HOW FAST DOES AIR TRAVEL WHEN YOU SNEEZE?
A hundred miles per hour.
WHAT MAKES YOUR KNUCKLES CRACK?
Bubbles popping! There is fluid around the joints of your finger bones. When you stretch your fingers, the pressure on the fluid changes, little bubbles form in the fluid and they pop. Want to crack the same knuckles again? You have to wait about 15 minutes.
HOW DO YOU GET "GOOSE BUMPS"?
Each hair on your body grows in its own shaft, called a follicle. If you get cold or scared, the smooth muscles around the follicles contract. This gives you goose bumps and makes the hairs stand upright.
HOW LONG DOES AN EYELASH LIVE?
About 150 days.
WHY DO SOME PEOPLE HAVE DIMPLES?
Dimples are caused by muscles on your face. These muscles are unusual because they are attached to the skin; most muscles are attached to bones. When people smile, certain muscles make dimples.
WHAT IS THE LARGEST BONE IN THE BODY?
The largest bone in the body is the thigh bone.
WHEN ARE PEOPLE THE HEALTHIEST?
People are the healthiest between the ages of five and 15.
WHEN DO KIDS STOP GROWING?
Boys achieve 98% of their height when they reach the age of 17 and three-fourths. Girls reach 98% of their height when they are 16 and a half.
HOW LONG DOES IT TAKE TO BLINK YOUR EYES?
About three-fourths of a second.
WHAT IS THE HEAVIEST ORGAN IN THE BODY?
The liver. It weighs three and a half pounds in an adult, or about five times more than the heart.
WHEN IS YOUR EYE STILL?
Never! The eye is always moving, even when you are staring at something. The tiny muscles in the eye move about 100,000 times a day to let you see. For your leg muscles to get the same exercise, you would have to walk 50 miles.
HOW MANY SOUNDS CAN YOU HEAR?
You can hear between 350,000 and 400,000 different sounds.
HOW MUCH AIR DO THE LUNGS USE IN ONE DAY?
About 12,500 quarts.
WHY DO PEOPLE YAWN?
In the lungs are millions of tiny air sacs called alveoli. Changes in the alveoli cause you to yawn. When you are sleepy, you are not breathing deeply enough oxygen. The alveoli are not filled with air. So your brain sends out a message telling you to take a long breath. That long breath is a yawn.
WHAT IS THE HARDEST SUBSTANCE IN THE BODY?
If you guessed that it is the bones, you are wrong. The hardest substance is the enamel that covers your teeth. However, like other parts of the body, the enamel cannot fix itself when it is damaged.
HOW MANY DIFFERENT SMELLS CAN HUMANS SMELL?
The average person knows 4,000 different smells. Some people with a very special sense of smell know 10,000 different scents. People who test perfumes have this talent.
HOW MANY MUSCLES DOES IT TAKE TO SMILE?
It takes 17 muscles to smile. Forty-three muscles are used when you frown.
HOW IMPORTANT IS THE THUMB?
The thumb does 45% of all the work done by your hand.
Condensed from Macmillan Illustrated Almanac for Kids
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