What's as light as smoke but strong as a brick?

The answer: aerogel.

Aerogel is the lightest solid on earth. It starts out as a kind of chemical Jello®. Then the gel is dried in a powerful pressure cooker and emerges as a very lightweight, dry, sponge- like material that looks like frozen smoke. Aerogel is also ninety-nine-point-eight percent air.

It's incredibly light--one thousand times less dense than glass. But it's also really strong and an excellent insulator. Scientists are using it to try to capture dust particles from the tail of a comet. When the particles slam into an aerogel panel aboard a space probe, they'll bury themselves inside and leave visible trails. Since aerogel is mostly air, it won't damage the particles.