2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/14869The rotation curves of disk galaxies exhibit a number of striking regularities. The amplitude of the rotation is correlated with luminosity (Tully-Fisher), the shape of the rotation curve is well predicted by the luminous mass distribution, and the magnitude of the mass discrepancy increases systematically with decreasing centripetal acceleration. These properties indicate a tight connection between light and mass, and impose strong constraints on theories of galaxy formation.8 pages, ASP LaTeX. Invited review for Galaxy Dynamics: from the Early Universe to the Present, eds. Combes, Mamon, & CharmandarisAstrophysicstext