The Science of Discworld IV

what was going on. We may be the most important thing in the universe as far as we are concerned, but nothing that happens outside our tiny planet depends on our existence, with a few obvious exceptions like various small but complicated bits of metal and plastic now littering the surface of the Moon and Mars, in orbit around Mercury, Jupiter and Saturn, or wandering through the outer edges of our solar system. We might say that the universe is indifferent to us, but even that statement is too self-conscious; it endows the universe with the human attribute of indifference. There is no ‘it’ to be indifferent. The system of the world does not function in human terms.
    We’ll refer to these ways of thinking as ‘human-centred’ and ‘universe-centred’. Many controversies that grab the headlines stem,to a greater or lesser extent, from the deep differences between them. Instead of assuming that one must be superior to the other, and then arguing vehemently about which one it is, we should first learn to recognise the difference. Both have advantages, in their proper spheres of influence. What causes trouble is when they tread on each other’s toes.
    Before the early twentieth century, scientists used to think that phenomena like light could either be particles or waves, but not both. They argued – often nastily – about which was correct. When quantum theory was invented, it turned out that matter had both aspects, inseparably intertwined. At about the time that all reputable scientists
knew
that light was a wave, photons turned up, and those were particles of light. Electrons, which were obviously particles when they were discovered, turned out to have wavelike features as well. So quantum physicists got used to the idea that things that seemed to be particles were actually tiny clumps of waves.
    Then quantum field theory came along, and the waves stopped being clumped. They could spread out. So now particle physicists have to know about quantum fields, and our best explanation of why ‘particles’ have mass is the existence of an all-pervading Higgs field. On the other hand, the current evidence only supports the existence of the particle-like aspect of this field: the Higgs boson. The field itself has not been observed. It might not exist, and that would be interesting, because it would overturn the way physicists currently think about particles and fields. It would also be somewhat annoying.
    In everyday life, we encounter solid, compact objects, such as rocks, and they make it easy for us to think about tiny particles. We encounter sloshy but well-defined structures that move around on water, and we feel comfortable with waves. In a human-centred view, there are no sloshy rocks, which makes us assume – almost without questioning it – that nothing can be both particle and wave at the same time. But universe-centred thinking has shown that this assumption can be wrong outside the human domain.
    The human-centred view is as old as humanity itself. It seems to be the default pattern of thinking for most of us, and that makes sound evolutionary sense. The universe-centred view appeared more recently. In the sense that we’re thinking of – science and the scientific method – universe-centred thinking has become widespread only in the last three or four hundred years. It is still a minority view, but a very influential one. To see why, we must understand two things: how science goes about its business, and what constitutes scientific evidence.
    For those of us who are willing to pay attention, the universe-centred view has revealed just how big, how ancient, and how awe-inspiring the universe is. Even on a human scale, it’s a very impressive place, but our parochial perceptions pale into insignificance when confronted by the mind-numbing reality.
    When early humans roamed the plains of Africa, the world must have
seemed
huge, but it was actually extremely small. A big distance was what you could walk in a month. An individual’s experience of the world was limited to the immediate region in which he or she lived. For most purposes, a human-centred view works very well for such a small world. The important plants and animals – the ones useful to specific groups of humans – were relatively few in number, and located in their immediate vicinity. One person could encompass them all, learn their names, know how to milk a goat or to make a roof from palm fronds. The deeper message of the Egyptian