EARLIER this year, an American physicist challenged the second law of thermodynamics, a cornerstone of physics. Carlton Caves of the University of Southern California, Los Angeles, suggested that a microscopic device, known as a Maxwell demon, might be able to transfer heat from a cold body to a hot body and obtain 'free' energy (New Scientist, Science, 14 July). Now Caves concedes that he overlooked a key fact.
Caves's idea has already attracted a flood of counter-arguments in a recent issue of Nature (vol 347, p 24). But now Caves and his colleagues have come up with the definitive rebuttal. He and a group of theorists found a flaw in the work at a seminar held at the Santa Fe Institute, New Mexico, in April.
A Maxwell demon is an imaginary creature which watches gas molecules in a box. When it sees a fast molecule approaching, it opens a small ...
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