Science of Discworld III

by Terry Pratchett

  It was about a foot across, at least on the outside. Inside, it was infinite; most wizards have no problem with facts of this sort. It contained everything there was, for a given value of ‘contained everything there was’, but in its default state it focused on one tiny part of everything there was, a small planet which was, currently, covered in ice.

  Ponder Stibbons swivelled the omniscope that was attached to the base of the glass dome, and stared down at the little frozen world. ‘Just debris at the equator,’ he reported. ‘They never built the big skyhook thing that allowed them to leave.2 There must have been something we missed.’

  ‘No, we sorted it all out,’ said Ridcully. ‘Remember? All the people did get away before the planet froze.’

  ‘Yes, Archchancellor,’ said Stibbons. ‘And, then again, no.’

  ‘If I ask you to explain that, would you tell me in words I can understand?’ said Ridcully.

  Ponder stared at the wall for a moment. His lips moved as he tried out sentences. ‘Yes,’ he said at last. ‘We changed the history of the world, sending it towards a future where the people could escape before it froze. It appears that something has happened to change it back since then.’

  ‘Again? Elves did it last time!’3

  ‘I doubt if they’ve tried again, sir.’

  ‘But we know the people left before the ice,’ said the Lecturer in Recent Runes. He looked from face to face, and added uncertainly, ‘Don’t we?’

  ‘We thought we knew before,’ said the Dean, gloomily.

  ‘In a way, sir,’ said Ponder. ‘But the Roundworld universe is somewhat … soft and mutable. Even though we can see a future happen, the past can change so that from the point of view of Roundworlders it doesn’t. It’s like … taking out the last page of a book and putting a new one in. You can still read the old page, but from the point of view of the characters, the ending has changed, or … possibly not.’

  Ridcully slapped him on the back. ‘Well done, Mr Stibbons! You didn’t mention quantum even once!’ he said.

  ‘Nevertheless, I suspect it may be involved,’ sighed Ponder.

  1 The N’tuitiv tribe of Howondaland created the post of Health and Safety Officer even before the post of Witch Doctor, and certainly before taming fire or inventing the spear. They hunt by waiting for animals to drop dead, and eat them raw.

  2 See The Science of Discworld (Ebury Press, 1999, revd 2000).

  3 See The Science of Discworld II (Ebury Press, 2002).

  TWO

  PALEY’S WATCH

  THE SCENE: A RADIO CHAT-SHOW in the Bible Belt of the United States, a few years ago. The host is running a phone-in about evolution, a concept that is anathema to every God-fearing southern fundamentalist. The conversation runs something like this:

  Such a conversation did occur, and the host was not being ironic. But Jerry’s point is not quite the knock-down argument he thought it was. Charles Robert Darwin died in 1882. The first Nobel Prize was awarded in 1901.

  Of course, well-meaning people are often ignorant about fine points of historical detail, and it is unfair to hold that against them. But it is perfectly fair to hold something else against them: the host and his guest didn’t have their brains in gear. After all, why were they having that discussion? Because, as every God-fearing southern fundamentalist knows, virtually every scientist views Darwin as one of the all-time greats. It was this assertion, in fact, that Jerry was attempting to shoot down. Now, it should be pretty obvious that winners of Nobel prizes (for science) are selected by a process that relies heavily on advice from scientists. And those, we already know, are overwhelmingly of the opinion that Darwin was somewhere near the top of the scientific tree. So if Darwin didn’t get a Nobel, it couldn’t have been (as listeners were intended to infer) because the committee didn’t think much of his work. There had to be another reason. As it happens, the main reason was that Darwin was dead.

  As this story shows, evolution is still a hot issue in the Bible Belt, where it is sometimes known as ‘evilution’ and generally viewed as the work of the Devil. More sophisticated religious believers – especially European ones, among them the Pope – worked out long ago that evolution poses no threat to religion: it is simply how God gets things done, in this case, the manufacture of living creatures. But the Bible-Belters, in their unsophisticated fundamentalist manner, recognise a threat, and they’re right. The sophisticated reconciliation of evolution with God is a wishy-washy compromise, a cop-out. Why? Because evolution knocks an enormous hole in what otherwise might be the best argument yet devised for convincing people of the existence of God, and that is the ‘argument from design’.1

  The universe is awesome in its size, astonishing in its intricacy. Every part of it fits neatly with every other part. Consider an ant, an anteater, an antirrhinum. Each is perfectly suited to its role (or ‘purpose’). The ant exists to be eaten by anteaters, the anteater exists to eat ants, and the antirrhinum … well, bees like it, and that’s a good thing. Each organism shows clear evidence of ‘design’, as if it had been made specifically to carry out some purpose. Ants are just the right size for anteaters’ tongues to lick up, anteaters have long tongues to get into ants’ nests. Antirrhinums are exactly the shape to be pollinated by visiting bees. And if we observe design, then surely a designer can’t be far away.

  Many people find this argument compelling, especially when it is developed at length and in detail, and ‘designer’ is given a capital ‘D’. But Darwin’s ‘dangerous idea’, as Daniel Dennett characterised it in his book with that title, puts a very big spoke into the wheel of cosmic design. It provides an alternative, very plausible, and apparently simple process, in which there is no role for design and no need for a designer. Darwin called that process ‘natural selection’; nowadays we call it ‘evolution’.

  There are many aspects of evolution that scientists don’t yet understand. The details behind Darwin’s theory are still up for grabs, and every year brings new shifts of opinion as scientists try to improve their understanding. Bible-Belters understand even less about evolution, and they typically distort it into a caricature: ‘blind chance’. They have no interest whatsoever in improving their understanding. But they do understand, far better than effete Europeans, that the theory of evolution constitutes a very dangerous attack on the psychology of religious belief. Not on its substance (because anything that science discovers can be attributed to the Deity and viewed as His mechanism for bringing the associated events about) but on its attitude. Once God is removed from the day-to-day running of the planet, and installed somewhere behind DNA biochemistry and the Second Law of Thermodynamics, it is no longer so obvious that He must be fundamental to people’s daily lives. In particular, there is no special reason to believe that He affects those lives in any way, or would wish to, so the fundamentalist preachers could well be out of a job. Which is how Darwin’s lack of a Nobel can become a debating point on American local radio. It is also the general line along which Darwin’s own thinking evolved – he began his adult life as a theology student and ended it as a somewhat tormented agnostic.

  *

  Seen from outside, and even more so from within, the process of scientific research is disorderly and confusing. It is tempting to deduce that scientists themselves are disorderly and confused. In a way, they are – that’s what research involves. If you knew what you. were doing it wouldn’t be research. But that’s just an apology, and there are better reasons for expecting, indeed, for valuing, that kind of confusion. The best reason is that it’s an extremely effective way of understanding the world, and having a fair degree of confidence in that understanding.

  In her book Defending Science – Reason the philosopher Susan Haack illuminates the messiness of science with a simple metaphor, the crossword puzzle. Enthusiasts know that solving a crossword puzzle is a messy business. You don’t solve the clues in numerical order and write them in their proper place, converging in an orderly manner to a correct solution, u
nless, perhaps, it’s a quick crossword and you’re an expert. Instead, you attack the clues rather randomly, guided only by a vague feeling of which ones look easiest to solve (some people find anagrams easy, others hate them). You cross-check proposed answers against others, to make sure everything fits. You detect mistakes, rub them out, write in corrections.

  It may not sound like a rational process, but the end result is entirely rational, and the checks and balances – do the answers fit the clues, do the letters all fit together? – are stringent. A few mistakes may still survive, where alternative words fit both the clue and the words that intersect them, but such errors are rare (and arguably aren’t really errors, just ambiguity on the part of the compiler).

  The process of scientific research, says Haack, is rather like solving a crossword puzzle. Solutions to nature’s riddles arrive erratically and piecemeal. When they are cross-checked against other solutions to other riddles, sometimes the answers don’t fit, and then something has to be changed. Theories that were once thought to be correct turn out to be nonsense and are thrown out. A few years ago, the best explanation of the origin of stars had one small flaw: it implied that the stars were older than the universe that contained them. At any given time, some of science’s answers appear to be very solid, some less so, some are dubious … and some are missing entirely.

  Again, it doesn’t sound like a rational process, but it leads to a rational result. Indeed, all that cross-checking, backtracking, and revision increases our confidence in the result. Remembering, always, that nothing is proved to the hilt, nothing is final.

  Critics often use this confused and confusing process of discovery as a reason to discredit science. Those stupid scientists can’t even agree among themselves, they keep changing their minds, everything they say is provisional – why should anyone else believe such a muddle? They thereby misrepresent one of science’s greatest strengths by portraying it as a weakness. A rational thinker must always be prepared to change his or her mind if the evidence requires it. In science, there is no place for dogma. Of course, many individual scientists fall short of this ideal; they are only human. Entire schools of scientific thought can get trapped in an intellectual blind alley and go into denial. On the whole, though, the errors are eventually exposed – by other scientists.

  Science is not the only area of human thought to develop in this flexible way. The humanities do similar things, in their own manner. But science imposes this kind of discipline upon itself more strongly, more systematically, and more effectively, than virtually any other style of thinking. And it uses experiments as a reality check.

  Religions, cults, and pseudoscientific movements do not behave like that. It is extremely rare for religious leaders to change their minds about anything that is already in their Holy Book. If your beliefs are held to be revealed truth, direct from the mouth of God, it’s tricky to admit to errors. All the more credit to the Catholics, then, for admitting that in Galileo’s day they got it wrong about the Earth being the centre of the universe, and until recently they got it wrong about evolution.

  Religions, cults and pseudoscientific movements have a different agenda from science. Science, at its best, keeps lines of enquiry open. It is always seeking new ways to test old theories, even when they seem well established. It doesn’t just look at the geology of the Grand Canyon and settle on the belief that the Earth is hundreds of millions of years old, or older. It cross-checks by taking new discoveries into account. After radioactivity was discovered, it became possible to obtain more accurate dates for geological events, and to compare those with the apparent record of sedimentation in the rocks. Many dates were then revised. When continental drift came in from left field, entirely new ways to find those dates arrived, and were quickly used. More dates were revised.

  Scientists – collectively – want to find their mistakes, so that they can get rid of them.

  Religions, cults, and pseudoscientific movements want to close down lines of enquiry. They want their followers to stop asking questions and accept the belief system. The difference is glaring. Suppose, for instance, that scientists became convinced that there was something worth taking seriously in the theories of Erich von Däniken, that ancient ruins and structures must have been the work of visiting aliens. They would then start asking questions. Where did the aliens come from? What sort of spaceships did they have? Why did they come here? Do ancient inscriptions suggest one kind of alien or many? What is the pattern to the visitations? Whereas believers in von Däniken’s theories are satisfied with generic aliens, and ask no more. Aliens explain the ruins and structures – that’s cracked it, problem solved.

  Similarly, to early proponents of divine design and their modern reincarnations creationism and ‘intelligent design’, the latest quasi-religious fad, once we know that living creatures were created (either by God, an alien, or an unspecified intelligent designer) then the problem is solved and we need look no further. We are not encouraged to look for evidence that might disprove our beliefs. Just things that confirm them. Accept what we tell you, don’t ask questions.

  Ah, yes, but science discourages questions too, say the cults and religions. You don’t take our views seriously, you don’t allow that sort of question. You try to stop us putting our ideas into school science lessons as alternatives to your world view.

  To some extent, that’s true – especially the bit about science lessons. But they are science lessons, so they should be teaching science. Whereas the claims of the cults and the creationists, and the closet theists who espouse intelligent design, are not science. Creationism is simply a theistic belief system and offers no credible scientific evidence whatsoever for its beliefs. Evidence for alien visitations is weak, incoherent, and most of it is readily explained by entirely ordinary aspects of ancient human culture. Intelligent design claims evidence for its views, but those claims fall apart under even casual scientific scrutiny, as documented in the 2004 books Why Intelligent Design Fails, edited by Matt Young and Taner Edis, and Debating Design, edited by William Dembski and Michael Ruse. And when people (none of the above, we hasten to point out) claim that the Grand Canyon is evidence for Noah’s flood – a notorious recent incident – it’s not terribly hard to prove them wrong.

  The principle of free speech implies that these views should not be suppressed, but it does not imply that they should be imported into science lessons, any more than scientific alternatives to God should be imported into the vicar’s Sunday sermon. If you want to get your world view into the science lesson, you’ve got to establish its scientific credentials. But because cults, religions and alternative belief systems stop people asking awkward questions, there’s no way they can ever get that kind of evidence. It’s not only chance that is blind.

  The scientific vision of the planet that is currently our only home, and of the creatures with which we share it and the universe around it, has attained its present form over thousands of years. The development of science is mostly an incremental process, a lake of understanding filled by the constant accumulation of innumerable tiny raindrops. Like the water in a lake, the pool of understanding can also evaporate again – for what we think we understand today can be exposed as nonsense tomorrow, just as what we thought we understood yesterday is exposed as nonsense today. We use the word ‘understanding’ rather than, ‘knowledge’ because science is both more than, and less than a collection of immutable facts. It is more, in that it encompasses organising principles that explain what we like to think of as facts: the strange paths of the planets in the sky make perfect sense once you understand that planets are moved by gravitational forces, and that these forces obey mathematical rules. It is less, because what may look like a fact today may turn out tomorrow to have been a misinterpretation of something else. On Discworld, where obvious things tend to be true, a tiny and insignificant Sun does indeed revolve round the grand, important world of people. We used to think our world was like that too: for centuries, it was a ‘fact’
, and an obvious one, that the Sun revolved round the Earth.

  The big organising principles of science are theories, coherent systems of thought that explain huge numbers of otherwise isolated facts, which have survived strenuous testing deliberately designed to break them if they do not accord with reality. They have not been merely accepted as some act of scientific faith: instead, people have tried to falsify them – to prove them wrong – but have so far failed. These failures do not prove that the theory is true, because there are always new sources of potential discord. Isaac Newton’s theory of gravitation, in conjunction with his laws of motion, was – and still is – good enough to explain the movements of the planets, asteroids and other bodies of the solar system in intricate detail, with high accuracy. But in some contexts, such as black holes, it has now been replaced by Albert Einstein’s theory of general relativity.

  Wait a few decades, and something else will surely replace that. There are plenty of signs that all is not well at the frontiers of physics. When cosmologists have to postulate bizarre ‘dark matter’ to explain why galaxies don’t obey the known laws of gravity, and then throw in even weirder ‘dark energy’ to explain why galaxies are moving apart at an increasing rate, and when the independent evidence for these two powers of darkness is pretty much non-existent, you can smell the coming paradigm shift.

  Most science is incremental, but some is more radical. Newton’s theory was one of the great breakthroughs of science – not a shower of rain disturbing the surface of the lake, but an intellectual storm that unleashed a raging torrent. Darwin’s Watch is about another intellectual storm: the theory of evolution. Darwin did for biology what Newton had done for physics, but in a very different way. Newton developed mathematical equations that let physicists calculate numbers and test them to many decimal places; it was a quantitative theory. Darwin’s idea is expressed in words, not equations, and it describes a qualitative process, not numbers. Despite that, its influence has been at least as great as Newton’s, possibly even greater. Darwin’s torrent still rages today.