What is it?
This is one of the theories that have been tied to the December 21, 2012 date. The idea is this: at noon on 12/21/2012, the solstice sun will be seen to be in exact alignment with the Galactic Equator. Or the Dark Rift. Or the black hole in the center of the galaxy. Whoever said pseudoscience was accurate? As anyone who claims to be in-the-know will tell you, the Maya were avid astronomers, so this phenomenon must be related to their long count calendar cycle ending, right?
Wait, what are those things?
The Great Rift (otherwise known as the Dark Rift) is an area of blackness seen near the center of the Milky Way. Scientists know it to be clouds of gas that block visible light coming from the bulge at the center of our galaxy. Behind these clouds is believed to be a black hole.
The Galactic Equator is something that needs some explanation. It's a concept created by the IAU (International Astronomical Union), which is often confused with the H1 plane. As you see in the image below, the H1 plane is a line that dissects our galaxy (which, by the way, the sun won't cross for another 30 million years or so). The "Reference plane" below represents the "equatorial plane of the galactic reference system", which is probably what is mistakenly referred to in 2012 literature as the Galactic Equator. This is a line that, by definition, passes through the sun and and the rotational center of the galaxy (Sgr A). That's right folks, the sun is ALWAYS on this line. A deeper explanation can be found here.
The sun is still going to cross through something, right?
Well guess what: the sun (as viewed on December solstice) will appear to cross through something or other - Dark Rift, Galactic Equator, etc. The thing is, any of these crossings will take about 36 years to complete. In fact, the mid point of the sun crossed the GE in 1998, so that means the sun will continue its crossing until 2016. What makes 2012 so important in this crossing? One argument is that the Maya didn't have our sophisticated measuring equipment, and the galactic equator was only defined in 1960. All the Maya saw was the Milky Way in the night sky. So perhaps their prediction isn't 100% accurate. Well, remember that, to start with, the Maya hadn't actually used their Long Count Calendar to predict anything. All we have here is the end of a cycle, and a galactic phenomenon that's been underway for the last 30 years or so. In fact, our millennium cycle ended even closer to the midpoint of the Galactic Alignment, and did anything happen then?
But alignment will happen?
Yes. The sun is going to appear to intersect with the midpoint of the Milky Way/Dark Rift. Just like it has done for the past few decades. You won't even be able to see it because, obviously, you can't see the sun and the Milky Way at the same time without some serious astronomy gear. Nothing scary is going to happen. These crossings are caused mostly by the earth's poles gradually changing orientation, a perfectly normal phenomenon called Precession. The tilt of the earth's rotation is what makes these alignments.
There are people out there who are making various claims about what this "Galactic Alignment" will do to us. I'll check them out in my following posts.