The world is coming to an end. In, like, 4 billion or 5 billion years. The sun will get old and cranky and eventually immolate the entire planet. The world, however, is not coming to an end on Dec. 21, 2012, contrary to the viral Internet rumor propounded by pseudo-scientists, hoaxers and Hollywood movie promoters. The notion that 2012 heralds the End of Time has something to do with a mysterious Planet X that will supposedly hurtle into, or perhaps merely perturb, Earth. Also, there might be geomagnetic storms, a Pole Reversal and a newfound unsteadiness in the planet's crustal plates. All of that, or variations thereof, can be studied in depth in scores of books now jostling for eschatological primacy with such titles as "Apocalypse 2012," "The World Cataclysm in 2012" and "How to Survive 2012." This is no joke to David Morrison, senior scientist for NASA's Astrobiology Institute. He's counted 200 different books for sale about 2012. As the a