have just check this in a yahoo article. . . my eyes ache by looking at this optical illusion, anyone who can explain this phenomenon?

Pulsing Vortex

If you stare at this one long enough you’ll notice a fast and pulsing multicolored vortex. Photo from Flickr

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Has a lot to do with the left and right hemispheres of the brain and the way it organizes and stores data. But to be quite honest, I can't explain it entirely! Good luck and let me know if you solve it! Thanks!!