December 21, 2012 has been called doomsday, the day of enlightenment, and even the day the earth will turn upside down by many different culture and civilizations throughout history. Although the prediction on what is actually going to happen is vague modern day scientists know we our planet is aligning with the galactic equator.
Every few years, doomsayers start popping up and talking about the planets in the solar system lining up. This alignment, they claim, will cause earthquakes, floods and in some cases split the planet in two like a cleaver through a head of lettuce. The last time this happened was in 1982, which, you may remember, is notable as the date on which the world did not end. The next alignment, so they say, is in May of 2000. Many doomsayers also point out that that's the year of the millennium (they're wrong, but that's another Bad Astronomy issue altogether)! Are we doomed this time?
The Geometry of Planetary Alignments
First of all, it is impossible for all the planets to form a straight line out from the Sun (or viewed superimposed on each other in the sky) because each planetary orbit is tilted slightly (and sometimes not slight at all in the case of Pluto) with respect to the Earth's orbit (whose plane we trace out on the night sky as a line completely around the sky and is called the ecliptic). These zealots confuse the term planetary alignment with the more accurate words that should be used, planetary configuration or a loose grouping of the planets in the sky. Actually the event that occurred in 1983 was that the planets (all eight of them -- we are on the ninth, Earth) would be within 96° of each other in the sky -- not in a straight line as most people would misinterpret with the term alignment. To have all of the planets on the same side of the Sun and virtually all within the same quadrant (i.e., 90°) happens approximately once every 200 years -- rare as far as humans are concerned, but not rare as far as the solar system is concerned.
The last series of planetary configurations or perhaps more accurately called multiple planetary conjunctions occurred in the year 2000. Did the Earth tilt over? No. Did tidal forces trigger earthquakes? No. Did the polar ice caps melt? No. Were you even be able to see the conjunctions? Not really.
For a detailed description of the origin of the Planet X / Nibiru cult see the discussion by Phil Plait on his Badastronomy website,
2012: Beginning of the End or Why the World Won't End? by NASA