Are you preparing for a certain fictional apocalypse this month?

The idea that the world is ending on December 21, 2012, comes from a misinterpretation of the Mayan calendar. Because their calendar ends on the 21st, some believe the world must be ending, as well.

This idea has become so widespread in popular culture that NASA Science has made repeated efforts to debunk it. They've now even gone so far as to produce a video for the 22nd of December, explaining (again) why the world didn't end:

[youtube=http://www.youtube.com/watch?v=QY_Gc1bF8ds]

The video should ease any fears you might have that all of humanity is headed for its demise this month.

Other doomsday theories for the 21st include the idea that a planet called Nibiru is on a collision course with Earth, a total blackout for the planet due to the "alignment of the universe," solar storms and meteor strikes. NASA says none of these events is actually a possibility and does a case-by-case debunking.