There's an insane optical illusion that makes a full moon look squished - here's why it happens

Who broke the moon?

Flickr/NASA's Marshall Spaceflight Center

Believe it or not, that's a real photo of the full moon taken in 2012 by an astronaut on board the International Space Station (ISS). Here's another photo with the moon even more squished:

Flickr/NASA's Marshall Spaceflight Center

Why does that happen?

It's actually an optical illusion created by Earth's atmosphere. The ISS orbits Earth 250 miles above the surface, which is well above the planet's lower atmosphere. 

This crazy trick-of-the-eye happens when the moon and the ISS are on opposite sides of the Earth. The light that bounces off the moon and into the astronauts' eyes has to first pass through Earth's atmosphere, which bends the light, distorting the image. Check out this amazing Vine of the same effect:

 If you've ever looked at a straw that's half in air and half in water, you've noticed that the part of the straw in the water looks larger than the part in air. That's because the water, just like Earth's atmosphere, bends the light that you see. So why, then does the Earth look squished and not bigger? 

It's all about the direction the light is bent.

Earth's atmosphere is thinner the higher you go, and the light from the top-half of the moon travels through less atmosphere than the bottom half. In order to reach the astronaut's eyes, the light from the bottom half is bent upward, which makes it look severed in half.