DK Children’s Encyclopedia ( PDFDrive )

Precious metals SEE ALSO
▸▸ Aircraft p.13
Precious metals are rare and worth a lot of money. They are ▸▸ Elements p.90
found in the ground as pure metal or combined with other ▸▸ Metals p.162
elements in rocks. Silver and gold are the best known and ▸▸ Money p.169
have been treasured for thousands of years. Other precious ▸▸ Gold pp.200–201
metals include platinum and beryllium. ▸▸ Rocks and

minerals p.214

Gold The highest quality Silver
flutes are made of
Pure gold is a very soft metal. solid silver. This precious metal,
To make it harder—so that we along with gold and
can make useful objects out of mercury, has been
it—we combine gold with small used by humans since
amounts of other metals. prehistoric times.

A mobile phone Gold This ancient Silver is used
contains just a tiny earrings Egyptian burial in many of today’s
amount of gold—about mask is covered batteries.
0.001 oz (0.025 g). in gold foil.

Cutlery

DVD

The most
valuable coins
have always been
made of gold.

Pieces of jewelry Mirror
are often made
from platinum. Platinum
bar

Catalytic converters Platinum is used in Watch Beryllium
in cars contain pacemakers. These
platinum. It makes devices can keep a Beryllium is a steel-gray precious metal.
exhaust fumes person’s heart beating. It is a vital component of computers,
less poisonous. cars, aircraft, phones,
199 medical equipment,
Platinum and many other
hi-tech gadgets.
Just a few hundred tons of
platinum are produced each year. Fighter aircraft
Because it is so rare, it is used in
very small amounts.

The story of... Meteor shower This gold mask
is thought to
Gold When Earth first formed, show the
gold and other metals sank deep Greek hero
Gold is a precious metal that has been into the core. Other gold, found Agamemnon.
used to make jewelry and decorations near the surface of our planet,
since ancient times. It is rare and very arrived later from space. Asteroids
expensive. But that’s just the start rained down in a powerful storm,
of its story. Gold has a glittering
history and is still popular bringing gold with them.
all over the world.
Gold nugget
Digging for gold

In the past, a single nugget could
change the life of a gold-digger.
When gold was found in the US
in the 1800s, it started a “gold
rush.” Thousands of people,
known as prospectors, traveled
to the US hoping to find

gold and become rich.

Large gold mines 25
have created
huge holes deep percent of all the
into the ground. world’s gold is stored

in a New York City
vault.

Gold mine Centuries
of sparkle
Pieces of gold found loose on
the Earth’s surface can be picked Gold was the first metal
to be discovered and used
up by hand. Bigger quantities by humans. It is beautiful and
deep underground must be dug shiny, as well as soft and bendy.
This makes it ideal for shaping
out in a process called mining.
Modern mines use heavy into jewelry, including
delicate rings, bracelets,
machines to dig chunks of rock and necklaces.
that contain traces of gold.

200

The world’s Golden money

oldest coins The first gold coins were made
by King Croesus in 564 bce. All coins
were made from used to be made of precious metals,
electrum—a including gold and silver. However,
modern coins are usually made of
mixture of gold
and silver. cheaper metals, such as copper,
nickel, and zinc.

Sacred manuscripts Gold leaf
were decorated
with gold leaf. For centuries, gold has been used
to decorate religious buildings,

works of art, and objects. As well
as using the solid metal, gold
can be thinned down into very
fine sheets called gold leaf.
Gold leaf is used to decorate
books and paintings.

A model of
the spacecraft
used in the
1969 moon
landing.

The mask was Golden craft The visors of
discovered by space helmets
archaeologists Space scientists use sheets of
in a burial tomb gold foil to cover parts of some are coated in a thin
in 1876. spacecraft and satellites they layer of gold to
send into space. The foil keep astronauts
protects them by reflecting cool and safe.
the sun’s harmful rays during

their journey.

201

Prehistoric life SEE ALSO
▸▸ Dinosaurs p.80
Earth has changed a lot over many millions of years. It has ▸▸ Early humans
not always been home to plants, animals, and people.
Many early living things no longer exist, so we only know p.82
about them from their remains. The distant past is known ▸▸ Earth p.83
as “prehistory.” ▸▸ Fossils p.111
▸▸ Habitats p.126
Ammonites were ▸▸ Oceans and seas
animals with shells
that lived in water. p.187

Forests
As Earth warmed up,
plants grew on land and

forests provided food
for different types
of animals.

Oceans
The first life was in
the oceans. There were
underwater plants
and early animals.

Dinosaurs were the
main land animal in
prehistoric forests.

Ice ages
In times when the
Earth cooled down,
most of it was covered
in ice. Animals had to
adapt to survive.

Woolly mammoths
had thick fur coats
to help them keep
warm in the ice ages.

Stone Age
After the last ice age, Earth

warmed up to how it is
today. A great variety
of plants and animals
live in many
different habitats,
such as deserts,
forests, and
polar regions.

Early humans
invented ways to
hunt and gather food,
and survive longer.

202

Radio SEE ALSO
▸▸ Atmosphere p.33
Radios pick up signals and turn them into sounds we can ▸▸ Books p.44
hear. They do this by using invisible waves that carry ▸▸ Communication
sound information. Thousands of different radio stations
play music, news, and drama to listeners all over the world. p.69
▸▸ Hearing p.127
▸▸ Navigation p.182
▸▸ Television p.251

How radio works 2. Radio waves 3. Radio antenna
Invisible radio waves carry An antenna is a thin
Radio towers turn sounds into sounds from radio towers to metal rod that picks
radio waves. Radios pick up radios in the home. up radio waves.
these waves and turn them
back into sounds that
you can hear.

1. Radio tower
Radio towers have
antennas on the top of
them. These antennas
send out radio waves.

Radio waves travel

at the speed of
light—about

186,000 miles
(300,000 km)

a second!

4. Speaker Remote Controller
The radio’s control Remote control toy car
speaker plays the
waves as sounds. Wireless gadgets use
radio waves to contact
Radio towers each other. For example,
are tall to make a remote control can
sure that radio tell a toy car how to
waves can travel move around.
over buildings.
203
Digital radio

Instead of radio waves,
digital radio uses digital
signals that don’t get broken
up like radio waves do. This
means they sound better.

Rain forests SEE ALSO
▸▸ Birds p.39
Rain forests are forests with tall trees and lots of rain. ▸▸ Forests p.109
Tropical rain forests are hot places. They are home to ▸▸ Habitats p.126
nearly half of all animals and plants in the world. The ▸▸ Materials p.157
trees are so thick with leaves that very little sunlight ▸▸ Plants p.194
reaches the forest floor. ▸▸ Trees p.261
▸▸ Weather p.271
Amazon rain forest This harpy eagle
hunts for animals Emergent layer
The world’s largest rain forest is in the treetops. Only the tallest trees reach
the Amazon in South America. This this top layer of the rain forest.
rain forest surrounds the Amazon
River. Its trees and plants provide Howler monkeys
food and shelter for many animals. get together and
howl each morning.
This large blue Morpho The leaves of Toco toucans use
butterfly is brown on the bromeliads catch their long beaks to
other side of its wings, so water that small reach fruit to eat.
it can hide when resting. animals come
to drink.
Canopy layer
This is a thick layer of leaves
and branches. Most rain forest
animals live here.

Emerald tree boas
squeeze animals to death
before eating them whole.

Jaguars hunt other A praying mantis Some trees have
animals and climb waits for other giant buttress roots
trees to rest and eat. insects to come that help them soak
close, then grabs up water quickly.
Understory and eats them.
Shrubs and new trees The bright red leaves
grow in this hot, dark This many-legged surrounding the flowers
layer of the rain forest. centipede can kill of the heliconia stricta
bigger frogs, spiders, look like lobster claws.
Forest floor and snakes.
This dark, damp layer is This long-tongued
covered in dead leaves that giant anteater can eat
have fallen from above. 30,000 ants a day.

Capybaras are
good swimmers
and eat water
plants.

204

Recycling SEE ALSO
▸▸ Changing world
Recycling means reusing garbage or making it into new
things rather than burning it or burying it in the ground. pp.50–51
Everything from paper, glass, metal, and plastic to phones
and computers can be recycled. The more we recycle our ▸▸ Climate change
waste, the less we damage our planet. p.60

▸▸ Computers p.71

▸▸ Metals p.162

▸▸ Plastic p.195

▸▸ Pollution p.198

Paper and Food waste
cardboard Leftover food can
Old paper and cardboard be fed to animals, such
can be mashed up in as pigs or chickens, or
water, then rolled used to make compost
flat and dried to to help plants grow.
make new paper

products.

Plastic Metal
Most of the plastic Cans can be melted
we throw away can be down. They are either
chopped up, melted remade into more cans
down, and re-formed or used to make other

into new items. metal goods.

Glass Electronics
Bottles and jars Devices such as
made of glass can be phones and laptops
cleaned and used again can be repaired or have
or melted down to make their valuable metal
new glass objects. parts taken out

to be reused.

205

The story of...

Festivals

Festivals are celebrated across the world.
Some festivals, like Eid or Christmas, mark
important religious events. Others, like the
Chinese New Year, mark the passing of time.
Festivals are often a time of joy. People might
put up lights, dance, or give each other presents.

Christmas Christmas trees
are often finished
Every year at Christmas, with a star or angel
Christians celebrate the birth of on top.
Jesus Christ. Some go to church and
sing carols or special songs about Presents are
the event. Most people give presents placed below
to each other and have a large a decorated
meal with special food. Many Christmas tree.
people spend Christmas
with friends and family.

The “Elegant Skull”
is a symbol of the Day
of the Dead.

Day of the Dead

In Mexico, people celebrate
the Day of the Dead for three
days at the start of November.
This ancient festival is held to
remember friends and family who
have died. People build shrines
to the dead and bring gifts

of food and drink to
their graves.

Elegant Skull A Chinese Dragon
statue puppet that is
used in festival
celebrations.

206

Chinese New Year Muslims say the Eid
special Eid prayer
Celebrations for the outside a mosque. Muslims celebrate the Eid
Chinese New Year last for al-Fitr holiday at the end of
15 days. Families clean their Ramadan. During Ramadan, they
houses to sweep away bad luck, fast, or go without food during
decorate their windows and the day. At Eid, Muslims give
doors with red paper shapes, and
enjoy a big feast together. Some money to charity, pray
people throw firecrackers to together, visit friends
make a big noise, and dragons and family, and enjoy
dance in the streets.
a feast.
At New Year, Passover
Passover is one of
Chinese parents Jewish people celebrate the most important
give their children Passover to remember the Jewish festivals, and
escape of the Jews from slavery
money in red in Egypt. The festival lasts for seven is more than
packets. or eight days and is marked with the
special seder, or meal, which includes 3,000
matzo—a flat, or unleavened, years old.
bread that hasn’t been
given time to rise.

Dancers control the
colorful dragons
using long sticks.

The special food Fireworks light up
on the plate the sky at Diwali,
tells the story the festival
of the Jews’ escape of lights.
from slavery.

Diwali

The Hindu festival of
Diwali takes place every fall in
the north of the world and every
spring in the south. It celebrates
the victory of light over darkness
and good over evil. People light

up their homes and public
places and set off
fireworks.

207

Religion SEE ALSO
▸▸ Ancient India
A religion is a set of beliefs. Religions often try to explain
the world, such as how it came to exist. Religion is an p.19
important part of many people’s lives. They agree with
their religion’s teachings, and try to behave by its rules, for ▸▸ Dance p.76
example, about how to treat other people. Many religions
have central figures that are prayed to, called gods. ▸▸ Festivals
pp.206–207

▸▸ Turkish Empire
p.262

▸▸ World p.275

Buddhism Special candlestick Judaism
Buddhists follow the called a Menorah Judaism dates back
teaching of Buddha, who 4,000 years. Jews
lived in India in the fifth believe in one God who
created the world.
century bce. They
meditate, which involves They trace their
history back to the
thinking deeply. They Hebrew people of
believe that they will be what is now Israel.

reborn after death.

Buddha statue

Sikhism Gurdwara World religions Islam
Sikhs follow the The followers of Islam
teachings of Guru Granth More than 75 percent of Mosque are called Muslims. They
Sahib. They believe that believers follow Buddhism, believe that the Quran,
all people are equally Islam, Christianity, or Hinduism. their holy book, is God’s
important. Sikhs pray in Judaism and Sikhism also have word told through his
grand buildings worldwide followings. There messenger Muhammad,
called Gurdwaras. are many other religions, but
fewer people follow them. whose teachings
they follow.

The H indu god Shiva

Hinduism Jesus on Christianity
Hinduism began in India the cross Christians have one God.
more than 2,500 years They believe that their
208 God’s son Jesus lived on
ago. Hindus pray to Earth 2,000 years ago.
many gods and believe He died nailed to a cross
so that Christians could
that life is a circle of
birth, death, and rebirth. have life after death.

Renaissance SEE ALSO
▸▸ Aircraft p.13
Italy experienced great change in science and art
between 1400 and 1600. This movement then spread ▸▸ Ancient Rome
across Europe. It was called the “Renaissance,” which p.20
means “rebirth,” because it looked at ideas that originally
came from ancient Rome and Greece. ▸▸ Art p.28

▸▸ Inventions
pp.136–137

▸▸ Religion p.208

▸▸ Writing p.280

Buildings The great dome Science
of the cathedral
Renaissance builders in Florence was Scientists began to
copied ancient styles built in 1436. carry out experiments for
to produce larger, more the first time. They made
elegant buildings. These important discoveries about This flying
buildings often had space, science, and medicine. machine was
columns and domes. designed by
Leonardo da
Vinci. It never
actually flew.

Art This painting, by Pietro The people at the front of
Perugino, shows Jesus the painting appear larger
Renaissance artists used a more realistic style giving the keys of than those farther away.
than previous artists. They tried to show light Heaven to St. Peter. This is called perspective.
and shade and came up with new types of
paint and materials. 209

Reptiles SEE ALSO
▸▸ Amphibians p.15
Reptiles are scaly-skinned, cold-blooded animals. Most ▸▸ Antarctica p.24
reptiles lay soft, leathery eggs. A baby reptile grows inside ▸▸ Deserts p.78
the egg and then, when it’s ready, breaks its way out. ▸▸ Dinosaurs p.80
There are four main groups of reptile. ▸▸ Eggs p.86
▸▸ Evolution p.95
▸▸ Sun p.247

All reptiles have Some lizards
scaly skin. can move their
eyes to look in
two directions
at once.

Lizards

These reptiles have many skills.
This chameleon can change the
color of its skin. Other reptiles can
run up walls, or break off their tails
to escape danger.

Tortoises have
hard shells.

Tortoises Reptiles live on Crocodiles Crocodiles and
and turtles and alligators alligators have
every continent strong jaws.
Turtles live in water These giant reptiles have
and tortoises live on except Antarctica. existed since before dinosaurs. Basking
the land. Their shells They hide under water, then
protect them, but are spring up to catch their prey Reptiles are cold-blooded
heavy, so they move and drag it under. animals. They get the heat
very slowly out their bodies need from the
of the water. world around them, lying in
the sunshine to warm up.
They hide in the shade to keep
themselves from overheating.

Snakes

All snakes swallow their prey
whole. They smell using their
tongues. Some snakes have
poisonous bites, but most
are not dangerous to people.

210

Rivers SEE ALSO
▸▸ Farming p.98
Starting as tiny streams, rivers flow from mountaintops
down to the ocean. They provide a home to lots of wildlife. ▸▸ Water
People transport things along rivers, grow crops next pp.120–121
to them, and even use rivers for spare-time activities,
such as sailing and fishing. ▸▸ Glaciers p.122

▸▸ Lakes p.143

▸▸ Water cycle
p.270

▸▸ Weather p.271

River system Small streams Rain and snow fall
flow downhill and to make streams.
Water flows down the mountains, come together
making small streams. These streams to make rivers.
join up to form rivers, which wind along
and then eventually flow into the ocean.

Some rivers
start from lakes.

Dams use water Farms use
movement to river water
create electricity. to grow crops.

On flatter ground,
rivers follow wide,
steady bends
called meanders.

Rivers become River habitats are
wider and deeper home to many
downstream. kinds of wildlife.

Rivers provide Fishing
nearby towns and
cities with water. The “mouth” of Water
a river is where sports
Mighty river it joins the ocean.
The further rivers get from
the mountains, the deeper Rivers are used to
and more slow-moving they transport people
become. Eventually they spill and goods to the
out into a lake or the ocean. ocean and beyond.

211

Robots SEE ALSO
▸▸ Computers p.71
Robots are computer-controlled machines that do jobs ▸▸ Factories p.97
for us. They can be used in many ways, such as helping ▸▸ Machines p.150
doctors, building things, and doing jobs that would be ▸▸ Medicine p.160
too dangerous for people to do. ▸▸ Space travel

p.237

Types of robot Eye sensors Humanoid robot
allow the Some robots are designed
Robots are carefully designed to robot to “see.” to look a bit like people. This
do their jobs. Each type of robot robot is called NAO. It can
has its own unique look. dance and speak.

Each “finger” has a Robots can see
different function. and feel, but not
like humans. Their

sensors use
code to interpret

feedback.

Medical robot Hand sensors
Robots are capable of performing very allow NAO to
delicate movements. They can help “feel” objects.
doctors operate on their patients.
Factory robot
Robots in space Robots are strong, and
are good at doing the
NASA uses robots to perform same thing over and
dangerous tasks in outer space. over again. This makes
This robot mends things on the them useful in factories.
International Space Station.
Motors allow the
Foot sensors are used for robot to move up
walking, climbing stairs, and down.
and detecting obstacles.

212

Rock cycle SEE ALSO
▸▸ Earth’s surface
Rock may be very hard, but it does not last forever.
It is constantly being worn away by wind, water, p.84
and ice. At the same time, new rock is being made
at the bottom of the sea and by volcanoes. This is ▸▸ Erosion p.93
called the rock cycle.
▸▸ Inside Earth p.135

▸▸ Mountains p.172

▸▸ Rocks and
minerals p.214

▸▸ Volcanoes p.268

Recycled rocks Cooling Heated and
Magma erupts squashed
Tiny pieces of volcanic rock are from volcanoes.
washed into the sea and settle on It cools and hardens Any rock can be changed
the sea bed. They become buried by to form a type of into metamorphic rock by
new layers of rock particles that get rock called volcanic, the heat and the weight
squashed together to form new rock. or igneous, rock. of the rock above it. Slate,
As this new rock is buried deeper, which is used to make roof
it gets hotter and melts to form tiles, is a common
magma. Magma rises and cools metamorphic rock.
to form new volcanic rock.

Breaking down
Volcanic rock is broken
up by wind, rain, and ice.
Tiny particles of the
broken rock are washed
into the ocean by rain.

Settling
Pieces of volcanic rock
settle on the sea bed.
They are buried and
squashed to make
a type of rock called
sedimentary rock.

Changing Melting Lots of layers
If sedimentary rock Deep in the Earth, where
is buried deep enough, it is extremely hot, rock Most rocks being formed
it is changed by heat melts to form magma. In today are sedimentary
and the weight of the some places, magma rises rocks. They are made from
rock above it into to the Earth’s surface, tiny pieces of older rocks
metamorphic rock. forming volcanoes. that build up on the sea bed
in layers. Sandstone is a
common sedimentary rock.

213

Rocks and minerals SEE ALSO
▸▸ Earth’s surface
The Earth’s surface is made up of hard natural
objects called rocks. Rocks are made up of a mixture p.84
of substances called minerals. There are many
different kinds of rocks and minerals. ▸▸ Elements p.90

▸▸ Gemstones
p.118

▸▸ Metals p.162

▸▸ Rock cycle p.213

▸▸ Volcanoes p.268

Rocks Metamorphic rock
Under great heat and pressure,
Types of rock have different metamorphic rock is formed
names depending on how they deep inside the Earth.
were formed. The three types
are called sedimentary, igneous,
and metamorphic.

Sedimentary rock
When particles of minerals settle
and are squashed together, they
slowly become sedimentary rock.

Minerals There are Igneous rock
This type of rock is formed
A mineral is a naturally occurring solid. It is made nearly 4,000 when melted rock cools
from chemical elements—simple substances down and becomes solid.
that cannot be broken down further. Minerals different types
grow together to form rocks. Glowing rocks
of minerals
Some rocks look plain in daylight, but
on Earth. their minerals change color under
special “ultraviolet” light. The glowing
minerals in this rock are called calcite
and willemite.

Serpentine Amethyst Garnet Opal
214

Satellites SEE ALSO
▸▸ Astronomy p.32
Satellites are objects that go around, or orbit, something
bigger. There are more than 2,000 artificial satellites ▸▸ Clouds p.64
orbiting the Earth. They are used for a variety of different
jobs. Some track the weather while others let us ▸▸ Communication
communicate with each other. p.69

GPS satellite ▸▸ Internet p.138

The global positioning system (GPS) ▸▸ Solar system
gives us our exact position on the p.23s
Earth. The system uses more than
20 satellites, working together ▸▸ Universe p.263
to pinpoint your location.

Local satellites This satellite always
stays over this area.
Some types of satellite
stay over the same area
as they orbit the Earth.
These are called
geostationary satellites.
To cover the whole
Earth, many satellites
are needed.

Photos of When this
the Earth flap is open,
are sent to the telescope
weather takes photos.
stations.
Solar panels
collect the sun’s
rays to power
the satellite.

Communication satellite Weather satellite Hubble space telescope

These satellites pick up signals and These satellites take pictures of the This satellite points away from the
send them to other places in the world. clouds and measure land and sea Earth and takes detailed images of the
They are used for phone calls and live temperatures. This information helps universe. It lets us see farther into
video communications. us to study and forecast the weather. space than we could from the Earth.

215

Saturn SEE ALSO
▸▸ Astronomy p.32
Saturn is the second largest planet in the solar system
after Jupiter and the sixth farthest planet from the sun. ▸▸ Atmosphere p.33
It is a “gas giant,” mainly made of hydrogen and helium,
and is best known for its rings. ▸▸ Jupiter p.141

▸▸ Moon p.171

▸▸ Exploration
pp.180–181

▸▸ Solar system
p.233

Ringed planet Icy rings
Saturn's rings are made
Saturn is surrounded by huge rings of chunks of ice, rocks,
that stretch over a vast distance. and dust.
However, they are only a few
hundred feet thick.

Saturn

Gaps between rings
The gaps between the
rings are areas with
less ice and dust.

Moons of Saturn The unmanned
spacecraft Cassini
Like Jupiter, Saturn has more
than 60 moons. Titan, the
largest moon, has lakes of
liquid methane and a thick
atmosphere. Enceladus,
Saturn's sixth largest moon,
shoots out water from its
south pole.

Titan Huygens probe Cassini-Huygens

The Cassini spacecraft explored
Saturn between 2004 and 2017.
A probe called Huygens, carried by
Cassini, landed on the surface of
Saturn's moon Titan in 2005.

216

Science SEE ALSO
▸▸ Astronomy p.32
Science is the search for truth and knowledge. It’s about ▸▸ Biology p.38
understanding the world and learning how and why things ▸▸ Chemistry p.58
work the way they do. Science includes doing experiments ▸▸ Medicine p.160
to test predictions and collect evidence. We divide science ▸▸ Physics p.192
into three main areas: chemistry, biology, and physics. ▸▸ The sciences

pp.218–219

Biology
The study of
living things and
their surroundings is
called biology. It includes
the human body,
plants, and animals.

Physics Chemistry
Physics studies Looking at what
light, sound, forces, things are made of is
waves, magnets, known as chemistry. This
electricity, energy, includes the tiny building
and the planets. blocks of all materials,

Scientists called atoms.

Scientists are people who investigate the world Science isn’t
to answer questions and find solutions to just facts in a book—
problems. They do experiments to see if ideas
are right or wrong, and they share information. it’s a whole way

Inventions Copy of Thomas Edison of thinking and
Edison’s invented the discovering.
Studying science helps us to light bulb electric light bulb
create new things. For example, in 1879, while
if we understand movement, we studying electricity.
can design better cars. If we
understand the body, we can
invent medicines to help
fight off sickness.

217

The story of...

The sciences

For thousands of years, people have been
observing the world around them and coming
up with ideas to explain why things behave
the way they do. Science is about answering
questions with ideas, evidence, and experience.

Child making Some of the earliest Notches around
a wave in a doctors were ancient the edge were
bottle lined up with
5,000Egyptian women, objects in the sky.
years ago.
Curing diseases
1. Bacteria
growing In 1928, Scottish scientist
Alexander Fleming noticed how

a mold called penicillin killed
bacteria. This discovery led to

a type of medicine called
antibiotics. They have been
killing germs in the human

body ever since.

Experiments 3. Bacteria
dies
In ancient Greece, a man
called Aristotle said that people 2. Penicillin
should look at nature and carry introduced
out experiments to find answers
to their questions. Scientist do Renaissance
experiments to test their ideas
Starting in the 15th
and to make new discoveries. century, the Renaissance
was an explosion of ideas that
Compasses helped transformed science and art in
explorers to travel Europe. Leading experiments,
the world and gathering evidence, and sharing
discover new ideas. ideas became popular—this

led to new inventions
and discoveries.

Early compass
218

Accidental inventions

Many great scientific discoveries have
been made by accident. For example,

German scientist Wilhelm Conrad
Röntgen accidentally discovered X-rays

in 1885. He was sending electricity
through tubes of gas when he noticed

that he could see what was inside
a nearby box. He then used this
finding to take pictures of the
bones inside his wife.

Nebra Sky Disk The night sky Early X-ray
X-rays pass
Renaissance One of the earliest sciences through skin and
artist and scientist was studying the movements flesh but bounce
of the moon, planets, and stars. back off bones.
Leonardo da This is now called astronomy. Moon
Vinci sketched calendars were first made about Scientific drawings
pictures of humans 10,000 years ago. Around 4,000
and animals he years ago, the Nebra Sky Disk Many scientists create beautiful,
was used to track seasons and precise drawings to record their findings.
had cut up. Mary Anning was a famous British fossil
the sun’s position. hunter who lived in the 1800s. Mary found
her first fossils as a child and made drawings
of them. Her discoveries helped scientists to
understand how life existed in the oceans

millions of years ago.

The Plesiosaurus’s Plesiosaurus drawn by Mary Anning in 1824
paddles have bones
that are also present
in legs and feet.

219

Seashore SEE ALSO
▸▸ Birds p.39
The area where land meets the sea or ocean is called the ▸▸ Habitats p.126
seashore. It may be sand, mud, or rock. Animals and plants ▸▸ Invertebrates p.139
that live here have to be able to survive crashing waves ▸▸ North America
and the water level changing twice a day.
p.184
Shore zones California gulls ▸▸ Oceans and seas
soar over the
The seashore has different zones, which are shores, searching p.187
divided by the distance they are from the ocean. for fish, insects, ▸▸ Tides p.254
Animals in the low tide zone are mostly in the and eggs to eat.
water all the time, while those in the high tide Brandt’s cormorants
zone have to survive in air when the tide is out. rest together on rocks
near the water.

California sea Brown pelicans Spray zone
lions rest on land have a pouch in This area is not underwater,
in large numbers. their beak to but is splashed by wave
store food. after wave.

Acorn barnacles
close up during
low tide.

High tide zone Sea otters have Kelp are tall
This area is only thick fur to keep sea plants.
covered in water when them warm.
the tide comes in.
Hermit crabs live in
California blue seashells to keep
mussels clean themselves safe
the sea water. from other animals.

Sculpin fish eat
small fish and
shellfish.

Purple sea urchins Green sea
move around using anemones are
suckers on their animals with long,
tube-shaped feet. armlike tentacles.

Low tide zone Purple ochre sea US Pacific coast
This area is stars can survive for This seashore is home to
covered in water eight hours without thousands of different animals
most of the time. being in water. and sea plants. The coastline
has cool temperatures.

220

Seasons SEE ALSO
▸▸ Climate change
In many parts of the world, the year has four seasons.
These seasons are winter, spring, summer, and autumn. p.60
The lives of plants and animals, the weather, and the hours
of daylight all change from one season to the next. In some ▸▸ Day and night p.77
hot parts of the world, there are just two seasons.
▸▸ Hibernation p.129

▸▸ Solar system
p.233

▸▸ Trees p.261

▸▸ Weather p.271

Changing seasons

In the cold winter, plants
stop growing. In spring,
they begin to grow again
and baby animals are born.
Summer sees the hottest
weather, and then
in autumn leaves
change color and
fall off the trees.

Winter Spring Summer Autumn

What causes December
the seasons?
March
The Earth travels around
the sun. It is tilted so some This part of the Earth
parts of it get stronger tilts away from the
sunlight than other parts. sun and has its winter.
As it moves, the amount
of sunlight reaching Sun
different parts of the
Earth changes. This This part of the Earth September Monsoons
gives us our seasons. tilts toward the sun
and has its summer. Tropical parts of the Earth are warm
Axis all year round. There are often just
June two seasons—a dry season and a
rainy season, called a monsoon.

221

Shapes SEE ALSO
▸▸ Constellations
Shapes are areas with different outlines. In math, there
are two types of shape. Two-dimensional shapes have p.73
length and width, while three-dimensional shapes have ▸▸ Flags p.102
length, width, and height. Shapes can be made of straight ▸▸ Maps p.155
or curved lines, or a mixture such as in a semicircle. ▸▸ Numbers p.185
▸▸ Symmetry p.248
▸▸ Volume p.269

What makes a shape? Edge Line
The side of a shape A straight line is the
A shape is named depending on the number is called an edge. shortest distance
of sides and angles it has. Regular shapes between two points.
have sides that are all the same length.

Angle Point
An angle is the A point is a place
place where two on a shape. It is
lines meet. shown with a dot.

Triangles have three sides and Circles have one long, round side. Squares have four equal sides and
three inside angles adding up to 180°. four right angles.

Angles Right angle Polygons
An angle of
Angles are measured in degrees (º) out exactly 90º. “Polygon” is the name
of 360. Angles have different names 90° for any flat, two-
depending on how big they are. dimensional shape.
240°
Acute angle Reflex angle Pentagons have five equal sides
An angle less An angle between and five inside angles.
than a right 180º and 360º.
angle (90º).
45° 222

Obtuse angle
An angle
between 90º
and 180º.

135°

Sharks SEE ALSO
▸▸ Conservation
Sharks are a type of fish. Almost all of them eat meat. They
are found in every ocean and some rivers. There are more p.72
than 400 types of sharks. Most are active during the day,
but some hunt at night. ▸▸ Fish p.101

▸▸ Food chains p.107

▸▸ Oceans and seas
p.187

▸▸ Prehistoric life
p.202

Sharks have good Great white shark
eyesight even when
there isn’t much light. This shark eats other
animals. It mainly hunts
and feeds on fish, but Sharks have
also eats turtles, been around for
dolphins, and seals.
more than
The front fins can
be used to slow 400 million
down the shark. years!

The pointed The tail moves from
nose is used to side to side to power
sniff for food. the shark forward.

The sharp, pointed
teeth are perfect
for ripping food.

Each whale Whale shark The back fins stop
shark has its the shark from
own pattern This is the largest fish rolling over.
of spots. in the world. It can travel
Sharks under threat
Hammerhead shark thousands of miles
every year. The number of sharks is getting smaller
Hammerhead sharks use their because they are hunted for their fins,
wide heads to pin down teeth, and fish oil. Scientists try to learn
stingrays on the about sharks, so that they can help them.
ocean floor.

The eyes are a long way
apart, letting the shark
see far to spot its prey.

223

Ships SEE ALSO
▸▸ Oceans and seas
Sea transportation comes in all shapes and sizes,
from tiny sailing boats to large cruise liners and p.187
gigantic container ships. They can be used for sports, ▸▸ Sports p.239
to take people on vacation, and to move things from ▸▸ Trade p.257
one country to another. ▸▸ Transportation

The captain Cranes load pp.258–259
steers the containers on ▸▸ Work p.274
ship from and off the ship.
the bridge. Container ship

Containers are Some of the largest boats
large metal boxes. on the oceans are container
Each container can ships. These giants of the
hold around 6,000 seas can transport more
shoe boxes. than 15,000 containers full
of items such as clothes,
toys, and televisions to
different countries.

Sailing boat The hold carries more Submersible
containers. Some store
This tiny boat doesn’t have an hundreds of cars. This craft doesn’t travel on the
engine. It is powered by wind, ocean, but underneath it. It can
which is caught in the sail take scientists deep underwater
to push the boat to look at sea life and study
across the water. the ocean floor.

Cruise ship

A cruise ship is a floating hotel that takes
tourists to different countries. On board are
swimming pools, theaters, and water slides.

224

Sickness SEE ALSO
▸▸ Body cells p.41

Tiny living things called germs can make us sick if they get ▸▸ Human body
inside our bodies. Germs are all around us—in the air, in our p.130
food, and on the things we touch. Our bodies have many
different ways to stop them from harming us. ▸▸ Medicine p.160

▸▸ Microscopic life
p.165

▸▸ Skin p.229

Body defenses ▸▸ Taste p.249

The body has a defense system to Tears
stop germs from getting in. It also Watery tears wash dirt
kills germs that find a way in. out of our eyes. They also
kill germs.

Mucus (nose and throat) Ear wax
Mucus traps germs we Ear wax flows out of our
breathe in. Hairs move the ears, pushing germs and
mucus to the mouth, where dirt out with it.
the germs and mucus get
swallowed. Saliva
Also known as spit, saliva
Senses protects your mouth by
Sight, smell, and taste killing germs.
help us avoid eating
food that has gone bad.

Skin White blood cells Avoiding
Skin stops germs Tiny white blood sickness
from entering the cells in your blood kill
body by forming a germs in the body. Covering our nose and
protective barrier. mouth when we sneeze
or cough stops germs from
1,000 Acid spreading through the air.
germs can fit on Chemicals in
the head of a pin. the stomach
They’re tiny! kill most germs
we swallow.

Good bacteria
Helpful bacteria in
our intestines stops
germs from growing.

225

Sight SEE ALSO
▸▸ Body cells p.41
Sight is seeing the shapes, sizes, and colors of ▸▸ Brain p.45
nearby and faraway objects within our surroundings. ▸▸ Cells p.56
When we see, colored light is bouncing off objects ▸▸ Hearing p.127
and into our eyes. ▸▸ Light p.147
▸▸ Muscles p.173
How we see Glasses ▸▸ Smell p.232

Tiny sensors at the back of the eye receive If an eye lens doesn’t focus Some people use glasses
light and send signals to the brain to make the light in the right place, to help them read
an image from the light we see. the image is blurred.
Glasses contain lenses that Retina
Eyelid change where the light In the retina at the
focuses in the eye, so the back of the eye, tiny
Eyelashes image becomes clear. sensors called “cells”
collect information
Tear duct about color, light,
Liquid is made and shape.
here. When we
blink, our eyelids
wipe our eyeballs
with the liquid, to
clean out dust.

Iris Pupil
The iris is the
colored part of Outer eye
the eye. It changes
the size of the Iris
round hole in the
middle—the pupil. Cornea
The cornea bends
the light entering
the eye.

Just one-sixth Pupil Eyeball
The pupil gets bigger
of the eyeball can to let in more light Optic nerve
when it’s dark and gets The optic nerve sends
be seen from smaller to let in less the light information
outside. light when it’s bright. collected in the eye
to the brain.
Lens
The lens focuses the
light at the back of
the eye. It makes the
picture we see clear.

Muscles
226

Sinking and floating SEE ALSO
▸▸ Forces p.108
When we place objects in water they can float on the ▸▸ Gases p.117
surface or sink below it. The heavier and more packed ▸▸ Gravity p.125
together a material is, the more likely it is to sink. Materials ▸▸ Materials p.157
like stone and metal usually sink, while wood and plastics ▸▸ Metals p.162
usually float. ▸▸ Ships p.224

Floating The weight Salt water has
of the duck
If the downward force of an pushes down. more buoyancy
object’s weight is less than
the force of the water The duck is full of than fresh water, so
pushing up on it, it will float. air, making it light
The more air an object and buoyant. we can float more
contains, the more likely
it is to float. easily in the ocean
than in a lake.

Buoyancy Buoyancy The weight
As the duck pushes some pushes the of the coin
of the water out of the duck upward. is pushing
way, the water pushes it down.
back on the duck. The
effect of the upward The coin sinks
push of the water is a because its weight
force called buoyancy. is greater than
its buoyancy.
Massive ships
Sinking
It seems amazing that huge metal ships float while
small metal coins sink. Ships float because they are An object sinks when
full of air and because they have a large surface area. the force of its weight
The force of buoyancy pushing upward is spread out pushing downward is
and is greater than the ship’s overall weight. greater than the force
of buoyancy pushing
The buoyancy of the back up on it.
coin pushes it up.

227

Skeleton SEE ALSO
▸▸ Brain p.45
All the bones in the human body fit together in the ▸▸ Heart p.128
skeleton. They make up the shape of the human body. ▸▸ Human body
The skeleton forms a protective cage around the soft,
inner organs like the lungs and the heart. p.130
▸▸ Lungs p.149
▸▸ Muscles p.173

Our bones Skull The hinge
The skull protects the joint lets the
The skeleton is made up delicate brain inside. arm move up
of 206 bones. The
bones are moved Ribcage Ball and and down.
by muscles. socket joint
Ball and socket Hinge joint
Saddle joint joints in the
A saddle joint shoulder and hip Joints
allows the allow a swivel
thumb to move movement. Joints are the places where one bone
in a circle. joins another to allow movement. They
Humerus Ulna let our bones move side to side, up and
down, or in circles. Joints have fluid in
Pelvis Radius them to help make movement smooth.

Spine
The spine is made
up of 24 bones
called vertebrae.

Femur Inside bones

The ends of The outer layer of bones Spongy bone
bones are harder is made from a strong
at the joints. substance called calcium.
Inside is the bone marrow,
Bone is which supplies blood cells
to the rest of the body.
stronger
Tibia Types of bone Bone marrow
than wood, Compact bone
concrete, There are two kinds of
or steel. bone inside each bone. Blood
Hard, compact bone gives
the bone strength and
protection. Spongy bone is
full of little holes that make
the bone lighter.

228

Skin SEE ALSO
▸▸ Body cells p.41
Skin is the stretchy outer layer of the body. It keeps our ▸▸ Cells p.56
inside parts inside and germs outside. It protects us from ▸▸ Genes p.119
water and sunshine, and keeps us at the right temperature. ▸▸ Heart p.128
The outer layer continually flakes off as new skin is made. ▸▸ Human body

Inside the skin Pore p.130
Sweat comes ▸▸ Touch p.256
The skin is split into layers. out of the skin
Below the outer layer that from holes Hair
you can see, there is a lot called pores. Thin hairs
going on. grow out of
tiny pits called
hair follicles.

Epidermis
The epidermis is
the stretchy
outer layer of
skin we can see.

Sweat gland Dermis
Produces sweat to cool This is the area
the skin. More sweat is where sweat
made if the body is warm. and oil are made
to keep the skin
Skin color stretchy.

A chemical in our skin Fat
called melanin controls Fat helps
skin color. The more cushion knocks
melanin you have in and bumps. It
your skin, the darker it also stores
is. It is made in the energy for
epidermis, the top layer the body.
of skin.
Nerves Blood vessels Skin is the body’s
Nerves send signals These tubes carry
to the brain that tell blood around the biggest organ.
us the texture, body. They get
temperature, and wider to allow more It weighs
pressure of the blood to flow and to
things we touch. help the body to 8.8 lbs (4 kg)!
cool down.

229

Slavery SEE ALSO
▸▸ Africa p.12
Slaves are people who have had their rights taken away and
are treated like property. They may have been captured in ▸▸ Ancient Rome
war, owe more money than they can pay, or have parents p.20
who are slaves. Slavery has been used throughout history,
but today it is against the law in every country in the world. ▸▸ Law p.145

▸▸ North America
p.184

▸▸ Ships p.224

▸▸ Trade p.257

Slave labor

In the early 1800s, big farms called plantations
in the US used slave labor to pick cotton, cut
sugar cane, and perform other tasks. Slaves
worked long hours in very bad conditions.

Slavery today

Though slavery is now illegal, more than 20
million people are still kept as slaves, mostly
in Asia and Africa. Groups around the world
are working to solve this terrible problem.

The slave trade People were often
chained and packed
To keep American plantations supplied with tightly into slave ships.
workers, ships carried slaves from Africa to
America. Between 1450 and 1850, 12 million 230
people crossed the Atlantic Ocean.

Sleep SEE ALSO
▸▸ Brain p.45
Every night we sleep and our bodies rest, repair, and grow.
While we sleep our brains sort through the information ▸▸ Eating
gathered from our senses and some of it is deleted and pp.104–105
some is stored as memories. We need sleep to stay
fit and healthy. ▸▸ Hibernation
p.129
Sleep patterns
▸▸ Human body
Our sleep follows a pattern of p.130
different stages. You go through
each stage several times every night. ▸▸ Sickness p.225

8 p.m. 9 p.m. 10 p.m. 11 p.m. 12 a.m. 1 a.m. 2 a.m. 3 a.m. 4 a.m. 5 a.m. 6 a.m. 7 a.m.

Awake Dreaming Light sleep Shallow sleep Deep sleep
When we wake up, We dream when we’re Breathing slows We move around This is when our
we become alert close to waking. We down but the brain is more during shallow bodies are growing
and aware of our have three to seven still active and you sleep than during and repairing muscle,
surroundings. dreams a night. can wake up easily. deep sleep. tissue, and bones.

Why do we Memory Energy You will
sleep? Our brain deletes useless If we don’t get enough
information and stores sleep, we lack energy spend one-third
Sleep is important more important things and want sugary food.
because without it our while we sleep. of your life asleep.
brain and body slowly Growth This is around
stop working. Healing Our bodies grow and repair
Our bodies heal better and muscles and bones while 30 years
faster when we get plenty we are in a deep sleep.
of solid sleep. in total!

231

Smell SEE ALSO
▸▸ Brain p.45
Smell is one of our senses. When tiny parts of something ▸▸ Hearing p.127
float through the air and into our nose we identify a smell. ▸▸ Human body
The brain tells us what it smells like compared to other
things we’ve smelled before. p.130
▸▸ Muscles p.173
This area works out what ▸▸ Skeleton p.228
the smell is and sends ▸▸ Taste p.249
information to the brain.
The brain
How we smell These cells are tells us about
sensors that the smell.
Anything that smells releases tiny detect smells.
particles into the air. The particles mix Mucus
with a sticky fluid in our nose called This sticky fluid mixes
mucus. Sensors in the nose detect with the smell to help
the smell and send signals to the brain the sensor cells
to identify it. detect what it is.

Nose bone

We can detect The smell enters the nose. Nose cavity
more than This is the main airway for
breathing. It is connected
10,000 to the throat and mouth.

different smells
with our nose!

The tongue
has sensors
for tasting
food.

Taste and smell

Smell and taste are closely
linked. If you hold your
nose, you will find it
harder to figure out what
something tastes like.

232

Solar system SEE ALSO
▸▸ Asteroids p.30
The solar system is made up of our star, the sun, and ▸▸ Comets p.68
everything that travels around it. This includes eight ▸▸ Earth p.83
planets and their moons, asteroids, and comets. Scientists ▸▸ Jupiter p.141
think the solar system formed 4.6 billion years ago, ▸▸ Neptune p.183
from a massive spinning cloud of gas and dust. ▸▸ Sun p.247
▸▸ Universe p.263

8
6

3

4 5
Sun 1

72

Asteroid belt

Orbiting planets 1. Mercury 2. Venus 3. Earth 4. Mars
Mercury is the The surface of Venus Earth has lots of Mars has a red,
The sun is the center of the smallest planet. is super-hot. liquid water. dusty surface.
solar system. Everything in
the solar system travels 5. Jupiter 6. Saturn 7. Uranus 8. Neptune
around, or orbits, the sun. Jupiter is the Saturn is famous for Uranus is thought to Neptune has strong
largest planet. the rings around it. be the coldest planet. winds and giant storms.

Types of planet Kepler-16b

There are three types of planet in the solar system. There are many other solar systems
The rocky planets orbit close to the sun, and the gas in the universe. Scientists have even
and ice giants orbit farther away. found a planet, called Kepler-16b,
iter that orbits two suns.
e
Earth
Neptun

Jup

Rocky planets Ice giants Gas giants
Mercury, Venus, Earth, and Uranus and Neptune are Jupiter and Saturn
Mars are small and rocky with made of a mixture of gas are huge planets

solid surfaces. and icy materials. made of gas.

233

Solids SEE ALSO
▸▸ Changing states
Solids are materials that keep their shape. They don’t
flow like water—they stay where you put them. Solids p.57
are useful for making many things, from mobile phones ▸▸ Gases p.117
to houses. They are usually hard materials, but soft ▸▸ Liquids p.148
materials that keep their shape are solid, too. ▸▸ Materials p.157
▸▸ Metals p.162
What solids do Particles ▸▸ Plastic p.195
Solids are made from tiny
Solids can be hard, bendy, particles that are close Cutting solids
strong, squishy, see-through, or together. If enough heat
magnetic. The behaviors of a is added, they start to We can cut solids into
solid are called its properties. move past each other different shapes. Wood is
to become liquid. a solid material that comes
from trees. We cut and
shape it to make furniture.

Solids make a
pile, not a pool
or puddle.

Chopped
wood

Solid rocks become Shaping solids

liquid lava when Metal is a hard solid we can
find underground. We heat
heated to very metal to make it soft, then
bend and hammer it into the
high temperatures. shape we want. When it
cools, metal keeps its shape.
Solids keep
their shape. A hot metal horseshoe

Making
new solids

We can make new solid materials Liquid gelatin Gets chilled
by mixing other materials together. Solid gelatin
For example, gelatin is made by
adding hot water to gelatin powder
to make a liquid. The liquid then
cools into a solid.

234

Sound SEE ALSO
▸▸ Gases p.117
A sound is made when something vibrates. The bigger the
vibration, the louder the sound is. The faster something ▸▸ Hearing p.127
vibrates, the higher pitched the sound is. Sound vibrations
travel through things to get to our ears. ▸▸ Liquids p.148

Sound vibrates ▸▸ Musical
through the air. instruments
p.175

▸▸ Music pp.176–177

▸▸ Solids p.234

The voice box Our ears detect
vibrates when the vibration
we speak, and our brain
making sound. understands
them as sound.
How sounds travel
Big, slow
Sounds travel by vibrating the air until it reaches vibrations
our ears and we hear the sound. The vibrations
are called sound waves. Sound waves can travel Big drum
through solids, liquids, and gases. The big drum vibrates more
slowly, so it has a lower note
Volume Small, fast compared to the small drum.
vibrations It’s bigger, so it makes bigger
Volume changes depending vibrations that are louder.
on how big a vibration is. The
bigger the vibration, the
louder the sound. How high or
low a sound is depends on
how fast something vibrates.
The faster the vibration, the
higher the sound.

Things sound Small drum
We can hit a small
louder when drum harder to
they are close make it louder, but
it vibrates at the
to us. same speed so it
has a constant note.

235

South America SEE ALSO
▸▸ Amphibians p.15
The continent of South America is surrounded by ocean,
except at the top where it joins with North America. ▸▸ Explorers p.96
One-third of the continent is covered by a huge jungle,
called the Amazon rain forest. The Andes mountain range ▸▸ Incas p.132
stretches all the way down one side of South America.
▸▸ North America
p.184

▸▸ Rain forests
p.204

▸▸ World p.275

The giant tortoises Virgen de Pitcher
of the Galápagos la Paz plant
Islands can live
for more than
150 years.

Giant tortoise Anaconda Amazon Canoes
theater Capybara
About Bogotá
South Cathedral
America
Piranha

Flute Kapok Qualea
tree grandiflora

Population: Andean Llama
422.5 million condor
Reed boat
Amazon
rain forest Leatherback
Soccer turtle
The world’s biggest
Highest point:
Aconcagua

forest, the Amazon, is Salt lakes Pampas Christ the This soapstone
home to thousands of grass Redeemer statue is 128 ft
species of plants and (39 m) high. It
Lowest point: animals. Many native, overlooks the
Laguna del Carbón Brazilian city of
Rio de Janeiro.
or indigenous, tribes

live in the forest, too. Polo Machu Picchu

Biggest desert: Built by Inca emperor
Atacama Desert Pachacuti in 15th-century
Peru, Machu Picchu is a
Longest river: Andean Inca builders used
Amazon goose interlocking stones spectacular mountain-top
that fitted together town. Many thousands of
The skin of the Perito Moreno very tightly. people visit it every year.
golden poison dart Glacier
frog is covered in
a deadly poison.

Magellanic
penguin

236

Space travel SEE ALSO
▸▸ Astronauts p.31
Space travel is how we explore the solar system
and learn about our place in the universe. Most space ▸▸ Moon p.171
travel is done using robot spacecraft called probes.
The farthest in space that humans have traveled ▸▸ Exploration
themselves is to the moon. pp.180–181

Humans in space ▸▸ Radio p.203

▸▸ Robots p.212

▸▸ Solar system
p.233

The outside fuel To get into space, people use super- It takes a
tank is filled with powered spaceships. Space shuttles like
liquid hydrogen and Atlantis were used to take people into robot spacecraft
oxygen to power space for 30 years. Now people use about six months to
the shuttle’s the Russian Soyuz spacecraft.
engines. travel to Mars.
Solar cells use
the sun’s power
to make the
probe work.

Astronauts Juno probe
sit in the
cockpit.

Robots in space Magnetometer
measures
magnetic fields.

Probes gather data using cameras,
magnetometers, and radars, then
send the data back to Earth.

This booster Extreme environment
rocket gives
extra power. Space is not an easy place for people to be in.
It can be both extremely hot and cold. There
Launch of the are dangerous rays from the sun and there is
space shuttle no air to breathe. Spaceships and stations are
Atlantis carefully designed to keep astronauts safe.

Astronaut Karen Nyberg washes
her hair on board the International

Space Station.

237

Spiders SEE ALSO
▸▸ Animal groups
Spiders are animals with two body segments and eight
legs. They are predators, hunting other small animals to p.22
eat. They do not chew their food, but turn it into liquid
before sucking it up. ▸▸ Animal homes p.23

Tarantula ▸▸ Food chains p.107

Some of the world’s ▸▸ Insects p.134
largest spiders are
tarantulas. As they get ▸▸ Invertebrates
bigger, their old skin p.139
comes off and they
grow a new one. ▸▸ Sight p.226

Tarantulas Leg hairs help
bite with their tarantulas feel the
venomous fangs, vibrations of other
but their bite is less animals nearby.
harmful to humans
than a bee’s sting. Spider webs

The row of eyes Spiders can Many spiders build webs,
help the jumping using silk that they make in
spider see all grow back their their bodies. Some spiders
around it. use their web to trap and
legs if they store the insects they eat.

break off.

Jumping spider The body
is designed
Jumping spiders can jump 30 times for speed.
their body size. They use their good
eyesight to spot other animals. Huntsman spider

These spiders don’t build webs, but
hunt and forage for insects. Females
can go for three weeks without eating.

238

Sports SEE ALSO
▸▸ Ancient Greece
Sports are physical activities performed by individuals or
teams of players. There are usually rules to sports, and p.18
team sports often take place in a set amount of time. ▸▸ Bicycles p.36
Individuals and teams compete against one another to ▸▸ Dance p.76
achieve the best result or the highest score. ▸▸ Games

Athletics Spectators pp.240–241
Spectators watch sports ▸▸ School
Athletics is a group of sports that take and cheer on their
place around a running track or on a favorite athletes. pp.272–273
sports field. Big athletic competitions
such as the Olympics have lots Archery
of events. Archers use a bow
to fire arrows at a
circular target.

Sprinting Javelin
A sprint is a race A javelin is a long
that is shorter spear thrown as far
than 400 m.
as possible.
Shotput High jump Long jump
Athletes compete High jumpers Long jumpers try to
to throw a small, compete to jump launch themselves
heavy ball the the highest over as far as possible
farthest distance. a bar. along a sandpit.

Judges Hurdles
Athletes jump over a series
of obstacles called hurdles
on a running track.

Team sports Gymnastics Winter sports

Sports such as football, rugby, Strong gymnasts use their bendy In cold weather, competitors
and cricket are played between two bodies for moves including flips and use snow and ice to ice-skate,
opposing teams. The team that scores handstands. They use the floor as well ski, snowboard, and bobsled.
the most goals or gets the highest as props such as balancing beams. Many winter sports involve
number of runs or points wins the game. performing tricky moves,
or racing.
Soccer teams Basketball teams Football players
pass a round ball pass a round ball pass an unusually- Skier
by foot. by hand. shaped ball by
hand.
Gymnasts can
do impressive
moves while
standing on
their hands.

239

The story of... Racket sports

Games Tennis, badminton, and
squash are sports played using a
A game is an activity or sport played racket on a special court. In tennis,
using a set of rules. Games are played opponents hit the ball across a
by individuals or by teams of players,
who compete against each other. Some central net, and in badminton
games use balls and bats or rackets they hit a shuttlecock. In
and are played on special courts; squash, the players hit the
others use boards with specially ball against a wall.
designed game pieces.
The tennis
racket frame
has strings
pulled tightly
across it.

Board games A chessboard has Ping
a grid of black and pong ball
Tabletop games, such as white squares.
chess and backgammon, are
played on specially built boards. The start of a
Each player has a number of game of chess
pieces, such as chessmen,
that they move according
to a set of rules. Board
games were first played

in ancient Egypt 5,500
years ago.

Stone ring to hit
the ball through.

Ball and wall games Australian Handball
rules football
The ancient Mayans of Central
America played a ball game on
long, narrow, stone-walled
courts. Players used a solid
rubber ball, which they had to
keep in play by using only their
hips and arms—they weren’t
allowed to touch it with

their hands or feet.

Stone-walled Baseball
Mayan ball court

240

The first The Olympics

Olympic Every four years, athletes
Games were compete for their country in

held in ancient the Olympic Games. The
Greece in Olympics includes lots of
776 bce. different sporting events,

Lacrosse including athletics,
ball gymnastics, and
team sports.

Olympic sprint relay race

Football

Golf ball The first

computer
game was

developed in 1947.
Players fired a dot

at a target.

Volleyball Computer games

Ball sports Soccer ball Computer games are played on
a computer or through a console
Ball sports are among the
most popular games of all. on a TV screen. Many games
Teams of up to 15 players per side include special effects and music.
play in matches of soccer, rugby,
basketball, football, Australian rules They can be one-player or
football, cricket, and other games. multi-player games.
Huge crowds watch these matches,
many of which are shown

on television.

Basketball

Rugby ball A child plays a computer game.
241

Stars SEE ALSO
▸▸ Color pp.26–27
Stars are balls of very hot gas, deep in space. From Earth,
they look like tiny dots but are actually huge. The smallest ▸▸ Galaxies p.116
ordinary star is about the same size as Jupiter. Stars shine
because the gases inside them constantly crash together ▸▸ Light p.147
in a process called fusion.
▸▸ Solar system
p.233

▸▸ Sun p.247

▸▸ Temperature
p.252

Sizes and colors

Stars come in different sizes
and colors. A star’s color
depends on how hot its
surface is. The hottest stars
are blue, and the coolest
ones are red.

Blue supergiant
These stars are
very young and
extremely hot.

Red giant star
Red giants are
older stars with
cool surface
temperatures.

Sun
Our sun is a
middle-aged,
medium-sized
star with a
medium surface
temperature.

The nearest star Star deaths

The star closest to the Earth Some stars end their
after our sun is Proxima lives in a spectacular
Centauri, a red dwarf with at explosion called a
least one planet. This star is supernova. Others
9,000 times farther away slowly fade as they
than Neptune, the planet run out of energy.
farthest from the sun.
242
Cloud of material from a
supernova explosion

Stone Age SEE ALSO
▸▸ Art p.28
The Stone Age was a period of time that began about ▸▸ Buildings p.48
3.3 million years ago and lasted until about 4,000 years ▸▸ Caves p.55
ago. In the Stone Age, people made tools out of stone for ▸▸ Early humans
the first time. They used them to cut meat and plants, to
build shelters, and, in the late Stone Age, for farming. p.82
▸▸ Farming p.98
▸▸ Food p.106

Stone tools Finding food Blueberries

Stone Age people began Finding food was the most Bison
making stone tools to do important part of life for Hunting for big
different tasks. Using tools people in the Stone Age. animals, such as
meant people could get They ate wild plants, and bison, could be
food or do work more animals from land and sea. dangerous.
quickly and easily.
Salmon
A stone axe helped
to chop wood and Buildings
dig into dirt.
The first Stone Age
People made handaxes buildings were made
to help them cut meat of wood and animal
and chop hard plants. skins. By the end of
the Stone Age, people
Cave painting had begun building
large stone structures
Some Stone Age people called megaliths.
made beautiful artwork on
cave walls, often showing the Stonehenge in England
animals they would hunt. These is a famous Stone Age
paintings are still being found today. megalith that is still
standing today.
Paint could
be made from
powdered fats
and minerals.

Lascaux cave paintings in France

243

The story of... Grand palaces

Homes The kings and queens of
Europe were very rich and
A home is a house or building in lived in magnificent palaces
which you live. That home might be and castles. They feasted in
built of canvas, stone, bricks, wood,
or ice. It could even be carved out of great halls and received
solid rock. Homes can be built visitors in grand
separately as single, detached throne rooms.
houses or built together as row
houses or terraces. Some homes are
built on top of each together in blocks
called apartments.

Early homes Some early Neuschwanstein Castle in Germany
people built simple
Some early people made
their homes in caves or grass shelters.

holes dug into sides The layering of
of mountains and hills. grasses is called
Others cut down trees to
build simple wooden huts, thatching.
which they draped with
Eco homes Solar panels on
animal skins. the roof make
Today, some homes are energy from
specially built to work with sunshine.

Caves were the natural world, or
easy to turn environment. They don't use
into homes, as
they didn't have up as much energy as
to be built! ordinary homes.

Caves in
Cappadocia,
Turkey

Rainwater is Walls have
collected for added layers
reuse. to save heat
(this is called
insulation).

244

Igloo Extreme homes

In the cold Arctic, some
Inuit people build shelters
called igloos out of blocks

of ice. Igloos keep out
the wind and are
warm inside.

Plan for Future homes House
3D-printed designed by
houses on the What will homes of the Antoni
planet Mars future look like? Some might be Gaudí
built using a method called “3D
Houseboat
in India printing.” With this method,
robots add material layer
upon layer to create a
three-dimensional
shape.

Moving homes

Some people live in homes
that can move from place to
place. They float in houseboats
on water or live in wheeled

caravans towed by
cars or horses.

Architecture

Architecture is the art
of designing and making
buildings. In Barcelona in Spain,
architect Antoni Gaudí was
inspired by nature and
decorated his buildings
with different materials

and colorful patterns.

245

Storms SEE ALSO
▸▸ Climate change
Storms are powerful winds that often bring rain, thunder
and lightning, snow, hail, dust, or sand. Storms can cause p.60
serious damage if they have very high wind speeds or
heavy rain that leads to flooding. Tornadoes, hurricanes, ▸▸ Clouds p.64
and thunderstorms are all types of storm.
▸▸ Electricity p.87

▸▸ Erosion p.93

▸▸ Water cycle
p.270

▸▸ Weather p.271

Tropical giants The hurricane's eye, The strongest
or center, is calm, with winds surround
The biggest and most destructive storms, very little wind. the storm's eye.
called hurricanes or typhoons, happen in
tropical areas, above warm water. They
begin when groups of smaller storms spin
together into a spiral shape.

Thunderstorms

Storms with thunder and
lightning are common in
summer. They often have
heavy rain or hail that can
break things and cause floods.

Hurricanes Tornadoes
are given people’s
names, such as Tornadoes are fast-
spinning columns of air
Alex, Matthew, that form during massive
and Patricia. thunderstorms. A tornado
can destroy everything
in its path.

246

Sun SEE ALSO
▸▸ Atmosphere p.33

▸▸ Atoms p.34

The sun is the star at the center of our solar system. It is ▸▸ Gases p.117

one of at least 100 billion stars in our Milky Way galaxy. ▸▸ Magnets p.151

The sun gives off light and heat, making it possible for life ▸▸ Milky Way p.167

to exist on Earth. ▸▸ Solar system p.233

Massive explosions ▸▸ Stars p.242
send jets of gas out
from the surface. Yellow dwarf

Astronomers describe the sun
as a yellow dwarf, although

it is a medium-sized star.
It is a hot ball of gases

Dark sunspots are that are constantly
the cooler regions on the move,
on the sun’s creating energy.
surface.

These bright
bursts of
energy are
called solar
flares.

1.3The sun is Loops of gas
are called
million prominences.

times bigger
than Earth.

Auroras Final stages
of the sun
Toward the top and
bottom of the Earth In about 5 billion years
(at its poles), particles time, the sun will have
from the sun meet used up most of the gases
Earth’s magnetic field. that keep it shining. It will
This colorful glow is collapse into a small, very
called an aurora. hot white dwarf. It will
then slowly cool down and
247 eventually fade away.

Symmetry SEE ALSO
▸▸ Art p.28
There are two types of symmetry. Reflective symmetry is
when lines can be drawn to divide a shape into identical ▸▸ Flowers p.103
parts. Rotational symmetry is when a shape can be turned
around (rotated) and still look the same. ▸▸ Human body
p.130

▸▸ Shapes p.222

▸▸ Sight p.226

▸▸ Games
pp.240–241

Reflective symmetry A regular octagon
has eight lines of
Lines of symmetry are like folding a shape in half. If a symmetry, through
shape is symmetrical, both sides of the fold will look the its sides and angles.
same. Shapes can have more than one line of symmetry.
This triangle has
Diamonds have two three lines of
lines of symmetry. symmetry, one
Each one splits the through each side.
diamond into two
equal parts.

Diamond Equilateral triangle Octagon

Symmetry in nature Rotational symmetry A circle has

Nature has many examples of both types of If a shape can be turned and a never-ending
symmetry. Most animals, including humans, are its outline looks the same, it
roughly the same on both sides—they have a line has rotational symmetry. This number of lines
of symmetry down the middle. sequence shows how a square of rotational
has rotational symmetry. symmetry.

Reflective Rotational Direction
symmetry symmetry of rotation

12 3 4
Point of rotation
Leaf Starfish A square can turn within
248 its shape four times.