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3 The quantum-mechanical vacuum

Quantum physics reveals that even an ideal vacuum, with a measured pressure of zero torr, isn't really empty. One reason is that the walls of the vacuum chamber emit light in the form of black-body radiation: visible light if they are at a temperature of thousands of degrees, infrared light if they are cooler. This soup of photons will be in thermodynamic equilibrium with the walls, and the vacuum can consequently be said to have a particular temperature. More fundamentally, there are quantum-mechanical fluctuations in the vacuum. This may be responsible for the observed value of the cosmological constant.

4 See also

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