NASA is so sure that the world won't end on December 21, 2012 (which just happens to be this Friday) that they've already produced a video for the day after!  So how can they be so sure, well they are smarter than the rest of us so we'll just have to trust them.

The main point of the theory is that the Mayan calendar doesn't actually end on December 21, 2012.  In fact, that date may be way off the mark anyway because some scientists think we have the start date of the calendar wrong.

The ending that everyone is worrying about is actually the calendar starting over, a lot like the odometer rolling over in a car.  I'm not sure how much of it I understand, but I know that if you really believe that the world is ending Friday you should probably give all of your belongings to me . . . because why not?!