In physics, social thermodynamics theory attempts to describe social phenomena using an approach with the mathematical structure of thermodynamics. It is based on the general variational principle of minimization of Fisher information, which is known that can be used as formal generator of equilibrium and non-equilibrium thermodynamics. This aim born with the derivation of Zipf's Law from first principles, the prediction of scale-free ideal gases, both the reproduction of city-size distributions and electoral results with competitive cluster growth processes on scale-free ideal networks, and the demonstration of the Dunbar's number as the cause of the 'six degrees of separation'. In fiction The idea of social thermodynamics shows some similarities to the fictional science of psychohistory in Isaac Asimovs Foundation series.