Aaron Manalaysay, the physics coordinator of Lawrence Berkeley National Lab's experiment, explains how the underground detector will interact with dark matter in the Sanford Underground Research Facility in Lead, S.D., on Dec. 8, 2019. Scientists have begun a new search for mysterious dark matter in a former gold mine a mile underground. Dark matter makes up the vast majority of the mass of the universe but scientists don't know what it is. (AP Photo/Stephen Groves)