The light side of dark matter

New technology and new thinking are pushing the dark matter hunt to lower and lower masses. It's a seemingly paradoxical but important question in particle physics: Can dark matter be light? Light in this case refers to the mass of the as-yet undiscovered particle or group of particles that may make up dark matter, the unseen stuff that accounts for about 85 percent of all matter in the universe. Ever-more-sensitive particle detectors, experimental hints and evolving theories about the makeup of...