Tracking bullets

Technologically, a bullet is pretty boring. It’s just a slug of metal that flies through the air at high speeds and hopefully kills somebody. Leave it to DARPA to try to jazz up simple munitions by making them able to adjust their course in mid-air. The agency’s Exacto program has constructed .50 caliber shells with inbound computer guidance systems that manipulate small fins on the bullet’s surface that allow it to make course corrections during flight to take environmental factors into account. They even work to home in on moving targets, which is pretty scary to see in action.