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PUBLIC LIBRARY FORT WAYNE AND ALLEN COUNTY, IND. ALLEN COUNTY EXTENSION DEPT.
AIR Irving and Ruth Adler
The John Day Company — New York
The "Reason Why" Series by Irving and Ruth Adler
NUMBERS OLD AND NEW THINGS THAT SPIN
SHADOWS THE STORY OF A NAIL RIVERS
why? A Book
© 1962 by Irving and Ruth Adler must not be reproduced in any form without permission. Published by The John Day Company, 62 West 45th Street, New York 36, N.Y., and simultaneously in Canada by Longmans Canada Limited, Toronto.
All rights reserved. This book, or parts thereof,
Library of Congress Catalogue Card Number: 62-10935
United States of America
Contents The Blanket Around Us
Oxygen and Living Things Carbon Dioxide and Living Things Nitrogen and Living Things Seeds, Pollen and the Wind Air Has Weight Barometers and Drinking Straws
Blanket for the Earth
14 16 18
The Weather Factory
Big Circle of Air
Molecules, Atoms and Ions
Mirrors and Whistles
Neon Lights in the Sky The Stratosphere
to the Air
Taking Care of Air
The Changing Atmosphere
covers the earth like
attention to the blanket of air in
to the air in a tire
when So we
do pay attention
a blanket. But most of the time
We pay attention to the air near a fire when the
begins to go out.
we blow on
air to the fire.
to the air
when we have been running very
gasp and pant because our bodies need
The gasping helps us
get the air
diver pays attention to the air he needs
can't get air
goes under the water.
from the water the way a
does. So he takes a tank of air
The spaceman pays attention to the air he needs to breathe when he goes off in a rocket. There
outer space. So the space-
takes an extra supply of air with
his rocket ship.
In this book
made of. We shall how it sometimes shall find out
shall find out
shall find out
gets in our way.
about some interesting things
in the earth's blanket of air.
earth's blanket of air
Put the upside-down glass into the pot of water
But the there
glass really isn't
is still fill
easy to show that
something in the glass after the milk
a large pot with water.
glass into the pot of water. glass
that ends this
take an "empty"
Now put the upside-down The water
something in the glass that keeps
the water out.
tip the glass
jump out do
over in the water. Noisy bubbles
of the glass to the top of the water
are bubbles of
Air was in the glass
when you put 6
the glass into the
Tip the glass over in the water
pot of water.
You could not
there just the same. Air
could do fill
gases that are mixed together. Air
mostly nitrogen (NY-tro-jen) and oxygen (OX-i-jen).
A gas always spreads out to
every crack and corner of
the glass, too.
four times as
nitrogen in the air as there
oxygen. Air has some carbon dioxide (CAR-bun di-OX-
The name of this gas is steam or water vapor. There is a small amount of water vapor in air. Air has a little bit of helium (HEEle-um) and hydrogen (HY-dro-jen) in it, too. Helium and water boils
hydrogen are very
You cannot air in
see the air in a glass.
your room. You cannot even see the
your house. Most of the time you cannot see
you are looking through a
look through a lot of
When you look at the sky above you on a sunny day, are looking through miles looks blue. Blue
the color of
The air looks blue when sunlight passes through it. The light of the sun is white. But white light is really
mixed together. Blue
one of the colors
light is really
Prebits of gas and dust
of the bright sky.
the blue light out of the sunlight and
to our eyes. It does
of tiny bits of gases. too.
There are tiny
bits of gas
bits of dust in the air,
scatter the light of the sun all over the sky. This
makes the sky look bright during the daytime.
bits of gas
and dust do not
of all the colors in sunlight.
scatter blue light
than light of any other color. Blue light comes to us from all
parts of the bright sky. So blue
ing the daytime. 9
the color of air dur-
Watch it burn for a Then cover the candle with a jar. Watch the flame.
Set a lighted candle in a dish. while. It gets
smaller and smaller. Soon
The candle burns
well in the open air because
taking something out of the air
oxygen out of the a
the candle takes oxygen out of the air in the
After a while
the oxygen in the jar
used up. The
candle cannot burn without oxygen. So the flame goes out.
burns. Paraffin has hydrogen
burns, the oxygen in the air comes together with the
hydrogen and carbon. The oxygen comes together with
The oxygen comes together with the carbon to make carbon dioxide. The burning also makes heat and light. The water vapor and
the hydrogen to
carbon dioxide become part of the
When wood burns,
makes carbon dioxide
and water vapor.
carbon dioxide and water
when things burn in it. We can make a fire burn better by giving it more oxygen. We do this when we blow on a fire gently. The blowvapor
to the fire quickly.
We can make a fire go out by taking away the oxygen it
needs to keep burning.
wish-er) works this way. It sprays carbon dioxide over
close to the
goes out because
from coming near the it
has no oxygen to keep
Carbon dioxide stays close to the fire, so the fire goes out.
Oxygen and Living Things There this fire
that burns inside
has no flame.
fuel for this fire
the time. Only is
the food you
You get the oxygen for the fire when you breathe. The tiniest part of your body is a cell (SELL). There
are hair cells cells.
There are bone
that burns inside every
must have food and oxygen. You eat food. Then your
blood carries the food you eat to every
gen from the
your lungs. Blood
take the oxy-
your lungs. Then your blood carries
the oxygen to every cell in your body.
The burning inside your cells is like the burning of the candle. The food you eat has carbon and hydrogen in it.
When the food burns inside your cells, oxygen come together
the hydrogen and
make water vapor. The carbon and oxygen come together to make carbon dioxide. The to
burning also makes heat and energy.
The heat made by the burning keeps your body warm. The energy made by the burning makes you able to do things. It
makes you able
to play. 12
to run, to
the water vapor and carbon
your lungs. The water vapor and carbon dioxide
the burning inside your
body when you breathe
You can show
cells. It carries
you breathe out water vapor.
Breathe out through your mouth against a window.
a cloud on the
window where your breath made of tiny drops of water.
The water vapor in your breath changed to tiny drops of water when it touched the window. Other animals need oxygen, too. They use it in the same way that you do. Plants also need oxygen for burning their food.
They get their oxygen through their leaves.
You breathe out carbon dioxide and water vapor
into your lungs
Blood takes water vapor and carbon dioxide from your eel Is
Blood cells take the oxygen from the air in
to your lungs
your lungs 4.
...to every cell in
Blood takes the oxygen
0m& Carbon Dioxide and Living Things All living things to
make heat and
need food. They need food
They need food
as a fuel
They make their food in their leaves. The food they make is sugar. Sugar is the food they need to make them grow. Green plants make
Carbon is one
of the things out of
Green plants get carbon from carbon dioxide
in the air.
another thing out of which sugar
Green plants get water from the ground through
carbon dioxide and water come together to
used up. Green plants get the
energy for making sugar from sunlight.
green plants use the energy of sunlight to help
called photosynthesis (foto-
Carbon dioxide has carbon and oxygen
make sugar, they take oxygen. Then the oxygen is
green plants use carbon dioxide to the carbon
The oxygen goes back
always oxygen in the
animals and plants to use
burning to take place.
always carbon dioxide in the
plants to use for photosynthesis.
Some of it gets there from volcanoes. Some of it gets there when things like coal and wood burn. And some of it gets there when
when plants and
animals burn their food.
dead things decay. Animals cannot make their like rabbits,
horses, get their food
green plants. Other animals, like lions and their food
by eating the animals
by eating tigers, get
that eat green plants.
People get their food by eating plants and animals. So all
animals need green plants to
their food for
them. Carbon dioxide
always carbon dioxide
green plants to use
Nitrogen and Living Things All living things build nitrogen into their bodies. is
nitrogen in the air
around them. But most living
things cannot use the nitrogen in the
Animals get their nitrogen from the plants or animals they
Most plants get
which they grow.
nitrogen comes together with hydrogen, am-
which plants grow. Plants get
gen from the ammonia in the
When nitrogen comes
ammonia in the some of their nitrois
together with oxygen and some
other chemicals, nitrates (NY-trates) are made. There are nitrates in the soil in
of their nitrogen
which plants grow. Plants get
nitrates in the soil.
So plants are always taking nitrogen out of the
Some the air
of the nitrogen in the soil
the time. There are tiny
being put back into
called bacteria (back-TEER-ee-a).
plants in the soil
away from the oxygen and other chemicals They put the nitrogen back into the air where
the nitrogen in nitrates.
most plants cannot use
Bacteria that put nitrogen into the soil
So the nitrogen
in the soil
being put back into the
being used up in two
would be no nitrogen
only this happened,
lucky that there are some plants that take nitro-
gen from the
back into the
are called legumes (leg-YOUMS).
bumps on their roots.
trogen so that the legumes can build
into their bodies.
the legumes put nitrogen into the
plants to use. Peas, beans, peanuts
Bacteria live in these bumps. These
bacteria take nitrogen from the
built into the bodies of plants.
the nitrogen in the
and clover are
root of a pea plant. Bacteria live in the
spreads these seeds
The air helps many plants spread their seeds. Some seeds are put in the ground by people when they plant gardens. Some seeds stick to the fur of animals. The seeds fall to the ground as the animals move. Some seeds are carried by the wind. The wind is moving air. Seeds that are carried by the wind must be very light. But the seeds are heavier than the So sooner or later they
air that carries
Seeds that are carried by the wind
like the seeds of
like little balls of fur, like the seeds of the
Sometimes the wind that
They may They may look
shapes that help them ride on the moving
by moving the plant become dry after they
have made their seeds. The dry plants break away from their stems.
ground. As the plants to the ground.
the dry plants over the
over and over, their seeds
their seeds in this
way. They are called tumbleweeds because the wind tumbles the dry plant over the ground. 18
The air also helps many plants make their seeds. It helps by carrying pollen (POLL-en). Pollen is a very fine powder that grows on flowers. Pollen helps to make a seed.
the pollen must be carried to the part of
the flower where the seed
insects carry pollen. Insects carry the poll-
en on their bodies.
Sometimes the wind carries pollen. The wind can carry the pollen of
Pollens carried fever.
by the wind give some people hay
eyes turn red. People of trees, grasses
them sneeze and makes
get hay fever from the pollen
Different kinds of pollen
Air has weight. Although air
weighed on a
light things like air. Air
of air doesn't
air in a
The It is
from the earth.
so light that
one cup of water.
you may think that a roomful
weigh very much.
the earth as
scientist has a special scale for
you do, you are wrong.
30 feet long, 20 feet wide
weighs almost 500 pounds!
above us reaches higher than any schoolroom.
up high above the is
pile of air
thousands of miles high.
spreads out to
can reach. But
never goes away
weight keeps pulling
Air pressure at sea level is
15 pounds per square inch
of the air
9 pounds per square
above the earth keeps pressing
down on everything on the earth. It keeps pressing down on you, too. More than 12 tons of air are pressing down on you right now. This is like having two large elephants pressing down on down on the earth.
you crushed by
that air isn't only around you.
side you, too.
you pushes back. This push
back keeps you from being crushed.
How hard of anything
the air presses
Air pressure It is
as air pressure
The bigger pile
the same everywhere on the earth.
greater near the ocean than
every square inch
on the top of a
a bigger pile of air
the ocean than on a mountain top.
of air has
more weight and
harder. Air pressure at sea level
square inch. 21
about 15 pounds per
pushes the mercury up the closed tube
down on the
A mercury barometer
Barometers and Drinking Straws
pressure with a barometer (bar-OM-
A barometer has a glass tube that is closed at one 22
The tube has mercury (MER-cure-ee) in it. The tube held upside down. The open end of the tube is in a
dish of mercury. There
of the tube
nothing in the closed end
above the mercury. There
a ruler next to
off in inches.
above the dish presses down on
of the air
The pressure on the mercury in the dish pushes the mercury up the tube. To measure the pressure, we read the number of inches that the mercury has climbed up the tube. At sea level, the mercury in the the mercury in the dish.
tube reaches 30 inches. So level
say, "Air pressure at sea
used in a barometer because mercury
very heavy. Water
lighter than mercury. Air
up an empty
pressure at sea level pushes water 30 feet tube. So a water barometer
Air pressure helps you drink water from a drinking straw.
You put one end
of the straw into a glass of water.
the other end of the straw into your mouth.
you drink from a drinking straw, you suck the
out of the straw.
of the air
tube of a
down on the water in the glass. The pressure on the water pushes the water up the straw into your mouth. 23
A You wear getting out. side
Blanket for the Earth
a coat to keep the heat of your
a coat to keep the cold winds out-
So your coat keeps you
on very cold days.
like a coat that the earth
thick blanket keeps the earth from getting
too cold at night and in the winter.
keeps the earth
from getting too hot during the daytime and mer.
keeps the temperature of the earth just right for
The sun sends
we get warm from
us light rays and heat rays. So
the light to see with and the heat to keep us
The sun sends us other rays, too. It is lucky for some of these rays never get through the earth's
the sun. us that
There are X-rays
Doctors sometimes use
X-rays to take pictures of the inside of your body.
do not use X-rays often because X-rays can hurt
The X-rays in sunlight never reach the earth. They are stopped by the earth's blanket of air. There are rays in sunlight that make you get sunburned on a bright summer day. They are called ultrathings.
violet rays. If all these rays got
you. Only a small
through to the earth they
of these rays
through. Most of these rays are stopped by the air high
up above the
X-rays and ultra-violet rays
The earth's atmosphere burns up most meteors
are stopped by the earth's
mo sph e re
There are pieces of metal and rock that travel around
most meteors burn up right away.
teors, the earth's
As they rub
into the earth's atmosphere.
against the air they get very hot.
are called meteors (MEE-te-ors).
across the sky.
get so hot that
We see them as bright By burning up
blanket keeps them from falling on us.
blanket can also get in your way.
from finding out what
can keep you
on the other side of the blanket.
We find out about the sun and the stars by the light that comes from them. The of the sunlight
earth's blanket of air stops
of the facts that
S AT-el-lites ) into space.
of the sun
get from this light.
scientists are putting satellites
can take pictures
from the other side of the
The Weather Factory
earth's blanket of air
But most of the above the
thousands of miles thick.
than 10 miles
lower part of the atmosphere
called the troposphere (TROP-a-sfeer).
and animals can
only near the bottom of
They must live near the surface of the earth where there is enough oxygen for them. They cannot live more than 3M miles above sea level without help.
Mountain climbers know
The temperature in
So they take oxygen with
are high up.
of the air in the troposphere
an interesting way. The higher you go into the tropo-
sphere, the colder
Then you reach
a place where
Radio Corporation of America
stops getting colder as
where the temperature
you go higher. You reach a place stays the
time and nighttime. This place
same during the daywhere the troposphere
The troposphere earth. It
called the weather factory of the
in the troposphere that all the things
weather happen. Here place to
make winds. Here
water vapor in the
most of the
where clouds form when
water vapor changes back to drops of water or ice.
moves from place
and snow. Here
storms are made.
on the ground measure the tempera-
of the air near the ground.
ure the speed of the wind. the
find out the direction
wind comes from.
Balloons with radios carry the tools of the weather-
high up into the troposphere. The radios send back
messages to the weather stations on the ground. In
pressure and winds are high
what the temperature, in the troposphere.
450 miles above the earth look
the troposphere from above.
They send back
pictures of the clouds.
these facts, the
He and why
going to be.
the weather changes
also tries to find out
storms take place.
big circle of air in a
Big Circle of Air
Electric heaters are sometimes used to
The hot wires of the heater heat the air around them. But when air is made hot it gets lighter than the rest of the air near it. So the lighter, warmer air around the heater wires begins to rise. When the warmer air rises, it leaves a space. Cool air moves in to fill this space. But then there is a space where the cool air had been. So air from above moves in to fill this new space. In this way the air in the room begins to move in a big circle. When air
in a circle like this
near the heater
the air circulates, the
parts of the room.
air in the
troposphere circulates, too.
when air near the ground is warmed by the
This makes the air place of this
makes surface winds. While the air in the troposphere cles,
in to take the
near the ground
in big cir-
the earth turns the surface winds.
picture shows the big circles of air in the tropo-
sphere and the paths the surface winds follow.
Atoms and Ions
smallest piece of anything .
Molecules are so small that they cannot be seen.
Molecules are moving
the time. Air has molecules of
nitrogen, oxygen, water vapor
Each molecule two atoms
and other gases
made up of bits called atoms AT-ums (
in the troposphere has
Each molecule of water vapor has hydrogen and one atom of oxygen. Atoms
atoms of oxygen in
of pieces of electricity.
They are called positive and negative electricity. Each atom has positive and negative electricity in it. The smallest piece of positive electricity is a proton (PRO-ton). The smallest piece There are two kinds of
of negative electricity of the time
an electron (ee-LEK-tron). Most
an atom or a molecule has the same amount
Sometimes an atom or a molecule trons.
lost electrons float
A hydrogen atom
in the air loses elec-
in the air.
An oxygen atom 30
atom or molecule has more positive
atom or molecule has a
atom or molecule picks up electrons that are around
in the air.
the atom or molecule has
negative electricity. So the atom or molecule has a negative charge.
called an ion (EYE-on).
an atom or molecule has a positive
molecule has a negative charge,
electrons that float
ions because they
an atom or
called an ion, too.
in the air are also called
Rays from outer space, X-rays and other rays from the sun stream into the earth's atmosphere. They change the molecules of
the upper part of the earth's atmosthis
full of ions.
called the ionosphere (eye-ON-a-sfeer).
The ionosphere begins 50
miles above the earth.
to the top of the earth's blanket. It goes to
A water molecule.
has two atoms of hydrogen and one atom
Mirrors and Whistles In 1901 a message was sent across the Atlantic Ocean. This message was not carried by wires.
was carried by
radio waves. Scientists
were surprised that a radio message could
travel so far.
Radio waves travel through the
But the earth
round. So the scientists
thought that the radio waves wouldn't travel around the
They thought the waves would go off into space or bump into the ground. The first picture shows you what they thought would happen. earth.
the message did cross the ocean, the scientists
tried to find the reason
sphere acted like
off into space.
that the ions in the iono-
Scientists thought a radio at
radio waves did not
sent back to the ground
B couldn't receive
the ions in the ionosphere.
picture shows you
the ionosphere helps radio waves travel long dis-
tances around the earth.
There are many other interesting things that happen in the ionosphere.
The ionosphere helps make whistlers (WHISS-lers). You can hear whistlers on the radio during thunderstorms. First you hear a click. This is when there is a flash of lightning. Then you hear a long, low whistle. This
Flashes of lightning send out radio waves.
They travel to where waves make the whistle
to the ionosphere.
the ionosphere ends. These radio
you hear on your
Whistlers have helped scientists figure out that the
ionosphere goes up 7,000 miles above the earth.
Lights in the Sky
clear nights the sky
In the north, the lights can be seen in the
northern sky. Scientists
call these lights
(or-OR-a bore-ee-A-lis). Aurora borealis means northern lights.
When we see aurora lights in the sky, earth's
to the earth
acting like a big neon light. Aurora
streams of electrons and protons that
from the sun.
into the ionosphere,
The protons come together with electrons in the ionosphere to make hydrogen atoms. When they do this,
wide bands of
Later on, the aurora lights look as though they came 34
^ and protons
Aurora lights are seen here
from great colored trons
atoms in the ionosphere.
from the sun
the atoms are
do not see these
way move back and
across the sky.
There are other
lights in the sky that are like aurora lights are in the sky all the time. lights
during the daytime. Daylight
hides them. At night they are hidden
moonlight. Scientists call these lights airglow.
though they cannot see airglow,
They know that oxygen atoms in the ionosphere make the red and green lights of airglow. They know that sodium (SO-dee-um) atoms in the ionosphere make the yellow light of airglow. Oxygen and sodium atoms make the colored lights when they are hit by ions that come from outer space.
about 40 miles thick.
a layer of air
between the troposphere and
The bottom sphere. This
of the stratosphere touches the tropo-
find the jet streams.
streams are very fast winds.
250 or 300 miles
Weathermen have made maps found that the
waves. The waves
of the jet streams.
streams follow paths that look like
move from west
carry large pieces of air from the troposphere with them.
These pieces jet
make our weather. By studying
what the weather
ing to be for the next few weeks.
The weather is best when there are some days that are sunny and some days when it rains. Too much sun makes plants dry up and die. Too much rain brings floods. Weathermen can tell when there will be days and days of rain. They can tell when there will be days and days of dry weather, too. They can tell by looking at the maps of the jet streams. The weather will be bad when the jet waves do not move for weeks and weeks. The stratosphere is a quiet layer of air. It is above the storms and winds of the troposphere. aurora
airglow and whistlers of the ionosphere. 36
of the air in the stratosphere never
changes very much. So the stratosphere for looking
at the earth's
a good place
atmosphere and outer
Very large sphere.
plastic balloons float
into the strato-
carry telescopes, cameras and other tools
of the scientist. Because the stratosphere
so quiet, the
balloons can stay in one place for a long time. eras
and telescopes take
fine pictures of clouds
the sun. Other tools study the gases that are found in the stratosphere.
Takes to the Air
Man saw insects and birds flying in the air. He saw seeds carried by the wind. Out of the things he saw, man built his dreams. He built dreams of First
he tried to
He tied great
body. But his body was not light
like a bird's. air
of a bird
spaces in them. So a bird's
strong wings can
bones have few
The wings man made were not strong enough to lift his heavy body into the air. Then man wanted to have the wind carry him like a seed. He drew pictures of his plans. Some of his pictures looked like parachutes.
Other pictures looked
was a long time ago. He never from
balloon was very light. small
his plans at that time.
in a balloon.
was made under the balloon.
into the balloon.
with the hot smoke. The
linen balloon filled with hot
The balloon climbed 300 feet carried a sheep, a rooster and a
A little later a balloon carried a man first
around it. So the balloon was
up by the o^
time. This balloon
the lightest gas there
safe to use. It burns easily.
used today. The balloons
which study the stratosphere are made tic.
hydrogen. But helium not burn.
A man has
into the air
isn't as light as
are filled with helium.
been carried 20 miles up
a plastic balloon.
parachute jump from the balloon. Balloons are useful for going high up into
They are not good for traveling long distances. They cannot travel fast because they are carried by the wind. the atmosphere.
Because balloons could not travel
man thought he would put an engine on a balloon. He built a balloon in the shape of a cigar. The engine made the balloon move fast. A balloon with an engine (DEER-ij-ibble).
called a dirigible
A dirigible carried many peo-
dirigible could travel faster than
Once a dirigible crossed Ocean in less than two days. But ship.
this dirigible fire as it
Many people died. Dirigibeen used much since then.
Airplanes are heavier than travel through the air.
into the air
But they can
Some airplanes have propellers (pro-PELLers). The propeller moves the air against the airplane wings.
Some airplanes have jet engines. are very strong. So a jet plane
over the ground before over the ground,
moves very off.
moves past jet
in the troposphere.
plane. Jets travel high
there are no storms to get in
way. So they can travel very
cross the Atlantic liners carry Still
in seven hours. Jet
other airplanes have rocket engines.
small. It carries only
The person is the pilot. The fastest rocket plane traveled more than 4,000 miles an hour. son.
Another rocket plane flew 40 miles above the earth. It flew in the stratosphere.
rocket fuel. So
could carry only a
Now man has
flew less than
Spaceships have carried him almost 200 miles
above the earth. Rockets carried ships up.
rockets traveled 18,000 miles an
spaceman traveled once around
the earth in his spaceship.
veled for a day in his spaceship. trips
Someday to the
a spaceship will take a
Los Angeles on a clear day
Division of Air Pollution
Department of Health, Education and Welfare
Taking Care of Air
We do not always take care of the air we breathe. We do not always keep air clean. We do not always keep
safe to breathe.
When we make air
are not taking care of the
a kind of
smog in the country on hot summer days. This smog is made by gases that are given off by plants. This smog cannot hurt us. But there is another kind of smog There
that can hurt us.
that can hurt us
makes people cough.
bothers their eyes. 42
and keeps them from growing. Smog some-
A London smog
1952 killed 4,000
lot of auto-
mobiles and factories. The gases that come from the auto-
pipes and the factory chimneys
Smogs are worst over some These
cities that are
near the sea.
have mountains around them. Los Angeles,
San Francisco and Rio de Janeiro
have bad smogs.
Harmful smogs can be stopped if people use other fuels in their
homes and factories. They can be stopped
build their cars in a different way.
Division of Air Pollution
of Health, Education
We don't take care of the air we breathe when we test atom bombs.
When we test atom bombs we put harmful
chemicals into the
can hurt us and even strontium
The light bits
where plants can get
of the air
them. Strontium 90 gets into the is
around the earth for a long
snow. They are carried into the
bits of the dust fall
and animals that are
of dust travel
time. Finally they are
carry the harmful chemicals
to the ground. Plants
kled by the dust
of these chemicals
dust with harmful chemicals
give off rays that
goes high up into the
After an atom in
acts like calcium
used by our bodies for build-
needed especially by
Children get calcium from the milk they drink. Milk
comes from cows. Cows get calcium from the plants they eat. Plants get
calcium from the
But strontium 90 tium 90 in the
acts like calcium. If there
into their bodies to-
Then cows build strontium 90 into milk together with calcium. Then little children
gether with calcium. their
build strontium 90 into their bones together with cal-
The strontium 90 can hurt
their bodies just as
Children can be strontium 90.
from the harmful rays of
They can be made
atom bombs. When we test atom bombs we putstmnj^
The strontium 90 is washed out of the air by rain and snow. It is
carried into the soi
where plants can get
eat the plants and build
Children drink the
milk and build
The Changing Atmosphere
billions of years ago. Scientists
atmosphere was not the same then
now. They think that the atmosphere has been changing the time.
earth was very hot
when it was young.
than the hottest part of the ionosphere. Nothing could
on the hot
was made up mostly
of hydrogen, helium
Hydrogen and helium are very light gases. Their weight was not strong enough to make them stay near the earth. So they got
outer space. That
hydrogen and helium
in the earth's
Even the ammonia got
As the earth began
inside of the earth
outside began to harden.
came out through
holes in the hard
The atmosphere of the young earth was made up mostly of hydrogen, helium and ammonia.
Hot gases from inside the earth became the new atmosphere. It had mostly carbon dioxide, water vapor and nitrogen
These holes were
openings of volcanoes.
gases were like the gases that
now. The gases became the
new atmosphere was mostly carbon dioxide, water vapor and nitrogen. As the earth got
fell as rain.
ried carbon dioxide
water vapor cooled,
the oceans with water.
most of the water vapor and carbon dioxide out of the air.
the air was mostly nitrogen.
of the carbon dioxide, water,
in the sea
and other chemicals
were tiny green
Some of the first They could make
own food. They made their own food by photosynthesis. The oxygen made by photosynthesis went into the atmosphere. In this way the atmosphere became mostly oxygen and nitrogen. That is the way the atmosphere is their
took most of the carbon
dioxide and water vapor out of the air.
So the atmosphere was mostly
Then green plants grew. They put oxygen into the atmosphere. So the atmosphere became mostly nitrogen and oxygen.
WORD Air Pressure (PRESH-er)
every square inch of something.
— The earth's blanket of air. Bacteria (back-TEER-ee-a) — Tiny little plants. They are so small
Atmosphere (AT-muss-f eer)
you need a microscope
to see them.
— A tool for measuring air pressure.
Barometer ( bar-OM-eh-ter )
— The tiniest part of a plant or animal. Circulate (SIR-kyou-late) — To move in a big circle. Ionosphere (eye-ON-a-sf eer) — The upper layer of Cell
goes up about 7,000 miles and has
Legumes (leg-YOUMS) the air and put
— Plants which help
take nitrogen from
into the soil for other plants to use. Peas,
beans, peanuts and clover are legumes.
Meteor (MEE-te-or) around
piece of metal or rock that travels
into the earth's atmos-
energy of sunlight to make their Pollen (POLL-en) It
helps the flower
green plants use the
very fine powder that grows on flowers.
— The middle
layer of the earth's
Troposphere (TROP-a-sf eer)
of the earth's
atmosphere. All weather takes place in the troposphere.