Terry Pratchett - The Science of Discworld

by Terry Pratchett

  If you want to understand biology, it is the physics of space ele­vators that you need, not the physics of rockets.

  How can Discworld’s magic illuminate Roundworld’s science? Just as the gulf between the physical and biological sciences is turning out to be far narrower than we used to think, so the gulf between science and magic is also becoming smaller The more advanced our technologies become, the less possible it is for the everyday user to have any idea of how they work. As a result, they look more and more like magic. As Clarke realized, this tendency is inevitable; Gregory Benford went further and declared it desirable.

  Technology works because whoever built it in the first place fig­ured out enough of the rules of the universe to make the technology do what was required of it. You don’t need to get the rules right to do this, just right enough -space rockets work fine even though their orbits are computed using Newton’s stab at the rules of grav­ity, which aren’t as accurate as Einstein’s. But what you can accomplish is severely constrained by what the universe will per­mit. With magic, in contrast, things work because people want them to. You still have to find the right spell, but what drives the development is human wishes (and, of course, the knowledge, skill and experience of the practitioner). This is one reason why science often seems inhuman, because it looks at how the universe drives us, rather than the other way round.

  Magic, however, is only one aspect of Discworld. There’s a lot of science on Discworld, too - or at least rational engineering. Balls get thrown and caught, the biology of the river Ankh resembles that of a typical terrestrial swamp or sewage farm, and light goes in more or less straight lines. Very slowly, though. As we read in The Light Fantastic: ’Another Disc day dawned, but very gradually, and this is why. When light encounters a strong magical field it loses all sense of urgency. It slows right down. And on the Discworld the magic was embarrassingly strong, which meant that the soft yellow light of dawn flowed over the sleeping landscape like the caress of a gentle lover or, as some, would have it, like golden syrup.’ The same quote tells us that as well as rational engineering there’s a lot of magic in Discworld: overt magic which slows light down; magic that allows the sun to orbit the world provided that occasionally one of the elephants lifts its leg to let the sun pass. The sun is small,

  nearby, and travels faster than its own light. This appears to cause no major problems.

  There is magic in our world, too, but of a different, less obvious kind. It happens around everybody all the time, in all those little causalities which we don’t understand but just accept. When we turn the switch and the light comes on. When we get into the car and start the engine. When we do all those improbable and ridicu­lous things that, thanks to biological causality, make babies. Certainly many people understand, often to quite a detailed degree, what is going on in particular areas - but sooner or later we all reach our Magical Event Horizon. Clarke’s Law states that any sufficiently advanced technology looks like magic. ’Advanced’ here is usually taken to mean ’shown to us by advanced aliens or people from the future’, like television shown to Neanderthals. But we should real­ize that television is magic to nearly everyone that uses it now - to those behind the camera as well as to those sitting on the couch in front of the moving picture in the funny box. At some point in the process, in the words of cartoonist

  S. Harris, ’a miracle occurs’.

  Science takes on the aura of magic because the design of a civi­lization proceeds by a type of narrative imperative - it makes a coherent story. In about 1970, Jack gave a lecture to a school audi­ence on ’The Possibility of Life on Other Planets’. He talked about evolution, what planets were made of - all the things that you’d expect in such a lecture. The first question was from a girl of about 15, who asked ’You believe in evolution, don’t you, sir?’ The teacher went on about it not being a ’proper’ question, but Jack answered it anyway, saying - rather pretentiously -’No, I don’t believe in evolu­tion, like people believe in God ... Science and technology are not advanced by people who believe, but by people who don’t know but are doing their best to find out ... steam engine ... spinning jenny ... television ...’At that, she was on her feet again: ’No, that ain’t how television was invented!’ The teacher tried to calm the discus­sion by asking her to explain how she thought television was invented. ’My father works for Fisher Ludlow making pressed steel for car bodies. He gets paid and he gives some of the money to the government to give him things. So he tells the government he wants to watch television, and they pay someone to invent television, and they do!’

  It’s very easy to make this mistake, because technology pro­gresses by pursuing goals. We get the feeling that if we pour in enough resources, we can achieve anything. Not so. Pour in enough resources, and we can achieve anything that is within reach of cur­rent know-how, or possibly just a bit beyond if we’re lucky. But nobody tells us about the inventions that fail. Nobody tries to raise funding for a project that they know can’t possibly work. No fund­ing body will pay for research projects in which we have no idea where to start. We could pour as much money as we liked into developing antigravity or faster-than-light travel, and we’d get nowhere.

  When you can take a machine to bits and see how it works, you get a clear feeling for the constraints within which it has to operate. In such cases, you’re not going to confuse science and magic. The first cars required an extremely hands-on starting system - you stuck a big handle into the engine and literally ’turned it over’. Whatever the engine did when it started, you knew it wasn’t magic. However, as technology develops it usually doesn’t remain trans­parent to the user. As more people began to use cars, more and more of the obvious technology was replaced by symbols. You worked switches with labels to get things to happen. That’s our version of the magic spell: you pull a knob called Cold Start and the engine does all the cold start things for itself. When Granny wants to drive she does not have to do much more than push the accelerator for ’Go’. Little imps do the rest, by magic.

  This process is the core of the relation between science and magic in our own world. The universe into which we were born, and in which our species evolved, runs by rules - and science is our way of trying to work out what the rules are. But the universe that we are now constructing for ourselves is one that, to anyone other than a member of the design team and very possibly even to them, works by magic.

  A special kind of magic is one of the many things that have made humans what they are. It’s called education. It’s how we pass on ideas from one generation to the next. If we were like computers, we’d be able to copy our minds into our children, so that they would grow up agreeing with every opinion that we hold dear. Well, actu­ally they wouldn’t, though they might start out that way. There is an aspect of education that we want to draw to your attention. We call it ’lies-to-children’. We’re aware that some readers may object to the word ’lie’ - it got Ianand Jack into terrible trouble with some literally-minded Swedes at a scientific conference who took it all terribly seriously and spent several days protesting that ’It’s not a for It is. It is for the best possible reasons, but it is still a lie. A lie-to-children is a statement that is false, but which nevertheless leads the child’s mind towards a more accurate explanation, one that the child will only be able to appreciate if it has been primed with the lie.

  The early stages of education have to include a lot of lies-to-chil­dren, because early explanations have to be simple. However, we live in a complex world, and lies-to-children must eventually be replaced by more complex stories if they are not to become delayed-action genuine lies. Unfortunately, what most of us know about science consists of vaguely remembered lies-to-children. For exam­ple, the rainbow. We all remember being told at school that glass and water split light into its constituent colours -there’s even a nice experiment where you can see them

  -and we were told that this is how rainbows form, fromlight passing through raindrops. When we were children, it
never occurred to us that while this explains the colours of the rainbow it doesn’t explain its shape. Neither does it explain how the light from the many different raindrops in a thundershower somehow combines to create a bright arc. Why doesn’t it all smudge out? This is not the place to tell you about the elegant geometry of the rainbow - but you can see why ’lie’ is not such a strong word after all. The school explanation diverts our attention from the real marvel of the rainbow, the cooperative effects of all the raindrops, by trying to pretend that once you’ve explained the colours, that’s it.

  Other examples of lies-to-children are the idea that the Earth’s magnetic field is like a huge bar magnet with N and S marked on it, the picture of an atom as a miniature solar system, the idea that a living amoeba is a billion-year-old ’primitive’ organism, the image of DNA as the blueprint for a living creature, and the connection between relativity and Einstein’s hairstyle (it’s the sort of crazy idea that only people with hair like that can come up with). Quantum mechanics lacks a public ’icon’ of this kind - it doesn’t tell a simple story that a non-specialist can grab and hang on to - so we feel uncomfortable about it.

  When you live in a complex world, you have to simplify it in order to understand it. Indeed, that’s what ’understand’ means. At different stages of education, different levels of simplification are appropriate. Liar-to-children is an honourable and vital profession, otherwise known as ’teacher’. But what teaching does not do -although many politicians think it does, which is one of the prob­lems - is erect a timeless edifice of ’facts’.[10] Every so often, you have to unlearn what you thought you already knew, and replace it by something more subtle. This process is what science is all about, and it never stops. It means that you shouldn’t take everything we say as gospel, either, for we belong to another, equally honourable profes­sion: Liar-to-readers.

  On Discworld, one of Ponder Stibbons’s lies-to-wizards is about to come seriously unstuck.

  FIVE THE ROUNDWORLD PROJECT

  ARCHCHANCELLOR RIDCULLY AWOKE FROM AN AFTERNOON NAP in which he had been crawling through a baking desert under a flamethrower sky, and found that this was more or less true.

  Superheated steam whistled from the joints of the radiator in the corner. Ridcully walked over through the stifling air and touched it gently.

  ’Ouch! Damnation!’

  Sucking his right hand and using his left hand to unwrap the scarf from his neck, he strode out into the corridor and what looked like Hell with the heat turned up. Steam rolled along the corridors, and from somewhere overhead came the once-heard-never-forgot-ten thwack of a high-energy magical discharge. Violet light filled the windows for a moment.

  ’Will someone tell me what the heck is going on?’ Ridcully demanded of the air in general.

  Something like an iceberg loomed out of the steam. It was the Dean.

  ’I would like to make it absolutely clear, Archchancellor, that this is nothing to do with me!’

  Ridcully wiped away the sweat that was beginning to trickle down his forehead.

  ’Why are you standin’ there in just your drawers, Dean?’

  ’I - well, my room is absolutely boiling hot -’

  ’I demand you put something on, man, you look thoroughly unhygienic!’

  There was another crack of discharged magic. Sparks flew off the end of Ridcully’s fingers.

  ’I felt that one!’ he said, 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.

  Tor 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 offt 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 HEX 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 HEX 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 up.’

  There was a moment’s silence. That is, the wizards were silent. Overhead, magic flared into the sky with a sound like roaring gas.

  ’Can’t let it build up here,’ Ridcully went on. ’What’s the Roundworld project then?’

  ’It was, er ... there was once some suggestion that it might be possible to create a ... an area where the laws of magic don’t apply,’ said Ponder. ’We could use it to learn more about magic.’

  ’Magic’s everywhere? said Ridcully.
’It’s part of what everywhere is’

  ’Yes, sir,’ said Ponder, watching the Archchancellor carefully.

  The ceiling creaked.

  ’What use would it be, anyway?’ said Ridcully, still thinking aloud.

  ’Well, sir, you could ask what use is a new-born child ...’

  ’No, that’s not the sort of question I ask,’ said Ridcully. ’And it’s a highly suspicious one, too.’

  The wizards ducked as the latest discharge crackled overhead. It was followed by a louder explosion.

  ’I think the balls have just exploded, sir,’ said Ponder.

  ’All right, then, how long would the project take to set up?’ said Ridcully.

  ’Months,’ said the Dean firmly.

  ’We’ve got about ten seconds to the next discharge, sir,’ said Ponder. ’Only ... now the balls have gone it will simply earth itself...’

  ’Ah. Oh. Really? Well, then ...’ Ridcully looked around at his fel­low wizards as the wall began to shake again. ’It’s been nice knowing you. Some of you. One or two of you, anyway ...’

  The whine of increasing magic rose in pitch.

  The Dean cleared his throat.

  ’I’d just like to say, Mustrum,’ he began.

  ’Yes, old friend?’

  ’I’d just like to say ... I think I’d have made a much

  better Archchancellor than you.’

  The whine stopped. The silence twanged. The wizards

  held their breath.

  Something went ’ping’.

  A globe about a foot across hung in the air between the

  faculty. It looked like glass, or the sheen of a pearl