It has often been said that the Theory of Evolution violates the second Law of Thermodynamics. If this was true then there would be no Theory of Evolution. Yes it really is that simple. Now for the, hopefully not impossible, task of trying to get the evolution deniers to understand why this is so.
Basically the second law states that entropy increases over time. Personally I prefer the description that the amount of energy left over for work will decrease over time. Both of these descriptions are valid for the 2nd law.
It is from another description of the 2nd law that I think the problem lies. This description states that the amount of disorder in a system will increase over time. While this description is true I think it has been misunderstood by certain people to mean something totally different. The reason I say this is when pressed for an explanation on why evolution violates the 2nd law often the answer is that you can’t get complexity from disorder or order from chaos. I’m going to answer the chaos question and from my answer, and what follows, it should become self evident that complexity, as it is meant in this instance, has nothing to do with disorder.
I’d like you to imagine a closed thermodynamic system (closed as in there in no input of energy from outside the system). If we knew the conditions of the system at a particular point in time then we could work out the amount of order and disorder in the system at any other particular point in time with a high degree of accuracy. In other words how much energy is left for work (order) and how much has been lost to waste heat (disorder). Chaos, in physics, is not the same as disorder. Basically a chaotic system is highly sensitive to initial conditions (minute changes of the initial conditions can lead to widely different outcomes). A good example of a chaotic system would be the weather, think of butterfly wings causing hurricanes. For this reason you cannot make accurate long term predictions for chaotic systems. Please note that a system can be deterministic (not random) and still be chaotic.
Let’s now look at Earth. Earth is not a closed thermodynamic system; we receive a lot of energy from the sun. You can say that the solar system is a closed thermodynamic system. Thermodynamically the Earth has two main sources of energy, the Earth’s core and the sun. At first blush it might seem that entropy is decreasing on earth, due to life, but that matters not because the entropy of the system (remember you have to include the whole solar system) has increased over time.
Now I know that people today prefer to read short articles so I’ve made this one as short as possible at the expense of a fuller and deeper explanation but I think that I have shown that evolution and thermodynamics are compatible, if not let me know and I might write a piece from the evolution angle.