Tag: Information Theory

Physicists Prove Knowledge is Power — Almost Literally

By Eric Wolff | November 15, 2010 4:00 am

maxwell-stairsMy teachers in grade school always said knowledge was power, but who knew they were being literal, if perhaps imprecise. Knowledge, it turns out, is energy, and it converts at a rate of 28 percent, according to Shoichi Toyabe, of Chuo University, and Masaki Sano, of the University of Tokyo.

Their experiment has its origins back in 1871, when James Maxwell proposed a thought experiment: A demon controls the only door in a wall separating two sealed chambers filled with gas molecules. The demon allows only fast moving particles to enter one room, and only slow moving particles to enter the other room. After a while, one room has only fast moving particles, and the other has only slow moving particles. The system has lost entropy, but without expending any energy, creating a seeming violation of the second law of thermodynamics.

Leo Szilard, a Hungarian physicist, offered a key insight into Maxwell’s paradox in 1929: The demon had to expend energy measuring the speed of the molecules, thus the overall system of demon plus gas actually required work and the expenditure of energy. The demon used energy to take a measurement, creating information, preserving the second law, and establishing the idea that information could be converted to energy, and vice versa.

Proving that idea in the lab took another eight decades.

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CATEGORIZED UNDER: Energy, Physics, Top Posts
MORE ABOUT: Information Theory

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