NASA Goddard rocks the Moon
NASA Goddard rocks the Moon
Bad Astronomy
The entire universe in blog form
March 2 2012 7:00 AM

NASA Goddard rocks the Moon

Wanna know what the Moon will look like at any time this year? And I mean what it really looks like, shadows and all?

Then go to the NASA Goddard Science Visualization Studio, where they have an amazing applet that shows you the Moon's appearance on an hourly basis for the entire year!

Phil Plait Phil Plait



Most times, websites showing you the phase of the Moon do it in big time chunks, like once per day or even per week, or they have a low-res image of the Moon with the dark part blacked out. But this one from NASA lets you enter the date and hour, for very high time resolution photo-realistic pictures.

The images are based on observations by the Lunar Reconnaissance Orbiter, which has been taken super-high-res images and altimetry data since it went into orbit our satellite in June 2009. The images show far more than just the lunar phase. For one thing, using the LRO altimeter data, it can calculate the lengths, directions, and positions of all the shadows of mountains, crater rims, and so on, knowing the angle of the Sun over the horizon.

After seeing it, my first thought was, "Someone should string these all together to make a video." I looked down the NASA page, et voila! They had! So I made it into a video on YouTube which I annotated. I also added music by Kevin MacLeod I rather like.

[Make sure to set it to HD for the full effect, which is mesmerizing.]

That weird rocking and tilting motion is real. It's called libration. The Moon's orbit around the Earth is elliptical, so sometimes it moves faster in its orbit than other times. However, the Moon's spin is constant. The geometry of these two things add together, allowing us to sometimes peek a little bit over the eastern and western horizons. Not only that, the Moon's orbit is tilted a bit with respect to our Equator, so we sometimes get a little peak over the north and south poles too.

I'll note that these views of the Moon are not designed for people at different latitudes; for example, from Australia the Moon looks upside-down compared to how I'm used to seeing it in Boulder! Instead, these views show the Moon as if you are at the center of the Earth with your head pointed toward the north pole. Still, it's an amazing thing, and well worth bookmarking. When I need to know what phase the Moon is in -- and it happens several times a month for me -- this is where I'll check.

Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio. Music for the video is "Five Armies" by Kevin MacLeod.