Aerogel bulletproof is not afraid of being bombed and not afraid of fire, so what is aerogel?

Aerogel is not the glue we know, it is a form of solid matter with a density of 3KG/m. Because of its extremely low density, it is also called "frozen smoke" or "blue smoke", which has won the Guinness Book of Records. "World's Lightest Solid" title. As early as 1931, SiO2 aerogel was successfully prepared by S. Kistler by supercritical drying method. Since more than 80% of the aerogel is air, it has a very good thermal insulation effect. One inch thick aerogel is equivalent to the thermal insulation function of 20 to 30 pieces of ordinary glass. Even if the aerogel was placed between the finger and the flame, the finger would remain unscathed.