“Only entropy comes easy”


Below is the abstract of an after-dinner speech I gave at the Australian Institute of Physics WA Branch annual general meeting and dinner, on 16 Nov 2016 (see also national AIP newsletter)

“Only entropy comes easy”, but it’s not always destructive
By his quote “Only entropy comes easy” Anton Chekhov captures one of the most robust principles physics has ever produced, the second law of thermodynamics: Entropy always increases! (*). Given the widespread notion that entropy equates to disorder, entropy does not seem to qualify as a driving force for the formation of ordered structures. However, in this talk I will describe some classical systems where, counter-intuitively, entropy is responsible for the formation of ordered structures. These include the formation of sparkling opal-like photonic crystals of highly-ordered arrays of tiny spherical particles. Fighting entropy is an uphill battle, and is best avoided. In nano-engineering of ordered materials, avoiding the battle against entropy and rather ‘making entropy your ally’ is a route to sustainable low-energy designs. As so often, nature has already explored this principle….(*) Except for the few situations where a system undergoes reversible processes where the entropy stays constant, and the statement is only true for the total entropy and for that of an isolated system.

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