Mayans were very smart when it came to astronomy and time keeping and if you look at what happens on 12/21/2012 in an astrological perspective, they say that the magnetic poles could shift and also around the same time I think the earth is supposed to align with the Milky Way or something (I canā??t remember too well). But if you look the Mayan calendar on wikpedia it shows 12/21/2012 to be the end of a big cycle, which could also be interpreted as rebirth.