A good moon rising?

Tonight, between 6 and 10 pm (GMT), prepare yourself for the moderate spectacle and minor astonishment of a partial lunar eclipse. Not only that, but nature brings this mildly amusing side-line/potentially disappointing little brother of the total solar eclipse, to a Harvest Moon. Which, sounds really cool and pagan, and looks kind of pretty I suppose, a bit.

I know, I know, it’s not like me to downplay science and nature, and I do feel kind of bad about it. Here’s the real sell.

Tonight, the moon will be a Harvest Moon. That means that it will be a full moon rising during sunset and will be very large and low in the sky around this time. If you hark back to one of the Holiday Blogs, you’ll recall that the atmosphere scatters away blue light. A harvest moon happens when the moon is very near the horizon. That means, for light to get to us from the moon, it has to pass all the way through our atmosphere, getting rid of all the blue light and the moon appears deep red. It really is quite beautiful.

Now, as the moon moves over the sky, it is going to pass behind the earth and into our shadow causing it to get darker. That’s the eclipse. I think that bit is awesome, just thinking about our planet blocking out the sun on the moon, imagine what an incredible sight it must be there. Solar eclipses are probably more beautiful, but for me, you only really get a true idea of the scale of the solar system, a real feeling for how it is constantly in motion, with a lunar eclipse.

moon

Thing is, this one is not a total lunar eclipse, where the moon all but disappears for a short time. This time, the moon is only going to graze our shadow and get dimmer, rather than vanish. But it should still be super cool, that is if there is any break in the cloud cover where you are (and sorry my American friends, but it won’t be visible to you guys).

Just before I go, I’m sure I can here you guys shouting “But why don’t we see this every full moon? If the moon is on the opposite side of the earth to the sun, surely it should always fall into our shadow!?”

It’s a good point. The reason that doesn’t happen is because the moon doesn’t orbit in the same plane as the earth. If you got a massive hula hoop and suspended it from the ceiling, and said that it represented the path the earth takes around the sun, then you took a small ring (like a bangle maybe?) and attached that to the hula hoop to represent the moon’s path around the earth, you’d need to tip the bangle by about 5 degrees, so it wasn’t flat with the hula hoop. That’s not much of a tilt, but it is enough to make it such that lunar and solar eclipses happen far more rarely than they would if the two orbits were in exactly the same plain.

moonorb

So, no need to wrap up warm, it should be fairly nice out so early in the evening, but head out where you get a good view of the horizon and, if you’re lucky enough to see the moon, watch as it hides behind our impressively massive shadow!


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