Space photos reveal the weird optical illusion of the squished Moon

These pictures offer a spectacular view of the rising Moon from the International Space Station. But look closely at the Moon in these photos and you can see how it appears to be strangely squished. What's causing this weird effect?

First of all, if you're not quite seeing the squished effect, check out these close-ups of the Moon in the various photos. The illusion is particularly strong just as the Moon is starting to rise in the first photo:

Space photos reveal the weird optical illusion of the squished Moon

Bad Astronomy's Phil Plait explains what's going on here:

It's an atmospheric effect, due to the air surrounding the Earth acting like a lens, bending (or, if you want to impress your friends, refracting) light. You've probably seen how a spoon looks bent when it sits in a glass of water, right? Same thing. Light passing from the vacuum of space through our air gets bent a bit. The amount of bending depends on how much air the light is going through; the thicker the air the more it's bent.

When an astronaut on the ISS sees the Moon near the Earth's limb, as in these shots, light from the top part of the Moon is passing through less air than the bottom. So the light from the bottom gets bent more, in this case, up. This makes it look as if the bottom of the Moon is being squished up into the top, like a clay ball that's been dropped on the ground. As the ISS orbits the Earth, and the Moon gets higher off the limb, the effect diminishes so in the two subsequent shots the Moon gets re-inflated.

This weird optical effect is most apparent up in space, but it's actually visible down here on Earth as well. Anyone who can watch the Sun set over a clear horizon - the Sun setting over the Pacific Ocean is perfect for this - will see a similar weird squishing illusion. These images and other amazing images like it are the work of astronaut Paolo Nespoli - you can check out more of his literally out-of-this-world images here. But be warned - once you start looking through those photos, you might be there for a while.

[Bad Astronomy]