It has saved lives around the world and can fit in your pocket. It's been used everywhere from earth-bound marathons to moon missions. It's real full name is metallised polyethylene terephthalate but you'll know it as the space blanket. This simple sheet that is thinner than a human hair has been used on every NASA space mission since its invention. In this episode Dr Marty Jopson explains why, before performing an experiment that shows how well this material can reflect heat.