A four-legged bipedal robot named Ranger, about as tall as a human adult truncated at the hips, has walked 40.5 miles on a single battery charge without stopping or any human hand-holding, smashing a world record, researchers reported this week.

The robot was built and programmed at Cornell University. It started walking around an indoor track on May 1 just after 2:00 p.m. ET and came to an abrupt stop May 2 at 9 p.m., after 30 hours, 49 minutes and 2 seconds. In that time, Ranger made 307.75 laps around the .13 mile track at an ambling pace of 1.3 mph.