Humpty Dumpty had a great fall. Thermodynamics in action.
Humpty Dumpty had a great fall. Thermodynamics in action.

On March 1, I briefly discussed what the First Law of Thermodynamics has to do with biological evolution.

I concluded quickly the First Law of Thermodynamics has nothing at all to do with evolution.

If you wish, you can review it here. It starts like this:

Thermodynamics! Doesn’t using that word make me sound smart? Unless you’re a scientist or an exceptionally well informed layman — layperson, sorry — I can say just about anything I want to about thermodynamics and you aren’t likely to know the difference. Right? If you just happen to be that scientist or exceptional layperson, then you know it is the science of heat and other forms of energy and how they relate to each other and to matter.

Since I was a young man, I’ve often heard creationists state authoritatively that the Second Law of Thermodynamics forbids biological evolution. These creationists are not scientists, of course. With few exceptions, they’re just people who slept through high school physics class and didn’t even take Biology because they were afraid of the dreaded E word. Evolution! But they heard somebody say “thermodynamics” and it sounded good to them.

I think I can safely claim to be an “exceptionally well informed layperson” on this subject, because I’m a nerd. I don’t claim to be informed about everything, but I’ve been informing myself about various scientific matters for a long time. I still find articles on thermodynamics that I don’t fully understand, but this part is easy.

I meant to discuss the second law within the next few days, but I got sidetracked. Sorry. Here is that very brief discussion now, and a substantial part of what I said about the first law also applies to the second.

Second Law of Thermodynamics:
Entropy in a closed system tends to increase.

That’s all. It really is that simple.

Entropy is a measure of disorder, and a closed (or isolated) system is any system that neither receives energy or matter from the outside nor passes its own energy or matter to the outside. The only completely closed system we know of is the universe, and we aren’t even sure of that!

But there are some systems that are almost closed. For example, a Styrofoam box with a lid is a semi-closed system. Fill it with ice and it’ll stay cold for a long time, but the ice will eventually melt because energy in the form of heat slowly seeps in through the sides of the box. It’s not truly closed, or isolated from the outside world. Even though the system is only partially closed, you’ll be able to see easily that entropy has increased, because the ice will be gone and water will have taken its place.

One of the most picturesque examples often given to illustrate this law is the observation that eggs break easily, but they never un-break. Remember, “All the King’s horses and all the King’s men couldn’t put Humpty together again.”

Books fall off a table, but they rarely jump back up onto it. Fuel gets burned, but it never gets unburned. Food spoils. but it doesn’t become fresh again.

So what does this have to do with biological evolution? Evolution is considered to be a decrease in entropy, which is said to be impossible in a closed system like earth. And that’s a violation of the second law, right?

Earth is not a closed system. Not even close.

Well, no. Because earth is by no means a closed system. Earth gets a huge influx of energy from the sun 24 hours a day. (When it’s dark here, it’s daylight somewhere else.) Besides that, there is a constant rain of meteors adding both matter and energy to the planet. Radioactive isotopes decay all through the planet, changing small amounts of matter into large amounts of energy. Several other more obscure sources of energy also constantly reach our planet.

There is one way the increase in entropy can be reversed. Energy pumped in from the outside can do the trick. Note that if energy is being pumped in from the outside, we do NOT have a closed system. Therefore, the Second Law of Thermodynamics says absolutely NOTHING about entropy or evolution on earth. Or anything else on earth, for that matter.

Next time a creationist tells you the Second Law of Thermodynamics forbids evolution, you’ll know he/she has no idea what he/she is talking about.


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