Make a Spinning Disc
Description: Students will learn about persistence of vision by making a spinning disc or motion toy
Purpose: To demonstrate persistence of vision
Length of Activity: 45 minutes; this activity can be split between two days. Note that it may be helpful for the instructor to make a spinning disc ahead of time to demonstrate for students.
- 3 x 5 inch index cards or heavy stock paper
- Compass or template for making 3 inch circles
- Glue or tape
- 2 pieces of string 15 inches long, per student
- Hole punch
- Crayons, markers, colored pencils
1. Give students 2 sheets of paper or cards. Have them trace a 3 inch circle on each.
2. Students should draw two pictures in the circles. These can be anything, but the spinning discs work best when the images are related so that together they would make one picture that made sense. For instance, a tree branch on one and a bird on the other.
3. Cut out the circles.
4. Glue or tape the circles back to back, drawing side out. One image should be right side up, the other upside down. This is important: if they are not opposite of each other, the trick won't work.
5. Punch a hole in either side of the cards, directly opposite of each other.
6. Loop the string through each hole.
7. Hold the strings out, one in each hand, and wind up the toy by flipping the disc over and over, making twists in the strings.
8. Let go and pull the strings gently to make the toy spin.
What’s Going On?
When things move very quickly in front of our eyes, it's difficult for the brain to keep each picture separate. Your brain actually continues to see one picture for a very brief moment even after the disc has flipped to the other side. This is called persistence of vision. When you spin the disc, your brain blends the two images into one.
Spinning discs or thaumatropes (tho-ma-tropes) were invented in 1827 by Dr. J.A. Paris. The name comes from the Greek, meaning "wonder turner."