The second law of thermodynamics

This is an easy one to address. I haven’t seen it being seriously argued anywhere lately, which might mean that it’s finally sinking in what nonsense it is, but maybe I’m just looking in the wrong places. Either way, it doesn’t take much to understand why the theory of evolution is in no way refuted by the second law of thermodynamics.

Without getting too sciencey (because heaven forfend that this blog ever actually becomes informative), the law says that the total entropy of the universe is always increasing. Entropy, as I’m sure you all remember from your physics PhDs, is a measure of disorder, or chaos – so the law essentially states that things are always getting messier. Everything tends toward randomness, and for things to spontaneously sort themselves out into a non-random pattern – for the milk to unmix itself from my tea, for instance, and sit on the top in a separate layer, or for a dropped heap of sand to simply fall into a magnificent castle, complete with turrets and drawbridge – is impossible.

Except, not quite. Although the universe’s total entropy is increasing, that doesn’t mean that every single point in it must be getting more and more random and disordered all the time. It’s possible to decrease entropy locally, in some small system, by doing some work (adding some energy) to bring some order to the proceedings. It is possible to build a sandcastle, obviously. You just have to provide some process by which effort is expended, and the sand is arranged into an ordered pattern – such as, pick up your spade and get to work.

It’s silly to think the law means that nothing can ever become more complicated. You can see examples everywhere of complicated and intricate systems arising out of simpler ones. You can take a pile of CDs strewn haphazardly across the floor and alphabetise them; you can plant an acorn, and watch a complete oak tree grow (though only if you have a hell of a lot of spare time).

The point is that these sandcastles and acorns aren’t all there is – in each case, there’s something outside that small system, providing the work that needs to be done to put things in order. For that to happen, the entropy outside needs to increase, so overall things are more chaotic, even if a small patch of organisation breaks out somewhere.

It’s easy to see how this applies to something like evolution. Organisms do increase in complexity and orderedness (which sounds like it should be a word) over time, but like the acorn growing into an oak tree, the rest of life on the planet takes in energy from various environmental sources, particularly the Sun. We’re more complex and less disordered than our ancestors, but increased entropy levels elsewhere mean that the thermodynamics police won’t be needing to make any arrests. Chaos in the universe overall is behaving as it should.

PZ Myers has some actual numbers on roughly how much energy the Earth would need to be provided with to account for the increasing complexity of evolution, and the actual energy it’s provided with by the Sun. Guess which one’s bigger.

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