We've been impressed in the past by aerogel, a lattice-like solid that's almost entirely made of air but can support weight and also has tremendous insulating properties. Then last year an ultralight metal caught our eye, weighing in at 99.99 percent air, which leaves 0.01 percent solid.
Now we are excited to meet aerographite, a sponge grown of carbon nanotubes that's the least dense solid ever: a cubic centimeter of it weighs just two ten-thousandths of a gram.
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.