Imagine you're sitting at your desk on the morning of Dec. 21, 2012 -- which falls on a Friday, unfortunately -- getting a little work done, perhaps planning a lunchtime Christmas shopping expedition, when suddenly, without warning, a flaming, 8,000-pound communications satellite smashes through your office park at terminal velocity. The building is now gaping, as if drilled by a giant awl. Through the opening, you gaze out into the city to see roaring fires engulfing whole blocks, dark tornadoes whirling down avenues, and about 17 different Kaiju monsters -- not just Mothra and Godzilla, but even the awkward, low-budget ones that nobody remembers, like Reptilicus -- all doing their thing. At this moment, you ask yourself in despair, "Why didn't I prepare for the 2012 apocalypse when I knew -- KNEW! -- that it was coming?"

If you haven't heard about the 2012 doomsday predictions, you've been living -- well, probably not quite under a rock, but at least without access to the Internet. Despite the ubiquity of the generic 2012 apocalypse idea, most people don't have a clue where this notion came from. Where did people get the impression that the world might end on this date?

One major contender is the Mayan calendar. Maybe you've heard that the Mayan Long Count calendar predicts the end of the world on Dec. 21, 2012. If so, you have been misled. It's true that the Mayan Long Count calendar will indeed cycle through a very rare reset point on this date -- kind of like if our Gregorian calendar only reached Jan. 1 once every few hundred years. But did this important date signal the End Times for the Mayans?

Not necessarily. Though there are a few ancient carvings prophesying fateful events to fall on this day, none of these events constitute the end of the world [source: Pappas]. Furthermore, if we're still curious about the significance of this date on the Mayan calendar, we can just ask the Maya themselves. Many people throughout Mesoamerica still identify as descendents of the ancient and classical Mayan civilizations. According to Robert Sitler, a Stetson University professor of Latin American studies who has interviewed many Maya about the phenomenon, the vast majority of modern Maya "scoff" at the idea that the conclusion of the Long Count calendar would have anything to do with the end of the world [source: Pappas]. It's generally approached more like New Year's Day -- a time for new beginnings.

But what if the 2012 end date is less an event of religious significance and more akin to a harrowing tale of science fiction? Based on the writings of Azerbaijani-American writer Zecharia Sitchin, some people believe that a planet known as Nibiru (or simply "Planet X"), which has long been locked in an extreme elliptical orbit around our sun, will suddenly swing back this way, crash into the Earth on Dec. 21, and end life as we know it (except for that secret colony of psychic chimpanzees we have on Mars, one supposes). So how does the Planet X theory hold up to empirical testing?

In an interview with NPR, NASA astrobiologist David Morrison set the record straight, "If there were anything out there like a planet headed for Earth, it would already be the brightest object in the sky after the sun and moon. Everybody on Earth could see it … Go out and look. It's not there. You don't need to ask the government or me, just use your eyes. There's no interloper out there headed into the solar system" [source: NPR].

So the main theories that have caused people to predict a December 2012 end date are clearly baloney. But it's just as clear that this doomsday notion had to come from somewhere. If so many people believe it, how could it be wrong?

In 2011, the California-based Christian radio personality Harold Camping foretold that the end of the world was indeed quite nigh. According to his prediction, on May 21, 2012, Jesus Christ would return to Earth, rapture his flock into heaven and set in motion the calamitous events that would destroy the planet once and for all. And before that, in 1980, another religious broadcaster, Pat Robertson, publicly predicted that the end of the world would arrive in 1982, on the tail of a violent struggle in the Middle East. Of course all of the Y2K believers thought a perfect storm of software malfunctions based on a date-counting error would bring civilization to its knees at midnight on Jan. 1, 2000. If we go back a few hundred years, we can read even the esteemed founders of thriving modern religious movements, from the Mormons to the Methodists, marking their calendars for many a now-debunked doomsday.

Clearly, people like to predict the end of the world. We do it all the time, and so far in history, we've always been wrong. So sleep tight.