Airbags could one day save the planet. At least, that is the view of one mathematician, who is suggesting that they could be used to nudge asteroids or comets that are on a collision course with the Earth gently out of harm’s way.

All sorts of ideas for deflecting objects heading for Earth have been touted since the comet Shoemaker-Levy 9 smashed into Jupiter in July 1994. These include detonating a nuclear bomb on their surface. But this might not work: some asteroids are more like a pile of rubble than a solid, and so would absorb the energy from a nuclear blast.