Radar guns capture a baseball’s speed using a single antenna in a four-to-nine-inch horn. This radar uses a flat array of 16 smaller antennas to track velocity, allowing the package to be about as small as an iPod. $200
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.