Brownian ratchet (nonfiction)

Diagram of a Brownian ratchet.

In the philosophy of thermal and statistical physics, the Brownian ratchet or Feynman-Smoluchowski ratchet is a thought experiment about an apparent perpetual motion machine.

It was first analysed in 1912 by Polish physicist Marian Smoluchowski, and later popularized by American Nobel laureate physicist Richard Feynman in a physics lecture at the California Institute of Technology on May 11, 1962, during his Messenger Lectures series The Character of Physical Law in Cornell University.

The simple machine, consisting of a tiny paddle wheel and a ratchet, appears to be an example of a Maxwell's demon, able to extract useful work from random fluctuations (heat) in a system at thermal equilibrium in violation of the second law of thermodynamics.

Detailed analysis by Feynman and others showed why it cannot actually do this.

Fiction cross-reference

• Brownian racket

Nonfiction cross-reference

• Maxwell's demon (nonfiction)
• Physics (nonfiction)
• Woodward effect (nonfiction)

External links:

• Brownian ratchet @ Wikipedia

Schematic figure of a Brownian ratchet (Feynman-Smoluchowski ratchet), a simple hypothetical mechanism used in a thought experiment by Marian Smoluchowski and Nobel laureate Richard Feynman to demonstrate the laws of thermodynamics.

The device is a tiny paddlewheel attached to a ratchet. It appears to be an example of a Maxwell's Demon, able to produce useful work from the random thermal motion of molecules at a constant temperature in violation of the Second Law of Thermodynamics. Feynman and others showed why it cannot actually produce work if T1 = T2

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