Absorbing the Arrow of Electromagnetic Radiation

TL;DR

This paper explores the electromagnetic radiation arrow as part of broader temporal asymmetries, proposing explanations rooted in initial conditions and statistical postulates rather than modifying physical laws or adopting direct interaction theories.

Contribution

It introduces a novel explanation for the electromagnetic arrow based on the past hypothesis and statistical postulate, contrasting it with existing approaches like boundary conditions and direct interaction theories.

Findings

The electromagnetic arrow can be explained by initial conditions and statistical postulates.

Alternative explanations include modifying laws, direct interactions, and Wheeler-Feynman theory.

The approach unifies electromagnetic asymmetry with broader temporal asymmetries in nature.

Abstract

We argue that the asymmetry between diverging and converging electromagnetic waves is just one of many asymmetries in observed phenomena that can be explained by a past hypothesis and statistical postulate (together assigning probabilities to different states of matter and field in the early universe). The arrow of electromagnetic radiation is thus absorbed into a broader account of temporal asymmetries in nature. We give an accessible introduction to the problem of explaining the arrow of radiation and compare our preferred strategy for explaining the arrow to three alternatives: (i) modifying the laws of electromagnetism by adding a radiation condition requiring that electromagnetic fields always be attributable to past sources, (ii) removing electromagnetic fields and having particles interact directly with one another through retarded action-at-a-distance, (iii) adopting the Wheeler-Feynman approach and having particles interact directly through half-retarded half-advanced action-at-a-distance. In addition to the asymmetry between diverging and converging waves, we also consider the related asymmetry of radiation reaction.