The Science of Discworld IV

it.
    The knife edge analogy depends on linear thinking – that’s why it uses a straight rod. But we live in a nonlinear universe, in which anything that is stable automatically tunes itself so that it works. That’s what stability
means
.
    Natural systems are like your arm, not like the knife. This is how the triple-alpha process tunes itself so exquisitely, and why your legs are exactly long enough to reach the ground. It is also why we, as evolved creatures, are so neatly adapted to the universe we inhabit. Analogous beings living in different universes would
also
be exquisitely adapted to their local conditions. This is why most of the Goldilocks arguments, that life elsewhere in the universe must be just like it is here, are probably nonsense. fn4 There are many genuine mysteries here, much to marvel at, and much yet to be understood. But there is no compelling scientific reason to believe that the universe was specially made for us.
    We are faced with two alternatives. Either the universe was set up in order to bring us into being, or we evolved to fit it. The first is human-centred: it raises humanity above the universe in all its awe-inspiring vastness and complexity. The second, a universe-centredview, puts us firmly in our place: we are perhaps an interesting development, complicated enough that we don’t understand exactly how it all works, but hardly the be-all and end-all of existence.
    We have been around for a few million years at most, perhaps only 200,000 if you restrict attention to ‘modern’ humans; the universe is about 13.5 billion years old. We occupy one world orbiting one of 200 billion stars in one galaxy, which itself is one of 200 billion galaxies. Isn’t it just a tiny bit arrogant to insist that the entire universe is merely a by-product of a process whose true purpose was to bring us into existence?
    fn1 This phrase is not found in his extant writings; it probably originated with the Irish theologian John Punch. The closest phrase in Occam’s work is ‘Plurality must never be posited without necessity’ in the
Sententiarum Petri Lombardi
of 1495. Not as pithy.
    fn2 ‘A universe containing sulphur has to be suitable for containing sulphur.’
    fn3 Fred C. Adams, Stars in other universes: stellar structure with different fundamental constants,
Journal of Cosmology and Astroparticle Physics
8 (2008) 010. doi:10.1088/1475-7516/2008/08/010. arXiv:0807.3697.
    fn4 See Jack Cohen and Ian Stewart,
What Does a Martian Look Like?

TWENTY-THREE
----
OVER-ZEALOUS ZEALOT

    Afterwards, Marjorie reflected on that aspect of the afternoon.
    Roundworld was the planet Earth, in theory anyway, and surely flinging it around and sloshing it about would cause the seas to also slosh about a bit, to say the least. Nevertheless, she automatically fielded the globe, which against all reason slotted into her palm with a decisive but moderate stinging sensation, which had gone in a second.
    The hooded man glared at her and drew out a curved knife. She could see the play of light on the blade and wondered how good her unarmed combat skills would prove to be against an opponent who clearly knew how to use a knife, especially since she was almost totally out of breath. The man screamed, ‘Om is good!’ and swung the blade at her.
    Marjorie jumped backwards and a very large wolf landed in between, just as a hailstorm of bats dropped out of the sky. For a moment Marjorie stared fixedly at this tableau, and then, well, it all got quite exciting. Suddenly the wolf had the knife and the man was on the ground, and the bats had disappeared in a flurry to be replaced by a naked young woman, who looked both ways along the alleyway and said, ‘Excellent work for a civilian! You ought to get a medal!’
    Still clutching Roundworld like a hot water-bottle, Marjorie managed to say, ‘But look! There’s still a wolf!’
    The wolf stood up on its hind legs, and the girl said, ‘Better turn your head. Captain Angua does not like to be seen when she is – how can I put this? – well, deshabillée. Give her some space, please.’
    Against all reason, Marjorie turned her back on the wolf, listened for a few seconds to what sounded like an autopsy in reverse, complete with unpleasant gurgling noises, and then a new voice said, ‘I’m impressed. Some people throw up just by listening. Allow me another minute to get into this dress, and we’ll be right with you.’
    Indeed, only a couple of seconds later she realised