What happens after 21 December 2012? A realistic approach from NASA
The general idea about 21 December 2012 is that, the date is not the end, but the beginning of the new long-count period.
As the most complex calendar system ever developed, the Mayan Long Count Calendar was keeping the tracks of the long intervals -the ruins reveal with the time references dating billion years ago.
For the scientists, it is, in fact, the end of this ancient calendar but not a “doomsday” with the new beginning of a 5,125-year cycle. No planetary alignment is likely to happen in the next decades for the scientists and they are also insisting that the polar shift theory is completely impossible.
A magnetic reversal is very unlikely to happen in the next few millennial and would not cause any harm to life on Earth.