What is the significance of December 21 2012?

First and foremost, there is the Astronomical significance 
- on December 21, 2012 , our Earth and Solar System
will have completed an astronomical cycle of Galactic proportions - one that occurs but once very 25,800
years (Plato's Great Year!!!)  This Galactic Alignment
is described in more detail more below.

Secondly, December 21, 2012 is a very significant date of the Ancient Mayan Calendar . Developed  by the Maya Civilization of pre-Columbian Mesoamerica (circa. 1800 BC),   The ancient Mayan Calendar  has a beginning date of  August 11, 3114 BC, and for reasons not yet completely understood, abruptly and inexplicably ends on December 21, 2012 !!

Thirdly, NASA has predicted the most intense Solar Maximum event fifty years for the year 2012.   If correct, the years ahead could produce a burst of solar activity second only to the historic Solar Maximum  of 1958.

Then there are the Ancient Prophets - and perhaps
the most significant of these was Nostradamus .  In a recently discovered manuscript titled "Nostradamus Vatinicia Code " and now known as " The Lost Book of Nostradamus ", the world renowned prophet described in detail an Armageddon -like, End of Days senerio --- which he predicted would ultimately occur at the end of a 20 year period, coming to a close in, or very near the year 2012 !!

And finally, there is the religious and cultural significance that many will attribute to this extraordinary event and time, as many religious and Biblical Prophecies, such as Apostle John's Book of Revelation , predict an Armageddon, or End of Days , when God will return to judge mankind and renew Heaven on Earth .

Milky Way Galactic Alignment

Our solar system is part of a huge disc shaped collection
of stars and planets called the Milky Way Galaxy.  Our Sun is 
located somewhere on the edge of the disc, slightly on top
of the narrow disc.  But very soon we'll be moving from the top plane of the disc to the bottom plane.  This change, from top to bottom, begins on December 21, 2012 .

On December 21, 2012 , the ecliptic of our solar system will intersect with the Galactic plane, also known as the "Galactic Equator " of the Milky Way Galaxy!  This Galactic Alignment occurs only once every 25,800 years (Plato's Great Year ),
and this is what the Ancient Maya were pointing to with the December 21, 2012 end-date of their Long Count Calendar .  The last time it occurred was on a fall equinox 6,450 years
ago, approximately the same time that man first established cities and civilization in an area of Ancient Mesopotamia
known as Sumer (today's Iraq).  On  December 21, 2012 ,
which is the winter solstice in the Northern Hemisphere, this center will align with our Sun once again!

From an astronomical perspective, the Milky Way Galactic Alignment expected to take place on December 21, 2012 can be visualized in the following illustration:

Position A is where the December solstice sun with respect to our own  Milky Way Galaxy some 3,000 years ago. Position B is 1,500 years ago, and position C represents "era-2012", when the December solstice sun will converge with the exact center-line of the Milky Way (the Galactic Equator ) as a result of the Precession of the Equinoxes, Notice that the place of alignment is where the 'nuclear bulge' of the Galactic Center is located.

But our Milky Way Galaxy actually revolves like a giant wheel  – we are actually on a slow wobble and the stars are just appearing to revolve.  This phenomenon , called Precession of the Equinoxes , or just Precession, results from the fact that as the Earth completes one annual orbit around the Sun, it does not return to the same exact astronomical location each year. 

This is because there is a slight retardation, or precess, which amounts to one degree (out of 360 in the circle) every 72 years.  Therefore it takes 25,800 years (Plato's Great Year) to complete one astronomical cycle, and it is within this cycle that we can observe astromonical conjunctions in the Heavens, between the stars and our own Solar System .