Szilard Engine

Szilard engine is a thought-experiment devised by Leo Szilard in 1929 to probe the relationship between information and thermodynamic work. It consists of a single molecule in a box, divided by a partition; a 'demon' measures which side the molecule occupies, then extracts work by letting the molecule push the partition. The engine demonstrated that information acquisition has thermodynamic consequences — a precursor to Landauer's Principle and the full framework of the thermodynamics of computation.

The resolution of the apparent paradox — that the demon seems to violate the Second Law of Thermodynamics — mirrors the resolution of Maxwell's Demon: the cost is paid in erasure, not in measurement. Szilard's engine is therefore not merely a historical curiosity but the foundational prototype of information-powered heat engines, devices that convert information into work with the same formal rigor as heat engines convert thermal gradients.