Stuff You'll Need

• two clear plastic party cups
• masking tape
• colored marker

How to do it

1. First, tape the two cups together so that the open ends are touching.
2. Then, color the tape with a marker.
3. Then, spin the cups. See the magic disc that appears in the center. Cool, huh?
4. The disc is "magically" created because your eye can't keep up with the speed of the spinning cup.
5. Your eye sees the center of the cup as one complete circle.
6. This is called persistence of vision. It's also why a flip book works.