The Science of Discworld IV: Judgement Day

Terry Pratchett, Ian Stewart and Jack Cohen

Ebury Press, £18.99

Judgement Day is the fourth in a series of popular science books written by Terry Pratchett, Ian Stewart and Jack Cohen. The Science of Discworld books are about as far as it is possible to get from The Science of Star Trek because The Science of Star Trek is, according to one of the writers, “absolutely fucking useless. So we got talking about how to make this kind of format work properly, and do some work while being entertaining and appealing to fans.”

The architecture of the first book has stuck for the series: – an original Discworld story is interleaved with chapters exploring the scientific issues it throws up. Jack Cohen: “The first Science of Discworld is very much about hands-on science; we thought it would be the only one, so we threw everything we could into it. Then, when we saw we had a series on our hands, we calmed down and concentrated on the topics that interested us at the time. Number two is about anthropology, mostly, and number three picked up on the Darwin centenary.”

When Arc’s editor Simon Ings met the authors, he began by asking them about this book – that is, The Science of Discworld III: Darwin’s Watch; the one that came out eight years ago, in 2005; the one before Judgement Day, the book they were all supposed to be talking about. In this way, he endeared himself forever to the trio’s long-suffering publicist Sally Wray, to whom we extend our grateful thanks.

Simon: Jack, you can start us off, since we’re talking about Darwin. For the tape: Jack Cohen is a reproductive biologist whose theory of sperm redundancy has been important in the treatment of infertility. He’s also responsible for some of television’s more plausible aliens. Gerald Durrell once said Jack had had contact with more creatures than anyone he’d ever known–

Jack: And that was a long time ago. Do you know, mantis shrimps have seven different visual pigments?

Simon: They have proper colour vision, don’t they?

Jack: I love mantis shrimps. I’ve had three. The last one learned to lift up scrabble letters when it wanted food. I wanted to see if it would lift up different scrabble letters for different foods, but it died.

Simon: I see.

Jack: But you should ask Terry about Darwin.

(Sir Terry Pratchett has sold over 70 million books worldwide in 37 languages. Now and again he makes people laugh, usually with tales set in his invented universe, Discworld, a flat disc balanced on the backs of four elephants standing on the back of a giant turtle.)

Terry: When I was in my early teens, one of our science teachers loaned me The Origin of Species and I went down with the flu. So I read Charles Darwin with the world spinning round and about – I was hallucinating, you see. To modern eyes the book’s a hard read, but I went through it like a bulldozer because I was tripping.

Simon: A while ago I read Simon Conway Morris’ book on – what is it, confluence evolution… congruent… Oh, God. If you live in the sea, you look like a fish…

Ian: Convergent evolution. Why do dolphins and sharks look the same when one’s a fish and one’s a mammal?

(Ian Stewart is a professor of mathematics at the University of Warwick, and the author of many popular books on mathematics, science and epistemology. In 1995 Stewart received the Michael Faraday Medal and in 1997 he gave the Royal Institution Christmas Lecture on “The Magical Maze”. He was elected as a Fellow of the Royal Society in 2001.)

Simon: Yes. And Conway-Morris ends that book with an image of Earth being the only place where there is intelligent life. And suddenly we’re in some sort of polite English drawing-room of a world, unable to imagine any other way of being, and I am sitting there thinking: I’ve been played. I’m not clever enough to know how I’ve been played, but I’ve definitely been played. In Judgement Day, though, you three take the anthropic priniciple apart. You show that this idea – that we’re balanced on a cosmological knife-edge – is actually not true.

Ian: Well, there’s a whole lot of difficult and different issues here, but they boil down to the distinction we make in Judgement Day about the difference between human-centered thinking and universe-centered thinking. Human-centered thinking says, we’re the most important thing around and everything that’s worth knowing about is there for us. What we have to work out is, what we can do with it?

Terry: It’s the kind of thinking the wizards of Discworld enjoy. The wizards are smart on the whole, but they have a rather direct view of things, because their worldview includes magic. If they want something to happen, they can make it happen.

Ian: And that’s also the kind of thinking a child enjoys, when it says the rain comes down so the crops can grow. Universe-centered thinking says, “No, no, rain’s been around for eons, crops are a human invention that only goes back 10,000 years. Rain’s not there for the benefit of the crops.”

Terry: The thing is, human-centered thinking is natural, it’s intuitive. The people of Discworld don’t regard Discworld as magical. They don’t go around saying, “Isn’t this amazing? We’re on the back of a turtle!” They know there’s a turtle, but they don’t bother about it much. In that, they’re like most of us here in Roundworld. We don’t actually interrogate what’s going on all the time. Why would we? Why should we?

Ian: Right: you have to actually work to acquire in this other, more imaginative, universe-centered way of thinking. Is life on Earth the only possible kind? Are we living in the only possible universe? Is this universe extraordinarily finely tuned so that life can exist? You get radically different answers depending on which mode of thinking you apply. It’s not about evidence, or scholarship, or rigour. Simon Conway Morris is a fantastic scientist and writer. But the way he thinks means that everything in the world converges on the same solution. The idea that that there may be different problems doesn’t interest him. If you watch the evolution of life on a planet that is very similar to Earth, I would not be at all surprised to find that you would get living things that look Earth-like. If you have oceans, you’ll have things like fish. Then Conway-Morris points out, correctly, that the chances of there being another markedly Earth-like world out there are vanishingly small – and draws what to me is a really strange conclusion: that complex, thought-bearing life is therefore probably unique to Earth. Really? Why?

Jack: Ian and I are science fiction fans. We’d love it if the aliens were out there, taking very bizarre forms, the sort created in good, properly worked-out science-fiction stories. So we’re a bit prejudiced. But it seems to me that the most interesting possibilities for alien life are the ones that are not very similar to us. How radically strange can life be? Are there wildly different kinds of life out there? That’s an important question, because if the answer’s yes, suddenly the range of possibilities and the number of alien civilisations that might be out there becomes much greater.

Ian: If you look at this planet, we haven’t all converged onto one creature. We’ve converged onto an enormous range of different creatures suited to particular habitats. There are precious few habitats where there isn’t something living. Even under the ice in the Antarctic, even deep in the earth, there are bacteria. That, I feel, is sending us a message.

Simon: Terry, your Discworld books convey their learning lightly, but, beyond the jokes, they also convey an essentially comic view of the universe.

Terry: Of course. The world is an amusing place. Shakespeare wrote tragedies and he wrote comedies, and both give insights into the human condition. But while the tragedies make you sit there thinking, Oh my God, how dreadful all this is, the comedies make you think, Well, we are a ridiculous creature, aren’t we? Look at the mess we get ourselves into! Wouldn’t it be sensible to try and avoid some of this?

Simon: But the books in The Science of Discworld series do a pretty comprehensive job of convincing us that the mess is unavoidable, the the world is bloody unreasonable on just about every scale, and from end to beginning. Assuming it has one. In Judgement Day, you have some fun pulling apart the Big Bang.

Terry: People tend to assume that the Big Bang is established science, that it’s proved, and this is how science works. But it’s much more interesting than that. To talk blithely of the Big Bang is rather like talking blithely about the world sitting on turtles.

Ian: Because we’re not cosmologists, we tend to sit back and look at things like the Big Bang with a certain ironical distance. This is the current favourite theory. There’s a lot of evidence that seems to fit it. You can’t dismiss it. You certainly can’t dismiss it because it seems crazy, because it’s no more crazy than anything else. But there is a growing belief among cosmologists that as they understand the theory of the Big Bang better and ask more subtle questions about it, parts of the idea don’t make as much sense as they used to.

Terry: It wouldn’t surprise me if, twenty years from now, everyone is saying, “Oh, they used to believe in the Big Bang. How foolish.”

Ian: The thing is, the deeper we go in uncovering the laws of nature, the further removed they seem from anything human. The things we see when we look out of the window make sense to us, but science doesn’t really understand how those things link back to the really deep, underlying laws. I look out of the window at the moment and it’s raining. And I know what rain is. It’s water condensing from clouds, and so forth. But if I go further, until I hit the quantum mechanics of the water molecule, I’ll discover that there’s no really good theoretical link between the water molecule and the fundamental equations of quantum mechanics. According to them, there’s no such thing as the water molecule, just this incredibly complicated seething mass of hydrogen and oxygen atoms that keep linking together in very strange ways. The more scientists look at water, the less they understand it.

Terry: This is the joke that runs throughout the entire Science of Discworld series, of course: Discworld actually makes far more sense than our world. Things happen because people want them to and the world’s flat so you don’t fall off. What could be more reasonable than that?

Simon: The virtual unknowability of the real world feeds your comedy. I think for a lot of people it’s a source of despair.

Terry: Despair? Really?

Simon: Well, our model of the physical world is certainly more accurate than the one the ancient Greeks had. But it seems to me that getting progressively more decentered hasn’t done much for our morale. In fact our moral and ethical thinking has hardly progressed at all.

Terry: Ah, I see. Well the problem is, we know more and more, but we can only ever engage fully with a tiny fraction of what we know. We know things, but we don’t take them on board. Right now, for example. we know we’re using up the resources of the planet, but we don’t really do very much about it. And sometimes, when I mention this, people say, “Well, science will find a way.” And I have to say, “Look, there’s only so much stuff around here. So unless you know where there’s a good rocket and a nice planet to go to, I don’t see how we can ever get any more of it.” The moment’s not very far off when we’ll be fighting for resources and using up those resources in fighting for them. This is hardly science fiction. Science fiction is the chap who came up to me saying, “Well, we’ll probably find all the stuff we need in Antarctica.” Once we start messing about with that place – once that seems like a good, sensible idea – I think we’re done.

Simon: There’s a lot of stuff on Mars that’s useful.

Terry: I don’t actually think we’ve enough money or time to go and do anything about it. What would you say?

Simon: I’m wondering in that case whether you think intelligence really has much of chance. Maybe it uses resources too fast to actually sustain itself. The stars are remarkably quiet.

Terry: Well, that’s a way of looking at it and it may be true.

Simon: So are you optimistic or…?

Terry: This is one of those situations where optimistic or pessimistic doesn’t really matter. Something’s going to happen, one way or the other, and we know it’s out of our hands.

TOMORROW: Part 2 of Arc’s Judgement Day interview, in which we explore The Science of Discworld and throw a piano off a hotel roof.