*** Find yourself a rainbow. Fixate on a part of the rainbow. Persist. Remember the eye naturally wanders. Suddenly you will become aware that the rainbow has vanished. Any motion of your eye will make it instantly reappear. The eye is a motion detector that requires constant movement to function. In truth if we could stop eye motion at will we could make any object fade away, the rainbow is just an easy subject because of its smoothness and lack of detail.

In the same respect, it is well-known that you can see the Pleiades, "The Seven Sisters," much more vividly if you don't look directly at them with the naked eye. When you look directly at the constellation, they tend to fade or disappear all-together.