It's like a pinwheel in the form of an optical illusion.
The original version of this illusion involved a piece of paper with this strange spiral on it, and you needed a method of getting the spiral to spin in order to create the illusion.
Now, thanks to the power of the computer, all the hard work has been done for you, and you can run the illusion right here on your screen.
Click here to download a small application file (Optical.exe 22KB). When you have downloaded the file, just double click to run the pinwheel on your computer screen. You need to stare at the centre of the pinwheel for 30 seconds, and then look away from the screen. Wow!
Thanks to Jerry Andrus who invented this illusion, which he calls the Tri-zonal Space Warp! And thanks to Jodi who drew this example of the illusion to our attention.
Jerry Andrus invented the multi-zone rotating spiral (with alternating expanding and contracting zones). The multiple zones produce a much stronger aftereffect than a simple spiral. Jerry is a well-known magician who has invented a number of unique illusions. He sent me several original newspaper articles describing his work including his 3-zone spiral which he calls the "Tri-Zonal Space Warper". The earliest article is in the May 12, 1978 issue of the "Willamette Valley Observer" (Eugene, Oregon, USA).
"I was aware of the spiral disc that gives that after effect. My intent was to make a spiral of my own and have it so that there would be a large disc turning one direction and in the center of it you would have a small disc turning in the opposite direction. This I would accomplish with one of the discs having a tubular center that fitted over the shaft the other disc was turning on.
Starting with that in mind, at least 1977 or earlier, I rigged up a way to make the original single spiral. Since the rate of the spiral had to change as it got nearer the center. I drew the spiral with the aid of a screw cutting metal lathe. A pen on an arm was held against the face plate, and descended rapidly at first and then gradually slowed down as in got nearer the center. By turning the lathe by hand it drew a single line of the proper spiral. I then repeated this until I had the finished spiral.
I soon realized that rather than going to the trouble of having a small and a large disc I could just photographically reverse one of them and paste it on the other. This I did and ended up with three zones on the one disc.
At some stage I enlarged the disc with three zones to almost four feet and have used in talks at Harvard, UCLA, etc. Also was on That's Incredible, Omni the New Frontier program, Bill Nye the Science Guy and many more with the Tri-Zonal Space Warper and other optical illusions, and some of my magic.
Over the years I have shown the Tri-Zonal Space Warper on television in 12 different countries from Japan to South America to Europe.
In 1981 one of Senior Editors of Omni Magazine came out for a week and did a feature story on me in Omni. In the article, May, 1981, starting on page 110, you will find a copy of my Trizonal Space Warper for them to copy or cut out and put on a turntable.
My friend Professor Ray Hyman thought of that name for it.
Rudy Coby did my Tri-Zonal Space Warper on TV with my permission and you will see my name was mentioned in the credits."