Behold a piece of "silica aerogel" -- possibly the weirdest substance on Earth. Remember two weeks ago when the Stardust space probe gathered material from a comet's tail? It was using a big chunk of this material as a net. Silica aerogel is made by mixing silicon dioxide with liquid alcohol, then drying out all the alcohol until you have the least-dense matter on earth: A piece of silica aerogel is 99.6 per cent empty space. When you look at it, your eyes can't quite focus because it scatters light the same way a hologram does.

It is also the best insulator on the planet. That picture above? It's hard to make it out at that tiny size, but it's a flower resting on a piece of thin slab of silica aerogel, perfectly insulated from a blowtorch going full steam below. According to a piece on the stuff in today's New York Times:

"It has 14 Guinness Book of World Records-type properties," Dr. Tsou said. "It's the lowest density of any solid, and it has the highest thermoinsulation properties. Though it would be very expensive, you could take a two- or three-bedroom house, insulate it with aerogel, and you could heat the house with a candle. But eventually the house would become too hot."

The true science geeks among you can check out the full Silica Aerogel web site.