Szilard’s demon

Szilard's demon
American quantum information theorist Charles Bennett's 1987 rendition of Szilard's demon collecting information on the particles of the system. [3]
In demons, Szilard’s demon is a hypothetical intelligent being noted for his sharp “vision” ability to continuously observe and collect “information” the speeds and positions of the various particles of two chambers of gas molecules separated by a frictionless sliding door. If the collecting powers of the demon are above or beyond the control of the second law the demon will be able to move heat from a cold body to a hot body without the expenditure of work; if conversely the act of collecting information requires energy, then, according to the second law, a loss of available energy will progress, as the entropy of the two systems combined increases as the motions of the total set of particles moves toward equilibrium. [1]

The Szilard demon was described in Hungarian physicist Leo Szilard's 1929 “On the Decrease in Entropy in a Thermodynamic System by the Intervention of Intelligent Beings”, in which an attempt was made to disprove the existence of a Maxwell's demon, by arguing that the logarithmic interpretation of entropy (S = k ln W) could be used to determine the entropy produced during the ‘measurement’ of information the demon discerns when viewing the speeds and positions of the particles in his two compartments. [2]

Evolution and heat death
In 1946, Belgian-born English thermodynamicist Alfred Ubbelohde seems to have used the Szilard demon model to argue that new findings in quantum physics and aspects of radiation thermodynamics might negate the heat death ultimatum of the universe. [1]

See also
Szilard’s paradox
Maxwell’s demon
Laplace’s demon

References
1. Ubbelohde, Alfred René. (1947). Time and Thermodynamics (pgs. 90-91). Oxford University Press.
2. Szilárd, Leó. (1929). “On the Decrease in Entropy in a Thermodynamic System by the Intervention of Intelligent Beings” (Uber die Entropieverminderung in einem thermodynamischen System bei Eingriffen intelligenter Wesen), Zeitschrift fur Physik, 53, 840-56.
3. Bennett, Charles H. (1987). “Demons, Engines, and the Second Law”, Scientific American, 257(5): 108-116, Nov.

Further reading
● Berger, Jorge. (1990). “Szilard’s Demon Revisited” (abstract), International Journal of Theoretical Physics, 29(9): 985-95.

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