MAXWELL'S DEMON AND THE CONNECTION BETWEEN ENTROPY AND INFORMATION

SZILARD, LEO.

Über die Entropieverminderung in einem thermodynamischen System bei Eingriffen intelligenter Wesen. [On the Decrease of Entrophy in a Thermodynamic System by the invention of intelligent Beings).

Berlin, Julius Springer, 1929.

8vo. Contemp. hcloth. Some wear to edges and spine. A stamp on title-page. In "Zeitschrift für Physik", vol. 53. The whole volume offered. VII,(1),889,(1) pp. Szilard's paper: pp. 840-856.

First edition of the important paper in which Szilard solved the puzzle of Maxwell's demon and discovered a theoretical model that serves both as a heat engine and an information engine, establishing the connection between entropy and information.

Szilard was the first to stress that any manipulator of molecules would have to rely on measurement and memory. If one assumed that the demon could perform such operations without causing any changes in the system, one would by that very assumption deny the second law of thermodynamics, which requires equivalent compensations for all decreases in entropy. Szilard therefore proposed that whatever negative entropy Maxwell's demon might be able to create should be considered as compensated by an equal entropy increase due to the measurements the demon had to make. In essence, Szilard made Maxwell's doorkeeper mortal - no longer granting this tiny intelligence the ability to 'see' molecules without actually seeing them, i.e., without the sensory exchanges of energy that all other existences require.

Szilard took this step for the sake of a grander vision, the dream that the adoption of his principle would lead to the discovery of a more general law of entropy in which there would be a completely universal relation for all measurements. Information theory has brought that vision to reality.

Order-nr.: 39204