2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35976The Thompson cross section for scattering of electromagnetic waves by a free electron in an expanding universe is derived here. The equations of motion of the electron are obtained using the Einstein-Infeld-Hoffmann (EIH) surface integral method. These integrals are evaluated approximately by perturbing off an Einstein-deSitter cosmological field. It is found that the Thompson cross section varies with time as the inverse square of the cosmic scale factor R(t).4 pagesGeneral Relativity and Quantum Cosmologytext