Awesome Visual Illusion

This visual illusion is really cool!

Note: I originally referred to this illusion as an "optical illusion", but my friend Steve Van Hooser, a visual neuroscientist, has pointed out my use of the incorrect term: "I know you are a stickler for details, and as a visual neuroscientist I feel you'd want to know: say "visual illusion" rather than "optical illusion". Because the visual system produces this illusion. There are true "optical" illusions, like the illusion of water on a hot road ahead. That is an optical illusion because it is the diffraction of light that causes the illusion." (I have made this same error on several prior blog posts, which I may eventually look up and correct.)