ScienceNow: Darth Vader might be disappointed to hear it, but the force of gravity does not have a dark side. Dark matter does not pull on other dark matter with any extra gravity or additional force, as some researchers have suggested, a pair of theoretical physicists reports. Based on observations of a pip-squeak galaxy orbiting our own, more massive, Milky Way galaxy, the argument could shoot down theories invented to explain other puzzling observations. Some researchers are skeptical, however.