Editing Fluctuation theorem (section)

{{Short description|Theorem in statistical mathematics}}
{{About-distinguish|entropy fluctuations|fluctuation-dissipation theorem}}
{{Technical|date=September 2010}}

The '''fluctuation theorem''' ('''FT'''), which originated from [[statistical mechanics]], deals with the relative probability that the [[Entropy (statistical thermodynamics)|entropy]] of a system which is currently away from [[thermodynamic equilibrium]] (i.e., maximum entropy) will increase or decrease over a given amount of time. While the [[second law of thermodynamics]] predicts that the entropy of an [[isolated system]] should tend to increase until it reaches equilibrium, it became apparent after the discovery of statistical mechanics that the second law is only a statistical one, suggesting that there should always be some nonzero probability that the entropy of an isolated system might spontaneously ''decrease''; the fluctuation theorem precisely quantifies this probability.