Berlin 2014 – wissenschaftliches Programm
AGPhil 8.2: Vortrag
Freitag, 21. März 2014, 18:00–18:30, SPA SR22
The radiation arrow of time is not a statistical arrow — •Wolfgang Pietsch1 and Mathias Frisch2 — 1TU München, Germany — 2University of Maryland, College Park, USA
We comment on the debate concerning the radiation arrow of time in classical electrodynamics starting with the Ritz-Einstein debate at the beginning of the 20th century up to more modern considerations involving among others Earman, Rohrlich, and Frisch. We first identify and distinguish several asymmetries, which have often been confused: between retarded and advanced fields, retarded and advanced potentials, converging and diverging fields, converging and diverging potentials, converging and diverging electromagnetic waves. Furthermore, a crucial issue regards whether we consider point or extended charges as sources. Some, but by no means all of these asymmetries can be shown to coincide. Various reasons are discussed for a non-statistical asymmetry concerning the way potentials or fields are generated by point charges or point charge elements. Most importantly, the main classical derivations of the radiation reaction either presuppose retarded solutions and would yield wrong results using advanced solutions or at least presuppose an asymmetric role for retarded and advanced potentials. The usual counterarguments are shown to employ other notions of symmetry that are compatible with the described non-statistical asymmetry, which by the way was already identified a century ago by Walther Ritz.