There have been countless theories throughout time about how the world will end and how -- or if -- life will cease to exist. At the turn of the 21st century, conspiracy theorists claimed that the Y2K bug was only a small part of the impending devastation: The new century would bring about total destruction, and no one would survive. Others believe that Earth is slated for another ice age, which will kill off all living things. And according to astronomers, billions of years from now, the sun will become a red giant, expanding to a size larger than the Earth's orbit and consuming Earth in the process. Even if the planet somehow survives, the sun will eventually shrink, becoming a white dwarf and gradually cooling off until it can no longer warm anything in the solar system.
In 2006, Mel Gibson released a movie about the Mayan civilization. "Apocalypto" follows one man's journey from slavery back to his family. During the course of the movie, a young woman prophesizes that a man will bring an end to the Mayans and wipe out their civilization. But in the real world, some speculators don't believe a man will be the end of the Mayans -- instead, they think a celestial event will be the cause. The Mayan calendar even gives us a potential date for the theoretical downfall: Dec. 21, 2012.