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Phoenix666 [soylentnews.org] writes:

Light consists of tiny indivisible portions, the photons. Under certain conditions, they, too, can condense, if they are cooled enough. Many thousands of these light packets then suddenly fuse into a kind of super-photon with unusual characteristics – a so-called Bose-Einstein condensate.

The physicists at the University of Bonn have now been able to show that the photon gas at this phase transition behaves according to the theoretical predictions of Bose and Einstein [phys.org]: Similar to water, it abruptly changes its heat storage capacity, meaning the ability to store thermal energy. "This behavior was already known from condensed atoms", explains Prof. Dr. Martin Weitz of the Institute of Applied Physics. "However, this is the first time that this phenomenon has been demonstrated for a condensate of light".

Atoms, too, form a Bose-Einstein condensate, when they are cooled greatly and enough of them are simultaneously concentrated in a small space. They then suddenly become indistinguishable: They act like a single giant atom. Twenty years ago, physicists already demonstrated that the heat capacity of atoms suddenly changes at this phase transition. How strong this change is, however, can be measured only imprecisely for atoms. "In our condensate, this can be done substantially better", emphasizes Dr. Jan Klärs, who has since moved from Bonn to ETH Zurich.

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