Lying Eyes

Sometimes, very occasionally, something comes along which is just so amazing. I was sent this by a friend who picked it up from http://antwrp.gsfc.nasa.gov/apod/ap091004.html and I have copied the picture below. Can you believe that squares A and B are actually the same shade and colour as each other. I didn't until I actually opened it in GIMP and used the colour picker to confirm that they are indeed the same colour.