The Science of Discworld IV

technology, which we use to remodel our world so that it seems to work like magic, as we said in
The Science of Discworld
. When you switch on the light, all sorts of complicated technology goes into action: electricity, conducting wires, plastic insulation, and so on. (If you think a light switch is simple, you’renot thinking about what makes it work and how it can be produced.) The electrician and the company that made the switch need to understand the technology in considerable detail, but the user does not. To them, it works ‘like magic’. If you could show an iPad to a mediaeval monk, he would probably declare it the work of the Devil. Who else could create moving pictures on a slate? He would certainly find it incomprehensible. So do almost all of its users today. We
want
our gadgets to work like magic, doing what we want because we want it.
    In contrast, science is mostly about how things happen ‘of their own accord’. Science is universe-centred; magic is human-centred. The two viewpoints come together in technology: here the human-centred view sets our goals, while the universe-centred view helps us to achieve them. So technological magic involves a special kind of causality. Not
natural
causality – the workings of nature’s laws – but
human
causality: how we can make nature do what we want.
    Our thinking about causality easily gets muddled. We don’t really understand what it is. Worry not: neither do scientists. In fact, anyone who claims to understand causality hasn’t fully understood the question.
    One of the big puzzles about causality is that once you start to trace the causes of even the simplest features of the world, you find an ever-branching backward tree, with many unlikely things coming together at just the right instant to make something else happen. We rest on an infinite pile of coincidences, and the pile gets wider the further back we go. The probability of anything specific happening seems to be zero.
    Dawkins starts
Unweaving the Rainbow
with the example of all the people that aren’t alive because they’ve never been born, the sperms that never made it to an egg for fertilisation, all the DNA combinations that were never actualised. These ‘potential people’, he says, outnumber the sands of Arabia. The ones who
have
been born are the tiniest of minorities.
    He quotes Desmond Morris ascribing his love of natural history to Napoleon: if Morris’s great-grandfather’s arm had not been removed by a cannonball in the Peninsular War, all would have gone differently. If
your
parents, or your grandparents, had never met … You can see where we’re going here: the events that have actually happened are the tiniest fraction of those that
might
have happened.
    It’s easy to sort this out for Discworld. Narrativium makes sure that things go as they ought, and if there’s a problem, there are always the History Monks to set things to rights. But Roundworld isn’t like that: when the wizards needed to produce Shakespeare all kinds of things went wrong before they got the right version of him. fn1
    How do you know that
you
are the right version?
    Let’s examine this problem: all the things that could have happened, versus the tiny fraction that actually did.
    Some physicists claim to believe (we find it hard to accept that they actually do, when they get up in the morning) that there’s a very simple answer to this conundrum.
All possible things happen.
Each distinct choice starts off a new universe, so that the Trousers of Time are forever bifurcating; everything happens somewhere. This seems absurd, making potential events as real as actual events. It’s as if you tossed a coin a hundred times and wrote down the list of what happened: HHTTTHH and so on. Fine. But then you claim that every possible series happened ‘somewhere’, that HHHHHH, all heads, and TTTTTTT, all tails, happened too, as well as all the other possible combinations. Only … they didn’t happen in this universe, they happened in other ones. You’re stuck in the universe where HHTTTHH happened, but somewhere else, the all-tails and all-heads options came up. The newspapers there must have been full of that news, mustn’t they? Or are they perhaps in the kind of universe where unlikely things happen all the time?
    This is the world of Schrödinger’s cat, alive and dead at the same time until someone takes a look. Ponder Stibbons alluded to it in chapter 1 . Well, it’s the world of