At the end of a long faculty meeting at NYU Physics, my colleague Shura Grosberg came to me to discuss a subject we have been discussing at a low rate for many months: How is it possible that my watch (my wristwatch) is powered purely by stochastic motions of my arm, when thermal ratchets are impossible? He presented to me a very simple model, in which my watch is seen a set of three coupled systems. One is the winder, which is a low-Q oscillator that works at long periods. The next is the escapement and spring, which is a high-Q oscillator that has a period of 0.2 seconds. The next is the thermal bath of noise to which the watch dissipates energy. If my arm delivers power only on long periods (or mainly on long periods), then it only couples well to the first of these. And then power can flow to the other two systems. Ah, I love physicists!
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