Darwin's Watch

by Terry Pratchett

  What does it mean, then, to ask whether time knits up any changes, or whether mischievous butterflies are ultimately responsible for the fall of empires?

  Here fictional conventions cease to fit the real world. From the point of view of the wizards, Roundworld time is a one-dimensional sequence that they can access two-dimensionally like a book. For narrative reasons, we have to depict it like this because of all those thin-thread-of-causality historical stories that our minds find so congenial. In a fictional context, we have little choice. However, here we want to think about the nature of causality and free will in the `real' universe, which - as we've made clear throughout the Science of Discworld series - does not have any narrativium. In that context, we have to understand that this simple image of Roundworld history is a fraud. The Trousers of Time also work well as a story, but as genuine physics they are a fraud: you can't be pushed from one leg to the other by an event. Worse, you can't tell that there has been such an event. As far as you are concerned, this is the world. It doesn't have `ifs' in its past.

  None of this stops us using `what ifs' (which by nature are fictions, not facts) to think about history. We can still ask, in our minds, what would have happened if, say, Lincoln had survived ... but in the real world he didn't, and we can't run a mock-up of `if he did' in the real world: only in our heads.

  Science runs into precisely this difficulty. For instance, the main problem in testing medical treatments is that we can't both give Mrs Jones the treatment and not give Mrs Jones the treatment, simultaneously, and compare the results. We can do it sequentially, but then the second treatment (whether it is placebo or real treatment) is of a different Mrs Jones, one who's had the first treatment. So what the testers do is to have quite a large panel, do treatment first on some, placebo first on others - and they should perhaps do two placebos on a few, and two treatments on a few others.

  What time-travel stories do, in our minds, is the same kind of test: `What would happen if Leonardo had really seen a submarine working?' or equivalently `Did Leonardo see a submarine working?' In The Science of Discworld, and more explicitly in The Science of Discworld II, we asked whether the interesting stories that we make up have some kind of coherent explanation, something like `evil' - which we personified in the second book as Elves. To what extent do such concepts relate to the real rules of the real world? Now we argue that we cannot know if any answer we get is useful; we can't even know whether we've got an answer at all. And that this is precisely why Dennett's kind of free will is the only one worth having. It's prospective, giving each of us the chance to make little items of an otherwise inevitable future evitable.

  When we look back on something we've changed by that kind of an act of free will, it's just as causal as everything else - and if the universe is in any sense determinate, then it is determinate in that sense. Think of Odysseus looking back at what happened as his ship failed to be caught by the Sirens. His men didn't hear them, and he, who could hear them, couldn't act to steer the ship. So he and his crew came through in that most unlikely of passages. There is a sense, of course, in which every sea passage is equally unique, just as every deal of cards is unique; but Odysseus's journey, like a onesuit-per-player deal of cards, is totally remarkable too. Looking back into history, can we find journeys, events, and processes so remarkable that they seem to be the results of previous acts of free will?

  What, then, is causality? For Damasio-like reasons, we tend to think that what gives history its dynamic is the big events, the `pivot points'. The fallacy is that we think big causes are needed to produce big effects. This is false (butterfly) but there is a problem: choosing the right tiny change (which butterfly?). And there are always billions of new butterflies, dragging new changes out from previously invisible differences `in the 13th decimal place', unobservable until their effects show up.

  Real history is like this; causes are often distributed, with huge numbers of tiny events all coming together. It is just this problem that leads Ridcully to employ such a huge number of wizards, doing such a bizarre set of trivial things, merely to get The Origin written.

  We only justify this sort of causality in retrospect: history didn't know `where it was going'. So changing the past creates a context for the future, not a causal chain, and this is how the wizards must operate, which is why we have thousands of them making endless trivial changes to Victorian history, instead of, say, assassinating Queen Victoria. Any Victorian, perhaps particularly the well-trained nursemaid, will tell you just that about your personal history: your heart must be pure (context) rather than your plans being subtle.

  SEVENTEEN

  GALAPAGOS ENCOUNTER

  CHARLES DARWIN WAS SITTING ON a grassy bank. Three types of bee buzzed among the flowers, and overhead examples of Hirundo rustica swooped after miscellaneous Ephemeroptera.

  His thoughts were complex, as human thoughts tend to be when the mind is idling, but included: this is an interesting bank of astonishing complexity; there might be fish for lunch; he had a sore throat; he hoped never to receive another letter about barnacles; the rash seemed to be getting worse; there was a strange buzzing sound; had he really experienced that apparition?; homeopathy transcended all common sense; he really should find out where the ovaria were situated in Phyllosoma; it really was a very loud buzzing ...

  Something like a yellow-brown smoke was issuing from a hole in the bank a few yards away, and resolved itself into a cloud of angry Vespula vulgaris. It bore down on the horrified Darwin -

  'Over here, waspies!'

  Darwin stared.

  This mission had created a difficult decision for Rincewind, when he'd been presented with the task of preventing Charles Darwin being stung to death by wasps. Right from the start it was obvious that Darwin would see, him, and if Rincewind was invisible the wasps wouldn't see him. He'd therefore undertaken the mission carrying

  two buckets of warm jam and wearing a pink tutu, an acid-green wig and a red nose, reasoning that (a) Darwin wouldn't believe that he had seen him and in any case (b) wouldn't dare tell anyone ...

  Darwin watched the apparition skip away over the fields. It was quite astonishing. He'd never seen wasps swarm in such a manner.

  A piece of paper fluttered to the ground. The curious clown must have dropped it.

  Darwin picked it up and read, aloud, "`Return me, Hex". What does-?'

  The afternoon dozed on. The grassy bank went back to its buzzing, humming, flowering busyness.

  On the forlorn shore, a man appeared, hid two buckets behind a rock, and removed his false nose.

  Rincewind scanned the landscape while extracting his hat from inside his shirt.

  This was one of the most famous islands in the history of technomancy? It looked, frankly, rather dull.

  He'd been expecting forests and streams and a riot of creatures. You couldn't move for vibrant, striving life on Mono Island, home of the God of Evolution. Everything wanted to leave. But this place had a skinflint look. You'd need to be tough to survive here. You'd have to fit in.

  He couldn't see any giant tortoises, but there were a couple of large, empty shells.

  Rincewind picked up a length of driftwood, baked by the sun into something like stone, and hurried up a narrow path.

  Hex was good. The man Rincewind was after was striding ahead of him along the track.

  `Mr Lawson, sir!'

  The man turned.

  `Yes? Are you from the Beagle?'

  `Yessir. Heave ho, sir,' said Rincewind. Lawson stared at him. `Why do you wear that hat with "Wizzard" written on it?' Rincewind thought fast. Thank goodness Roundworld had some

  strange customs.

  `Crossing the Line ceremony, sir,' he said. `Took a fancy to it!' `Oh, King Neptune and so forth,' said Lawson, backing away a little. Jolly good. How can I help you?'

  'Just wanted to shake you by the hand and say how glad we all are that you're doing such a wonderful job out here, sir,' said Rincewind, pumping the man's unresis
ting arm vigorously. `We ... that's is very kind of you, Mr - what was that noise?' `Sorry? Shiver my timber, by the way.'

  `That ... whistling noise ... ' said Lawson, uncertainly.

  `Probably one of the tortoises?' said Rincewind, helpfully.

  `They hiss or - wasn't that a thump?' said Lawson. Behind him, a small cloud of dust rose above the bushes.

  `Didn't hear one, yo ho,' said Rincewind, still shaking the hand. `Well, don't let me keep you, sir.'

  Lawson gave him the look of a man who feels has inadvertently fallen into dribbling company. The hat was clearly preying on his mind.

  `Thank you, my man,' he said, pulling his hand away. `Indeed, I must go.'

  He headed away at some speed, which increased when he noticed Rincewind following him, and completely failed to notice what was, after all, just another small, rubble-filled hole among many. Rincewind spotted it, though, and after some effort pulled out a small, warm lump.

  Something hissed, behind him.

  Rincewind had ascertained that the only way a giant tortoise could go as fast as him was by falling over a cliff, and also that they were highly unlikely to savage a man to death. Still, he was ready.

  He turned, stick upraised.

  Something, a greyish something, something just transparent enough to show the landscape behind it in a dreary light, was hovering a few feet away. It looked like a monk's robe for a very small monk, and minus the monk. The empty hood was more worrying than almost anything that could have filled it. There were no eyes, there was no face, but there was nevertheless a stare, as malignant as razorblade pants.

  Other robe-shadows appeared around the shape and began drifting towards it. When they reached it they vanished, and the central shape became darker and, somehow, more present.

  Rincewind didn't turn and run. There was no point in trying to run from Auditors; they were certainly faster than anything with legs. But that wasn't the reason. If it was time to run, he'd considered, no other calculations applied. He wouldn't even worry that his escape route was blocked by solid lava; most things could be overcome if you ran at them hard enough. There was, however, another reason. It had pink toes.

  `Why meddle?' said the Auditor. The voice sounded windy and uncertain, as if the speaker was having to assemble the words by hand. `Entropy will always triumph.'

  `Is it true that you die if you have an emotion?' said Rincewind. The Auditor was quite dark now, which meant that it has assembled enough mass to move something quite heavy, like a human head.

  `We do not have emotion,' said the Auditor. `It is a human aberration. In you we detect the physical manifestation recognisable to us as fear.'

  `You can't just kill people, you know,' said Rincewind. `That's against the rules.'

  `We believe there may be no rules here,' said the Auditor, moving forward.

  `Wait, wait, wait!' said Rincewind, trying to back away into solid rock. `You're saying you don't know what fear is, right?'

  `We have no requirement to do so,' said the Auditor. `Prepare to cease coherent function.'

  `Turn around,' said Rincewind.

  And a weakness of the Auditors is that they find a direct command hard to disobey, at least for a second or two. It turned, or, rather, flowed through itself to face the other way.

  The lid of the Luggage closed with a `clop' like the sound of a trout taking an unwary mayfly.

  I wonder if it found out what fear really is, Rincewind thought. But more grey shapes were distilling out of the air. Now it was time to run.

  EIGHTEEN

  STEAM ENGINE TIME

  THERE WAS DARWIN, SITTING ON a bank, watching the

  bees, the wasps, the flowers ... In the last paragraph of The Origin we find a beautiful and important passage that hints at afternoons of that kind:

  It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.

  Go ahead Paley, make my day.

  All that wizardly effort to get him to write The Origin, not The Ology. It mattered to Darwin, of course, and it matters to those who chart the course of history. But, just as we can ask whether Lincoln's assassination really had much effect on subsequent events, so we can ask the same about Darwin's life's work. Would it really have mattered if the wizards had failed?

  Metaphorical wizards, you appreciate. Yes, those happy coincidences that got Charles on board the Beagle and kept him there do look a tad suspicious, but wizards?

  Let's ask the question in a more respectable way. How radical was Darwin's theory of natural selection, really? Did he have insights that no one before him had considered? Or did he just happen to be the person who caught the public eye, with an idea that had been floating around for some time? How much credit should he be given?

  The same can be - and has been - asked of many `revolutionary' scientific concepts. Robert Hooke got the idea of inverse square-law gravity before Newton did. Minkowski, Poincare, and others worked out much of special relativity before Einstein did. Fractals were around, in some form, for at least a century before Benoit Mandelbrot energetically promoted them and they developed into a major branch of applied mathematics. The earliest sniff of chaos theory can be found in Poincare's prize-winning memoir on the stability of the solar system in 1890, probably 75 years before the subject was perceived as `taking off.

  How do scientific revolutions get started, and what decides who gets the credit? Is it talent? A flair for publicity? A lottery?

  Part of the answer to these questions can be found in Robert Thurston's 1878 study of another important Victorian innovation, which Ponder Stibbons unerringly homed in on in Chapter 3. The book is A History of the Growth of the Steam Engine. The second paragraph says:

  History illustrates the very important truth: inventions are never, as great discoveries are seldom, the work of any one mind. Every great invention is really either an aggregation of minor inventions, or the final step in a progression. It is not a creation, but a growth as truly so as is that of the trees in the forest. The same invention is frequently brought out in several countries, and by several individuals, simultaneously.

  Thurston's topic reminds us of a common metaphor for this kind of apparently simultaneous invention: steam engine time. When it's steam engine time, suddenly everyone is making steam engines. When it's evolution time, everyone is inventing a theory of evolution. When it's VCR time, everyone is making video cassette

  recorders. When it's Dotcom time, everyone is setting up Internet trading systems. And when it's Dotcom-going-bust time, all the Dotcoms are going bust.

  There are times when human affairs really do seem to run on preconstructed tracks. Some development becomes inevitable, and suddenly it's everywhere. Yet, just before that propitious moment, it wasn't inevitable at all, otherwise it would have happened already. `Steam engine time' is a convenient metaphor for this curious process. The invention of the steam engine wasn't the first example, and it certainly wasn't the last, but it is one of the best known, and it's quite well documented.

  Thurston distinguishes invention from discovery. He says that inventions are never the creation of a single individual, whereas great discoveries seldom are. However, the distinction isn't always clearcut. Did ancient humans discover fire as a phenomenon of nature, or did they invent fire as a technology to keep predators away, light the cave, and cook food? The natural phenomenon surely came first, in the form of brush- or forest fires triggered by lightning, or possibly a droplet of water accidentally acting as a lens to concentrate the Sun's rays on to a piece of dry grass.[1]

  However, that kind of `discovery' doesn't go anywhere until someone finds a use for it. It was the idea of controlling fire that made the difference, and th
at seems more of an invention than a discovery. Except ... you find out how to control fire by discovering that fires don't spread (so easily) across bare soil, that they can be spread very easily indeed by picking up a burning stick and dropping it into dry brushwood, or taking it home to the cave ...

  The inventive step, if there is such a thing, consists of putting together several independent discoveries so that what emerges has genuine novelty.

  Dry grass and drops of water are not commonly associated, but perhaps a damp elephant had just emerged from a river crossing on to dry savannah ... Oh, invent your own explanation.

  So inventions are often preceded by a series of discoveries. Similarly, discoveries are often preceded by inventions. The discovery of sunspots rested on the invention of the telescope, the discovery of amoebas and parameciums in pond water rested on the invention of the microscope. In short, invention and discovery are intimately entwined, and it's probably pointless to try to separate them. Moreover, the significant instances of both are much easier to spot in retrospect than they were at the time they first happened. Hindsight is a wondrous thing, but it does have the virtue of providing an explicit context for working out what did, or did not, matter. Hindsight lets us organise the remarkably messy process of invention/discovery, and tell convincing stories about it.

  The problem is, most of those stories aren't true.

  As children, many of us learned how the steam engine was invented. The young James Watt, aged about six, was watching a kettle boil, and he noticed that the pressure of the steam could lift the lid. In a classic `eureka' moment, it dawned on him that a really big kettle could lift really heavy bits of metal, and the steam engine was born.

  The original teller of this story was the French mathematician Francois Arago, author of one of the first biographies of Watt. For all we know, the story may be true, though it is more likely a `lie-tochildren', or educational aid,* like Newton's apple. Even if the young Watt was indeed suddenly inspired by a boiling kettle, he was by no means the first person to make the connection between steam and motive power. He wasn't even the first person to build a working steam engine. His claim to fame rests on something more complex, yet more significant. In Watt's hands, the steam engine became an effective and reliable tool. He didn't `perfect' it - many smaller improvements were made after Watt - but he brought it into pretty much its final form.