The Science of Discworld IV Judgement Da - By Terry Pratchett, Ian Stewart Page 0,1
everything can – and usually does – move.
This includes Roundworld the planet. It does have a sun, but this sun does not go round the planet. Instead, the planet goes round the sun. Worse, that doesn’t create day and night; instead, it produces seasons, because the planet is tilted. Also, the orbit isn’t circular. It’s a bit squashed, which is typical of Roundworld’s jerry-built construction. So to get day and night, the planet has to spin as well. It works, in its way: if you’re really stupid, you can be fooled into imagining that the sun goes round the planet. But – wouldn’t you just know it – the spin also prevented Roundworld from being a sensible sphere, because when it was molten it got sort of squashed, just like its orbit … oh, forget it.
As a consequence of this hopelessly bungled arrangement, the sun has to be enormous, and a very long distance away. So it has to be ridiculously hot: so hot that special new rules have to come into play to allow it to burn. And then almost all of its prodigious energy output is wasted, trying to warm up empty space.
Roundworld has no supports. It appears to think it’s a turtle, because it swims through space, tugged along by those mysterious forces. Its human inhabitants are not bothered by a sphere that swims, despite the absence of flippers. But then, people turned up at most four hundred thousand years ago, one hundredth of a per cent of the lifetime of the planet. And they seem to have turned up by accident, starting out as little blobs and then spontaneously becoming more complex – but they argue a lot about that. They’re not terribly bright, to be honest, and they only started to work out modern scientific rules of the universe they live in four hundred years ago, so they’ve got a lot of catching up to do.
The inhabitants refer to themselves optimistically as Homo sapiens, meaning ‘wise man’ in an appropriately dead language. Their activities seldom fit that description, but there are occasional glorious exceptions. They should really be called Pan narrans, the storytelling ape, because nothing appeals to them more than a rollicking good yarn. They are narrativium incarnate, and they are currently refashioning their world to resemble Discworld, so that things do happen because people want them to. They have invented their own form of magic, with spells like ‘make a dugout canoe’, ‘switch on the light’, and ‘login to Twitter’. This kind of magic cheats by using the rules behind the scenes, but if you’re really, really stupid you can ignore that and pretend it’s magic.
The first The Science of Discworld explained all that, and much more, including the giant limpet and the ill-fated crab civilisation’s great leap sideways. An endless series of natural disasters established something that the wizards intuitively knew from the word go: a round world is not a safe place to be. Fast-forwarding through Roundworld history, they managed to skip from some not very promising apes huddled around a black monolith to the collapse of the space elevators, as some presumably highly intelligent creatures, having finally got the message, fled the planet and headed for the stars to escape yet another ice age.
They couldn’t really be descended from those apes, could they? The apes seemed to have only two interests: sex, and bashing each other over the head.
In The Science of Discworld II, the wizards were surprised to find that the intelligent star-farers were indeed descended from the apes – a strange new use of the word ‘descend’, and one that caused serious trouble later. They found that out because Roundworld had taken the wrong leg of the Trousers of Time and had therefore deviated from its original timeline. Its ape-derived humans had become barbarians, their society vicious and riddled with superstition. They would never leave the planet in time to escape their doom. Something had interfered with Roundworld’s history.
Feeling somehow responsible for the planet’s fate, much as one might worry about a sick gerbil, the wizards entered their bizarre creation, to find that it was infested by elves. Discworld’s elves are not the noble creatures of some Roundworld myths. If an elf told you to eat your own head, you’d do it. But going back in time to when the elves had arrived, and kicking them out, just made everything worse. The evil had gone, but it had taken with it any shred of innovation.