No fear of 2012, Part 1

There's a lot of stir these days about disastrous things happening in the year 2012. I would like to start out, therefore, with one very definite statement: to the best of my knowledge, there is no scientific reason to believe that there will be any sort of global catastrophe in 2012. Further, as an astronomer, let me say that I'm quite sure that there's no evidence for any astronomical catastrophe that will doom the Earth (or the Earth's human inhabitants) in 2012, or indeed at any time in the near future.

That said, several astronomical scenarios have been tossed around as possibly ending the world in 2012. In this and succeeding articles, I'll examine a few of those I've heard.

Follow up:

A TV program (History Channel, shame on you!) posed the question: Will the Earth and Sun somehow line up with the center of the galaxy, causing disaster for Earth?

Every year, as the Earth goes around the Sun, the Sun's position in our sky changes. At the spring and autumn equinoxes, the Sun appears to be right over Earth's equator. At the summer solstice, the Sun is its furthest north of that position over Earth's equator, and at the winter solstice, it's at its furthest south. This happens because the plane of Earth's equator is tilted by 23.5 degrees to the ecliptic plane - the plane of the Earth's orbit around the Sun. (Our seasons are related to this phenomenon.)

Now, the Sun is one of over a hundred billion stars orbiting the center of our Milky Way galaxy. From a distance, most of our galaxy looks like a disk - think of a dinner plate with a softball somehow embedded in the center. The plane of the disk (the dinner-plate part) can be called the plane of the Galactic equator. The plane of Earth's equator is currently tilted by about 63 degrees to the plane of the Galactic equator.

It just so happens that in the year 2012, as the Sun would be on the winter solstice as seen from Earth, it will also happen to be fairly close to the plane of the Galactic equator. If you drew a line from the Earth to the Sun at that day, you could keep the line going and end up reasonably close to the center of the Milky Way galaxy. (If you want to know where that is in your sky, it's in the direction of the constellation Sagittarius.)

My response to this is pretty much a big, "So what?" By the late 1990s, you could draw the same line on the winter solstice of that year, and land pretty close to the Galactic center. Works for the summer solstice, too, though in that case the line would go from the Sun to the Earth to the Galactic center. You could keep doing that every year on the solstices up through oh, the 2020s or so, depending how close you want to come. Nothing disastrous has been happening on the winter solstices that I've noticed. As I understand it, in 2012 the line will be closest to the Galactic center than in any of these other years.

But there's something important to keep in mind here - you could have drawn that Earth-Sun-Galaxy Center line in every single year since there has been an Earth and a Sun. The only thing special about the 1990s-2020s is that during this period, that line-up will tend to happen on or around the winter and summer solstices. (The Earth's equator shifts a little over the millennia, due to a wobble called precession.) In other words, we've been periodically lining up with the center of the Galaxy during your whole life, and nothing's happened. Why should the fact that, these decades, it'll happen around the longest and shortest days of the year make any difference whatsoever?

In fact, the whole "2012 scare" thing got started, I suspect, because of archeologicical studies of the calendar of the ancient Mayan civilization. The Mayans kept track of years, but also cycles of years (the "Long Count") in which each cycle was a little over five thousand years. The year 2012 would, in the Mayan calendar, be the end of one Long Count cycle and the beginning of the next - rather like your odometer rolling over. Some people wondered, of course, what the Mayans based the whole Long Count thing on. Most ancient calendars were based on astronomical cycles - a year is one orbit of Earth around the Sun, a month is one cycle of the Moon around the Earth, and so forth. Was there some astronomical cycle the Mayans knew of that lasted over 5000 years?

Well, some bright folks pointed out there is a cycle - the 26,000 year cycle of Earth's precession - that will bring the winter solstice point in line with the Galaxy center in 2012. Could the Mayans have known that this point in the Milky Way was special somehow, and devised a calendar around it? (I can't comment on the hypothesis itself, not being an archaeo-astronomer.) The whole "And then the world will end!!!" part seems to have been tacked on to an interesting question in archeo-astronomy, and turned it into a scare story.

Continue to No fear of 2012, Part 2.