Have you ever looked through an electric fan and seen a shimmering pattern of light and dark areas around the center? This is a type of optical illusion called a moiré (pronounced mwar-ay). It happens when two see-through patterns of lines overlap, like the wires on the front and back of the fan.
Try this easy experiment to make your own moiré patterns!
How we did it:
- plastic canvas - used in needlepoint
- lazy susan
- black paint
- smartphone - optional
Gather your materials.
Cut the canvas into two 6" squares.
Paint both sides of each canvas black. Let them dry for at least 30 minutes.
Place one of the canvases in the middle of the lazy susan.
Hold the second canvas centered over the first canvas and slowly spin the lazy susan. What do you observe? What happens when you spin faster? What about slower?
If you have trouble seeing the patterns, ask a friend to take a video of you spinning the lazy susan from directly above. In a video, you can see the patterns moiré clearly!
When you spin the canvases, the interaction you see between them is a kind of optical illusion. You see moiré patterns because it’s tough for your brain to process lots of criss-crossing lines. Instead, it simplifies things into a pattern of dark areas (where the lines are close) and light areas (where they aren’t).
As the bottom canvas rotates on the lazy susan, it creates a new pattern with the one you’re holding steady above it. That’s moiré!