One of my retired Agency friends just sent me this. Concentrate on the black dot in the center of the image. Then move your head slowly closer to and then father from the image as you continue to concentrate on the center dot.
(http://i2.photobucket.com/albums/y30/RichardS/opticalillusionmovingcircles.jpg)
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Now . . . just tell us where you were on the night of . . . . ;)