Optical illusions

The BBC has this article about optical illusions which we were discussing in the pub after the seminar today. I thought this would be a good chance to share one of my favourites. Have a look at the picture below:

The blue squares on the top in the left-hand picture are the same colour as the yellow squares on the top in the right-hand picture.
Don't believe me?

That grey line is the same colour all the way along. If you still don't believe me, use some sort of graphics programme and determine what the colours are for yourself.

I can't remember where I downloaded these pictures from, it was ages ago - if anyone knows who this illusion was made by, I'll put in  link.

If you want some more illusions, have a look here I particularly recommend the break of the curveball and the color dove, but the whole site is full of pretty awesome stuff.