2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/34389Some standard definitions and results concerning foliations of dimension one and codimension one are introduced. A proper time foliation of Minkowski space is defined and contrasted with the foliation that is defined by the time coordinate. The extent to which a Lorentz structure on a manifold defines foliations, and the issues concerning the extension of the proper time foliation of Minkowski space to a Lorentz manifold are discussed, such as proper time sections of a geodesic flow.27 pages, 3 figuresGeneral Relativity and Quantum Cosmologytext