Friday, 14 September 2012

Thermodynamics? Who cares?

I was writing something yesterday for a book I'm currently working on about thermodynamics. It sounds, frankly, a bit of a dull subject. The name implies it's about the way heat moves around. And it is, sort of. It sounds like the sort of old fashioned science that dates from the age of the steam engine. And it is, sort of. Part of its origins certainly came from the need to understand steam engines better. But it is so much more.

One of the reasons for this is that surprisingly early on it was developed from thinking about engines to basics like atoms and molecules. How they interact and how we can look statistically at a whole bunch of them, because we certainly aren't going to be able to work on each one individually - there are just too many. I say 'surprisingly early' because when this theory was being developed a lot of scientists doubted that atoms existed at all, thinking they were just convenient mathematical models for working out the numbers. It was said for a long time that one of the reasons the remarkable Ludwig Boltzmann, one of the leading lights in the field, committed suicide was because there was so much opposition to his theories which were based on the reality of atoms. These days it's popular for historians of science to say his suicide was down to the depressive phase of bipolar disorder - which may be true, but it's hard to think such fervent opposition didn't make things worse.

I'm not going to drone through all four of the 'laws' of thermodynamics (terrible word to use in science, 'law' - it should be banned), but the one that is most exciting is the second law. This can be stated in a loose way as 'entropy (disorder) in a close system stays the same or increases', or 'you can't make a change in a closed system without increasing entropy' or for the steam engine enthusiasts, 'left to its own devices, heat will flow from a hotter to a cooler part of a system.' Or in the vernacular TANSTAAFL - there ain't no such thing as a free lunch.

This may all sound highly esoteric (apart from TANSTAAFL), but the second law is at the fundamental heart of existence. Every time anything changes - which, let's face it, is the interesting bit of life - the second law comes into play. It even explains teenage bedrooms - without the input of energy, disorder increases - and the eventual fate of the universe. Because the second law is so fundamental, it was the example C. P. Snow gave in his famous 'Two Cultures' ponderings as the equivalent of reading Shakespeare. He pointed out that most scientists have probably encountered Shakespeare, but very few artists have a clue about the second law of thermodynamics. Arguably they should.

The second law also produced a famous quote from one of the early twentieth century’s greatest scientists, Arthur Eddington, which I will leave you with. He said:
 ‘If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations [the equations that describe how electromagnetism works] – then so much the worse for Maxwell’s equations. If it is found to be contradicted by observation – well these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in the deepest humiliation.’

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