Friday, December 20, 2002

Doug Wilson, Evolution, and The 2nd Law of Thermodynamics

I was google-ing around for articles dealing with science and Christianity when I came across something Douglas Wilson wrote for Credenda Agenda. If you want to read the article first, before reading my comments on it, the article is here.

I have read Wilson’s article at least four times, to make sure it is not tongue-in-cheek. I do not think that it is. I think it is Wilson trying to tell us that he understands the usual scientific comeback to the usual misuse of the second law of thermodynamics, and that he has discovered how to ratchet up the argument and catch science without an answer. (Why do I always envision him writing with a smirk? I have the same negative impression of Jonah Goldberg. I need to work on this.)

There are so many things wrong with Wilson’s argument I hardly know where to begin. (Oh Lord, save us from foolish Christians who think that science is your enemy! And save us from the well-meaning but self-deluded who think that they understand enough science to use science against itself.)

My problem is I don’t think I am a good enough teacher to explain why Wilson is wrong, because the second law of thermodynamics and the concept of entropy are not trivial. In physics they are defined in a precise manner, and if one applies the second law without understanding the details, then the results one obtains and the conclusions reached are meaningless. Still, I'll give it a go.

The Second law of Thermodynamics

The second law of thermodynamics was developed to tell us why certain things happen in a certain direction. For example, if you put ice cubes into a room temperature drink, heat flows from the liquid (resulting in a temperature reduction) into the ice (which then melts). Why doesn’t heat flow from the ice cubes into the drink, leaving the drink even warmer and the ice cubes even colder? This does not violate other laws of physics, such as the conservation of energy. Yet we know it does not happen. Heat always flows from hot to cold, never the other way around.

This "common sense" result is of little use to physicists, other than as a guide. We need something quantitative so that predictions can be made. The concept of entropy was developed to give some teeth to our common sense.

Entropy is not easy to define—in fact the second law really deals with changes in entropy, not its precise value. Yet we know it is related to order. Highly ordered systems have less entropy than disordered ones. And we know that ordered systems (low entropy) decay into disordered systems (high entropy).

If you clean up your bedroom, you put it in a state of high order and low entropy. From there, assuming you arrange it "perfectly", there is no place to go but downhill. Any change to your perfect arrangement, just removing one book from your bookshelf and placing it on your nightstand, brings in a small amount of disorder, and the entropy increases. As we all know, an ordered room will decay into a disordered one. Entropy will increase.

Here we see another way to think of entropy. In a sense there is only one, or maybe a few, "perfect" and highly ordered arrangements of your room, but a gazillion imperfect ones. So entropy is also related to the probability of an arrangement. If a tornado swept through your room, mixed everything around and deposited everything randomly, an ordered arrangement is highly unlikely. When related to probability, we see that low probability corresponds to low entropy (and high order), and high probability to high entropy (and low order).

A System and its Surroundings

One more concept is important, that is the idea of a system and its surroundings. A system is whatever we are studying. For example our room, or the earth. The surroundings are everything with which our system can exchange matter or energy. For our room, it might be the rest of our house. For example, I can alter the entropy of my room by taking the trash out of the room. For the earth, vast amounts of energy enters the earth from the sun. The earth also radiates energy out into space. Matter is constantly bombarding the earth.

If a system has no surroundings, it is said to be a closed system. The universe as a whole is a closed system (apart from God), and in some sense the only one. However, we can approximate a closed system by putting it in an insulated container so that no heat, energy, or matter can enter or exit the box. Since there is no perfect insulator, there is no perfectly closed system, but we can get pretty close.

In light of all this, here is how the second law of thermodynamics can be expressed:

The change in entropy of the system, PLUS the change in entropy of the surroundings, is greater than or equal to zero.

If we have a closed system, such as the universe, then it simplifies to:

The change in entropy of the system is greater than or equal to zero.

If the change in something, such as entropy, is "greater than zero", it means that it increases. If it is "greater than or equal to zero", it means it does not decrease.

So the fate a closed system is somewhat known. Everything that happens, every process in a closed system either leaves the entropy unchanged or increases it. It never decreases. Eventually a maximum entropy is reached, a state of maximum disorder, a state that is also called equilibrium.

The Second Law and Evolution

In Wilson’s article he first presents the most trivial misuse of the second law and then, properly, allows it to be shot down. This misuse of the law is:

Evolution represents increased order, but the 2nd law says order will decrease, therefore evolution violates the second law. (Note: Wilson uses complexity instead of order, which is imprecise and fraught with its own problems—but let’s ignore that.)

Wilson writes, if I may paraphrase, yeah, yeah but the earth is not a closed system so that does not mean anything, which is the usual response to this argument.

However, it is a misleading response, and only partially correct, because even if the earth were a closed system it (the second law) would not rule out evolution. Let us go back to the room example. Suppose my room was (a) a mess (high entropy) and (b) a closed system (no windows or doors, insulated walls) and (c) I was locked inside. Before I starved, I might decide to clean my room. I put everything away neatly. The stuff in my room "evolved" from disorder to order, entropy (appears) to have decreased, and yet I am in a closed system—doesn’t that violate the second law? No, because my room contains all my stuff and it also contains me. The entropy of my stuff may have decreased, but how did that happen? I worked. I picked things up. I moved them. To do that required energy. I got the energy by burning fat. To account for all the entropy changes in my closed system, I would need to include in the accounting all the complicated processes going on inside my body while I was ordering my stuff. The second law states that if I account for everything, the entropy as a whole did not decrease (and probably increased), even though my stuff "evolved" into an ordered state. That increased order came at the expense of a greater-or-equal increased disorder from biological processes.

Wilson’s Next Argument

Wilson then tries to ratchet-up the argument. He has a disassembled watch wrapped inside a handkerchief. He agrees that inside the handkerchief the pieces are in a closed system. So entropy cannot decrease, the watch components cannot reassemble themselves into a more ordered state.

Wilson then "opens" the system by smashing the handkerchief with a hammer, pumping energy into the system. Then he smugly notes that the pieces now look even less like a watch. Although we now have an open system, the watch is still not reassembling itself (not "evolving"), the entropy of the watch pieces is still increasing. Wilson concludes the article:
"Hmmm," I said, "It seems to be going in the wrong direction. Looks less like a watch."
"Hit it again," said Jocko.
Samuel (the scientist) muttered sullenly, "You don't understand. You creationists will never understand."
"You are right about one thing," I said. "I don't understand how energy input will do anything other than increase the rate (sic) of entropy. I mean to say, look at my watch."

Now it is possible that Wilson is just making a joke, but it does not smell that way to me. First of all, it is not funny unless it demonstrates how foolish the scientist (Samuel) is. It has to be a joke at his expense, or there is no joke. So even if it is a joke, it relies on the science being so "bad" that it can easily be used against itself.

The problems with Wilson’s arguments are many. He correctly points out that he now has an open system, namely the parts of the watch (which is the system proper) and the hammer (which is the surroundings). Thus we have the second law in the open system form:

The change in entropy of the system (watch parts) , PLUS the change in entropy of the surroundings (hammer), is greater than or equal to zero.

Here is the fatal flaw in Wilson’s logic: The fact that we have system and the surroundings in this equation allows the possibility that the entropy of the system decreases (to be at least compensated by the increase in entropy of the surroundings), but it doesn’t demand it. Both the system and the surroundings might experience an increase, or the surroundings might have a decrease at the expense of the system, but the second law does not say that either one must have a decrease, it only says that it is possible for one or the other to decrease.

To summarize: the second law, when applied to an open system, does not demand nor preclude the possibility that either the system or the surroundings experiences a decrease in entropy. It might happen, or it might not. Whether it does depends on the details of the overall system.

There is no violation of the second law. Wilson joins a long line of well-intended but ultimately harmful apologists whose misuse of science fosters the image of Christians as a bunch of bozos.


Evolution is wrong, but it is not so easy to dismiss, and the second law is not the way to attack it. Evolutionists will understand the flaw in both the trivial misuse of it, and in Wilson’s misguided "improvement".

What would make the watch parts "evolve" back into a watch? It requires something that the second law doesn’t deal with, something in the details of the processes. The second law speaks in broad terms and provides broad constraints, it says little about what happens under the hood.

Evolutionists argue that the complex molecules necessary for life resulted "not just" because the earth is an open system, but because of the details, which include a tendency in some systems to self-organize into structured arrangements. No time to go into what that means at length, but a simple example is sand dunes. From a purely entropy-style argument you might expect the wind to create an unordered bland distribution of sand in a desert. Yet from above, as viewed from a airplane, we see highly ordered and regularly spaced sand dunes. This is a form of self organization. The second law is not violated, and the second law does not demand that dunes are formed (that’s the Wilson mistake), but the second law does not preclude it. It is the details of sand dynamics that produces unexpected structure and order, within the bounds of the second law.

Evolution can be attacked here, but it requires much more sophistication than Wilson’s primitive and flawed argument.

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