We’re not sure what brand of batteries it was using, but the Cornell Ranger robot just kept going and going April 3 when it set an unofficial world record by walking nonstop for 45 laps — a little over 9 kilometers or 5.6 miles — around the Barton Hall running track.Developed by a team of students working with Andy Ruina, Cornell professor of theoretical and applied mechanics, the robot walked (and walked) until it finally stopped and fell backward, perhaps because its battery ran down. “We need to do some careful analysis to find out for sure,” said Greg Stiesberg, a graduate student on the team.An earlier version of the same robot had already set a record by free-walking a bit over 1 kilometer, about .62 miles. (Another robot has walked 2.5 kilometers [1.55 miles] on a treadmill, Ruina noted. A six-legged robot has walked a bit more than 2 kilometers, and there’s some debate over whether or not that counts.)…Read the rest here.