As ropes get thinner, traditional self-locking belay devices, like Petzl's Grigri, can slip. Mammut's Smart Belay device locks automatically in case of a fall, like the Grigri, and it can handle ropes from 8.9 to 10.5 millimeters. The true beauty of this device is that it has no moving parts and is totally intuitive. To release it, you pull up on the lever, not down, which is instinctive in the case of a fall. It's for climb and lower only, not autoblocking for anchor clipping.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.