Science Friction

How can a children’s nursery rhyme teach you about the laws of Thermodynamics? “Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall.” This is an illustration of the second law of thermos dynamics. “All the King’s horses and all the king’s men couldn’t put Humpty together again.” This is an illustration of the first law of thermodynamics.

Let’s look at Humpty falling down first. In short, things fall down; they don’t fall up. Left to their own devices, things always eventually proceed from energy states of higher order to energy states of lower order. When Humpty is sitting on the wall, he (is Humpty a he? I don’t know that Humpty’s gender has ever been definitively stated) he has potential energy. In the act of falling, Humpty has kinetic energy, the energy of motion. When Humpty comes to the big stop at the end he becomes less orderly. Yeah, in fact he is a mess. But also the kinetic energy is converted to heat (infrared radiation) which is the least orderly state of energy. Heat tends to just disperse into the universe. Oh, sometimes heat can be captured and transferred to other kinds of energy, like a steam engine or a coal fired power plant. But that transfer of energy from heat to other forms is always very inefficient. You are always losing more energy (as waste heat) than you are gaining. Things always progress to a state of less order, or more disorder. Scientists have a term for this measure of disorderliness, it is called ‘entropy’.

But wait, you say, there are lots of examples of things becoming more ordered. Say you have a bunch of random rocks in a mountain, and quarrymen dig those rocks out and construction workers assemble them with other material to create a beautiful new building. Obviously the building is more orderly than the rocks it came from, right? Nope. Quarrying the rocks and constructing the building took a lot of energy. From the fossil fuels used to run the machinery to the food all of the workers consumed. The food and fuel was converted into less useful waste byproducts (like carbon dioxide). A vast amount of waste heat was generated in the construction of that building. The net result is that the universe as a whole is now less ordered that it was before the building was constructed.

Now to the first law. All those horses and men couldn’t put Humpty together again because of the conservation of energy. That is: energy cannot be created or destroyed (though it can be changed from one form to another. When I said that waste heat is lost to the universe, it is not destroyed. It is simply dispersed through the universe. It is like if you were to squeeze one drop of orange juice into the ocean, you are not destroying the orange juice. The individual molecules are still there, but you are probably not going to be able to extract that drop back out and get any use out of that juice.

These laws are the reason that a perpetual motion machine will never work. You cannot keep a machine running without adding energy. There have been some ingenious attempts at making one, like using a wheel that has an odd number of weights distributed around it, that pivot so there will always be more weights on one side of the wheel than the other. But friction always brings these things to a halt. Friction produces heat and heat is the waste energy that is sapped out of the machine as it loses its kinetic energy. You can have a machine that produces ‘perpetual motion’ if you perpetually add energy to it. Of course you will always get back less that you put in.

Sometimes creationists use thermodynamic as proof that that evolution can’t work because evolution is making things more orderly, which is a violation of the second law. Sorry, that argument doesn’t work. Biological systems on earth have become more orderly because the earth is not a closed system. It being flooded with outside energy, namely solar energy. This energy drives the formation of chemical energy in plants that move up the food chain, or eventually become fossil fuels.  But even with all this seeming orderliness, the universe as a whole has become less orderly when you factor in all the waste heat and carbon dioxide that has been generated by every plant and animal that has ever existed.

You can slow down entropy, but you cannot stop it. It is as relentless as death and taxes. Some people are depressed by the thought of increasing disorder, as the universe gradually disperses, thins, and dissipates into nothingness (though this will take billions of years, it still bothers some people). If you are the kind of person who worries about such things I cannot offer you much comfort. But I can recommend you read a science fiction short story by Isaac Asimov entitled The Last Question. You may find it “enlightening.”

(My novel Star Liner, is now available in paperback or as an e-book through Amazon, or the other usual online sources)

Star Liner