The Science of Discworld IV

how nature works, we find some who want that, but others who think they already
know
how nature works, and will use any trick in the book to ram their answer down everybody else’s throats. Scientific doubt provides the latter with a useful weapon: it opens science up to the criticism that it doesn’t actually
know
anything.
    Scientists do not make laws, or enforce them, or try to wriggle out of them. They do not, as social relativists and postmodernists seem to imagine, get together, decide what laws will suit their purposes and then declare them to be correct. Instead, the scientists of Roundworld, and their predecessors – the natural philosophers – have always spent much of their time investigating the potential consequences of hypothetical versions of natural law, hoping either to support theories or to demolish them. Being human, they tend to prefer support for their own theories and demolition of the opposition’s, but most of them make a genuine effort to avoid that kind of bias if the evidence that they are wrong becomes sufficiently strong.
    A topical example is Richard Muller, leader of the 2009 Berkeley Earth Project and (until July 2012) a prominent climate change sceptic. In an analysis aimed at refuting claimed evidence of man-made global warming, the Project (funded by groups that support lobbying to resist action on climate change) made a fresh analysis of historical data on the Earth’s temperature over the last two hundred and fifty years. In the event, the study was entirely in line with, and strengthened, the existing evidence in favour of man-made global warming. The analysis showed that during that period, the Earth’s average land temperature increased by 1.5°C. Nearly two thirds of that rise occurred in the last fifty years.
    Muller promptly fn1 announced that his previous concerns about possible errors of data collection and analysis had proved unfounded. ‘Last year,’ he said, ‘I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: humans are almost entirely the cause.’
    That’s the difference between scepticism and denial.
    There are two big philosophical problems about laws of nature. What are they? Where do they come from?
    To complicate matters, the phrase itself can mean several different things. The philosopher Thomas Hobbes, who published
Leviathan
in 1651, proposed essentially God-given laws: ‘The first law of nature is that every man ought to endeavour peace, as far as he has hope of obtaining it’ – which determined what humankind should do. Another usage was that of John Locke, an early Fellow of the Royal Society, who cheerfully assumed that God had ruled against slavery: ‘The state of nature has a law of nature to govern it, which obliges every one: and reason, which is that law, teaches all mankind, who will but consult it, that being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions.’ Fine: consult reason and produce a system with liberty for all. That’s all right to start with, perhaps. But then you must make exceptions: for witches, of course; or for children caught stealing bread; or for malefactors in general. For a given value of ‘mal’.
    Laws of nature in these senses were much nearer to human laws than is our common usage today, physical law. Examples are the law of gravity and Ohm’s law about the relation between voltage, current and resistance in electrical circuits. This meaning seems much closer to ‘how things work’, and it will be our starting point.
    In
The Nature of Physical Law
, Richard Feynman wrote that in order to discover a law of nature, we start with a hypothesis, like Newton’s theory of gravitational attraction. Then we do some calculations, to see if examples fit our hypothesis. If all goes well, we call it a theory and try it out on many other examples. To the extent that these examples get wider and wider – from the famous apple fn2 to the Moon, to planetary orbits, then to the discovery that large heavy spheres attract each other very slightly in the laboratory,
and
that galaxies seem to have gravitational interactions with each other over vast distances – we can then elevate the theory to the status of a law.
    That brings us back to the Large Hadron Collider and its dramatic discovery of the Higgs boson, a long-sought fundamental particle that sorts out the masses of the