Friday, November 28, 2008

Second law of thermodynamics fallacy

The original form of the Second Law of Thermodynamics states simply that heat within a system will tend to become  evenly distributed over time.  This is intuitive enough that most reasonable people would be willing to accept it as axiomatic, and therefore worthy of the name "law".

Unfortunately, over time it has been extrapolated and misconstrued to an almost unrecognizable conjecture which states roughly:  The level of entropy in a closed system increases over time.  In this context entropy is defined roughly to mean disorder, or chaos.  Essentially this means that things tend to become less organized and more "random" over time.

In this modified form, on its surface, this may still appear intuitive.  After all, we're all familiar with things breaking down over time.  A broken glass is hard to fix.  A dead hamster cannot be brought back to life.  Indeed, this new form of the law is taught widely in universities and accepted by most engineers and physicists unquestioningly.

There's only one problem with this version of the 2nd law:  it's unequivocally not true!



The glass, hamster, and millions of other examples may be compelling.  But think of the counter-examples:  
  • the creation of progressively more complex atoms from sub-atomic particles
  • the creation of molecules of increasing complexity from those atoms
  • the organization of matter from plasma to stars, planets, and galaxies all orbiting in regular, predictable patterns
  • the evolution of this matter into complex and diverse lifeforms organized in complex webs of interdepencence resulting in self-supporting ecosystems

The standard objection to these examples is that the the 2nd law only applies to closed systems.  The idea behind this argument is that the trivial examples supporting the entropy version of the 2nd law are indeed closed systems, but the counter-examples of astronomical and universal significance are not.  Let's examine this more closely.

What exactly is a closed system.  I don't mean theoretically.  As philosophical abstraction we can all imagine one.  But can you actually think of an example in the real world?  Is it possible, even in theory to engineer an isolation chamber that prevents the entering or leaving of all energy, matter, even gravity?  Of course not.

So the entropy interpretation of the 2nd law is a law of nature that only applies to a theoretical system that can never actually occur in nature!

If you're willing to loosen the definition of "closed system" to allow for systems that are approximately closed, then we need a slightly longer discussion to refute the law.  However, once you're willing to accept this flexibility, the refutation is still inevitable.  For every example of entropy spontaneously increasing, I can merely increase the size of the system to include a far more impressive counter example.  

While the glass may have broken, the factory producing the glasses, and the existence of all the other unbroken glasses from large quantities of sand is far more compelling.

The unfortunate hamster is no longer with us.  But the mere existence of a hamster (even a dead one) if far more impressive.  Ah yes, you say, but the hamster's corpse will now begin to decay!  Only, in fact, if you open the system to inject microorganisms and oxygen.  If the microorganisms were there in the first place...where did they come from?  Did they evolve spontaneously within your "closed" system?  If so...quite an impressive contravention of the "law".

Another objection by apologists for the entropy interpretation is that I've got my definition of entropy wrong.  Fair enough.  That represents progress for my argument, since my argument is that the commonly held definition of the 2nd law is wrong...not that there is no possible interpretation of the law which is correct.

The Wiktionary definition (at least at the time I'm writing this) is:


  1. strictly thermodynamic entropy. A measure of the amount of energy in a physical system which cannot be used to domechanical work.
  2. A measure of the disorder present in a system (now becoming obsolete in chemistry)

I believe I've adequately refuted the second law as it is commonly understood, which is with definition number 2.  If we use definition number 1, I believe we end up with the original intent of the second law, which I readily accept.

I've had this rather geeky argument with numerous people whose knowledge and intellect I greatly respect, including physicists and philosophers.  I have yet to encounter someone who can come up with a convincing argument that the entropy interpretation 2nd law is even a reasonable proposition as commonly understood.

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