This is insane. As Phil Plait at Bad Astronomy — where I found this video — says:
I promise you, this is real. It’s not a trick, it’s not Photoshop, nothing like that. It’s an honest to goodness optical illusion completely inside your head. I can prove it, and you can prove it for yourself.
Click over to Bad Astronomy to see how to do it yourself.
Plait says this, too:
We humans are convinced that we see the world as it really is, but that’s complete rubbish. We don’t. We see things filtered not just through our fallible senses, but also then interpreted by our ridiculously pliable minds.
Whoa.
