2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/156723We give a derivation of the Einstein equation for gravity which employs a definition of the local energy density of the gravitational field as a symmetric second rank tensor whose value for each observer gives the trace of the spatial part of the energy-stress tensor as seen by that observer. We give a physical motivation for this choice using light pressure.Mathematical PhysicsDifferential Geometry83C05; 83C40; 83C99text