2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35839We show that the gravitational modification of the phase of a neutron beam (the COW experiment) has a classical origin, being due to the time delay which classical particles experience in traversing a background gravitational field. Similarly, we show that classical light waves also undergo a phase shift in traversing a gravitational field. We show that the COW experiment respects the equivalence principle even in the presence of quantum mechanics.LaTeX, 8 pages plus two figures in one postscript fileGeneral Relativity and Quantum CosmologyQuantum Physicstext