Notes on Non-Equilibrium Thermodynamics

– The basic principle of NET, as developed by Ilya Prigogine, is that systems far-from-equilibrium (FFE) are sources of order.

– Classical thermodynamics is primarily concerned with closed systems and the equilibrium obtained therein – that is, the state of the closed system as being one of maximum entropy, or disorder, and temperature uniformity. This is generally seen as a static state.

– Key things about closed systems: there is no decrease in entropy – that is, disorder only increases. Another way of putting it is that organization and organized activity in the system only decrease.

– Non-equilibrium systems differ, obviously enough, by not being in a state of maximal disorder and not being in the state of uniform temperature. Paul Davies uses he example of a sealed flask of liquid and a boiling teapot: the former is in a maximal state of disorder (despite appearances) while the latter is FFE.

– The interesting thing about FFE systems is that their behaviour can change abruptly when the system is pushed FFE.

– A key point of difference between open and closed systems is that a closed system, as its name implies, is closed off to its environment, whereas an open system, is (surprise) open to its environment – in other words, the former receives no energy from its environment while the latter does.

– Prigogine is noted for his discovery/development of dissipative structures – systems which, when pushed FFE by an outside energy source, dissipate the energy/entropy that pushes them towards disorder and adopt a stable form.

– In a nutshell, dissipative structures can get around the second law of thermodynamics by dissipating the entropy/energy to their environments, resulting in an increase in organized activity, and showing that systems FFE can be a source of order – as Prigogine puts it, non-equilbrium systems bring order out of chaos.

*edit – a friend of mine notes that ‘NETherm does not so much get around the second law as was said, but shows how local entropy reduction at systems far from equilibrium which are easily perturbed can occur within its confines.’