2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/200127A cosmological time variable is emerged from the Hamiltonian formulation of Friedmann model to measure the evolution of dynamical observables in the theory. A set of observables has been identified for the theory on the null hypersurfaces that its evolution is with respect to the volume clock introduced by the cosmological time variable.11 pagesGeneral Relativity and Quantum Cosmologytext