Hunting for Dark Matter

Scientists have built extraordinary experiments to detect dark matter directly. Labs deep underground, in old mines, shield their detectors from the cosmic-ray noise found at the surface. The leading suspects are WIMPs — Weakly Interacting Massive Particles. Detectors use ultra-pure xenon or germanium crystals cooled near absolute zero, waiting for a rare collision that would leave a tiny flash of light or heat. Decades of searching have turned up nothing, pushing physicists toward alternatives like axions, much lighter hypothetical particles that are now a hot research target.