Why Are Two Eyes Better Than One?

Did you ever wonder why you need two eyes? One reason is that they help you see depth. To find out how different your depth perception would be with only one eye, try this experiment with a friend.

You'll need:

• a cup
• a penny

1. Put the cup on a table and stand about 3 m (9 feet) away.
2. Cover one eye. Have your friend hold the penny at arm's length above the cup, but slightly in front of it.
3. Watching only the cup and the penny, tell your friend where to move his arm so that the penny will fall into the cup when he drops it.
4. Tell him to drop the penny and see how close you came. Why are you such a bad shot?

What's happening?

Excerpt from The Jumbo Book of Science by the Ontario Science Centre, used by permission of Kids Can Press Ltd., Toronto.