This week, researchers working with the Large Underground Xenon (LUX) detector at the Sanford Underground Research Facility in Lead, South Dakota, announced that they see no signs of the lightweight dark matter particles hinted at by other experiments. LUX stalks weakly interacting massive particles (WIMPs), physicists' best guess at what makes up dark matter. Most theorists estimate that WIMPs, if they exist, weigh a few hundreds of times as much as a proton, but a few experiments have reported signs of WIMPs weighing less than 10 times as much as a proton. LUX researchers say their detector, which started taking data in April, is so sensitive that it should have seen hundreds of light WIMPs if they were there. It saw none. If the result is confirmed, it could settle a long-standing debate.