Still Frames, Moving Ball

In the picture

1. 1Retina: the back surface of the eye where each image lingers for a moment.
2. 2Frame strip: separate still pictures, each with the ball in a slightly different position.
3. 3Current ball image: the newest picture that has just reached the eye.
4. 4Previous ball image: the faint earlier picture still overlapping the new one.

Examples

• A flipbook makes a drawn figure move when you flip the pages quickly.
• A movie or cartoon is a series of still pictures shown fast enough to look continuous.

Quiz: Still Frames, Moving Ball (Age 12)

1. 1

   Why does a fast series of still pictures look like smooth movement?

   • The eye briefly holds each image, and the brain blends the images together.
   • Each still picture already contains a blurred path of the ball.
   • The eye jumps so quickly between images that the gaps are not noticed.
2. 2

   What happens to an image in the eye right after it is gone?

   • It disappears instantly without leaving anything.
   • It stays clearly until the eye blinks.
   • It lingers in the eye for a very short time.
3. 3

   What does the brain do with quick, separate images?

   • It joins them into the feeling of smooth movement.
   • It keeps them completely separate in your mind.
   • It slows them down so you notice every still picture.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.