Category Archives: HOW?
227.HOW DO EYEGLASSES CORRECT VISION?
Just imagine what life was like for millions of people before eyeglasses were invented! If you were near-sighted and you looked up at night you couldn’t see the stars. You couldn’t see clouds or distant mountains, or birds flying through the air.
Today near-sighted people can see as much as people with normal eyes, because eyeglasses can correct their vision. To begin very simply, we can see because light enters our eye and falls on the retina in the eye, which is like the sensitized plate of a camera. Obviously, if the light falls in back of the retina or in front of it, we won’t be able to see. So the eye has a lens to focus the light and make it fall in the right place.
203.HOW LONG ARE OUR INTESTINES?
Most of us have a vague idea that somewhere inside of us there are coils and coils of intestines, amazing passageways through which food passes in the process of digestion. But few people have a clear understanding of just how they work.
The length of the large intestine in animals depends on the kind of food they eat. Meat-eating animals have shorter intestines because there is less digestive work to do. The food they live on has already done part of the job of digestion. People who live on vegetables are supposed to have longer intestines than meat-eating people.
202.HOW FAST DOES HAIR GROW?
For men who are becoming a little bald, hair doesn’t grow fast enough! But in the case of a young boy, the hair seems to grow too fast!
The rate at which hair grows has actually been measured and found to be about 12 millimeters a month. The hair doesn’t grow at the same rate throughout the day but seems to follow a kind of rhythm.
