Astrophysicist Fritz Zwicky calculated that the Coma cluster, one of the densest known galaxy clusters, needed to contain about 400 times its apparent mass--otherwise it would fly apart.
The stars at the edge of the Andromeda galaxy seem like they should move more slowly than those in the center, but astronomer Vera Rubin discovered that they were traveling at about the same speed.
The DAMA/LIBRA experiment sees an annual modulation in its signals from possible dark matter particles, which could be caused by Earth's rotation around the sun.
The AMS experiment, attached to the International Space Station, this year found an excess of positrons that could point to dark matter.
The LUX experiment is currently the world's most sensitive dark-matter detector.
The LUX experiment recently released its first results, which contradicted another experiment's previous possible dark-matter detection.
Scientists at experiments at the Large Hadron Collider hope to produce and detect dark matter particles.