How old is the universe?
A dynamical model of the decaying vacuum energy is presented, which is based on Jordan-Brans-Dicke theory with a scalar field ??. The solution of an evolutionary differential equation for the scalar field ?? drives the vacuum energy towards a cosmological constant at the present epoch that can give for the age of the universe, t0 ??? 13.5 Gyr for ??0 = 1, which is consistent with the age of globular clusters. ?? 1995.