A futuristic, magnetic-levitation train derailed in northwestern Germany this week, killing 23 people. The high-speed maglev train was a demonstration vehicle used to show off the technology to potential buyers. It was going nearly 125 mph along a 20-mile test track when it slammed into a maintenance cart. Most of the passengers were train employees and their family members. Magnetic-levitation trains have superstrong magnets that keep them hovering just above the tracks, allowing them to race along without friction and reach speeds of more than 300 mph. Though maglev technology has been touted for years, the trains only operate commercially in two countries, China and Japan.