The Science of Discworld IV

some standard stories about famous mathematicians, and the stories never change, but the famous mathematicians often do; the important point is that they should be famous. After that, it doesn’t greatly matter who they were – the story is just as funny, whoever you choose. The turtle joke in the next section is an example.
    The logic of mythology can also sometimes shed a little light on scientific issues, by reminding us of the principal reason for adopting the scientific method: the human tendency towards self-deception. We all too easily accept some kinds of evidence, or some types of argument, when they confirm what we want to believe; we tend to reject them if they conflict with our beliefs.
    In 2012 a Gallup poll found that 46% of American adults agreed that ‘God created human beings pretty much in their present form at one time within the last 10,000 years or so’. It was agreed by 32% that ‘Human beings developed over millions of years from less advanced forms of life, but God guided this process’. And 15% believed that ‘Human beings have developed over millions of years from less advanced forms of life, but God had no part in this process’. The scientific figures, based on a variety of evidence, place the first members of genus
Homo
at about 2.5 million years ago, and
Homo sapiens
– anatomically modern humans – at about 200,000 years ago, with archaic forms dating back perhaps twice as far.
    We’ve mentioned Young Earth creationists in chapter 2 . They argue that since Biblical scholarship dates the creation of humans to at most 10,000 years ago, and both the planet and humanity were created a few days apart, the Earth itself must also be less than 10,000 years old. As we saw, the scientific evidence that the planet is far older – homing in on about 4.5 billion years – is extensive, consistent, andcomes from a variety of independent lines of thought, all supported by observations. If you insist on denying all of that, however, there is a straightforward way to do so: the scientific view rests on logical inference, not just direct personal experience.
    It would seem strange, however, that a creator god should have gone to such extreme lengths, less than 10,000 years ago, to give his creation every appearance of being billions of years old, with humans existing for hundreds of thousands of years. It could be a test of faith, the universal get-out clause, but that’s a peculiar reason for deceiving your own creations. fn5
    The turtle-and-elephant universe features early on in Stephen Hawking’s rampant bestseller
A Brief History of Time
. He tells us that a famous scientist, possibly Bertrand Russell, fn6 was giving a public lecture, explaining how the Earth goes round the Sun and the Sun shares the rotation of the Galaxy. When he asked for questions, a proverbial little old lady complained that his theories were nonsense: the world was flat and rode on the back of a giant tortoise. ‘What does the tortoise stand on?’ the lecturer enquired. ‘You’re very clever, young man,’ said the old lady, ‘but it’s turtles all the way down!’ fn7
    Before the Big Bang theory became the orthodoxy, cosmologists espoused the steady-state theory: the universe has always existed and is essentially static. Although they have now abandoned the steady-state theory, many people still find it more congenial than any theory with an origin. In particular, an origin seems to require a precursor, so it seems natural to ask ‘What happened before the Big Bang?’
    Until recently most cosmologists would have answered that since time began with the Big Bang, there
was
no before: it’s like asking what lies north of the North Pole. In the last few years, however, many cosmologists have started to wonder if something more interesting might be going on, and whether there is a sensible series of events that led up to the Big Bang – in effect happening ‘before’ it in a causal sense, even if not a strictly temporal one. In
Figments of Reality
, Ian and Jack wrote:
    Most people seem perfectly happy with ‘it’s always been like that’, finding no difficulty in conceiving of a universe that goes back for ever. Yet nearly everybody finds an infinite pile of turtles highly incongruous … So why are we so happy with an infinite pile of causality: today’s universe riding on the back of yesterday’s, which rides in turn on the day before’s? It’s
universes all the way back
.
    Mathematical