Devices (artist’s illustration) kept aloft by sunlight could take sensors into an understudied layer of the atmosphere.Credit: Schafer et al. Nature (2025)Theory and mathematics said his device would fly. But Ben Schafer was still pleasantly surprised the first time he flipped a switch and watched the centimetre-square device his team had built levitate, if only for a moment before flipping over.It was a proof of concept for a design that has been published today in Nature1. One day, it might en...