Light is composed of different colors.Observe how a spectroscope splits the light from the stars and planets.
Straight drinking glass
Make a long, narrow cut from the bottom of the poster board to just above the height of the glass.
Sit the glass in front of a window that lets in a lot of sun, and place the poster board between the glass and the window. Remember to have the cut in the poster board running the length of the glass.
You should see the light split into colors.
Fun Fact: Spectroscopes have allowed astronomers to study what the Universe is actually made of. Astronomers who study this are called astrophysicists.