Motion of Ratchet

 Asymmetry: Can asymmetric boundaries rectify fluctuations to force and motion?

This is clearly not possible in thermal equilibrium (time reversal symmetry).

Non-equilibrium fluctuations can indeed generate force and motion

• Feynman's ratchet and pawl:  (youtube)                

• Random motion of bacteria:                                   

 Nonequilibrium fluctuations + asymmetry can potentially lead to motive force

 Radiative heat transfer as source of nonequilibrium fluctuations

Next (Heat) Outline Force Motion Heat Reciprocity Efficiency Summary