There are however a lot of theories knocking around the Internet which use the end of this calendar cycle to predict the end of the world. They often also mention the fact that Dec 21st is the winter solstice, and that the Sun on the solstice that year is "aligned" with the plane of the galaxy. On the winter solstice, the Sun always has a Declination of -23.5 degrees, and a Right Ascension of 18 hours, but exactly where this is on the sky relative to more distant stars changes very slowly due to the "precession of the equinoxes". We have a posted answer explaining this effect but how it's important in this answer (and how it was first noticed) is by the fact that it moves the position of the equinoxes, and solstices with a period of 26,000 years in a complete circle around the sky westward along the ecliptic. So the position of the winter solstice moves 360 degrees in 26,000 years. That means that it moves 360/26000 = 0.01 degrees a year.
Defining an exact boundary for the plane of the Milky Way is tough, but it's at least 10-20 degrees wide across much of the sky, meaning that the solstice can be described as being "in the plane of the Milky Way" for 700-1400 years! To put it another way, the winter solstice that just past (2005) was only 0.1 degrees away from where it will be in 2012, a distance smaller than the size of the Sun itself (which is about 0.5 degrees in diameter). In any case the Sun crosses the plane of the Galaxy twice every year as we orbit around it, with no ill effect on Earth. http://curious.astro.cornell.edu/question.php?number=686Today, yesterday, and tomorrow, the sun does not lie in the galactic midplane, but it is about 35-70 light-years “above” it (since there’s no “up” in space, you could also say it lies below it). It is also currently still traveling “upwards” in the direction of the North Galactic Pole at a rate of 7-8 km/sec.
It is also not on a perfectly circular orbit relative to the plane of the galaxy, moving presently inward at a rate of 10-11 km/sec. Its rotational velocity around the center of the galaxy is about 200 km/sec.
I should also note that the center of our galaxy, the supergiant black hole known as Sag A* (pronounced “Sag A-star” or “Sagittarius A-star”), is the celestial coordinates 17 h 45m 40s RA, -29° 00′ 28.00″ DEC. What those actually mean is unimportant at the moment, just keep it in mind.
...
Jenkins’ premise is actually somewhat correct in the sense that, yes, the Milky Way will be somewhat near the plane of the galaxy as seen from Earth around the winter solstice in 2012. But not anywhere near Sag A*. And there’s nothing mystical about the plane of the galaxy … in fact, the sun passes “through” it as seen from Earth once a year. It just so happens that for the last ~300 years through the next ~300 years, this will happen to coincide with mid-December - winter solstice in the Northern hemisphere and summer in the Southern. There is really NOTHING special about this other than New-Age woo and mysticism.
http://pseudoastro.wordpress.com/2009/01/27/planet-x-and-2012-the-pseudoastronomy-or-just-plain-wrong-astronomy-about-a-galactic-alignment/(I believe the first sentence in the final paragraph ought to read "... the
Sun will be somewhat near the plane of the galaxy as seen from Earth ..." - the Milky Way is the galaxy, after all)
I'm not quite sure what you mean by the 'solar meridian'. A meridian, in astronomy, is the line connecting due north, the zenith, and due south, for the observer. If 'solar meridian' means a similar line, but passing through the sun rather than north/south, then the meridian would cross the galactic equator (ie the line of it, as seen from earth) every day. As those excerpts point out, the sun itself crosses the line twice a year.
The earth will not "align itself with the center of the galaxy" in 2012, as the second excerpt points out; those coordinates for Sag A* are several degrees away from the Sun at winter solstice (18h 0m 0s RA, -23° 26’ Decl), and it can only get about 0.1 degrees closer between now and 012; if I've used the Stellarium program correctly, the winter solstice point won't even get to its closest to the galactic centre for another 200 years or so, although that's still a degree or two away (but I may have done that wrong).
Anyway, the winter solstice is the time when the earth's north pole is pointing as far away from the sun as it ever does; why would having the galactic centre, sun and earth in a straight line at that time mean anything special?
"astronomically, I beg to differ" - please, tell me you don't really consider what you have done as 'astronomy'.