The Science of Discworld Revised Edition

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 3 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 …
    Clearly, as the wizards of Unseen University believe, this world is a parody of the Discworld one. If we, or they, compare Discworld’s magic to Roundworld science, the more similarities and parallels we find. And when we didn’t discover parallels, 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 are 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, D ECEMBER 1998
    PS We have, we are afraid, mentioned in the ensuing pages Schrödinger’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.
    PPS Sometimes scientists change their minds. New developments cause a rethink. If this bothers you, consider how much damage is being done to the world by people for whom new developments do
not
cause a rethink.
    This second edition has been changed to reflect three years of scientific progress … forwards or backwards. (You will find both.) And we’ve added two completely new chapters: one on the life of dinosaurs, because the existing chapter on the death of dinosaurs seemed a bit depressing; and one on cosmic disasters,