Answer: Airplanes

Magic Eraser cleaning sponges might seem magic when they remove that ugly stain from your patio furniture or brighten up the plastic on an old toy, but it’s not magic (no matter how impressive), but microscopic science. Magic Erasers are made from a compound known, formally, as melamine foam, and melamine is a micro-abrasive. The reason the erasers remove stains that your other cleaning products wouldn’t touch is because you’re sanding, with a very very fine grit, the surface of the object and physically removing the stain.

In addition to serving as an excellent micro-abrasive, melamine foam has properties that make it useful in the construction of airplanes (as well as high speed trains and other transportation applications). First, the melamine component of melamine foam is naturally fire retardant as it is 67 percent nitrogen by mass and, when mixed with resins, releases lots of fire-retarding nitrogen gas when burned. More importantly, however, and the reason it is used in newer planes and trains, it is an extremely lightweight but highly sound deadening material and an excellent insulator.

Pack the empty spaces in a plane’s body with melamine foam and you add hardly any weight (a cubic foot of the foam weighs a fraction of an ounce), but you add significant amounts of sound and heat insulation.