2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123753It is pointed out that in curved spacetime, one cannot define the sum of energy-momemtum 4-vector over a space-like hypersurface. The difficulty in finding satisfactory gravitational energy-momentum complex stems from misunderstanding of this question. The law of conservation of energy-momentum holds valid only approximately when spacetime is not seriously curved.15 pages, 0 figureGeneral Relativity and Quantum Cosmologytext