Earlier this year, a robot completed a half-marathon in Beijing in just under 2 hours and 40 minutes. That’s slower than the human winner, who clocked in at just over an hour—but it’s still a remarkable feat. Many recreational runners would be proud of that time. The robot kept its pace for more than 13 miles (21 kilometers).

But it didn’t do so on a single charge. Along the way, the robot had to stop and have its batteries swapped three times. That detail, while easy to overlook, speaks volumes about a deeper challenge in robotics: energy.

Modern robots can move with incredible agility, mimicking animal locomotion and executing complex tasks with mechanical precision. In many ways, they rival biology in coordination and efficiency. But when it comes to endurance, robots still fall short

See Full Page