Translucent, ethereal blue and over 96% air, aerogels are the lightest solids in the world. They’re not actually frozen smoke—they’re an artificial material—but the nickname fits. They owe their creation to a bet between two chemists, Charles Learned and Samuel Stephens Kistler, in 1931: they wanted to see if they could take a gel and replace its constituent liquid with gas, without causing shrinkage. Kistler won.
Though aerogels have been improved upon in the years since, his original premise is the same: a polymer is combined with a solvent to form a gel, then the liquid is extracted from it and replaced with air, hence creating aerogel. The crucial part is that the aerogel must maintain the gel’s structure, so they’re solid to the touch and don’t disintegrate.
Aerogels are actually pretty remarkable—they’re the world’s best insulators, being extremely porous but low in density; they can withstand explosive damager; and they can support several thousand times their weight. Silica-based aerogels are quite fragile, but newer polymer-based ones are extremely strong and flexible.
Aerogels have been used to insulate electronics on a Mars Rover, and because they’ll perform well in differeny gravity situations, they have a lot of space-related applications such as in space suits or for use in cryogenics. There are more down-to-Earth applications too, such as insulating blankets or tents, and uses in refrigeration and construction.