(Quote) "This illusion has been doing the rounds this week (see Bad Astronomy and Richard Wiseman for a couple of science blogs I like that picked it up), but it's so good I thought it needed to be posted here also.
Look carefully at the image below. Do you see a couple of spirals, one blue and one green? Well, take a closer look - in actual fact, the blue and green are actually the same color!
Don't believe me? Copy the image and open it up in PhotoShop or Paint and take a closer look....
You will notice that the orange curves move through the "green" spirals, but not the blue. And the purple curves don't move through the green.
(left)If we blow this picture up even more, we can see that the colors are becoming more and more similar.
(Above)The blue and green appear to be different colors because our brain works out colors by comparing them to other surrounding colors and it does a bit of mixing. When we look at the "blue" spiral, we also take in the purple curves moving through it. This makes it look more blue. When we look at the "green" spiral, we take in the orange curves, which makes it look more green.
I know that's not a great explanation, so I'd be happy to hear a better one!" (End Quote)
All text and images via Mr Science Show