We love DARPA's unsettlingly-lifelike BigDog bot. We love it in spite of the fact that it's absolutely terrifying in motion. Now it has some bestial competition: the DARPA Cheetah. Ugh. Its legs. Its legs are so frightening.
Above, the Cheetah sets a speed record for four-legged robots, at 18 MPH. Herculean Olympian speed impossibility Usain Bolt can sprint at around 23 MPH. And he's a mutant of physical capability.