2002/06/20 by G. Gilat, Gilat, G.
Chemistry · Neuroscience · Physics and Astronomy · #Biological Physics (physics.bio-ph) #FOS: Physical sciences #Origins and Evolution of Life #Photochemistry and Electron Transfer Studies #Photoreceptor and optogenetics research #physics.bio-ph
paper · pdf · doi:10.48550/arxiv.physics/0206074
openalex publication_date 2002/06/20 · arxiv created 2002/06/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Chirality is considered by many scientists to be mainly a geometric concept. There exists also a physical aspect of chirality which is largely being overlooked at. Two examples of mechanical devices are introduced here that represent ``Physical Chirality''. These are a rotating water sprinkler and a variant of Crookes' radiometer. When interacting with appropriate media, they both choose only one mode of rotation out of two possible ones. Such a behavior does not obey time-reversal invariance, which is regarded to be a rule in classical mechanics. This is due to their chiral nature. Instead, they do obey a space-time (ST) law of invariance, that is, what is rotating in the opposite direction is the mirror-image of the given device. In a recent experiment of Koumura et al. they discovered a similar behavior of a molecular rotor. The possible biological significance of physical chirality is emphasized hereby, and the conclusion is that chiral molecular systems do not reach readily thermal equilibrium. In other words: ``Physical chirality does feed on negative entropy'', and therefore, it may well be of crucial value to life.