Here is another example of reflected light, which you yourself can control. Do you remember the fairy _Tinker Bell_, in “Peter Pan”; how she appeared as a patch of light, dancing over the walls? Very likely when you returned from the theater you made her appear on the walls of your home. As you sat at the breakfast table you picked up a tumbler of water, or a bright bladed knife, and moved it about until it caught the light and tossed it across the room on to the wall, where you could make the fairy hover by gently shaking the glass or knife. On the other hand by changing the position of the glass or knife you could cause her to disappear; to reappear if you wished it, on another part of the wall.