First Of All I have to tell that 2012 December 21 the world will never be End. In 2012 December it will be a cool winter. So in 2012 there is no any threat for Earth as most of the Scientists said that Earth will be fine more than 4 billion years with out any harm.
This "End of the world" prediction story started from "Niburu", "Niburu" is a planet and some are said that it headed to earth and it will contact with Earth then worlds End in 2003 May. But in 2003 there was no any harm for world then it moved to 2012. Then another fact came to front that the ancient Mayans calendar will end in 2012 December 21. So this "Niburu" case and Mayans calendar case connected and this Prediction of worlds end came to the stage.More News In NASA
https://bestworldstuff.blogspot.com/2010/03/true-story-behind-world-end-in-2012.html