For science-fiction aficionados the collaboration of Sir Terry Pratchett and Stephen Baxter on a series of novels based on the multiverse is a dream come true.
Science fiction and real-earth technology seem to be fundamentally intertwined. For at least two centuries writers have speculated on what the world would be like if scientific advancements, seemingly beyond the reach of current technological thinking, came into being. From Frankenstein's monster to the space-pioneering novels of the mid-20th century, the best visions of the future, it seems, have been from the pens of writers capable of blending the creative imagination with a plausible understanding of where technology might lead us.
There are few sci-fi novelists of the status of either Sir Terry Pratchett or Stephen Baxter who set as much stock by the scientific credibility of their work. Both British, both are established leaders in their fields, with Sir Terry - who is best known for his 'Discworld' fantasy novel sequence - one of the highest-selling and best-loved UK authors of his generation.
Baxter's reputation as an exponent of the 'hard science' approach to fiction makes him one of the most respected authors in the sci-fi community. Baxter has separate degrees in engineering, mathematics and business administration, but having found that neither the life of an IT professional nor that of a maths and physics teacher suited him, he decided to follow his star and write. For the record Baxter has written 40 books, while Pratchett's 'Discworld' series alone accounts for the same number.
These two masters of the genre have joined forces on a parallel-world novel sequence known as 'Long Earth'. In July they visited the IET's London headquarters to launch the second installment, 'The Long War', which examines the state of affairs in the Long Earth multiverse a generation after the opening novel 'The Long Earth'.
The central idea the writers explore is the notion of a series of alternative 'Earths' similar to our Earth, where the closer the alternative reality is to the real Earth ('Datum Earth') the more similar it will be. One of the rules of the Long Earth, however, is that once you step out of Datum Earth, using a simple device called a 'stepper', you will no longer encounter humans. In fact, in the other worlds there never have been humans, allowing the authors to speculate on the counterfactual of what would have happened here if we had never happened.
This idea evolves into a familiar Pratchett motif of a world without shortages, where land and natural resources are abundant. By the time we get to the Long War, mankind has spread through the multiverse where the original inhabitants - elves and trolls - are becoming restless with human colonisation.
We caught up with the two authors at the launch of 'The Long War'.
E&T: There seems to be an interesting parallel between the alternative worlds you create, in which you are masters of your own physical laws, and such a famous institution as the IET being associated with so many of the great engineers from history...
Stephen Baxter: That's true. Of course you must remember that we launched the first book in the 'Long Earth' series at the Royal Institution, another great establishment. We're actually going around stealing the drinks coasters of the learned societies of London! But the series, including the new book - 'The Long War' - is about the scientific imagination. The idea of the multiverse is all over the place in science.
It seems to me that while physics is driven in one direction, relativity and quantum mechanics is driving in another direction. But ideas of the multiverse crop up all over the place. Our Long Earth is a multiverse, but it is a very domesticated one.
Sir Terry Pratchett: It's just Earth, really. It can be any kind of Earth that Earth can be. But you don't know what Earth you're going to get when you take the next step. It might be very similar to the step you've just taken. Or there might be volcanoes or an ice age, or nothing.
How important is it to ensure that you get the internal logic of the science, engineering and technology right in the alternative realities you create?
SB: I'd say it's very important, if only because the alternative is getting it wrong and readers will pick up on that. In the case of the Long Earth, although the geography is all invented, we've tried to keep it consistent. And so if World 1,000,005 is a certain way, it will stay that way.
TP: Also, you can't have dragons that fly. And that's because dragons can't fly on Earth. And so the things that can't happen are not allowed to happen.
Does that mean when you have dragons flying around in fantasy books such as 'The Hobbit' or the 'Narnia' chronicles, that's something that shouldn't be allowed?
TP: It's allowed in their world. I'm not going to have a fight with anyone on that. But what I'm interested in, and what I really like, is the idea that we ought to be able to exist on any Earth whatsoever. Mind you, if the volcanoes were erupting all the time, you might have a bit of a problem.
SB: I see the Long Earth as the tip of a huge probability tree. All the chance events that have led to the here and now, that could have gone slightly differently, go back to the origins of the Earth. And so the further back you go, the more extreme the physical differences will be.
But the unique thing about our Earth is that it's the only one with humans. There are humanoids elsewhere in the Long Earth, but we are the only planet with humans.
Being an author is traditionally regarded as a solitary occupation, but you have collaborated on this sequence. What's it like to write with someone else?
TP: You have to start at the beginning of everything, really. I don't know why, but quite a long time ago I had an idea, which ultimately was going to be the 'Long Earth' series. And it stayed with me quite a long time. I was only just into 'Discworld' at that point, and I suddenly had this series of ideas which turned out to be 'the voice in the shell', if you know what I mean. And it was going to be the Long Earth.
I realised that I didn't know enough to do it properly. And then I thought: "who do I know that's good at quantum stuff?" Within the science fiction world you meet people all the time at conventions. I knew Steve and we got talking about it, and, well, that was it.
SB: Where we really collaborate is on generating ideas. So you've got the seed from Terry's old material. Some of the characters are still there. But it was like the first chapter of a beginning.
TP: Ultimately 'The Long War' is our book. It's as simple as that.
How important are imagined technological inventions in science fiction generally?
TP: Well, you have to imagine them before'you can have them! I read lots of science fiction in my youth - and that is exactly the right time to do that - and it does'start you thinking about things. I'm happy I read all that science fiction. But to tell you the truth, and I think I talk for the pair of us on this, it's about imagining things.
SB: I see this as a virtuous circle. In order to go to the Moon you must have the fantasy of going to the Moon, just like the Greeks. That then feeds back into people who come later like Jules Verne, who imagined a huge cannon. That's vaguely plausible, I suppose, and that expressed itself in the 20th century with engineers coming up with rockets. But you have to have the vision of going to the Moon in the first place, which is where science fiction comes in. It's a feedback loop of the imagination.
Certainly the classic sci-fi authors such as HG Wells and Mary Shelley predicted scenarios that came true to a certain extent. What do you think there is in your writing that will come true?
TP: (laughs) I don't know how the world is going to change. I don't think we're living in the Long Earth world today.
In my mind, I wonder what would happen if the playing field for humanity was changed so that we could reach a point where you could have everything you ever wanted. What would happen if you just went to the Earth next door, where there is no shortage of anything? What do humans end up being like then?
At the moment we strive, and have wars. But what if there was suddenly no reason to be like that? Is there a devil inside us that means we're going to have a war sooner or later anyway, just because it's interesting?
And that devil is the advance in technology, as with the Manhattan Project?
TP: How much technology do you want? You can't really talk about 'good' because it's just technology. It can never be evil, but people possibly can be.
SB: It also depends on what you mean by technology. Let's go back to farming, for instance. That's been good because it's delivered a world of billions of people when it once was only millions. But it is also bad because many of those billions are condemned to a life of backbreaking toil in the fields to grow the food that will feed all these extra people.
TP: As a result we developed tractors so that our backs wouldn't break so easily...
SB: But then we get poisoned by the fumes...
TP: But this applies to anything, which is other than just sitting at your desk writing!
Does this mean that the Long Earth, devoid of humans, is a form of utopianism?
SB: That's right. One of the dreams that the Long Earth allows us to imagine is a post-scarcity world, a world where you don't have to work too hard to stay alive. And that is one thing that technology could conceivably deliver. It does so in Iain M Banks' books and in the 'Star Trek' universe. And so everybody is assured of the basic means of life. Now you might wonder if that is a utopia or a dystopia? Will we start doing things that are meaningful, or will we all become couch potatoes?
TP: We already are... that's the trouble.
With the Long Earth multiverse, is it the case that when you speculate about alternative realities you're doing so to cast light upon our own reality?
TP: Yes. Science fiction does that and to some extent the fantasy genre does it too. Ask yourself how often rockets were going to the Moon in science fiction way before we ever did in reality.
SB: In the Long Earth the worlds next door are how this Earth would be without humans. The only difference is humans - not even prehistoric humans. And so England is covered with forest and the mega fauna is still around. This gives you a very vivid sense of how much we have done to our planet.
Was this the specific counterfactual you had in mind when you started, or did it develop as you went along?
TP: You're pulled through it really, because'once you've decided that something can happen then that in turn leads to the idea that something else can follow. And you follow that path. It's a strange way of doing things.
The first thing that struck me was that from now on everyone is going to be richer than any king that has ever been. But gold isn't worth anything except that it is very, very shiny and you can do things with it. Throughout the life of mankind, up to now, everything has been scarce, simply because that is the nature of things. In the Long Earth there is no scarcity whatsoever. And what does humanity do about that?
SB: And so the question is what do we do all day when there is no need to scrabble to survive?
TP: We imagined at one point the hunter-gatherers, who more or less stay in the same place - possibly where a certain apple tree is - going from Earth to Earth...
It was the science fiction author from a generation ago, Robert Heinlein, who described the genre as being 'realistic speculation about future events'. Does that seem a reasonable description of your new book?
SB: It can be that way, but it doesn't have to be. And I think that our new book is a case in point. And that's because I don't think that we can say that we're expecting to discover the Long Earth tomorrow. But it is a resonant metaphor for some of the conditions that we can expect to happen.
It draws on what we know about the multiverse and so on. But I don't think we can predict that it will happen this way. Science fiction is like a distorting mirror.
TP: But you also have to remember that science fiction is like one of those things you peddle without actually going anywhere. Just to keep your hand in. You know what I mean. An exercise bike or a treadmill at the gym. It's never going to take you anywhere, but it can certainly beef up the muscles that might do that sooner or later.
The second installment of the Long Earth series - 'The Long War' by Terry Pratchett and Stephen Baxter - is out now, published by Doubleday, £18.99.