Sunday, September 23, 2007

Fall equinox

It's the autumnal equinox today, the day when the Sun appears to cross over into the southern sky. The stirrings of winter are beginning--little reminders of the fragile nature of our comfort zone on this planet. This last week in the evening twilight the first-quarter moon barely peeked above the trees and buildings to the south, showing roughly where the Sun would be in three months time. It seemed a little low for the winter noon, though, so I checked and indeed the Moon is at its greatest distance from the ecliptic, some 5 degrees south. I have some discussion of the tilt at this previous post. And, to confirm it, there was a lunar eclipse in late August, meaning the nodes (the points where the Moon's orbit meet the ecliptic) of the Moon's orbit were aligned in the Earth-Sun line, which meant my first-quarter moon should have been above or below the ecliptic.

And it now occurs to me the root of eclipse and ecliptic are the same, a point I never realized. This will require another post.

1 comment:

Jennifer said...

I have a suggestion from a friend who wants to see a photo of the full moon either rising or setting between the buildings downtown a la Manhattanhenge. I told him that I don't know how to calculate that and I have a crummy camera anyway, but it sounds like something you could do...