Q. Do you know which is the world’s lowest density (lightest) solid?
Ans. The world's lowest density or the lightest solid material is Aerogel which is composed of about 99.98% air by volume. It is usually composed of silica or carbon compounds. It is a synthetic material that is dry, translucent, porous and solid framework of a gel. In general, aerogels are pretty fragile. Due to its appearance and ultra-lightweigth, it is also named 'frozen smoke'.