Time reversal invariance and the arrow of time in classical electrodynamics.
Time reversal invariance, T, is well known to hold in quantum electrodynamics. However, it has caused difficulties in classical electrodynamics (CED). These are shown to be conceptual misunderstandings. When corrected: (1) the classical equations of motion of a charge are T invariant despite the explicit occurrence of retarded fields in the equations of motion. (2) Advanced fields violate causality and occur neither in nature nor in the CED that describes it. (3) The nonexistence of advanced fields in nature implies an "arrow of time" for electromagnetic radiation: radiation emission is an overall dissipative phenomenon. This electromagnetic "arrow of time" does not contradict time reversal invariance.
Rohrlich
Fritz
F
Department of Physics, Syracuse University, Syracuse, New York 13214, USA. Rohrlich@syr.edu