Doomsday predictions are about as common as instances of surviving doomsday prognostications. Prophets of doom can have religious or secular motivations. The latest scare, that the world will end in 2012, is rooted in myths of the Mayan calendar. Doomsday scenarios have been concocted around Halley's Comet, comet Hale-Bopp, Y2K and of course the writings of Nostradamus. But the world has not ended.  (Live Science )