I’m preparing for another pop-up craft fair where I’ll have fort kits and some new items – including these amazing tops! Tops are the original toy. They have been found in archaeological digs as far back as 3500 BC. Their spinning motion and balance is pure physics – and pure fun!
But right now I want to show how tops can be a tool for investigating the color addition of light.
If you’ve every mixed paint colors you know that the more colors you add, the darker and dingier the result is. But if you could mix light colors you would get quite a different result! When you mix all the colors of light together you get white!
Light comes in all the colors in the rainbow. When it hits a colored object, most light is absorbed and only one color is reflected. A blue object, for example, absorbs almost the full spectrum of light, reflecting blue only.
Our eye is able to see color because of light-sensitive photoreceptor cells called rods and cones that are in the retina at the back of the eye. Cones sense the different light colors and send signals to the brain.
An easy way to show how colored light is mixed or added together is with a spinning top. You can make a top simply by printing out the patterns here on card stock or heavy paper. Cut out one of the discs, cut a slit in the center and insert a penny. You can grab the top of the penny to spin your top on any hard flat surface. Or, if you already have a top, just cut a hole in the center of the disc and slide it over the top of your top.
Start with a disk that has an equal amount of red, blue and green. These are the primary colors of light. If you had a red, green and blue flashlight and pointed them all at the same spot, the colored lights would add up to make white.
With the spinning top, the colors change so fast that you trick your eyeballs into doing the same thing. The top spins so much faster than the rods and cones in the back of your eye can figure out what color you are seeing that it adds the red, blue and green light together for you. The spinning top should appear almost white (depending on how true the color is on your printer).
Pull out your markers and crayons to try other color combinations! The image here shows how colored light combines. For example red and green makes yellow! (You can read more about the physics of color addition here.)