I take this course at university called Waves and Optics, and a few lectures ago our teacher talked about the Fluctuation Dissipation theorem but I didn't really understand it. The math behind it is a total mystery for me because I still don't understand Poisson brackets and Liouville equation, among other things. Anyway, I'm not interested in the math part just yet, for now I'd just like to know the physics of this theorem i.e. what kind of phenomenon it describes, why is it helpful/necessary/(elegant/beautiful?), how it roughly works etc.. I would like to get just a general understanding. Once I get that, the math will become obvious I think.
closed as too broad by ACuriousMind♦, Danu, BMS, Kyle Kanos, Brandon Enright Oct 30 '14 at 6:08
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