The Moon is flat!

Bad Astronomy
The entire universe in blog form
Sept. 12 2011 8:33 AM

The Moon is flat!

When I got up this morning, I was greeted by a stunning view of the full Moon setting over the Rocky Mountains, glowing golden from the rays of the rising Sun. It was stunning and gorgeous.

But from a few hundred kilometers above, astronaut Soichi Noguchi had a slightly different view. Check. This. Out.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


How bizarre is that? [Click to inflatenate.] In May 2010, Soichi was on the International Space Station, and was seeing the Moon through the thickest part of the Earth's atmosphere. Under those circumstances the air acts like a lens, bending the light from the Moon, squashing it down -- I've posted images like this before but I have never seen it squished to this degree. That's amazing.

You can also see the change in color from the bottom to the top; it's redder at the bottom. The more air you look through, the more junk (particles, smog, and so on) there is, and this stuff tends to scatter bluer light -- think of it like bumpers in a pinball game bouncing the ball around, changing its path. In this case, the blue light from the Moon gets scattered away, and only the redder light gets through -- that's the same reason the setting Sun can look red. The closer to the Earth's horizon you look, the more air you're looking through, and the redder the Moon looks.

You can see that in the diagram here; the ISS is on the right, the Moon on the left, and the Earth with its atmosphere is in the middle. Light from the bottom of the Moon passes through more air as seen by the ISS, so the effects are greater.

In the picture you can also see ripples at the top of the Moon. That's from different layers in the atmosphere having different temperatures, bending the Moon's light by different amounts. When this phenomenon is strong enough, it can cause the famous Green Flash in the setting Sun.

So Soichi's view was maybe a little bit better than mine. Not that I'm jealous! But man, how cool would it be to see something like that with your own eyes, just once?

Image credit: NASA. Tip o' the lens cap to NASA Goddard on Twitter. Note: the way this was originally posted, I made it seem as if this picture was new, but it was actually taken in 2010. My apologies for that.

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