Blog post: swansont: Four Legs Good, Two Legs Bad

DARPA's Cheetah robot—already the fastest legged robot in history—just broke its own land speed record of 18 miles per hour (mph). In the process, Cheetah also surpassed another very fast mover: Usain Bolt. According to the International Association of Athletics Federations, Bolt set the world speed record for a human in 2009 when he reached a peak speed of 27.78 mph for a 20-meter split during the 100-meter sprint. Cheetah was recently clocked at 28.3 mph for a 20-meter split. The Cheetah had a slight advantage over Bolt as it ran on a treadmill, the equivalent of a 28.3 mph tail wind, but most of the power Cheetah used was to swing its legs fast enough, not to propel itself forward.