An asteroid with the power to unleash an explosion one hundred times greater than an atomic bomb has triggered global space agency alarms. The odds that the space rock dubbed Y4, which is nearly the size of a football field at between 130 and 300 feet wide, could hit Earth is now too close to ignore, they warn. “If you put it over Paris or London or New York, you basically wipe out the whole city and some of the environs,” Bruce Betts, chief scientist of The Planetary Society, told Agence France-Presse last week. The asteroid was first observed on...