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Three or four more WIMP-like interactions recorded over the next few years by the experiment, now being upgraded with detectors containing three times as much germanium, would constitute proof of dark matter, Hogan says.

“That would be a huge transformation in how we do science,” he notes. “We would have a new form of matter to study.”

The late astronomer Fritz Zwicky first proposed the existence of dark matter in the 1930s when he calculated that the amount of ordinary matter in the Coma cluster of galaxies wasn’t enough to keep the cluster from flying apart. Additional, unseen material could provide the extra gravitational tug, he suggested. Since the 1970s astronomers have accumulated further evidence that the Milky Way and other galaxies are bathed in dark matter.

“We’ve seen evidence from many parts of the universe that dark matter is out there,” Hsu said.

Depending on the exact nature of dark matter, it could unify the subatomic world with the cosmic canvas. While astronomers need dark matter to explain the growth and motions of galaxies, particle physicists who subscribe to a theory called supersymmetry have proposed that every subatomic particle has an as yet undetected heavier partner. The least massive, electrically neutral of those partners might be the WIMP.

It was only a month ago that the researchers realized that they had found possible evidence of dark matter. During a videoconference on November 5, several members of the team presented independent findings on data analyzed in 2007 and 2008. To avoid unintentional bias, those analyses cataloged all the signals without focusing on those that might match WIMP signatures. Then, as the videoconference continued, Zeeshan Ahmed of Caltech and Matthew Fritts of the University of Minnesota in Twin Cities ran their own analyses. Ahmed’s results popped up first on a computer screen, revealing the detection of two candidate WIMPs. For the next 30 seconds, there was stunned silence on the videoconference, broken by a cacophony of excited comments.

WIMP fingerprints might be detected by a slew of experiments on the ground and in space (SN: 5/10/08, p. 12, p. 8; SN: 9/27/08) including collisions of high-energy protons at the world’s most powerful atom smasher, the Large Hadron Collider near Geneva. Physicists using the LHC, which has now resumed operation after a year of repairs, plan to look for what would be missing: a deficit of energy in the collision debris could be evidence for dark matter particles. (SN: 7/19/08, p. 16).