Aerogel, AKA "Frozen Smoke"
The phrase "frozen smoke" describes the world's lightest solid material. Known as aerogel, this material is 95-99% air. There are many different kinds of aerogels, made from substances from silica to carbon nanotubes. All of them are incredibly light, because their liquid component has been replaced with a gas. They're typically around 20 times heavier than air, though a silica aerogel has been created that was only three times heavier than air.
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Key Facts In This Video
Aerogel has had its liquid component removed, leaving its molecular structure intact. (0:35)
Aerogel can hold up to 4,000 times its weight in force, but it's also very brittle. (1:06)
Aerogel tiles are used in space to collect dust from comets. (1:48)