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'Asteroid defence' has always focused on huge weaponry such as nuclear warheads or lasers - but Strathclyde researchers believe throwing a handful of rocks could do the trick instead. Two engineers at the University of Strathclyde think that instead of the huge, cumbersome laser weapons proposed by earlier projects, a 'swarm' of tiny spacecraft weighing 1,000lbs would deflect it. Speaking at a conference in Atlanta Georgia, Alison Gibbings and Massimiliano Vasile, the two engineers propose a 'swarm' of solar-powered pebbles could deflect an asteroid by 22,000 miles - enough to miss Earth entirely.