What is Brownian ratchet?
The archetypal Brownian ratchet, is a ratchet wheel connected to a vane as part of a thought experiment. The whole device is microscopic and so the Brownian motion of air molecules drives the vane. The ratchet wheel rectifies the motion and so you can get useful work out of the device. This device only works if the vane is kept hotter than the ratchet. At thermal equillibrium it cannot work, otherwise there would be a thermodynamic violation. But it is perfectly legal if a temperature difference is maintained, as this constitutes nett energy into the system. This device was first discussed by the French physicist Lippmann in 1900 and then first explained correctly by Smoluchowski in 1912. In 1963, Feynman was the first to apply Boltzmann statistics to mathematically explain the behaviour of the device at thermal equillibrium. Abbott, in 1980, first questioned Feyman’s analysis, which to this day has not been rigourously derived from first principles. In 1996, Parrondo & Español demonst
