Thursday, January 20, 2011

Entropy - on large and small scales

As stated by the Second Law of thermodynamics, entropy in the entire universe continually increases as time progresses into the future, entropy being a measure of 'disorder' or 'randomness'.
While this holds true at the scale of the entire universe, local decreases in entropy seem to be a fundamental requirement for life. All living things are remarkably ordered (and thus improbable) arrangements of matter. Enormous amounts of energy are dedicated to producing this localised order. Eventually, however, all life is doomed as the global increase in entropy progresses. Of course this will take a very long time, so for now life is still safe.
Where does this energy come from that maintains life? The Sun, our nearest star. It is also the main provider of low entropy. Apparently, the dense organisation of matter in the Sun reduces the number of degrees of freedom, compared to this matter or energy being radiated into the vacuum of space. This matter and energy can take on many more configurations outside the Sun than inside the sun.
So on a larger scale, even with all the unlikely arrangements of molecules inside living organisms, the entropy of the sun is still much lower than that of Earth. Eventually, most of this energy will evaporate into space, approaching a uniform distribution. According to the Second Law, this is the fate of our universe: an inert uniform distribution of matter and energy at a global thermal equilibrium, the state of maximum entropy.