Chapter 4
Your Ears
Touch your ears. What do they feel like? Curvy and spiraled? Your ears are designed to capture vibrations in the air caused by sound waves. These vibrations are amplified inside the inner ear and then passed on to the brain, which recognizes or learns the sound. That is how you hear.
TRY THIS
SOUND SLEUTH
Close your eyes. Do you hear any sounds nearby? Have you ever been in complete silence? It's pretty difficult to experience that since there's always some kind of noise going on around us — a dog barking, a car honking, a bird chirping, a breeze blowing, your breathing. Our ears tell us amazing things about what's going on in our world.
FUN FACT
Fake Effects
Did you know that sometimes the sounds you hear on the radio and in the movies are fake? On radio shows, wooden blocks can imitate horses' hooves. In the movies, sound effects people use things like large sheets of aluminum to mimic thunder.
QUESTION
Can you tell where a sound is coming from?
WHAT YOU NEED
A friend
WHAT TO DO
FAN FACT
Did You Hear?
Some animals have unique ways of hearing the world around them. Crickets use thin layers of skin on their legs to hear. Bats and dolphins send out sounds that bounce off of objects around them and make echoes. The echoes indicate how far away the objects are. Dolphins have much better hearing than humans — 14 times better in fact!
WORD to KNOW
echolocation: using echoes to determine the location of something. Bats and dolphins rely on echolocation to find their way.
WHAT'S HAPPENING
You were able to tell which direction the sounds were coming from because you have one ear on each side of your head. If your friend was standing on your left side, your left ear heard a louder sound than your right ear did. Your brain can tell the difference. If you heard a sound that was far away, your brain processed the time it took for the sound to reach you and figured out that the sound did not happen nearby.
Your ears also help you keep your balance. They contain a liquid that moves and presses against nerve endings in your ears as you move. This movement tells your brain that your body is in motion. If you spin very fast, the liquid pushes the hairs on the nerve endings in all different directions, disorienting your brain. So you feel dizzy. Your brain is confused about which way is up.
Many animals rely on their hearing to tell them if predators or prey are nearby. Certain owls have special feathers, called ruff, that channel sound up to their large ear holes, enabling them to hear very well. This helps them hunt at night when visibility is not as good. Owls' brains also do what our brains do and calculate the time it takes for sound to reach each ear. They can judge the distance of their prey based on that calculation.
YOUR NOTES
Hum
Clap
Whistle
Stomp
Yell
Whisper
Open and Shut
The directions for this exper-eye-ment are in a grid that has been cut into pieces. Match the pattern of black squares, and figure out where each piece goes. Then write the letters into the empty grid. To complete the experiment you will need a bathroom with a mirror and light over the sink.
TRY THIS
BOOMING BALLOON
QUESTION
Can a balloon help you hear better?
WHAT YOU NEED
A balloon
A friend
WHAT TO DO
WHAT'S HAPPENING
Sound begins with a vibration in the air and travels to your ear in waves. When you blew up the balloon, you pushed the molecules of air into a small space. Sound waves pass more easily through this compressed air, which is why you heard a loud sound through the balloon. If you were to tap lightly on a balloon that is not near your ear, it would not sound as loud.
Sounds have pitch, which indicates how high or low the sound is. A tiny bell makes a high-pitched sound, while a big bell makes a low-pitched sound. You have a higher-pitched voice than your father does, for instance, even if you're a boy.
But sometimes this pitch can seem to shift, especially when it's coming from a moving object, like a fire truck or a police siren. What's happening is that your ear is first detecting long sound waves, which have a low pitch. This is usually when the police car is far away. Then as the car and its siren get closer, the waves get shorter and shorter, raising the pitch. As the car then passes you by, the waves get longer and longer again, dropping the pitch as the car drives away.
YOUR NOTES
Where can you take your balloon amplifier to hear highpitched sounds? How about low-pitched sounds? Can you feel the balloon vibrating, too?
TRY THIS
TELE-CUP
Now that you know how sound moves, let's put those waves to work!
QUESTION
Sound can travel through the air, but can it travel along a string?
WHAT YOU NEED
Two plastic cups
Scissors
feet of string
Friend
WORD to KNOW
vibrate: to move back and forth, or to and fro, rhythmically and rapidly.
FUN FACT
Sounds in the Earth
Plates in the Earth's crust are constantly in motion. Sometimes they push up against each other and cause an earthquake. The force of an earthquake sends sound waves rippling through the ground. Scientists called seismologists use a seismograph to measure those waves and determine the strength of the quake.
WHAT TO DO
WORDS to KNOW
amplifier: something that amplifies, or increases, current, voltage, or power.
WHAT'S HAPPENING
When you pull the string tight and talk into the cup, the vibrations in your voice travel down the string to the other cup. Your friend's ears receive the vibrations and his brain processes them into the words you said. And just like that, you have your very own telephone!
A regular telephone has its own little brain, translating sound waves into electrical signals and then translating them back into sound waves, creating a two-way exchange of sound. Telephones have come in all kinds of designs, some with handsets that are wired to a body with a rotating dial, others with handsets that are separate from the bodies, and now cellular telephones that receive wireless signals.
What's as big as a person but weighs nothing?
Its shadow!
YOUR NOTES
Try talking quietly into your telephone. How low can you whisper and still be heard by your friend?
Try using different materials to make your phone — metal cans and fishing wire, for instance. Do you notice a difference? Make sure the metal cans are safe and don't have any sharp edges.
Try using cups that are different sizes. Try loosening the string. What happens?
Cool Quotes
Why are things the way they are and not otherwise?
— Johannes Kepler
What's That Sound?
Hold an empty glass up to your ear. What is that whooshing sound you hear? Some people joke that it is the sound of the ocean! To learn what the mystery noise really is, start at the white T marked with a dot. Read just the white letters as you travel clockwise around the border. When you reach the dark and empty box, turn around and continue reading just the dark letters until you are back at the beginning.
SCIENCE LAB: THE VANISHING FLAME
So now we know that sound moves in waves, the waves can be long and short, sound can have a high pitch and a low pitch, and our ears send signals to our brain about the nature of a sound and its location. But what if we could actually see sound moving?
QUESTION
Can you see sound waves?
WHAT YOU NEED
Scissors
Cardboard tube
Cellophane tape
Enough plastic wrap to fit around the top and bottom of the tube
Small candle
WHAT TO DO
WHAT'S HAPPENING
Sound waves are not visible, normally. But when you tapped the plastic wrap, the air inside the tube vibrated. The vibrations were strong enough to travel through the hole and blow out the flame. So you can see the effects of sound waves.
Another way you can detect sound is by feeling it. Touch the small bump at your throat while you say “Hello” a few times. Can you feel vibrations through your skin? We have two sections of stretchy tissue in the throat that are called vocal chords. They vibrate when air passes through them, causing the sounds we call speech. The bump you touched is called the larynx. There are muscles around the larynx that determine the pitch of your speech. Can you make your voice go really high or really low? What does that feel like?
YOUR NOTES
Try lighting two candles. How hard do you have to hit the drum to blow them both out?
Try using a bigger or a smaller tube. Are your results any different?
Near or Far
Depth perception is the ability to judge how near or far objects are. What can change depth perception? Figure out the Vowel code to get directions for a simple test to help you learn more!
Funny Bones
You will need to break three different codes to get the answers to these wacky riddles!
Your Skin
What is one of the most amazing organs in your body? Here are some clues: it keeps you dry, safe, and healthy. And it warms up and cools down all by itself. If you guessed your skin, you're right! Humans all pretty much have the same skin — it's made of all the same molecules and it performs the same functions. It covers our bones and muscles and tissues and organs.
But animals and birds have completely different kinds of skin. Some animals, like polar bears, have dense fur that keeps them warm in cold climates. Other animals have no hair, such as Chihuahuas and seals. Chihuahuas live in warm climates, and seals have layers of fat called blubber that keep them warm in cold ocean water. Fish have scaly skin that helps them move through water. Birds have feathers that are specially designed to help them fly.
TRY THIS
FEET FEELERS
Humans have incredibly sensitive skin, especially on our feet. Unless you walk around outside in bare feet all the time, the soles of your feet are quite soft. In this experiment, you'll rely on that sensitivity to give you clues about the things around you.
QUESTION
How does your skin help you recognize your world?
WHAT YOU NEED
Friend
Various objects with different textures, such as flannel, sandpaper, wool, Styrofoam, tape, towel, saucepan, ice cube, and so on
FUN FACT
Super Skin
Did you know that your skin is the largest organ in your body? Full of oils and glands and layers upon layers of cells, it protects and covers your insides. Give yourself, and your skin, a big hug!
FUN FACT
Bones
When you were a kid, you had 300 bones in your body. But as you get older, some bones will fuse together. So when you become an adult, you will have 206 bones in your body.
WHAT TO DO
What can you feel under your feet?
WHAT'S HAPPENING
The skin is the largest organ in the human body and is made up of two layers. The outer layer is called the epidermis, and the inner layer is the dermis. The dermis has certain areas on it, called receptors, that send messages to the brain whenever the skin is cold or hot, wet or dry, smooth or rough.
There are certain areas on your body that are covered in hair. The hairs protect your skin from sun exposure and cold. When skin does get cold, tiny raised areas can appear, called goose bumps. They make the hairs on the skin stand up. Goose bumps can also appear when you're frightened. The action that causes goose bumps is called the pilomotor reflex and it is similar to a porcupine raising its quills when it's threatened.
YOUR NOTES
Which textures were easy to identify?
Which were difficult?
TRY THIS
SKIN IS COOL!
What feels better on a hot day than a breeze? You instantly feel calmer, cooler, and happier. But are you actually cooler? Has your body temperature changed at all?
QUESTION
When it's hot outside, how does your body stay cool?
WHAT YOU NEED
A warm day
A fan
A household thermometer
WHAT TO DO
FUN FACT
Shedding Skin
When you become an adult, you will have more than 20 square feet of skin on your body. And you will have shed more than 40 pounds of skin! Ew!
WHAT'S HAPPENING
All over your skin are tiny holes called pores. If your body temperature rises above 98.6°F, glands under your skin release a liquid called sweat that seeps through your pores and out onto the skin. This process is called perspiration. Blowing air from the fan evaporates the sweat, turning the liquid into vapor. Even if the temperature of the room doesn't change, your body is cooling down, which makes you feel better!
Your body makes more than ten ounces of sweat a day, even in winter. It's important, though, to drink lots of water, even if you're feeling cool. Your body loses moisture through perspiration and you have to stay hydrated.
Plants have their own way of releasing moisture, though it's not called perspiration, and it's not because they're hot. Plants sometimes absorb too much moisture from the ground, and so they release the water as vapor through tiny holes in their leaves called stomata. The process is called transpiration.
WORD to KNOW
evaporation: the process by which a liquid changes into a vapor.
YOUR NOTES
Room temperature: 
How you feel before using the fan:
How you feel after using the fan:
SCIENCE LAB: CAUGHT IN THE ACT
When police officers are trying to solve a crime, they look for fingerprints. In this experiment, you will gather fingerprints from your family members, your friends, and yourself and look at the prints closely. Now that's some good police work!
QUESTION
How does your fingerprint identify you?
WHAT YOU NEED
Pencil (try not to use a mechanical pencil, use a wooden one instead)
3 sheets of white paper
Rubber gloves
Transparent tape
Family members and friends
Magnifying glass
WHAT TO DO
WHAT'S HAPPENING
Your skin has natural oils on it that keep the skin smooth and healthy. When you touch something, you leave behind an oily impression of your skin on the object. That impression is a fingerprint. Skin is extremely flexible and elastic so it can move and stretch in all kinds of ways. As a result, no two fingerprints are exactly alike. Even identical twins will not have exactly the same prints.
Fingerprints are made up of three basic parts known as whorls, arches, and loops. Nowadays, prints are entered into a computer database to make it easier to search a print. But once upon a time, prints were identified by hand. Detectives would use the loops, whorls, and arches to figure out the owner of a fingerprint.
WORD to KNOW
dactyloscopy: fingerprint identification.
YOUR NOTES
Draw a picture of the most unusual fingerprint. Who does it belong to?
Tick Tock
You can watch your heart beat without having to look at your heart!
You will need a small lump of soft clay and a drinking straw.
Poke the straw into the clay, pointing up.
Connect the dots in this puzzle. X marks the spot where you should stick the “ticker” you have made.
Your Eyes
Have you ever looked closely at your eyes? The colored part is called the iris. It can be brown, blue, black, or hazel. The black part inside the iris is the pupil, which can enlarge to let in light and contract to block out too much light. There are parts of the eye you can't see, too. There is a curved and transparent part that sits in front of the iris called the cornea. Another transparent section that sits behind the pupil is called the lens. Light moves through the lens and then through a jelly contained in the eye, all the way to the retina. From there, receptors tell the brain what colors the eye is seeing.
FUN FACT
Do You See Color?
Different animals see different amounts of color. Dogs and cats can see some colors. Whales, sea lions, and dolphins are colorblind, meaning they see only light and dark, not colors. Monkeys and apes see as many colors as we do. And owls can see at night — some scientists even think owls can see colors in the dark!
TRY THIS
COLOR GO ROUND
Our world is incredibly colorful. From a brilliant blue sky to a crimson sports car, almost everyone sees the vast spectrum of color around us. What are your favorite colors? Which ones do you like to wear? Do you like certain foods because of their color? Or do you think about certain colors when your mood changes?
QUESTION
Why do colors seem to run together when you see them go by quickly?
WHAT YOU NEED
Small plate
Piece of cardboard
Small screw
Pen
Red marker
Blue marker
Scissors
Hole punch
WORD to KNOW
colorblindness: inability to see one or more colors.
WHAT TO DO
FAN FACT
Mirage
Have you ever looked down a road in summer and seen a shimmer? Your eyes are playing tricks on you. It looks like there's water on the road, but in reality there's nothing there. This phenomenon is known as a mirage.
FUN FACT
Blinkathon
The human eye blinks more than 4 million times in one year!
WHAT'S HAPPENING
When you spin the wheel quickly, your brain cannot distinguish each color. So it sees a mixture of the two colors. A wheel with red and yellow sections looks orange. A wheel with red and blue sections looks purple.
Red, yellow, and blue are called primary colors. They are used to make the secondary colors of orange, green, and purple. Color wheels also display pairs of complementary colors, which, when mixed properly, yield a bland color like white, black, or gray.
Some people experience colorblindness. While they're not technically blind, they do have trouble seeing certain colors. This can be caused by damage to the eye or the brain, or it can be genetic, which means the person inherited it from the parents. Some people who are colorblind have difficulty telling the difference between red and green. Others have trouble with blue and yellow. And still others cannot see any color. Imagine what that must be like.
YOUR NOTES
Red and blue make
Red and yellow make
Yellow and blue make
Ghost Nose
Here's an easy trick to play on your brain! Follow the directions to learn how to find your own ghost nose.
TRY THIS
BUSY BOOK
Nowadays, cartoon animation is often done by a computer program, which uses math to manipulate images in a way that creates a picture that looks so realistic it's hard to tell it's a cartoon. But once upon a time, people sat and drew images and then filmed them to give the illusion of movement and life.
QUESTION
How do you make a still image move?
WHAT YOU NEED
10 square sheets of paper
Pencil
Stapler
WHAT TO DO
WHAT'S HAPPENING
If you flip through the book slowly, your eye can detect the individual images. But when you flip quickly, your eye cannot keep up, and the images seem to “move” on their own. This is a similar effect to the color wheel experiment at the beginning of this section.
When you watch TV or a movie, you are watching a series of still images scrolling at a very fast speed to trick your eye into believing the images are actually moving. It's important to remember when you're drawing these kinds of movements, however, to make your changes slight and minimal but numerous so that the motion can appear as seamless as possible.
YOUR NOTES
What other images could you draw in a flip book? Perhaps a flower opening or a caterpillar turning into a butterfly?
What did the left eye say to the right eye?
Between you and me, something smells!
SCIENCE LAB: MEMORY TEST
Have you ever played a card game called Concentration? Grab a friend and lay out the entire deck of cards face down on the floor in front of you. Turn over a pair of cards. Try and remember what you've seen and where you saw them. Flip them back over. Now it's your friend's turn. Can she remember the cards you turned over and hers as well?
QUESTION
How well do you remember what you see around you?
WHAT YOU NEED
3 sheets of paper
Pencil
Tray
Ordinary objects, such as utensils, paper clips, scissors, ruler, stapler, bottle cap, and hairbrush
Stopwatch
WHAT TO DO
WHAT'S HAPPENING
Your brain is an incredible machine. One particular part of your brain is called the cerebral cortex. It handles signals from your senses. It is also in charge of helping you think and remember.
There are four kinds of memory:
Your short-term memory is what allows you to do the previous experiment.
Starting when you are about three years old, your brain starts making memories of your experiences and actions. As you get older, you lose some memories. This is natural — the brain has to make room for new ones. But some people lose too many of their memories and it becomes hard for them to function. This is why many people work on their memory, testing it with exercises like the ones you just did, to keep their brains sharp and alert.
YOUR NOTES
Number of words you remembered:
Number of objects you remembered:
Numbers you remembered: