Avoiding Armegeddon: The hunt is on for dangerous asteroids
More than 1,000 people were injured last February in Chelyabinsk, Russia, when a meteor exploded over the city. The collision shattered windows and pelted startled residents with shards of glass and debris. In the aftermath, the world was transfixed by extraordinary videos of the huge fireball as it streaked across the sky. Many wondered, why on earth did no one see it coming?