When rockets go fast, they break the sound barrier. And when the sound barrier breaks, we get the Prandtl–Glauert singularity. That's the official term for the beautiful cone of vapor that forms around a craft moving very, very fast through the atmosphere. And it makes for a great photo.
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.