look, put it this way.
our earths been around for like billions of years yeah? and nothings destroyed it yet has it? so whats to say that some old mayan guy who probly doesn't know shit can predict that our world will end long after he dies? where HIS scientific proof?
anyway, this planet X thing'll probly just go past us and that'll be that.
PS: Wasn't the world meant to end on 1st january 2000?