Ranger, a four legged bi-pedal robot, set an unofficial record at Cornell last month for walking 23 kilometers (14.3 miles), untethered, in 10 hours and 40 minutes. Walking at an average pace of 2.1 km/h (1.3 miles per hour), Ranger circled the indoor track at Cornell’s Barton Hall 108.5 times, taking 65,185 steps before it had to stop and recharge. Ranger walks much like a human, using gravity and momentum to help swing its legs forward, though its looks like a boom box on stilts. Its swinging gait is like a human on crutches since the robot has no knees, and its two exterior legs are connected at the top and its two interior legs are connected at the bottom.