Three decades have passed since the first direct search for dark matter, a modest attempt at recycling the data from a particle detector originally built for another purpose. This work was a rapid response to a proposal by theoretical physicists Mark Goodman and Edward Witten, who called attention to the possibility of detecting dark matter via nuclear recoils.
The experimental approach proposed is similar to playing billiards with an invisible cue ball. If you see a colored billiard ball (an atomic nucleus in the body of the detector) suddenly veering off for no apparent reason, you know it must have been struck by something you can’t see directly (a dark-matter particle).
The hypothetical cue balls were clumped together under one witty denomination: WIMPs, for Weakly Interacting Massive Particles. This rather generic term encompasses all new particles able to produce nuclear recoils, while not partaking of other mechanisms of interaction favored by the riffraff of known particles.