【適合背誦的雙語文章】為什么我們會走成兩個(gè)大圓圈？

"Pin the Tail on the Donkey" is always fun when you're watching rather than pinning. It is somewhat surprising to see how the blindfolded performers act. Instead of going straight, they always wander off to one side or the other. The greater the distance to the donkey, the farther they go astray. Have you ever wondered why they are unable to walk straight ahead?

It is a well-known fact that a person will move in a circle when he cannot use his eyes to control his direction. Dark nights, dense fogs, blinding snowstorms, thick forests - all these can keep a traveler from seeing where he is going. Then he is unable to move in any fixed direction, but walks in circles.

Animals act the same way. You have probably heard the saying "running around like a chicken with its head cut off." Well, a chicken with its head cut off actually does run around in circles. Blind birds fly in circles. And a blindfolded dog will swim in circles. A Norwegian biologist, F.O.Guldberg, decided that this problem of circular movement was worth investigating. He collected many true stories on the subject. ?

One of his stories is about people rowing on a lake during a fog on a dark night. One group of rowers who tried to cross three miles of water in foggy weather never succeeded in reaching their goal. Without knowing it, they rowed in two large circles. When they finally got to the shore, they discovered that they were at the spot they had started from.

After studying many stories such as this, Professor Guldberg wrote an article in which he discussed "Circular Motion as the Basic Motion of Animals." A simple example will help you to understand his explanation of why we walk in circles.

Have you ever wound up a toy automobile and started it off across the floor? Then you know that it will rarely travel in a straight path. It will travel, instead, in some kind of arc, or curve. If it is to travel in a straight line, the wheels on both sides have to be of exactly equal size. If they are not, the little automobile turns toward the side with the smaller wheels.

Circular movement in walking is caused in much the same way. Usually a man walking will "watch his step" and "look where he is going." He needs his senses, especially his eyes, to get to the point he intends to reach. When he cannot use his eyes to guide his steps, he will walk straight only if he takes a step of the same length with each foot.

In most people, however, muscle development is not the same in both legs, so that it is probable that the steps will be uneven. The difference may be so small that no one is aware of it. But small as it is, it can cause circular movement.

Let us suppose that a man's left foot takes a step 20 inches long and that his right foot takes a step 30 inches long. Now suppose he takes ten step - five with his left foot and five with his right. His left foot will travel 100 inches. His right foot will travel 150 inches. This sounds impossible. One foot cannot remain 50 inches behind the other. What really happens? At each step the man turns a little bit to the left. Sooner or later he makes a complete circle. The tracks of his feet, however, make two circles, one inside the other. His left foot makes the smaller circle because it is taking larger steps. This is why a person may walk in an arc when he sets out in a straight line.

The muscles of a man's arms are no more identical than the muscles of his legs. This explains why the rowers who set out to cross the lake at night rowed in a circle. By the same rule, a bird's wings do not develop evenly, and so it will fly in circles when blinded. Thus, dear readers, our circular mystery has a very straight answer.