  In this paper we point out that the radius R, the age t and the mass M of the
observable Universe are proportional to Planck units for length lp, time tp and
mass mp.This hypothesis is related, by a cosmological model linking the
universal expansion to the speed of light, with a time variation of c and of
the Planck constant, which implies that lp and tp increase with time while mp
remains constant. We discuss some of the implications these relationships could
have on quantum cosmology and obtain that the Universe entropy associated to
the event horizon is constant along its history. Quantum effects were smaller
in the past, in such a way that their conflict with general relativity about
the Planck era vanishes.
