The Science of Discworld I

1

In a manner of speaking. They happen because things obey the rules of the universe. A rock has no detectable opinion about gravity.

2

Like the denizens of any Roundworld university, they have unlimited time for research, unlimited funds and no worries about tenure. They are also hy turns erratic, inventively malicious, resistant to new ideas until they've become old ideas, highly creative at odd moments and perpetually argumentative - in this respect they bear no relation to their Roundworld counterparts at all.

3

Wizard or 'Real' Squash bears very little relationship to the high speed sweat bath played elsewhere. Wizards see no point in moving fast. The ball is lobbed lazily. Certain magical inconsistencies are built into the floor and walls, however, so that the wall a ball hits is not necessarily the wall it rebounds from. This was one of the factors which, Ponder Stibbons realized some time after­wards, he really ought to have taken into consideration. Nothing excites a magical particle like meeting itself coming the other way.

4

Or at least, less radioactive. We can but hope.

5

He was the victim of a magical accident, which he rather enjoyed. But you know this.

6

They say that every formula halves the sales of a popular science book. This is rubbish - if it was true, then The Emperor's New Mind by Roger Penrose would have sold one-eighth of a copy, whereas its actual sales were in the hun­dreds of thousands. However, just in case there is some truth to the myth, we have adopted this way of describing the formula to double our potential sales. You all know which formula we mean. You can find it written out in symbols on page 118 of Stephen Hawking's A Brief History of Time - so if the myth is right, he could have sold twice as many copies, which is a mindboggling thought.

7

The fine structure constant is defined to be the square of the charge of an electron, divided by 2 times Planck's constant times the speed of light times the permittivity of the vacuum (as a handy lie, the last term might be thought as 'the way it reacts to an electric charge'). Thank you.

8

As yet unmeasured, but believed to be faster than light owing to its ability to move so quickly out of light's way.

9

Actually you can eat salt. But nobody outside Discworld goes to a restaurant to order a basalt balti.

10

As humans, we have invented lots of useful kinds of lie. As well as lies-to-children ('as much as they can understand') there are lies-to-bosses ('as much as they need to know') lies-to-patients ('they won't worry about what they don't know') and, for all sorts of reasons, lies-to-ourselves. Lies-to-children is simply a prevalent and necessary kind of lie. Universities are very familiar with bright, qualified school-leavers who arrive and then go into shock on finding that biology or physics isn't quite what they've been taught so far. ‘Yes, but you needed to understand that,’ they are told, ‘so that now we can tell you why it isn't exactly true’. Discworld teachers know this, and use it to demonstrate why universites are truly storehouses of knowledge: students arrive from school confident that they know very nearly everything, and they leave years later certain that they know practically nothing. Where did the knowledge go in the meantime? Into the university, of course, where it is carefully dried and stored.

11

'What You Get Is What You're Given And It's No Good Whining.'

12

Not while these are still in the polar bear.

13

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'.

14

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

15

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.

16

Silicon might also be able to do this, but nowhere near as readily; if you want other exotic lifeforms you have to start thinking in terms of organized vortices in the upper reaches of a sun, weird quantum assemblages in interstellar plasma, or completely implausible creatures based on non-material concepts such as information, thought, or narrativium. DNA is a different matter entirely: you could surely base lifeforms on other carbon-rich molecules. We can do it now, in laboratories, with minor variants of DNA.

17

Ask Mummy or Daddy if you have no idea what we're talking about.

18

There also ought to be 'Population III' stars, older than Population II and consisting entirely of hydrogen and helium. These would explain the occurence of some heavy elements in Population II. However, nobody has ever found a Population III star. This may be because they were short-lived. Or, a more recent theory: very soon after the Big Bang there were heavy elements around, even before any stars formed. So when the first stars condensed, they already were Population II. This contradicts what we say in the main text - lies-to-children, of course.

19

'Most civilizations' is admittedly not the same as 'most people'. 'Most people' through the history of the planet have not needed to concern themselves with what shape the world is, provided it supports, somewhere, the next meal.

20

This rule does require some special assumptions, such as the chronic and irreversible stupidity of humanity.

21

As Nanny Ogg always says, 'He's just a big softy.'

22

Omnianism had taught for thousands of years that the Discworld was in fact a sphere, and violently persecuted those who preferred to believe the evidence of their own eyes. At the time of writing, Omnianism was teaching that there was something to be said for every point of view.

23

A magical accident had once turned the University's Librarian into an orangutan, a state which he enjoyed sufficiently to threaten, with simple and graphic gestures, anyone who suggested turning him back. The wizards noticed no difference now. An orangutan seemed such a natural shape for a librarian.

24

Moreover, until the last few decades of human history, most women did not cycle. Nearly all the time, they were either pregnant or lactating. And for the great apes, the cycle is a week or so longer than for humans, and for gibbons it's shorter. So it looks as though the relation with the Moon is coincidental.

25

A phrase meaning 'I'm not sure you know this.'

26

And if so: congratulations! You are a human being, thinking narratively.

27

Light on the Disc travels at about the same speed as sound. This does not appear to cause problems.

28

And a terrible thing it is, akin to a state of horrible depression. Hence the affliction of Captain Vimes in Guards! Guards! who needs a couple of drinks simply to become sober.

29

Well ... most people.

30

'Desperate' is another privative - it means 'no hope'.

31

Death's apprentice - well, he'd have to train a successor. Not in case he dies: so he can retire. Which he does (temporarily) in Reaper Man.

32

Indeed, it is a 'fundamental constant' of the Discworld universe that things exist because they're believed in.

33

'Truth' is a privative in the same way that 'sober' is - until you invent lies, you don't know what the truth is. Nature appears to, otherwise animals would not have invested so much effort on very effective camouflage.

34

Everyone knows what science fiction is - until you start asking questions like 'Is a book set five years in the future automatically SF? Is it SF just because it's set on another world, or is it simply fantasy with nuts and bolts on the out­side? Is it SF if the author thinks it isn't? Does it have to be set in the future? Does the presence of Doug McClure mean that a movie is SF, or merely that the men-in-rubber-monster-suits quotient is going to be high?' One of the best SF books ever written was the late Roy Lewis's The Evolution Man; there is no technology in it more sophisticated than a bow, it's set in the far past, the characters are barely more than ape-men ... but it is science fiction, nonethe­less.

35

They were fortunate, given the names of some places in Australia, that they ended up merely sounding like a minor Star Trek species.

36

'Reddish-brown'.

37

... which had engrossed wizards for many years. The debate ran like this: it was quite easy to turn someone into a frog, and fairly easy to turn them into, say, a white mouse. Strangely, considering the basic similarity of size and shape, turning someone into an orangutan took a vast amount of power and it was only an explosion in the intense thaumic confines of the Library which had managed the trick. Turning someone into a tree was much, much harder even than that, although turning a pumpkin into a coach was so easy that even a crazy old woman with a wand could do it. Was there some kind of framework into which all this fitted?

The current hypothesis was that most Change spells unravelled the vic­tim's morphic field down to some very basic level and then 'bounced' them back. A frog was quite simple, so they wouldn't have to bounce far. An ape, being quite human-like in many respects, would mean a very long return jour­ney indeed. You couldn't turn someone into a tree because there was no way to get there from here, but a pumpkin could be turned into a wooden coach because it was quite close to it in vegetable space.

The wizards agreed that this all seemed to fit nicely, and was therefore true.

If William of Occam had been a wizard at Unseen University, he would have grown a beard.

38

The quantity of bacon per trotter is on average slightly more than one quar­ter of the amount per head.

39

Wizards seldom bothered to look things up if they could reach an answer by bickering at cross-purposes.

40

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.

41

There's a silly reason for this, and a sensible one. The silly reason is that species are usually defined to be different if they don't interbreed. If two sep­arate species don't interbreed, it's difficult to put them back together again. The sensible one is that evolution occurs by random mutations - changes to the DNA code - followed by selection. Once a change has occurred, it's unlikely for it to be undone by further random mutations. It's like driving along country roads at random, reaching some particular place, and then con­tinuing at random. What you don't expect is to reverse your previous path and end up back where you started.

42

According to the most recent dating methods, the Cambrian began 543 mil­lion years ago. The Burgess shale was deposited about 530-520 million years ago.

43

In the words of Discworlcd's God of Evolution: 'The purpose of the whole thing is to be the whole thing.'

44

Indeed, it is a fundamental part of story telling. If the hero did not overcome huge odds, what would be the point?

45

Possibly he was holding a large axe at the time.

46

Readers of the Discworld book The Last Continent will recall that, by an amazing coincidence, beetles were something of a passion for the God of Evolution.

47

Rincewind would add some more:

'Is it safe?'

'Are you sure?'

'Are you absolutely sure?'

48

A worse case is what used to be called Eohippus, the Dawn Horse - a beau­tiful, poetic name for the animal that formed the main stem of the horse's family tree. It is now called Hyracotherium, because somewhat earlier some­body had given that name to a creature that they thought was a relative of the hyrax, represented by a single fossil shoulder-blade. Then it turned out that the bone was actually part of an Eohippus. Unfortunately, whoever officially names a species first must get priority, so now the Dawn Horse has a silly, unpoetic name that commemorates a mistake.

We lost 'Brontosaurus' - thunder-lizard - for a similar reason. Thunder Lizard ... what a marvellous name. 'Apatosaurus'? It probably means 'Gravitationally challenged Lizard'.

The moral of this tale is that when learned committees of elderly scientists meet to discuss an exceptional issue they can always be trusted to make a com­pletely ridiculous decision. Quite unlike the wizards of Unseen University, naturally.

49

Lots of ammonite species died out 5-10 million years before the K/T boundary, so it looks as if their extinction genuinely was gradual. But what­ever it was that happened at the K/T boundary finished them off.

50

OK, if you insist ... Our favoured line here is 'hairy'. But hairs don't fos­silize, so how can you tell? If you have hair, you need grooming. All over the body. This requires flexible backbones, and you can tell how flexible they are from the shape of the vertebrae. Which do fossilize. (Sometimes scientists can be very ingenious.) Evolution crossed that line about 230 million years ago.

51

How many recipe books do you have that tell you to boil water, but never specify the altitude at which this should be done? It matters: higher up, water boils at lower temperatures.

52

There was a television programme called The Magic Roundabout. One of the characters was a dog called Dougal, which looked a bit like a hairbrush. Mauds shrimps have the same general form, though not with hair.

53

This is probably another lie. Alien microbes are unlikely to find us edible. So are alien tigers, although they might do us quite a lot of damage in finding out. But certainly an alien world will have a whole host of nasty surprises, if we are not very careful. We can't tell you what they'll be. They'll be a surprise.

54

We apologize to any real gods.

55

Unfortunately, huge malicious destructive force is a god-like power.