When two or more colors are quickly spun together, our eyes may perceive a different color altogether. This is because the eye has the ability to retain or remember the individual colors and add them. Prove this with the pencil tops below.
2 sharpened pencils
2 3x5" cards
red, blue, yellow, green permanent markers
(1) Use the compass to draw a circle 3" in diameter on the blank sides of each of the 3x5 cards.
(2) Divide each circle through the center into 8 equal wedges. On the first circle, color every other section red and blue. On the second circle, color every other section yellow and green.
(3) Push a pencil point through the center of each disc so that the colored sides are facing the pencils' erasers. For better balance, keep the disc down near the point end of the pencil.
(4) Holding the pencil upright, spin it on the floor like a top. What color does the disc appear to be?