I just got back from (finally) watching World War Z with my father. He has been a long time zombie fanatic, and got me into zombies when I was a kid. As we all know, World War Z the book by Max Brooks is pretty much one of the most fantastic zombie books. And the movie was also fantastic. However, one thing that has always bugged me about zombies, not just the zombies in World War Z but ALL zombies in general, is the fact that they blatantly ignore thermodynamics!
Specifically, the Second Law of Thermodynamics. It basically states that in a closed system entropy never decreases. I mean, this can be stated in hundreds of different ways, but the basic concept is the same: once something uses up its energy, it needs more energy to continue to cause itself to move. This page puts it beatifully:
The Second Law of Thermodynamics states that "in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state." … Once the potential energy locked in carbohydrates is converted into kinetic energy (energy in use or motion), the organism will get no more until energy is input again. In the process of energy transfer, some energy will dissipate as heat. Entropy is a measure of disorder: cells are NOT disordered and so have low entropy. The flow of energy maintains order and life. Entropy wins when organisms cease to take in energy and die.
A zombie represents a pretty good model of a more or less isolated system. They don't (have to) eat, they don't drink; Hell, I don't even think they have to breathe! (Though their ability to make very zombie-like sounds would imply that air IS moving through them.) So it's a pretty safe assumption that theses zombies aren't taking in much potential energy. Which means they should not be able to just stand there shuffling around all day when they're bored as fuck because they already ate up all the humans. They should eventually use up all their energy and DIE!
I'm no zombie expert, so I guess there COULD be plausible explanations. For instance, maybe whatever turns someone into a zombie also makes them capable of photosynthesis. That sure would explain the green skin tone zombies typically get. Maybe I'm not a physics major and therefore fundamentally don't understand what I'm ranting about. Maybe we're all zombies, and zombies are actually alive. And maybe, just maybe, zombies display the aforementioned disregard of the Second Law of Thermodynamics because they are a product of the entertainment industry and wouldn't be nearly as cool if they did.