This came to my attention via Kisrael.com. I know what some of you might be saying, I said the same thing when I first saw it. "How the heck does this classify itself as an optical illusion? For that answer you'll have to read the full article.
(c) Nobuyuki Kayahara 2003
This is very much like the Ferris Wheel optical illusion I posted previously, depending on how you look at her she will either be spinning clockwise or counter-clockwise. You don't believe that it is possible for your mind to see this image rotating any way but the way you see it now, do you?
One of the reasons that this is possible is that it is a silhouette and the very nature of a silhouette is ambiguous.
Try looking at the reflection and see if she reverses direction. I shift my focus to the side and can tell in my peripheral vision that she has changed direction, I then move my eyes back on the silhouette and walla she is rotating in the other direction.
What is even more amazing is that if you see her spinning clockwise then it is her right leg and arm that is up in the air, but if you see her spinning counter-clockwise then it is her left leg and arm that are up in the air.
My initial view of this illusion is that she is rotating counter-clockwise, but once I manage to see her spinning the opposite way it is hard to switch back. Which way does she appear to spin to you? Can you see her spin in either direction?