The Time Arrow of Radiation
After a stone has been dropped into a pond, one observes concentrically diverging waves. Similarly, after an electric current has been switched on, one finds a ‘retarded’ electromagnetic field that is moving away from its source. Since the fundamental laws of nature, which describe these phenomena correctly, are invariant under time-reversal, they are equally compatible with the reverse phenomena, in which, for example, concentrically focusing waves (and whatever had been caused by the stone — such as heat) would ‘conspire’ in order to eject a stone out of the water. Deviations from the time reversal symmetry of the laws would modify this argument only in detail, as one merely had to alter the reverse phenomena correspondingly (cf. the Introduction). Such reverse phenomena have, however, never been observed in nature. The absence of focusing processes in high-dimensional configuration space may similarly describe the time arrow of thermodynamics (Chap. 3) or, when applied to wave functions, possibly even that of quantum theory (see Sect. 4.6).
KeywordsStein Nite Cady
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