An extension of the MIT bag model, developed to describe the strong interaction inside the hadronic matter (nucleons), is proposed as a means to account for the confinement of matter in the universe. The basic hypotheses of the MIT bag model are worked out in a very simplified way and are also translated in terms of the gravitational force. We call the nucleon "microcosmos" and the bag-universe "macrocosmos." We have found a vacuum pressure of 10-15 atm at the boundary of the bag-universe as compared with a pressure of 1029 atm at the boundary of the nucleon. Both universes are also analyzed in the light of Sciama's theory of inertia, which links the inertial mass of a body to its interaction with the rest of the universe. One of the consequences of this work is that the Weinberg mass can be interpreted as a threshold mass, namely the mass where the frequency of the small oscillations of a particle coupled to the universe matches its de Broglie frequency. Finally, we estimate an averaged density of matter in the universe, corresponding to [Formula: see text] of the critical or closure density.