight into what zebras actually do by contemplating, for a moment, the possibility that they might have done something else.

  Another, more serious example is the question ’Is the solar sys­tem stable?’, which means ’Could it change dramatically as a result of some tiny disturbance?’ In 1887 King Oscar II of Sweden offered a prize of 2,500 crowns for the answer It took about a century for the world’s mathematicians to come up with a definite answer: ’Maybe’. (It was a good answer, but they didn’t get paid. The prize had already been awarded to someone who didn’t get the answer and whose prizewinning article had a big mistake right at the most interesting part. But when he put it right, at his own expense, he invented Chaos Theory and paved the way for the ’maybe’. Sometimes, the best answer is a more interesting question.) The point here is that
stability is not about what a system is actually doing: it is about how the system would change if you disturbed it. Stability, by definition, deals with ’what if?’.

  Because a lot of science is really about this non-existent world of thought experiments, our understanding of science must concern itself with worlds of the imagination as well as with worlds of real­ity. Imagination, rather than mere intelligence, is the truly human quality. And what better world of the imagination to start from than Discworld? Discworld is a consistent, well-developed universe with its own kinds of rules, and convincingly real people live on it despite the substantial differences between their universe’s rules and ours. Many of them also have a thoroughgoing grounding in ’common sense’, one of science’s natural enemies.

  Appearing regularly within the Discworld canon are the buildings and faculty of Unseen University, the Discworld’s premier col­lege of magic. The wizards[2] are a lively bunch, always ready to open any door that has ’This door to be kept shut’ written on it or pick up anything that has just started to fizz. It seemed to us that they could be useful ...

  If we, or they, compare Discworld’s magic to Roundworld sci­ence, the more similarities and parallels we find. Clearly, as the wizards of Unseen University believe, this world is a parody of the Discworld one.

  And when we didn’t discover those, we found that the differences were very revealing. Science takes on a new character when you stop asking questions like ’What does newt DNA look like?’ and instead ask ’I wonder how the wizards would react to this way of thinking about newts?’

  There is no science as such on Discworld. So we have put some there. By magical means, the wizards on Discworld must be led to create their own brand of science - some kind of pocket universe’ in which magic no longer works, but rules do. Then, as the wizards learn to understand how the rules make interesting things happen -rocks, bacteria, civilizations - we watch them watching ... well, us. It’s a sort of recursive thought experiment, or a Russian doll wherein the smaller dolls are opened up to find the largest doll inside.

  And then we found that ... ah, but that is another story.

  TP, IS, & JC, DECEMBER 1998

  PS We have, we are afraid, mentioned in the ensuing pages Schrodinger’s Cat, the Twins Paradox, and that bit about shining a torch ahead of a spaceship travelling at the speed of light. This is because, under the rules of the Guild of Science Writers, they have to be included. We have, however, tried to keep them short.

  We’ve managed to be very, very brief about the Trousers of Time, as well.

  ONE

  SPLITTING THE THAUM

  SOME QUESTIONS SHOULD NOT BE ASKED. However, someone always does,

  ’How does it work?’ said Archchancellor Mustrum Ridcully, the Master of Unseen University.

  This was the kind of question that Ponder Stibbons hated almost as much as ’How much will it cost?’ They were two of the hardest questions a researcher ever had to face. As the university’s de facto head of magical development, he especially tried to avoid questions of finance at all costs.

  ’In quite a complex way.’ he ventured at last.

  ’Ah.’

  ’What I’d like to know,’ said the Senior Wrangler, ’is when we’re going to get the squash court back.’

  ’You never play, Senior Wrangler,’ said Ridcully, looking up at the towering black construction that now occupied the centre of the old university court.[3]

  ’I might want to one day. It’ll be damn hard with that thing in the way, that’s my point. We’ll have to completely rewrite the rules.’

  Outside, snow piled up against the high windows. This was turn­ing out to be the longest winter in living memory - so long, in fact, that living memory itself was being shortened as some of the older citizens succumbed. The cold had penetrated even the thick and ancient walls of Unseen University itself, to the general concern and annoyance of the faculty. Wizards can put up with any amount of deprivation and discomfort, provided it is not happening to them.

  And so, at long last, Ponder Stibbons’s project had been author­ized. He’d been waiting three years for it. His plea that splitting the thaum would push back the boundaries of human knowledge had fallen on deaf ears; the wizards considered that pushing back the boundaries of anything was akin to lifting up a very large, damp stone. His assertion that splitting the thaum might significantly increase the sum total of human happiness met with the rejoinder that everyone seemed pretty happy enough already.

  Finally he’d ventured that splitting the thaum would produce vast amounts of raw magic that could very easily be converted into cheap heat. That worked. The Faculty were lukewarm on the sub­ject of knowledge for knowledge’s sake, but they were boiling hot on the subject of warm bedrooms.

  Now the other senior wizards wandered around the suddenly-cramped court, prodding the new thing. Their Archchancellor took out his pipe and absent-mindedly knocked out the ashes on its matt black side.

  ’Um ... please don’t do that, sir,’ said Ponder.

  ’Why not?’

  ’There might be ... it might... there’s a chance that...’ Ponder stopped. ’It will make the place untidy, sir,’ he said.

  ’Ah. Good point. So it’s not that the whole thing might explode, then?’

  ’Er ... no, sir. Haha,’ said Ponder miserably. ’It’d take a lot more than that, sir -’

  There was a whack as a squash ball ricocheted off the wall, rebounded off the casing, and knocked the Archchancellor’s pipe out of his mouth.

  ’That was you. Dean,’ said Ridcully accusingly. ’Honestly, you fellows haven’t taken any notice of this place in years and suddenly you all want to - Mr Stibbons? Mr Stibbons?’

  He nudged the small mound that was the hunched figure of the University’s chief research wizard. Ponder Stibbons uncurled slightly and peered between his fingers.

  ’I really think it might be a good idea if they stopped playing squash, sir,’ he whispered.

  ’Me too. There’s nothing worse than a sweaty wizard. Stop it, you fellows. And gather round. Mr Stibbons is going to do his pres­entation.’ The Archchancellor gave Ponder Stibbons a rather sharp look. ’It is going to be very informative and interesting, isn’t it, Mister Stibbons. He’s going to tell us what he spent AM$55,879.45p on.’

  ’And why he’s ruined a perfectly good squash court,’ said the Senior Wrangler, tapping the side of the thing with his squash racket.

  ’And if this is safe? said the Dean. ’I’magainst dabbling in physics,’

  Ponder Stibbons winced.

  ’I assure you, Dean, that the chances of anyone being killed by the, er, reacting engine are even greater than the chance of being knocked down while crossing the street,’ he said.

  ’Really? Oh, well ... all right then.’

  Ponder reconsidered the impromptu sentence he’d just uttered and decided, in the circumstances, not to correct it. Talking to the senior wizards was like building a house of cards; if you got anything to stay upright, you just breathed out gently and moved on.

  Ponder had invented a little system he’d called, in the privacy of his head, Lies-to-Wizards. It was for their own good, he told him­self. There was no point in telling your bosses everything; they were busy men, they didn’t want explanations. There was no point in bur­dening them. What they wanted was little stories that they felt they could understand, and then they’d go away and stop worrying.

  He’d got his students to set up a small display at the far end of the squash court. Beside it, with pipes looping away through the wall into the High Energy Magic building next door, was a termi­nal to HEX, the University’s thinking engine. And beside that was a plinth on which was a very large red lever, around which someone had tied a pink ribbon.

  Ponder looked at his notes, and then surveyed the faculty.

  ’Ahem ...’ he began.

  ’I’ve got a throat sweet somewhere,’ said the Senior Wrangler, patting his pockets.

  Pond
er looked at his notes again, and a horrible sense of hope­lessness overcame him. He realized that he could explain thaumic fission very well, provided that the person listening already knew all about it. With the senior wizards, though, he’d need to explain the meaning of every word. In some cases this would mean words like ’the’ and ’and’.

  He glanced down at the water jug on his lectern, and decided to extemporize.

  Ponder held up a glass of water.

  ’Do you realize, gentlemen,’ he said, ’that the thaumic potential in this water ... that is, I mean to say, the magical field generated by its narrativium content which tells it that it is water and lets it keep on being water instead of, haha, a pigeon or a frog ... would, if we could release it, be enough to move this whole university all the way to the moon?’

  He beamed at them.

  ’Better leave it in there, then,’ said the Chair of Indefinite Studies.

  Ponder’s smile froze.

  ’Obviously we cannot extract all of it,’ he said, ’But we -’

  ’Enough to get a small part of the university to the moon?’ said the Lecturer in Recent Runes.

  ’The Dean could do with a holiday,’ said the Archchancellor.

  ’I resent that remark, Archchancellor’

  ’Just trying to lighten the mood, Dean.’

  ’But we can release just enough for all kinds of useful work,’ said Ponder, already struggling.

  ’Like heating my study,’ said the Lecturer in Recent Runes. ’My water jug was iced up again this morning.’

  ’Exactly!’ said Ponder, striking out madly for a useful Lie-to-Wizards. ’We can use it to boil a great big kettle! That’s all it is! It’s perfectly harmless! Not dangerous in any way! That’s why the University Council let me build it! You wouldn’t have let me build it if it was dangerous, would you?’

  He gulped down the water.

  As one man, the assembled wizards took several steps back­wards.

  ’Let us know what it’s like up there,’ said the Dean.

  ’Bring us back some rocks. Or something,’ said the Lecturer in Recent Runes.