Mark French, a professor at Purdue University, created this cannon that'll accelerate a fragile ping-pong ball up to Mach 1.2--that's 900mph. This video goes into some nice physics-y depth about the logistics of getting a thin sphere of plastic up to that speed, and then the payoff at the end is just great. Turns out a 900mph ping-pong ball blasts clear through a paddle. [YouTube via Gizmodo]
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.