Landauer's_principle
Landauer's principle is a physical principle pertaining to a lower theoretical limit of energy consumption of computation. It holds that an irreversible change in information stored in a computer, such as merging two computational paths, dissipates a minimum amount of heat to its surroundings. In the formulation of Charles H. Bennett, any logically irreversible manipulation of information, such as the erasure of a bit or the merging of two computation paths, must be accompanied by a corresponding entropy increase in non-information-bearing degrees of freedom of the information-processing apparatus or its environment; the entropy thus resides in the physical hardware and its surroundings, not in the bit as a logical entity. It is hypothesized that energy consumption below this lower bound would require the development of reversible computing.