Weakly interacting massive particles, or WIMPs, are a theoretical construct which was proposed to account for apparently missing mass in the galaxy. These particles would have to have much more mass than traditional hard-to-detect particles like neutrinos, so that they could account for enough of the mass of the galaxy. However, they would have to interact exclusively with the weak force, making it difficult for them to be observed by other, more traditional means. They could not emit light or otherwise interact with the electromagnetic strong forces, making them almost impossible to detect directly.

The rate of the universe's expansion can be measured, and by the current measurements, it is much slower than it ought to be for the amount of matter detected by current standards. Also, the observed movements of galaxies and galactic clusters is not consistent with the gravitational forces...