The moon reflects light and can be seen only when light from the sun illuminates it. When a moon is new, it cannot be seen from the earth, because the illuminated half faces away. Cut a circle from poster board and cover it in tinfoil. Punch a small hole in the top of the moon and hang it from the ceiling with a piece of string. Use a flashlight to show how the moon lights up only when it reflects light from the flashlight.
What people call a half moon is actually a quarter moon, because light is reflected on one half of the half of the moon that faces the earth. Use a dark-colored modeling clay to form a fist-sized ball. Apply a thin layer of bright-colored clay to one quarter of the ball from top to bottom. This ball now models a first-quarter moon when the right illuminated side is facing the earth and a third-quarter moon when the left portion is illuminated.
Two weeks into the moon's cycle, the entire illuminated half can be seen from the earth and is called a full moon. Cut a piece of construction paper into a large circle. Draw lines that simulate moon craters on the paper. Cover the lines with craft glue. When the glue dries, paint the glue lines with watercolor paints.