Benham's Disk - A rotating black-and-white disk produces the illusion of color!

    Benham's Disk A rotating black-and-white disk produces the illusion of color. When you rotate this black-and-white pattern at the right speed, the pattern appears to contain colored rings. You see color because the different color receptors in your eyes respond at different rates. Posterboard or cardboard Glue stick or other suitable adhesive Pattern disk (provided here) Access to a copy machine A black marking pen A rotator You can use a turntable, variable speed electric drill, hand drill, portable electric mixer, or electric screw driver....

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Balancing Stick - Does it matter which end is up?

Balancing Stick   Does it matter which end is up? The distribution of the mass of an object determines the position of its center of gravity, its angular momentum, and your ability to balance it!    One 1/2 inch (1.25 cm) wooden dowel, approximately 3 feet (90 cm) long. A lump of clay. (such as electrical tape).    (5 minutes or less) Place a lump of clay about the size of your fist 8 inches (20 cm) from the end of the dowel. (5 minutes or more) Balance the stick on the tip of your finger, putting your finger under...

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Balancing Ball - Suspend a ball in a stream of air!

Balancing Ball   Suspend a ball in a stream of air A ball stably levitated on an invisible stream of air is a dramatic sight. When you try to pull the ball out of the airstream, you can feel a force pulling it back in. You can alsofeel that the airstream is being deflected by the ball. This Snack shows one of the forces that give airplanes lift.    Small Snack A hair dryer (blower) A spherical balloon or table tennis ball Tissue paper Optional: a stand for the blower Large Snack A vacuum cleaner It should come with a reversible hose, like...

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Anti-Gravity Mirror - It's all done with mirrors!

Anti-Gravity Mirror   It's all done with mirrors. A reflection of your right side can appear to be your left side. With this Snack, you can appear to perform many gravity-defying stunts.    A large, flat, plastic mirror, 2 x 3 feet (60 x 90 cm) or larger It is important to get a good, flat mirror, since distortions will ruin the effect. Plastic mirrors are expensive, but glass mirrors can be dangerous. Look in your local yellow pages for a nearby plastics store. A length of 2 x 4 inch wood and a router tool, or ring stands and clamps, This...

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A flash of light prints a lingering image in your eye.

  Afterimage A flash of light prints a lingering image in your eye. After looking at something bright--such as a lamp or a camera's flash--you may continue to see an image of that object when you look away. This lingering visual impression is called an afterimage.  A flashlight White paper Opaque black tape (such as electrical tape). (15 minutes or less) Tape a piece of white paper over a flashlight lens. Cover most of this paper with strips of opaque tape. In the center of the lens, leave an area uncovered, so that the light can shine through the paper. This area should be...

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