Brownian ratchet

== English == === Etymology === In reference to Brownian motion. === Noun === Brownian ratchet (plural Brownian ratchets) (physics) An apparent perpetual motion machine, the subject of a thought experiment, that would consist of a tiny paddle wheel and a ratchet, and might seem to be able to extract useful work from random fluctuations (heat) in a system at thermal equilibrium, in violation of the second law of thermodynamics. Synonym: Feynman-Smoluchowski ratchet ==== See also ==== Maxwell's demon