But a number of WIMP experiments around the world are nearly ready to announce results, so confirmation or repudiation could come soon. The NY Times article referenced above notes that, at the presumed mass of the presumed neutralino, the galaxy would be imbedded in a cloud with a density of around one WIMP per teacup of space. Good thing they interact only weakly. Not all of the matter in the universe is luminous. Dark matter is anything that doesn't shine brightly enough for us to detect it across whatever gap separates us.
Luminous matter is also insufficient to explain the rotation of galaxies.
One explanation for this is that the galaxies are embedded in haloes of invisible matter far larger and more massive than the luminous parts we can see. The CC would cause the expansion of the universe to accelerate over time. Weirdly enough, this is exactly what researchers inferred from data on distant supernovas beginning about 2 years ago. The most straightforward interpretation of these events is that they represent a significant component of the dark halo of the Milky Way. Alternative explanations have been advanced, and it has proved difficult to distinguish between the various suggestions.