Dark matter makes up about 90 percent of the universe's mass—but it's invisible. How do you detect the invisible? First you have to figure out what you're looking for. One theory says that dark matter exists alongside normal matter in the form of weakly interacting massive particles (WIMPs). So researchers built this thing, the DarkSide-50. It's one of the most sensitive dark matter detectors on the planet, and it will be switched on early next year at Gran Sasso National Laboratory, a sprawling subterranean playground for particle physicists northwest of Rome.
The DarkSide-50 is a 36-foot-tall steel cylinder that houses a steel sphere, 13 feet in diameter, which contains a 3-foot-tall cylinder-shaped cryostat that keeps 110 pounds of liquid argon extremely cold. The DarkSide-50 aims to detect the WIMPs as they pass through the super-pure argon. If all goes according to plan, a WIMP or two will collide with an argon nucleus, which will emit a flash of light. Invisible fingers crossed.
