Thursday, February 21, 2008

Dorkin' out for science!


Last night there was a total lunar eclipse!! It was pretty amazing. I almost forgot about it until my mom called me and reminded me to go look at it.

I tried to take a picture, but it only came out as a little speck of light on my shitty camera. Anyway, this was apparently our last total lunar eclipse until 2010, so I hope everyone enjoyed it. I think my upstairs porch is probably the best place for viewing lunar eclipses, as it's on the 4th floor facing east. I had an awesome view of the moon, which was almost fully eclipsed when I went to look at it.

I decided to read up on lunar eclipses at NASA's website for last night's event, because I couldn't remember much about them from 6th grade science. Apparently, the type of lunar eclipse we see has do do with geometry, because it all depends on the angle of Earth's shadow. Most of the time, the moon doesn't line up with Earth's orbit at all, which is why we don't get a lunar eclipse at every full moon. A partial eclipse happens when part of the moon passes through the Earth's umbral shadow, or the "zone" in which Earth's shadow blocks all light from reaching the moon. Of course, last night's total eclipse meant that the entire moon passed through the umbral shadow.

There is actually a third type of eclipse, a penumbral eclipse, which has to do with another type of shadow cast by the earth. The penumbral shadow zone is actually a larger zone which contains the umbral shadow at its center. In the penumbral zone, Earth's shadow blocks some of the light from reaching the surface of the moon, but not all the light is blocked. Penumbral eclipses are usually only observed by astronomers because they are much more subtle. Here's a diagram from NASA's website:
You may also wonder why the moon appears red or orange during a lunar eclipse. The answer has to do with our atmosphere. When the moon passes through the Earth's umbral shadow, the Earth is blocking all direct sunlight from reaching the moon's surface. Some light does still reach the surface of the moon, but this light is indirect sunlight which has to pass through the Earth's atmosphere to get there. Because Earth's atmosphere filters out most of the blue colored light, the light that reaches the moon is a reddish orangy color instead of the bright white from direct sunlight. If the Earth had no atmosphere at all, the moon would be invisible during a lunar eclipse.

So now you know all about lunar eclipses! You should probably look at that website, because it has a list of all the upcoming lunar eclipses until 2012. Unless you don't care, that is. "For me, it's solar or nothing!"


1 comment:

Libby said...

you are so smart at science!!