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THE MOVIES
THANKS TO EDISON

      During the middle years of his life, Thomas Edison’s interest focused mainly on his secret “toy,” the motion picture camera. He could see no practical future for it. Yet he could not bring himself to abandon the project. Perhaps he felt it was a logical extension of his work on the phonograph, which he had invented years earlier and was still improving.

     In 1888, Edison filed a document with the U.S. Patent Office stating: “I am experimenting upon an instrument which does for the eye what the phonograph does for ear . . . . This apparatus I call a Kinetoscope.”

     The Kinetoscope offered the first motion picture show in history. With it, the viewer could look through a peephole and see a sequence of stop- and-go photographs that gave the illusion of con- tinuous motion. Persistence of vision made this il- lusion possible.

     Although today’s motion picture equipment is vastly superior to what Edison developed, persistence of vision is still necessary for it to work. What is persistence of vision? It is the tendency of the eye to continue seeing an object for about 1/10 of a second after the object disappears. Here’s a simple experiment to demonstrate the effect.

Experiment 5

The Spirit of 1776

Materials: 2” disc of cardboard. 12” of string. Glue.

SETTING THE STAGE. On the left half of the disc draw a large 17. Flip the disc over in bottom- to-top fashion, and draw a large 76 on the right half. After laying a thin bead of glue across either side in the horizontal direction, stretch the string firmly and place it on the glue.

SEEING IS BELIEVING. When the glue has dried, twirl the disc rapidly back and forth with the string. Thanks to the persistence of vision we all have, you will see our country’s birthyear as a complete number. In addition, you will see what lies directly behind the disc, which would normally be blocked out.