Also...
Astrologers in almost every country have predicted that on 12/21/2012, the Sun will be in alignment with the center of our galaxy for the first time in more than 5000 years, and that our moon will be in eclips at the same time. (the two events have never happened together before) At the same time, our planet completes a rotational (wobble) cycle bringing it almost horizontal to the plane of the galaxy.
Theory is that this could cause some odd gravitational effects, and create "signiificant" tidal action.
Oh jeez.
The sun is in Sagittarius (the center of the galaxy) every December. Lunar eclipses happen somewhere on the globe several times a year. That this is the "first" time both have happened in December is just plain BS. The last total lunar eclipse during Sagittarius occurred in 1993 (29 Nov), and we survived it. If that's too far for you, another total lunar eclipse occurred on 9 Dec, 1992, and another on 20 Dec., 1983, and yet another on 30 Dec., 1982. I really think that if the world had ended four times over in the last 25 years, I would have noticed. And even more amusingly, the 21 Dec. total lunar eclipse will take place TWO YEARS TOO EARLY, in 2010. Oops.
Given that the mass of the galaxy is about 100 million solar masses and the center is some 8000 light years (about 80 million AU) away and gravity is inverse-square (TIDAL gravity -- gravity that's different on one part of the planet than on others due to a remote object -- is inverse cube), it's VERY easy to calculate how much gravitational force we get from the center of the galaxy (even assuming all the mass is in the center, which overestimates its contribution some) as compared to the sun. Do this before believing the astrological BS.
As for "every" culture predicting 21 Dec 2012 is the end of the "world," no. The MAYAN calendar ends there. That's it. And nothing special is going to happen. I'll place a $100 bet with any takers that most of us are still alive on 22 Dec 2012.
If you want to screw with gravity on the Earth, you have to mess with the moon or the sun. NOTHING else is remotely significant.
Some nuctase predicts the end of the world several times a year. Last I checked, we were all still here...
PLEASE be a bit more discriminating about what "science" you disseminate. Yes, that includes the climate change stuff. Picking one scientist out of some 8000 who says what you want to hear is a bit, well, disingenuous.