Published online by Cambridge University Press: 24 October 2008
Recent discoveries have shown that two light quanta with total energy not less than 2mc2 can create a pair of electrons (inverse process to the ordinary annihilation). Hence it follows that ordinary black-body radiation no longer represents an equilibrium state. In thermodynamic equilibrium a certain number of electron pairs must be present, the number of which will depend upon the temperature. It can be calculated as follows.
* Note added in proof. The probability of the creation of a pair by two light quanta has in the meantime been calculated by Breit, J. and Wheeler, T. A., Phys. Rev. 46 (1934), 1087.Google Scholar
* If, besides the electron pairs, a certain additional number of negative electrons are present, the left-hand side of (5) has to be replaced by √N + N −, where N − represents the total number of negative electrons.