Al Read: Vanisher
Our little science center is in the physics and chemistry building of State University College at Oneonta, New York, where I taught physics for about thirty years, including a large share of a one-semester course for non-majors. The Center has been my retirement project.
I find that my background in teaching physics to apprehensive, desperate, and naive non-majors gave me an insight into gentle and attractive ways to engage them in various aspects of the subject, leading them into developing an understanding of significant topics. It is also important, and even necessary, to lubricate the path with a bit of appropriate humor and whimsy. One of the more successful exhibits developed along these lines is described below. Enjoy.
The Vanisher is a box, about the size of a breadbox, with a slot in the top and a window front. The visitor drops a large metal washer through the slot while watching through the window for it to appear inside the box. It never appears! It has vanished, and didn't even make a sound when it went. The children shown in the photograph have just inserted a washer and are trying to see what happened to it. A few days later during a visit of an Elder hostel group I saw three senior citizens in exactly the same pose, but I wasn't quick enough with my camera.
To heighten the illusion, the visitor can look upward through the front window at the bottom of the lid, and apparently see the bottom of the slot. Nothing comes through. The mystery deepens.
The visitor can then lift the lid of the box to get the washers back. What is seen is a sloping area inside taking up about half the box. The area is cushioned with carpet so the washers don't make much sound when they drop through. At first, most visitors quickly notice that the illusion uses a mirror, but can't exactly explain how it is used. Then as they look carefully through the front window they can see the edges of the mirror as they join the left and right sides of the box on a diagonal line sloping from the front top to the back bottom.
The "slot" seen on the bottom side of the lid when looking upward through the front window is really a reflection of a horizontal strip of black electrician's tape stuck to the inside of the front window.
A small model of the Vanisher's essential partsthe diagonal acrylic plastic mirror and the triangular ends covered with the same diagonal-checkerboard shelfpaperis kept nearby. It is a great help to parents who try explaining to their children how the illusion is done.
A box 9 inches by 9 1/2 inches high by 18 inches wide works well in a small museum. Note the diagonal-square pattern on the ends so the mirror break is not too obvious, but can be seen if looked for.
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