Before the end of this decade, three competing experiments (ALPHA, AEGIS and GBAR) will discover if atoms of antihydrogen fall up or down. We wonder what the major changes in astrophysics and cosmology would be if it is experimentally confirmed that antimatter falls upward. The key point is: if antiparticles have negative gravitational charge, the quantum vacuum, well established in the Standard Model of Particles and Fields, contains virtual gravitational dipoles. The main conclusions are: (1) the physical vacuum enriched with gravitational dipoles is compatible with a cyclic universe alternatively dominated by matter and antimatter, without initial singularity and without the need for cosmic inflation; (2) the virtual dipoles might explain the phenomena usually attributed to dark matter and dark energy. While what we have presented is still far from a complete theory, hopefully it can stimulate a radically different and potentially important way of thinking.