Limits to the second law of thermodynamics

[Christophe]

Source: CIRS, 22/07/2002


For the first time, researchers have experimentally demonstrated that the second law of thermodynamics does not apply in certain cases.

This law stipulates that in an isolated and closed system, disorder, measured by a quantity called entropy, will increase or at least will not decrease over time. Denis Evans and his colleagues at the Australian National University observed that this was not true for small systems over short periods. This confirms the prediction made by them a few years ago, thanks to the fluctuation theorem they developed . According to this theorem, on the human scale, the second law of thermodynamics dominates and the evolution of things can only be done in one direction, but at the molecular scale, and over very short periods, an evolution in either direction is possible.

In order to test their theory, the researchers conducted an experiment involving a laser beam and microscopic latex grains. They found that in a system as tiny as a grain of latex, entropy could sometimes recede. This was especially true for periods of about a tenth of a second. Over periods approaching two seconds, the decline in entropy continued to occur, but with a much lower frequency, and beyond two seconds the phenomenon no longer occurred. The team also observed that its results closely matched those of a computer simulation of the fluctuation theorem.

The discovery could, according to Evans and his colleagues, have a significant impact on the emerging science of nanotechnology. This result, they said, has profound consequences for all the physical and chemical processes occurring over short periods of time in small "regions".