The Science of Discworld IV: Judgement Day
Terry Pratchett, Ian Stewart and Jack Cohen
Ebury Press, £18.99
Simon Ings: How are the Science of Discworld books assembled?
Ian Stewart: We think of the Discworld story first, because without that, the books just don’t work. There has to be something Terry can get his teeth into. And then we start looking for good science topics to fit into that story. And over the years we’ve got fairly good at this. It’s not completely foolproof. From time to time we’ve written entire chapters and thrown them away again.
Simon: How did the idea get started?
Jack Cohen: I knew Terry from science fiction conventions, but only casually. And then there was a meeting in the Hague, a big European science fiction convention. And three rich science fiction authors were giving talks to an audience of around 300 people. Bob Silverberg spoke first. He said he sold his first story at fourteen, and that by the time he was twenty-five he didn’t know how much money he had in the bank: ten thousand dollars more or less wouldn’t have touched his radar. But money isn’t important. And the place got a bit restive at that. Then Larry Niven stood up and explained his grandfather gifted him 21 million dollars when he was twenty-one, but he still had to go through all the rites of passage of growing up, and he finished by saying, “Look, although I have all this money, I have to tell you, money is not important.” At which point the audience started throwing things. Terry Pratchett came on next – you could see he was on the edge – and someone threw food and it hit him, and he lost it. And he said, “What the fuck do you think we’re doing? We’re rich science fiction authors. We don’t have to come and talk to you here, you could at least be polite. And the money isn’t important.” And I stood up – I was standing at the back of this big theatre – and I said, you’re both right. Money is like air and love. If you’ve got it, it doesn’t matter. The absence of it is desperate. Afterwards Terry took me aside and said, Let me buy you a drink. We got talking and I explained I was writing a book with Ian and we were finding it really difficult to get the chapters to gel. He said, let’s have a proper meeting. Which ended up taking place – I can’t remember why – in a Mongolian restaurant in Berlin. Ian and I took along our plan of Figments of Reality and Terry said, Give it to me and give me a month. Two weeks later we met in the same restaurant and Terry said, This is the way you do it. And the structure he’d cooked up worked beautifully.
Terry Pratchett: Then I said, Look, I’ve had a play in your field, why don’t you have a play in mine? The idea for this one goes back five or six years. We were planning to do it much earlier, but because of my posterior cortical atrophy the project was put on the back burner until we were all confident it would be possible to go ahead and do it. Our overall storyline here is a debate between scientific thinking and belief.
Ian: We try to take a fairly moderate view on that, because there are a lot of longstanding human beliefs which are rational within a historically sanctioned framework, and a lot of people people find them to their taste. If somebody invented these things tomorrow, these same people, I’m sure, would look at them in a rather different way. But religious beliefs, in particular, have thousands of years of history at their back. If I say to you, a religious person, “You are irrational,” that’s certainly presumptuous and probably stupid. Chances are you’re not in the least bit irrational. Some of your premises might be irrational and, in some circumstances, I would argue that they’ll trip you up quite badly. But they don’t make you an irrational person.
Jack:: I grew up to be a rabbi. My father had expressed a wish to become a rabbi, but he died shortly after the war and the mantle fell on my shoulders. From fourteen to seventeen, I went to yeshivas. I eventually came to the conclusion there was no God. But I still went to synagogue, because so much of what I’d learned there made sense to me. The absence of God didn’t suddenly make that place worthless.
Terry: Anyway, I got it into my head that the Omnian religion on Discworld is trying to get its hands on Roundworld, because its shape is so significant for them. For the longest time, you see, the Omnians believed Flatland was really a sphere – quite preposterous! And this story suggested to Jack and Ian that we should explore the social side of science. How does science really work?
Ian: Science isn’t just observation, you see. It’s inference. You think about things. You produce theories. You test things. And you use indirect reasoning. You have to, because science tries to understand things you can’t look at directly. If we could look at them directly, we’d have understood them much longer ago. It’s a bit like an ant on the surface of the earth wondering what shape its planet is. The ant can’t go very far, or see very far, so there’s a limit to what it can apprehend. But let it infer things about the world, and there’s quite a bit the ant can learn about its world. Stand on a low island somewhere in the middle of the Caribbean, with sea all around you, and look at the horizon. If you entertain the idea that the earth is a sphere, you can work out how big the sphere is, because the size of sphere determines how far away the horizon is. Once you ask yourself the question, “What if this thing was a sphere?” you don’t actually need a lot of apparatus to come up with a reasonable estimate for the size of the earth. The trouble is, you don’t know for absolute certain, until you circumnavigate the thing, that the world is a sphere. We’re in that kind of position when we try to imagine the shape of the universe. There are hints of structure, and if we make some sweeping, reasonable-sounding assumptions, then we can start to make informed guesses about the shape of the universe. But we’re never going to be able to circumnavigate the universe, any more than an ant is going to book a round-the-world cruise, so it’s hard to see how we’ll ever know for sure that our oh-so-reasonable assumptions are actually correct.
Simon: This comes up when you and Jack debate the usefulness of studying very small particles at very high energies.
Ian:: We don’t agree, which ought to be a problem. But as they say in show business, if you’ve got a wooden leg, wave it. Being a mathematician, I think that quantum field theory is extraordinarily interesting. Jack, being a biologist, looks at the things he’s been working on like frogs and mice, and thinks, the link from Ian’s sort of mathematics to my frogs and mice is extraordinarily tenuous. There’s a kind of story here, and each bit in the story makes sense. But there are gaps – big ones.
Jack: When you’re probing scales of measurement so tiny that, even to infer something about them, you need a machine five miles across and a supercomputer to actually detect anything, can you really be sure that your picture is accurate? Or have you wandered off into some realm of deduction where you’re simply plugging the gaps in logic left by the previous stage of your argument?
Ian: And Jack and I differ on this. I would be inclined to say, the quarks and the Higgs boson do really exist. We’re not quite sure what a particle is anymore, but we have pretty good evidence that we’re not just making these things up.
Jack: And I say, even if that’s right, actually very little science rests on it. We know how a mouse will behave when you change its genes in certain ways. The existence or otherwise of the Higgs boson doesn’t impact the solid knowledge we have of the mouse genome in any way. People say the Higgs boson is a fundamental particle. Yes, it’s fundamental in the sense that its a required component of the universe. But it’s not fundamental in the sense that you need it to work out everything else about what’s around us.
Simon: So from your point of view, Jack, it’s almost as if big physics is falling through the hole that it’s just kicked in its own floor.
Jack: Well, I’m inclined to think that if we’d started our atomic physics with some phenomenon other than electricity, we’d have a different view of what particles are, and it would work equally well. And physicists mostly don’t think that way. They think that protons are real, that electrons are real, and even the more exotic particles are all real. It depends what you mean by real, but you know what I mean.
Simon: This reminds me of M John Harrison’s novel Light, in which advanced civilisations have over time cooked up six perfectly workable, mutually contradictory theories of everything. They can’t all be right, but every one of them gives you the tools you need to build a hyperspace drive that can take you from one side of the galaxy to the other.
Jack:: I like the idea because, let’s be fair, the scientific theories that underpin most of our technology have turned out to be incomplete, if not plain wrong.
Simon: There is a tremendous passage in Judgement Day in which a bunch of learned and ingenious pianologists are trying to work out how a piano works. They can’t see the piano, or touch the piano, but they can throw small stones at it and by listening to the sounds that come out of the piano when the stones hit the keyboard, they‘ve developed a fairly good understanding of how the piano works. Then one of them says, “We need to take this further. Why don’t we take this thing to the top of the hotel and push it off the roof?” And suddenly their theory is full of complex, conjectural particles called thudons and twangons and such-like, and they think they’re coming to a more profound understanding of the piano when all they’ve done is make it behave in extraordinary and uncharacteristic ways.
Jack: Ian loves that sort of thing. He had great fun.
Ian: Jack has the feeling at the back of his mind that some of the laws of physics aren’t really there until the universe is pushed into some very extreme situation: that the universe makes things up as it goes along. So how do we distinguish between understanding laws that always operated, whether we knew about them or not, and laws that maybe weren’t really there until we started poking sticks in the right places? Until you create a star with nuclear reactions going on in its core, is there actually a set of laws governing nuclear reactions? My feeling is, there has to be, otherwise the star wouldn’t know what to do. The alternative is a bit Rupert Sheldrake for my taste; he voiced a similar idea a while ago that the universe adapts to the experiments you do on it.
Terry: Of course the magicians of Discworld would be very, very comfortable with this idea. It would seem obvious to them that when you start asking questions of the universe, you actually change it.
Ian: Certainly, when you stress the natural world in new ways, you reveal new behaviours that nobody knew existed before. And there seems to be this unlimited richness to the way the world can behave. There really doesn’t seem to be an end to this. If there’s an end to scientific knowledge, we’re nowhere near it right now.
SI It’s the gift that keeps on giving. Like natural selection: no matter the number of turnings you didn’t take that maybe you should have taken, no matter the catalogue of blind alleys you get stuck in, there always turn out to be more design possibilities after each generation than there were before it.
Terry: Depending on your point of view, this is either something that’s terribly, terribly obvious or deeply perplexing and mysterious. I’m inclined to say it’s deeply mysterious.
Ian: If you don’t think it’s mysterious, you haven’t understood the problem. Certainly, as a research mathematician – and I’ve been in the business for forty-odd years now – I’ve seen problem after problem being solved. The great problems – Fermat’s last theorem, the four colour theorem – have all been polished off. And my subject, far from shrinking, is getting bigger. As your territory gets bigger, the frontier gets longer. Yes?
Simon: Sure.
Ian: Of course, that’s not actually true on a sphere like the surface of the earth. If you push the frontiers far enough you go past the equator and everything starts to get smaller again. So, if the world of mathematical knowledge was finite, there would come a point at which you start saying, “We’re running out of ideas here.” But mathematics doesn’t seem to be like that. And the frontiers of the sciences are even bigger, of course, because they’re about the real universe in all its richness.
TOMORROW: the final part of Arc’s Judgement Day interview, in which Terry Pratchett, Ian Stewart and Jack Cohen explore magic, human folly, and science porn.
Read Jeff VanderMeer’s “Komodo” in Arc 1.2: Post human conditions, out now.
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