Thermodynamics and Evolution

Creations sometimes argue that evolution is impossible because it violates the second law of thermodynamics. It is an argument rooted in a misunderstanding of thermodynamics.

What thermodynamics says is that we can only get useful work out of a physical system if we have a difference in energy levels. For example, if we have a high potential in one place and a low potential in another we can get useful work out of the current flow. Thermo also says we will lose some of the available energy along the way; increased entropy is a way of saying that we have lost usable energy.

Now the Earth is constantly radiating energy into empty space which has a very low energy level. It is intercepting energy from the Sun which has a very high energy level. This flow of energy through the Earth is available for useful work; biological life is a small ripple in this energy flow.

In a closed system where there is nothing coming in or going out everything goes to equilibrium, i.e. the energy level everywhere is the same; this is know as heat death. In an open system where there is energy constantly flowing through system you can have local complex perturbations that are not in equilibrium. Life is a local complex perturbation.

The important thing to understand from the viewpoint of thermodynamics is that evolution is irrelevant to the thermodynamics of life. Each cell is a little island of reduced entropy. If we are calculating the reduction in entropy due to life, it doesn’t matter how the cells are arranged; all that matters is the total volume of cells. It is also important to realize that life is really a very small perturbation in the over all energy flow.