General Relativity: An Introduction for Physicists · Problem 7.2
The equivalence principle and spacetime curvature — Hobson, Efstathiou & Lasenby
Physics · equivalence-principle-radiation
Problem
A charged object held stationary in a laboratory on the surface of the Earth does not emit electromagnetic radiation. If the object is then dropped so that it is in free fall, it will begin to radiate. Reconcile these observations with the principle of equivalence. Hint: Consider the spatial extent of the electric field of the charge.