Maxwell’s equations are well-known to include both “advanced” and “retarded” solutions. The retarded solution \[ \phi_{\text{ret}}(r,t) = \int dr' \rho\frac{(r', t- \frac{\lvert r'-r\rvert}{c})}{\lvert r'-r\rvert} \] gives the field amplitude \(\phi_{\text{ret}}\) at \(r,t\) by finding the source density \(r\) at \(r'\) at earlier times. The advanced solution \[ \phi_{\text{adv}}(r,t) = \int dr' \rho\frac{(r', t+ \frac{\lvert r'-r\rvert}{c})}{\lvert r'-r\rvert} \] gives the field amplitude in terms of the source density at \(r'\) at later times. Physicists routinely discard the advanced solutions for reasons of “causality”. It is not so clear thermodynamic considerations are behind this rejection of solutions, an asymmetry made all the harder to see given the freedom electromagnetism has to rewrite retarded fields in terms of advanced fields and outgoing sourceless radiation (and vice versa). Electromagnetism is also said to be allow emissions and not absorptions. Accelerating charges are also damped and not anti-damped by the field. With so many arrows besides the wave asymmetry—emission/absorption, in/out, retarded/advanced, damped/anti-damped—it’s premature to say that the thermodynamic arrow is the one arrow to rule them all. Most agree that the wave asymmetry is ultimately “thermodynamic” but after that matters are contested.