2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/209685A bimetric description of the universe is proposed, which explains cosmic acceleration deduced from optically observed high-redshift objects. This phenomenon is classically charged to a mysterious repulsive "dark energy" whose true nature is unknown. This is identified in this model with a set of particles having negative mass and energy. These negative mass particles, emitting negative energy photons, are not observable using optical instruments.14 pages,1 figureGeneral Physics83D05;83B05;83F05text