How Things Work Encyclopedia

1

Light on Lucrezia: A Novel of the Borgias Broadway Jean Plaidy Year: 2011 Language: english File: MOBI , 908 KB

2

Heresia Arqueiro S J Parris Year: 2011 Language: portuguese File: PDF, 5.01 MB

How Things Work

Encyclopedia
Machines+Biology

Technology+Robots

A first reference guide for inquisitive minds

How Things Work
Encyclopedia

DK PUBLISHING

LONDON, NEW YORK,
MELBOURNE, MUNICH, and DELHI

Senior Editors Carrie Love, Penny Smith
Senior Designer Rachael Grady
Design team Lauren Rosier, Pamela Shiels,
Karen Hood, Hedi Gutt, Mary Sandberg, Sadie Thomas,
Claire Patane, Laura Roberts-Jensen, and Poppy Joslin
Editorial team Lorrie Mack, Elinor Greenwood,
Alexander Cox, Fleur Star, Caroline Bingham,
Wendy Horobin, and Ben Morgan
Picture Researcher Myriam Megharbi
Proofreader Anneka Wahlhaus

Contents

Consultant Roger Bridgman
Publishing Manager Bridget Giles
Art Director Rachael Foster
Category Publisher Mary Ling
Production Editor Sean Daly
Production Controller Claire Pearson
Jacket Designer Natalie Godwin
Jacket Editor Mariza O’Keeffe
US Editor Margaret Parrish
First published in the United States in 2010 by
DK Publishing
375 Hudson Street
New York, New York 10014

Technology
4–5
6–7
8–9
10–11
12–13

Inventions
Better by design
Early inventions
Modern technology
Technology all around us

Copyright © 2010 Dorling Kindersley Limited
10 11 12 13 14 10 9 8 7 6 5 4 3 2 1
175932—11/09
All rights reserved under International and Pan-American Copyright
Conventions. No part of this publication may be reproduced, stored
in a retrieval system, or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording, or otherwise, without
the prior written permission of the copyright owner. Published in
Great Britain by Dorling Kindersley Limited.
A catalog record for this book
is available from the Library of Congress.
ISBN 978-0-7566-5835-9

Color reproduction by MDP, UK
Printed and bound by Toppan, China
Discover more at

Hard at work
14–15
16–17
18–19
20–21

Simple machines
Using levers
Construction work
Moving stuff

Getting around
22–23
24–25
26–27
28–29
30–31

Getting around
Wheels and axles
Pedal power
Holding the road
Piston power

www.dk.com

2

There is a question at the bottom of each page...

Bits and bytes

Engines of fire
Race cars
Up to speed
Powering up
Trains and tracks

94–95
96–97
98–99
100–101
102–103
104–105
106–107
108–109
110–111
112–113
114–115

Air and water
Gases and liquids
How fluids work
Float that boat
Floating balloons
Roller coaster
How do planes fly?
Blastoff!

In the future
116–119 Near future?
120–121 Not-so-near future

What is energy?
What is energy?
It’s electric!
The power of magnets
Power plants
Running out
Renewable energy
What’s cooking?
Keeping cool
Energy efficiency

Light and sound
Light and sound
Now you see it...
Light and bubbles
Mirror,rorriM
Lenses
How light works
Fireworks
Measuring sound
How ears hear
Electric guitar

122–125 Glossary
126–127 Index
128
Picture credits
About this book
The pages of this book have special features that
will show you how to get your hands on as much
information as possible! Look for these:
Gases and liquids

Gases and liquids
Curiosity quiz

Gases and
liquids

Gas molecule

Air and water are
important examples
of two types of
substance—liquids
and gases. They behave
in different ways.

Air is a gas. The molecules in
a gas have a lot of energy and are
always moving and colliding. This
movement means they will fill up any
container you put them in. If there is
no container they will spread out as
far as possible. Because there is a
lot of empty space between gas
molecules, gases can be
squashed into small
spaces.

What’s a molecule?

carbon dioxide

42

oxygen

carbon

oxygen

oxygen

Look through the “Gases
and liquids” pages and
see if you can identify
the picture clues below.

Liquid

Liquids always take on the
shape of their container. The
molecules in a liquid are closer
together than in a gas, but have less
energy to move around. Special
forces hold the liquid molecules
together. It is very difficult to
squash a liquid into a
Water
smaller space.
molecule

Gas

Liquids and gases are made
of molecules. Molecules are so
tiny you can’t see them with
the naked eye. Molecules are
made of even tinier particles
called atoms. Everything in the
universe is made from atoms.

Feel the breeze
You can feel air molecules
moving when the wind blows.
Wind is simply air molecules
being pushed by a force we
call pressure.

Scientists call
water molecules
H 2O (H stands for
hydrogen and
O stands for
oxygen).

Air molecules
Air is made up of lots of
different atoms bonded
together in groups called
molecules. The main
molecules in air are nitrogen,
oxygen, and carbon dioxide.

hydrogen
oxygen

nitrogen

Become
an expert...
on how ships float
46–47
on how airplanes
fly 52–53

43

Bits and bytes

Speech and music are turned into
electrical signals by a microphone
in a radio studio.

Traditional radio sets pick up
the radio waves and turn them
back into speech and music.

Digital transmission
Digital radios also use a transmitter,
but the waves they use are different
from those of a traditional radio.

What’s inside?
The main parts of a
radio are an antenna,
a circuit board with a
tuner and amplifier,
and a loudspeaker.

Baird’s
televisor

Images on the
televisor were
grainy. The
mechanical system
was soon replaced
with a better quality
electronic system.

Digital radio
When you listen to a digital radio there
is little or no interference, such as hissing
noises. Digital transmitters send out
sound codes all mixed up together so
that interference can’t affect them much
and your radio will usually be able to
understand them.

Digital radios use codes
made from lots of ones
and zeros. They are
transmitted over a large
band of radio waves.

First TV
The scientific research for televisions
began in the late 1800s. Baird’s
televisor was the first ever TV to work.
A rotating disk transformed light
from a scene into lines
forming a moving
image.

TV inventor
John Logie Baird
demonstrated
the first television
broadcasts
in 1929.

Transmission today
Television stations
transmit programs
through electrical waves.

Label

Tucked behind
the radio is the
antenna. This picks
up radio waves.

106

A neon lamp
sent light into
holes in a
spinning disk.

It’s hard to imagine life without
radio or TV. We use both for
information and entertainment.
There are millions of programs,
but how do they get to our radios
and TVs?

Inside the radio
is a tuner and a
computer chip that
decodes the waves
and converts them
into sound.

Television pictures are
created by cameras in
TV studios.

The light coming through the spinning
disk lit up a scene and made a moving
image. The red light from the neon
lamp made the image appear red.

LCD TV
LCD screens have been used since the 1970s in
calculators and watches, but only recently for
TVs. A modern LCD TV screen is made up of
millions of tiny squares called pixels.
If you look
very closely
at an LCD
TV screen
you can see
the pixels.

Programs can be sent up to
satellites in space and then
sent back to Earth.
Satellite dishes can pick up
the microwaves and send
them to TVs along a cable.
A TV turns the waves into
the pictures and sound that
make up a TV program.

w ei

Color
squares
Pixels contain
blue, red, and
green. When the
pixels are turned
on or off the
colors merge,
forming pictures.

What does LCD stand for?

Programs are sent out from
the TV studio over wires
or microwaves.

r d o r w h at ?

rd
ei

or wha
t
?

How do radios work?
First called a wireless, the radio
didn’t need wires to connect
the transmitter and receiver.

The radio transmitter
sends out radio waves
from the radio station.

Every page is color-coded to
show you which section it
is in.

Radio and TV

Radio and TV

Who invented radio?
Guglielmo Marconi is
credited with building
the first radio system.
In 1901, he transmitted
radio signals across the
Atlantic Ocean.

The electrical signals from the
speech and music travel through
wires to a radio transmitter.

The Curiosity quiz will get
you searching through each
section for the answers.
Become an expert tells
you where to look for more
information on a subject.

Water molecules
Water molecules are
made of two hydrogen
atoms bonded to one
oxygen atom. Water
molecules are so sticky
they clump together to
form drops.

What do we call materials in which the atoms cannot move?

... check here for the answer.

74–75
76–77
78–79
80–81
82–83
84–85
86–87
88–89
90–91
92–93

Reference section

w

56–57
58–59
60–61
62–63
64–65
66–67
68–69
70–71
72–73

These buttons
give extra weird
and wonderful
facts.

There are roughly 1.5
billion television sets
in the world. That’s
one TV for every four
people on the planet.

Liquid-crystal display.

42–43
44–45
46–47
48–49
50–51
52–53
54–55

Bits and bytes
Inside a laptop
Binary code
Sharing data
Cell phones
Digital photography
Radio and TV
Bar codes
The Internet
Search engines
Robots

Solids.

32–33
34–35
36–37
38–39
40–41

107

3

Technology

Accidental ideas
Inventions can
happen by
accident. Chemist
John Wesley Hyatt
was trying to find
a material for
billiard balls. He
spilled a liquid
that dried into a
tough, flexible
film—“celluloid”
that was later used
as camera film.

Inventions
Any new idea or product that
has been created by a person
can be called an invention.
Inventions change the way
people live their lives—they
make things safer, easier,
faster, or cheaper.

Knowing your stuff
Technology is the science of how things work.
The inventors of these shoes knew that a coiled
spring is a source of stored energy. They used
this technology to make powered shoes.
Expensive origins
Some of the things in
everyday use were
developed for the
space program.
Smoke detectors, for
example, were first
used on Skylab.

“Discovery consists of seeing what everyb
ody h

as seen and

Telephone
Refractometer

Faraday’s
induction ring

Electric
light bulb
Cathode
ray tube

Wheel
Eyeglasses

4

When was the first pair of shoes invented?

Inventions
I can find a use for that!
Some inventions end up very
different from what was planned.
Scientist Dr. Spence Silver invented
a glue that wasn’t sticky enough,
so he thought it was useless. But his
coworker Art Fry used it to stick
bookmarks into his hymn book.
The bookmarks wouldn’t fall out,
but they could be moved around.
And so the sticky note was born!

Inventors
Inventors are creative
people. The Italian artist
and scientist Leonardo
da Vinci was an avid
inventor. He designed
hundreds of machines,
including airplanes,
pumps, and
cannons, that were
centuries ahead of
their time.

The first military helicopter,
designed by Igor Sikorsky, took
to the skies in the 1940s.

How long does an invention take?
An invention has to begin with an
idea. It can sometimes take hundreds
of years before the science, technology,
or materials are advanced enough to
make the idea work. The idea for a
helicopter may have come from China
as far back as 400 BCE.

thinking wh

else
y
d
o
b
at no

Wimhurst voltage
generator

Leo
n
des ardo
ign
da
V
yea
f
rs b or a h inci sk
suc
cess efore elicopt etched
th
e
ful
plan e first r 500 a
e fl
ight
.

has thoug
ht.”

Electric
guitar

Albert Szent-Györgyi

Teamaker

Microscope
Camera

5

In 1500 BCE, people in Mesopotamia made the first leather shoe.

Technology

Better by
design
Anyone can be an inventor.
Many successful inventions
came from engineers who used
their knowledge of materials
(such as iron) to try new things.

The Eddystone Lighthouse in Devon,
England is also known as Smeaton’s Tower.

New and improved
Design engineer John
Smeaton didn’t invent
lighthouses, but he did
design a new shape. The
curved tower was wider at
the base than the top and
could stand up
to storms.

American inventor Thomas
Edison patented an amazing
1,093 inventions.

That was my idea!
If someone thinks their idea is
good, they can patent it. Patents
are official documents that
describe the idea and show who
came up with it, so no one else
can steal it and say it’s theirs.

From that...
Since the telephone was invented more
than 130 years ago, people have
changed the design to make it better.
Early telephones were large and boxy.
Making a call may have
involved winding a
handle or turning a dial.

6

When was the first telephone patented?

John
base Smeaton
d
on t his des
he s
ign
ha
an o
ak t pe of
ree.

Better by design
Meet an engineer
Isambard Kingdom Brunel was a 19th century
engineer who designed bridges, tunnels, ships,
and even an entire railroad. He worked a
lot with iron and knew it could be used in
ways that had never been tried before.

Will it sell?

Brunel’s Royal Albert Railway
Bridge was built in 1859.
It’s the only one of its kind.

Making a difference
The way something looks
can be just as important as
how it works. The first
colorful Apple iMac design
made it stand out from
other computers, so more
people bought it.

Even the best inventions
can fail if people don’t
want what you’ve made.
Sinclair C5 Failure. Not
many people wanted to buy
a battery-powered tricycle.
Lego Success! These plastic
bricks are one of the bestselling toys in the world.
Microwave oven Success!
It has completely changed
the way many people cook.
Sneakers Success! Can you
imagine playing sports in
any other shoes?

... to this!
Today’s cell phones are tiny by
comparison, and you can do
much more than just talk on
them. You don’t even
need to use your
hands to call a
friend.

What will
they think
of next?

7

Alexander Graham Bell registered the patent in 1876.

Technology

Early inventions
Some discoveries and inventions seem so
basic it’s hard to imagine life without them.
Yet someone had to be the first to create fire,
wheels, shoes, paper...
c. 7000

c. 2500

c. 3500

BCE

The first wheel was made from
solid wood. Experts think it was
invented in Mesopotamia
(modern-day Iraq).

BCE

Early welding
involved hammering
heated metal parts
together until they
joined. Now all kinds
of metal objects
could be made.

7000 BCE

2250 BCE

c. 1700
c. 3000
BCE

Reed boats were made from
bundles of papyrus reeds by
the ancient Egyptians, who
used them for trade.

c. 4000

8

BCE

Spoked wheels were lighter
and more useful than solid ones.
Two-wheeled chariots could
move very fast.

BCE

For the first time, people knew
how to start a fire. Later, they
would be using fire in metalwork
to create tools.

c. 6000

c. 2000

BCE

Reed pens and
brushes were used
by the ancient
Egyptians for
drawing signs on
papyrus (which was
used before the
invention of paper).

BCE

Evidence of early plumbing (drains and
pipes) can be found among the ruins of the
Palace of Knossos, on the island of Crete.

c. 2500

BCE

The first specially
made mirror was
made of polished
bronze. Before then,
people could see their
reflections in water.

BCE

Wooden plows were pulled by animals to
cut and turn soil for farming.

What does the “c.” mean by the dates?

Early inventions

c. 500

c. 1000

BCE

The earliest underfloor heating system is found
in modern-day Alaska. The Romans invented their
own system in Europe around 500 years later.

c. 1000

BCE

The Greek abacus was a table
with counters that people used
to make calculations. Today’s
familiar abacus with rods and
beads was invented in China
almost 2,000 years later.

c. 300

BCE

The Chinese discovered that
a free-moving magnet will
point north—and so the
compass was born.

BCE

The first magnets
were simply lumps
of magnetite, a
naturally magnetic
mineral. Modern
magnets are
made of steel.

c. 50

1200 BCE
c. 1500

c. 640

BCE

Most early peoples wore
sandals, but in Mesopotamia
people crafted leather shoes
to protect
their feet.

c. 1200

BCE

Paper was invented in
China more than 2,000
years ago, but the
invention was kept a
secret for 700 years.

100 BCE
c. 20

BCE

Before the first specially
made coins, people paid
for goods with beads,
shells, tools, and even
deer skins!

c. 200

BCE

The Archimedes screw
is named after the Greek
scientist Archimedes, who
explained that water can
travel upward along a
turning screw.

BCE

Although glassmaking had
been around for more than
2,000 years, the invention
of glassblowing in Syria
meant lots of new shapes
could be made.

BCE

The first ships were built by
Phoenicians and
Greeks to carry
large amounts of
cargo for
trade.

9

It stands for “circa,” which means “approximately.”

Technology

Modern technology
Today, the phrase “modern technology” is usually used to
mean computers. But a few hundred years ago, steam power
and mechanical presses were new and exciting technology.
1455
Before Gutenberg’s movable type
and printing press, books were
copied by hand. Now they could
be produced more quickly.

1400

1826

1565

The first photographic image was taken
by Joseph Niépce in France. He had to
leave his camera still for 8 hours!

Historians think the first pencil
was invented by Conrad Gesner
in Germany.

1500

1608
In Holland,
Hans Lipperhay
invented the
telescope—
although some
people think
his children
made one
while playing!

1700

1600

1800

Important ideas
Sometimes one invention
leads to so many others,
it changes the world.
1700s

The first machines and
factories used to massproduce goods led to the
Industrial Revolution.

1800s

For the first time, people
could safely harness the
power of electricity.

1970s

The microprocessor
made computers
smaller and started
the information age.

10

1829
1764
James Hargreaves’
spinning jenny
made thread for cloth
faster than ever before.

1769
James Watt’s improved
steam engine was used to
power all kinds of machines.

Why was the printing press so important?

Stephenson’s Rocket
pulled the first
successful steam
train. It reached
12 mph (19 km/h).

Modern technology
1903
The first powered flight
took place in the US.
The plane, the Wright
Flyer, was made of
wood and cloth.

1878

The first personal computers
were large, chunky machines
that had very little memory
compared to today’s models.

1957

The light bulb was
invented around the same
time in two different
countries—by Thomas
Edison in the US and
Joseph Swan in Britain.

1876

1977

The Soviet Union’s
Sputnik 1 was the
first man-made
space satellite.

Alexander Graham Bell
got the first patent for
a telephone, although
others nearly beat him
to it.

1982
The first compact discs
were jointly
produced by
electronics
companies
Philips
and Sony
Corporation.

1926
The Televisor was the first kind
of television. It was replaced by
electronic television in 1936.

2000

1900
WWW
1885

1990

Karl Benz made the first gasolinepowered car in Germany. By 1896,
there were 130 Benz cars on the roads.

The World Wide Web
meant anyone could get
information from across the
world over the Internet.

1895

German scientist
Wilhelm Röntgen accidentally
discovered X-rays as a way
of seeing through tissue.

1938
Laszlo and Georg Biró’s ballpoint
pen had fast-drying ink and didn’t
need to be refilled very often.

1979
This year saw the
first public cellphone system,
in Japan.

1998
The first handheld E-book
reader could store 10
books or 4,000 pages.

11

More books were made, so knowledge and ideas could spread more easily.

Technology

Technology all around us
Which te
c

ogy is yo
l
o
u
hn
Become
an expert...

on space travel,
pages 54–55
on robots,
pages 114–115

avorite?
rf

The use of science to provide new
and better machines and ways of
doing things is called technology.
Every day, you use technology in
one of its many different forms.
Here are a few of them.

Mechanical
Mechanical technology is the design,
production, and use of machines like
wind-up clocks and other appliances
that do not use electrical, electronic,
or computer technology.
Chemical technology
is used to make
plastics and refine
gasoline.

Chemical
When the science of chemistry is
used to turn raw materials into
more useful things like plastics,
cosmetics, or drugs, this is called
chemical technology.

Electrical
Technology that deals with electrical
circuits and equipment is known as
electrical technology. It is commonly
used in the design and construction of
machines and power grids.
12

How does nanotechnology get its name?

Digital

Technology all around us

In digital technology, information is
recorded using combinations of 0 and 1
to represent words and pictures. This
system allows huge amounts of data to
be squeezed into tiny spaces.

Biotechnology
This term refers to technology that is
based on biology—the study of living
things. Biotechnology is commonly used
in agriculture and food production.
Genetic engineering is biotechnology.

Medical
Anything (like a tool, machine, process,
or substance) that is used to diagnose,
observe, treat, cure, or prevent people’s
illnesses or injuries comes under the
heading of medical technology.

Information
The study, design, and use of electronic
information systems is known as
information technology. The term covers
machines like computers (hardware) and
the programs they run (software).

When you log on to
a computer, you use
information technology.

Modern science can create materials
and simple machines much too small for
you to see under a normal microscope.
This nanotechnology is used in products
like special sunscreens and textiles.

Antibacterial
bandage

Sunscreen

Nanotechnology

NO

NA

N

SU

SPF

Odorresistant socks

13

“Nano” is Greek and originally meant “dwarf.”

Hard at work

Simple
machines

It’s hard to hit a nail into wood
with your hand, but much easier
with a hammer. Tools such as this
are called simple machines. They
help people work faster and better.
A small movement from your hand
travels down the handle to the head.
As the head moves, it stores energy.

When the head hits the nail, the
stored energy is released as a
large force that can split wood.

Class 1 lever
Levers consist of a solid part that
turns around a fixed point, called
the fulcrum. In class 1 levers, the
fulcrum is in the middle. The force
you apply at one end is magnified
at the other end.
Magnified
force

Solid part

Force you
apply

Loa

d

Fulcrum

Class 2 lever
In class 2 levers, the fulcrum is at
one end and your hands apply a
force at the other end. This creates
a magnified force in the middle.
Magnified force

Force you
apply

Loa

d

Feel the force
Tools, levers, and pulleys are all simple machines.
They increase the size of the force you apply, so you
can perform a job with less effort. When you use a
hammer, you only need to move the handle a small
way to give the head enough energy to push the nail
through wood.

Levers move loads

Fulcrum

Class 3 lever
Class 3 levers reduce the force you
apply. They are used in tweezers
and other tools that pick up small,
delicate objects.

Levers are simple machines that work
by magnifying or reducing a force.
A wheelbarrow is a kind of lever. It
magnifies the lifting force from your arms so
that you can lift and move much heavier
loads. There are three different types of
lever: class 1, class 2, and class 3.
14

What is a force?

Reduced
force
Force you
apply

Fulcrum

Loa

d

Simple machines
Curiosity quiz

Pulley power
Fulcrum

A pair of scissors is made of two class 1
levers. You apply force with your fingers,
and this force is magnified at the blades,
giving them the power they need to cut
through paper or other materials.

Pulleys are used to lift
heavy loads. A pulley is
a length of rope wrapped
around a wheel. Adding
more wheels to the
pulley system creates
more lifting force—but
you have to pull the rope
farther to lift the load.

Look through the “Hard
at work” pages and see
if you can identify the
picture clues below.

Wheel

Edge-on
view of a
pulley
wheel

Pulling on the end
of the rope will
shorten the rope
that’s wrapped
around the pulley
and lift the weight.

Fulcrum
A wheelbarrow is a class 2 lever. It
magnifies the weak force from your
arms to pick up the heavy load.

Rope
Rope
Fulcrum

The rope sits in a
groove in the
wheel so it won’t
slip out.

Become
an
expert...
The fulcrum in this pair of chopsticks is
where they rest in the girl’s hand. Her
fingers apply the force that opens and
closes the chopsticks to pick up food.

on cranes, pages 18–19
on conveyors,
pages 20–21

15

The power that makes things move. Simply put—a push or a pull.

Hard at work

Using levers

Levers at home
These are all compound
levers—tools made up of
more than one lever.

Every time you open a door, ride a
bike, or even bend your arm, you are
using levers. Many of the objects we
use every day depend on leverage to
magnify forces and make tasks easier.

Nutcrackers are a pair of
class 2 levers that are
joined at the fulcrum.
Tweezers are made up of
two class 3 levers. They
reduce the force you apply.

Magnifying forces

Scissors are class 1 levers.
The strongest cutting force
is nearest the hinge.

The amount by which a lever magnifies a force
depends on how far the force you apply and the
force the lever produces are from the fulcrum.
Force you
apply

Force you
apply
Force from
lever

Force from
lever

Fulcrum
If the force you apply is the same distance from
the fulcrum as the force the lever produces, the
two forces are equal.

Crowbar
One of the simplest kinds of
lever is the crowbar, which
is a class 1 lever. You use a
crowbar to prize very heavy
objects off the ground. The
longer the crowbar is, the
more the force is magnified at
the other end. However, you
have to move the long end of
the crowbar much farther
than the short end will move.

16

Force you
apply
Force from
lever

Fulcrum

Fulcrum

If the force you apply is twice as far from the
fulcrum as the force the lever produces, the
lever doubles the force.

If the force you apply is three times as far from
the fulcrum as the force the lever produces, the
lever triples the force.

Force you apply
Force from
lever

Load

Fulcrum
Moving the crowbar a long way
provides enough force to lift the
heavy rock a short distance.

Can you name other compound levers found around the home?

Force from
lever

Using levers
Human body
Your arms and legs are
levers. When you stand on
tiptoes, your lower leg
works as a class 2 lever.
The powerful calf muscle
pulls up your heel, lifting your
body weight (the load), while
your toes form the fulcrum.

Force you
apply

Load

Fulcrum

Fishing rod
When you use a fishing rod to
cast a line, the rod works as a
class 3 lever. Your hand applies
a powerful force near the base
of the rod to create a smaller
force at the tip of the rod.
Although the force is weaker,
the tip moves much farther
and faster than your hands,
magnifying the speed.

Force you
apply

Load

The rod also works as a class 3 lever
when you haul in a fish.

Fulcrum

Seesaw
A seesaw is a class 1 lever. You use the force of your
body weight to move the seesaw. If two people of
equal weight sit at equal distance from the fulcrum,
their weight will balance. But if one of them sits
farther from the fulcrum, their weight is magnified
and the seesaw tips over.

A small child could
balance the weight of
an elephant by sitting far
enough from the fulcrum.

Force you apply

Fulcrum

17

Pliers are class 1 compound levers. Tongs are class 3 compound levers.

Hard at work

The long arm
of the crane is
called the jib.

Construction
work
Digging dirt, lifting loads—
there’s lots of heavy work to do
on a construction site, and lots of
large machinery to do it. Yet
most of these machines use fairly
simple science to do their jobs.

The crane’s
operator sits
inside a
small cab.

A wheeled cart
runs along tracks
in the jib to move
the load outward.

A slew ring allows the
top of the crane to turn
around in a circle.

Tower

Why don’t cranes fall over?
Tower cranes pick up and move the
massive blocks of concrete and steel
used to construct big buildings. A huge
concrete “counterweight” on the rear
arm of the crane balances the load
carried by the main arm (jib). This
stops the crane from toppling over.

Hydraulic
ram

Large weights must be lifted close to the
main tower, while small weights can be
picked up at the end of the jib.
Jib
20 tons

Counterweight

Tower

20 tons

10 tons

7 tons

Each of these loads is balanced, but the
crane could not pick up all three at once.

18

What is a crane’s first job when it arrives at a construction site?

Pulleys in action
Cranes lift objects with a hook and
pulley. A steel cable is looped around
pulley wheels on the hook and jib
and is wound in by a motor in
the crane’s rear arm. Each
loop of cable magnifies
the crane’s lifting
force.

Diggers
Diggers use a set of connected levers to
scoop earth out of the ground. The levers
are joined like the parts of a human arm,
the bucket forming the “hand.” They are
moved by hydraulic rams—
metal tubes that extend as
oil is pumped into them.

Construction work

Hydraulic cranes
Mobile cranes, such as those on fire engines,
are hydraulic cranes. Like diggers, they use
hydraulic rams to transmit the force needed
to lift loads. By varying the size of the metal
tubes in the rams, the hydraulic system
creates huge lifting forces—enough to raise
bridges, trains, and even entire buildings.

Hydraulic ram

Like pulleys
and levers, hydraulic
rams can magnify forces.
Boom
When the bucket
is pushed inward,
its sharp teeth dig
into the ground to
scoop out earth.

Slew
ring

Bucket

The slew ring at the
base of the arm
allows the arm to
rotate (turn around).

19

It builds itself, adding one section at a time to its tower.

Hard at work

Moving stuff
From airports and factories to stores and offices,
conveyors are used in all kinds of places to make
it easier to move loads from one point to another.

A gravity conveyor
seen from above.

Move along
The simplest type of conveyor is a gravity conveyor. This
is made up of lots of rollers or wheels in a frame. As each
roller or wheel turns, the load gets shifted along to the next.

Luggage and other
cargo are moved on
conveyors behind the
scenes at an airport.

The drive pulley,
connected to an electric
motor, does the work.

Up, down, and sideways
Belt conveyors can move loads
up, down, and sideways. The
load sits on a belt that turns
around rollers called pulleys.
The drive pulley is connected to
a motor, which makes it rotate.
Chain

20

Sprocket

When was the first escalator used?

The motor is hidden
away under the bed
to take up less room.

The motor turns fast—1,750
times a minute! A speed
reducer is added so the drive
pulley will not turn so quickly.

Moving stuff
How to drive
The parts that make a
conveyor belt turn are
called the conveyor drive.
Sprockets and chains are
part of this. The chain
sits in the gaps between
the sprocket’s teeth so it
doesn’t slip. When the
motor sprocket turns, the
chain moves and turns
the drive pulley sprocket.
Sprocket

Going up!
It’s not just boxes that are moved
around on conveyors—people are,
too. Escalators are moving staircases
with each separate step connected
to a conveyor belt. Even when the
steps turn around the
belt, they always
The steps are
stay level.
connected to two belts.
Wheels near the top of
each step follow the
drive belt, which is
turned by the motor.

Electric
motor

An escalator can carry more
than 10,000 people in an hour.

The handrail is also
turned by the motor so
you can hold on safely.

Drive
pulley

Inner rail

The steps flatten
out at the top and
bottom of the
escalator so you
don’t trip getting
on and off.

Sprocket
Drive
belt

The belt loops all the way
around the bed and pulleys.

Bed

To stop the belt from sagging
underneath, it might be
tucked around small rollers
called return idlers.

Guide wheels at the
bottom of each step roll
along the inner rail to
keep the steps stable.

Tail
pulley

The tail pulley
turns by itself.

21

The first working model was made in the US in 1895—as a fairground ride!

Getting around

Getting around = Energy
We can all use our legs for getting
around, but they’re a bit slow and
won’t take us far without making us
tired. What we need is something that
can get us from A to B fast—a vehicle
of some kind.

Energy sources
To move or do any
kind of work you need
energy. We get energy
from our food; vehicles
use fuel or electricity.

But what does it take
to get a car racing
along a road?

Energy-rich oil
One of the best
sources of energy
is oil. When oil is
burned it releases
lots of energy.

Types of fuel
Vehicles can get their
energy from many
different types of fuel:

P

Gasoline is made from oil.
Most cars run on gas
burned in the engine.

D

Diesel is also made from
oil. It produces more
energy than gasoline.
Electricity can be used to
power some cars but is
mainly used by trains.
Solar energy comes from
the Sun. It can be stored
for use by cars.

22

What moves faster than anything else in the universe?

Force

Movement

Getting going

On the move

Once you have enough
energy, you can use it
to create forces that
will help you move.
Forces are simply
pushes or pulls.

When you apply a
force, things move.
When you don’t, they
stay still. The greater
the force, the faster
something goes.

Getting around
Curiosity quiz
Look through the
“Getting around” pages
and see if you can identify
the picture clues below.

PUSH

Speeding up
Speed is the key to getting
somewhere fast. To increase
your speed you need to be
able to provide a lot of
power quickly. A good
engine and the right kind
of fuel help.

Wheels turn by
using opposing
forces. As the tire
pushes back against
the road, the road
pushes the wheel
forward.

Friction
Friction is a force that stops
things from moving by
pulling them in the other
direction. Without its
gripping action, you couldn’t
walk or drive anywhere.

Brakes work
by pushing
pads or disks
against the
wheels.

Slowing down
If you push against
a moving object it
will slow down
and eventually
stop. This is
called braking.

Light.

PULL

Become
an expert...
on how bicycles
work, 26–27
on car engines,
32–33

23

Getting around

Wheels and axles
An axle is a simple rod that connects two
wheels. For nearly 6,000 years, the wheel
and axle have made it easy to move objects.
Friction
Friction is the force
created when two
surfaces touch. As you
slide an object along, you
create a lot of friction.
When you roll it on
wheels, you create less.

Fixed axle
A fixed axle can be found on simple
carts. The axle is attached to the cart
and the wheels turn independently,
Wheel
allowing the cart to move.

The axle does
not turn

Axle
Pushing this box is
hard work. The large
area of the box in
contact with the floor
creates sliding friction.

Some friction is
created as the
wheel turns
against the axle.

A lot of friction

Put the box on wheels
and it gets easier.
The wheels turn and
change sliding friction
into the less forceful
rolling friction

Carts have big
wheels so they don’t
get stuck on bumpy
roads. The large wheel
gives it extra grip.

Less friction

History wheels
Historians believe the very
first wheels were used 8,000
years ago by potters to make
pots. Then the wheel was
used to help move and
transport objects.

24

The first use
of wheels
and an axle
was on
horse-drawn
chariots
around
3500 BCE.

What is the largest wheel in the world?

Bicycles,
which allow
us to create
our own
power, have
been popular
for over
100 years.

Outer rim
Spoke support
The little rods that connect the outer rim
to the inner hub of the wheel are called
spokes. They make the wheel lighter
but are strong enough to take the
weight. They also spread the weight
evenly, and transfer power from the axle.

Wheels don’t just move
you or your belongings.
They have a diverse
range of uses:
Hub

A steering wheel is the
fifth wheel on a car and
helps guide it.

Rolling axle
Modern cars and vehicles use a
rolling axle system. The axle is
connected to the engine and
helps turn the wheels.

The wheels turn with
the axle

Wheel

Spoke

Wheels and axles
Other wheels

Gears
Axle

Gears use interlocking
“teeth” to transfer
movement and power.
Pulleys and levers use
wheels to pick up and
move heavy objects.

The engine turns a rod known
as the driveshaft. This uses
gears to transfer the engine’s
power into the axle.

Waterwheels create
mechanical energy when a
river’s current turns them.

Driveshaft

The turning
force created by
the axle moves
the wheel.

rd
wei

or what

?

The tweel is a brand new
car wheel that doesn’t need
a tire. Instead, it uses flexible
spokes, which bend with the
bumps in the road. The
tweel will never get a
flat like a tire.
In “two-wheel drive” cars, one
axle powers just two wheels.
“Four-wheel drive” cars are
powered by both axles.

With the
invention of
the engine,
bigger vehicles
needed bigger
wheels to help
move heavy
cargo.

After a few
early designs,
the automobile
was built and
its wheels
were covered
with air-filled
rubber tires.

The modern-day
wheel is a
hi-tech device.
Race cars use
special wheels
for different
racing
conditions.

25

The observation wheel The Singapore Flyer stands 541 ft (165 m) high.

Getting around
The history of bikes

The dandy horse (1817) The first
bikes had no pedals at all. Riders had
to push them along with their feet
until they came to a downhill slope.

The velocipede (1863) The pedals on
this bike were fixed to its wheels, and
it had no gears. This meant the wheel
turned once for every turn of the pedal.
It took a huge effort to travel fast.

Pedal power
A bicycle is a lean, mean
travel machine. Bikes are
so efficient, they can turn
90 percent of the
energy you put into
pedaling into
forward motion.

Get in gear
Bikes can have up to 30
gears. They are cogs, or
wheels with teeth, that are
linked by a chain. Using different
gears makes pedaling easier or faster.
When a small gear
at the front wheel is
connected to a large
gear at the back, the
bike is in low gear.
This turns the wheel
slowly but forcefully,
so is ideal for
traveling uphill.

The penny farthing (1872) These
bikes got around the problem of fixed
pedals by having a huge front wheel.
They were faster but also dangerous—
it was a long fall down from the seat.

The safety bicycle (around 1884)
This was the original name for a
bicycle with gears—the same basic
design that is used today.

When a large gear at the front wheel is
connected to a small gear at the back, the bike
is in high gear. The wheel will turn several times
for each rotation of the pedals. This is ideal for
speeding along a flat surface or racing downhill.

26
The main picture shows a BMX bike. What does BMX stand for?

Pedal power
Handlebars These are used
to control the front wheel.
Moving the handlebars lets you
change direction and also helps
you keep your balance as you
cycle along. Handlebars are
levers, and the longer they are,
the easier they are to turn.

Brakes When you squeeze the brake
lever on the handlebars, it pulls a cable
that’s connected to brake shoes on
either side of the wheel. The rubber
shoes grip onto the wheel like a clamp.
This creates friction against the wheel,
slowing it down.

Bike types

Utility bikes are used for everyday
cycling. A chain guard stops the oily
chain from getting your clothes dirty, and
bags can sit safely in the front basket.
Frame Most modern
bikes have a “diamond”
frame—a shape made
up of two triangles of
hollow steel, which is
light but strong.

Mountain bikes have
a strong frame and
wide tires for extra grip
on rough ground.

Pedals These turn the
up-and-down motion of
your legs into the circular
movement of the wheels.

Tires Patterns called
treads on the tires
increase friction between
the bike wheel and the
road surface, so that the
bike is easy to control
and keeps a good grip,
even in rainy conditions.

Wheels The spokes near the top
of each wheel carry the weight
of the bike and rider.

ir
e
w

d or what
?

The world’s longest
true bicycle (one with
just two wheels) was
built in The Netherlands
in 2002. It was 92¼ ft
(28.1 m) long!

Track-racing bikes are designed for
speed. The rider must bend low to hold
the handlebars, making a streamlined
shape. These bikes have no brakes!

Recumbent bikes have frames that
make the rider lean back in their seat.
Some have covers, too. They can be
tricky to ride, but can go very fast.

27

Bicycle Motocross, a sport based on motocycle racing (”motocross”).

Getting around

Holding
the road
Why do trucks and tractors
need such big wheels? It’s
to help them get a grip on
slippery surfaces and move
easily while pulling loads.

Sticking to the surface
Heavy vehicles need big tires to help spread
the weight of the truck and its load. It is the
tires that move the vehicle, using friction. As
the tires press down and backward on the
road, the road pushes the vehicle forward.
Losing your grip
This car’s wheels can’t get
enough grip to move. Mud is
wet and slimy and does not
have any snags and bumps
to provide friction. The car’s
wheels are too small and
smooth to provide enough
surface area to reduce the
pressure of the heavy
weight of the car
on the ground.

28

Tractors overcome this
problem by having
wide tires with
deep treads
that provide
a better grip.

Tractor

Car

How big is the world’s largest tire?

The sloping ridges
push mud out from
under the tire.

Holding the road
Monster trucks
What do you get if you put
the body of a pickup truck
on a bus axle? The answer
is a monster truck.
Add some tractor
wheels and a good
suspension system
and you can
bounce over
anything.

Smoothing out the bumps
When you hit a bump in the
road your wheels move up and
down. The suspension system is
designed to absorb the impact
through the tires, springs, and
shock absorbers.

Inside the shock absorber is
a piston that pushes against
a gas. The gas slows the
piston down and turns its
energy into heat.

Spring

Crosssection

Shock
absorber

Tire

Tires
Tires are left slightly soft so they
can squash over small bumps
without moving up and down.

Springs
There is a spring around each shock
absorber that reduces the impact by
squeezing and stretching.

Shock absorbers
These are pumps filled with gas
that absorb the energy of the wheel
hitting the ground.

29

It measures 13 ft (4 m) across and weighs 8 tons (7.3 metric tons).

Getting around

Piston power
Many forms of transportation use
wheels, which push against the ground
and use friction to move. But what
makes the wheels turn?
Up and down, around and around
To ride a bike, you move your legs up and
down on the pedals. The pedals turn cranks
around and around to turn the wheels.
A car’s wheels move in a similar way.
Cylinder

Gear
Crank

Pistons

Pedal

Crankshaft
Cranks

Rear-wheel drive
A bike’s cranks turn a chain that is connected
to the back wheel, so when you pedal, you are
actually only powering one wheel. Many bikes
have gears to make pedaling easier.

Types of engine
Different vehicles
have different
numbers of cylinders.
Generally, the larger
the vehicle, the more
they have.

30

A lawnmower has only one
cylinder (so only one piston
going up and down to turn
the wheels).

A car has pistons rather than
pedals to move the cranks.

This motorcycle has two
large cylinders. Their slow
up-and-down motion gives
the Harley its distinctive
sound. Thump! Thump!

Lawnmower

What is a “four-wheel drive” car?

Harley Davidson

Piston power
Secret cylinders

d by its back w
forwar
heel
s.

is

There is a row of metal pistons
hidden deep in a car’s engine.
The pistons pump up and
en
v
i
down, just like your
dr
feet on a bike.
,

4

et

h

lik

Start at 1 to see
how the pistons
power the
wheels.

ik e
b
e

i
Th

,
r
a
sc

2

Axle
Axle

Car pistons are also
attached to levers called
cranks. These turn the
crankshaft.

Pistons
The pistons pump up
and down like legs.

1

Driveshaft

Gearbox

Rotation relay
The pistons are
connected to the crankshaft. The crankshaft is
connected to the driveshaft. The driveshaft is connected
to the axles, and the wheels go around and around...

Formula 1 car

This huge cargo
ship is five stories
high and weighs
over 2,750 tons
(2,500 metric tons).
It has 14 cylinders,
each one bigger
than a person.

3

The crankshaft turns
the driveshaft
through the gearbox.

Crankshaft

A Formula 1 race car needs an
extremely fast and powerful engine.
It has 8 cylinders.

The driveshaft turns the
wheel axles and the wheel
axles turn the wheels.

Become
an expert...
on internal
combustion engines,
32–33
on racing cars,
34–35

Emma Maersk

31

When the pistons are connected to all four wheels of the car so they all turn.

Getting around

Engines of fire
Cars, and other vehicles, must
burn fuel to release the energy
needed to move. This happens
inside an “internal combustion
engine”—an engine that is
powered by lots of little fires.

Recipe for fire:

Fuel + oxygen + a spark = fire.

What makes it burn?
Fuels such as gasoline and diesel burn
easily. All they need are a spark and
oxygen. Oxygen is found in the air.

Exploding with power
At normal speed, a car’s engine lights
around 50 little fires every second.
The fires make pistons shoot up and
down, with four “strokes” for every
fire—suck, squeeze, bang, and blow.

Air is sucked in
through this valve.

2

1
Suck
The piston moves
down, sucking in air
through a valve. A
tiny squirt of
gasoline is injected
into the air at the
same time.

Crankshaft turns

32

Air and gas

Squeeze
The valve that lets in
the air at the top
closes, trapping
everything inside.
The piston moves up,
squeezing the air and
gasoline tightly
together.
The crankshaft
turns around, pushing
the piston up.

What actually is fire?

Engines of fire
The cylinders
The combustion (burning)
happens in an engine’s
cylinders. The energy let
off by each tiny explosion
is directed to the pistons
and causes them to move
up and down. This drives
the crankshaft around
and around, turning the
wheels (see pages 30-31).

The pistons are found
deep in the engine, fitting
snugly into hollow
cylinders.

Fuel burns inside
the cylinders.
These valves
let air and
gasoline in.

Cylinder

Piston

Crankshaft

3
Bang

The spark plug
releases a spark
into the mix—
BANG!

When the piston
reaches the top, a
carefully timed spark
sets fire to the
gasoline. The gasoline
burns very quickly,
forcing the piston
back down.

4
Blow
Finally, the piston
moves back up
and pushes the
burned gases out
of the outlet valve.
These gases leave
the car through the
exhaust.

Waste gases blow
out of this valve,
on the way to the
exhaust pipe.

33

It’s a high-speed chemical reaction that produces heat and light.

Getting around

Race cars
Formula 1 cars are like normal cars in
many ways. They have gas engines,
gears, and steering wheels. However,
they are built with only one thing in
mind, and that’s WINNING RACES!
A technical masterpiece
Every bit of a Formula 1 (F1) car is light and
very strong. At its peak speed of 225 mph
(360 kph) air flows over it with the
force of a tornado, so it is as low and
streamlined as possible.

Pit-stop pressure
At pit stops, a driver refuels
and gets new tires. This is
all done in about 30 seconds.
That’s about the same amount
of time as it takes to read this
paragraph!
The car’s spoilers create a
downward force that stops the car
from taking off at high speed.

Even the driver’s helmet is
part of the streamlining.

The blue arrows show
how air flows over
the car as it races.

34

What is the minimum weight of a Formula 1 race car?

Race cars
G-force

The car accelerates

A Formula 1 driver is shoved around
violently inside his car as it twists
around the track. A pushing force
called g-force, which can be up to six
times more powerful than gravity,
shoves him backward, forward, and
sideways as he races. You see g-force
at work in a normal car by watching
water sloshing in a cup.

Water spills out backward.

The car brakes

Water spills out forward.

The car turns right

This driver’s helmet
is attached to his
seat to stop his
head from swinging
around because
of g-force.

Water spills out to the left.

The car turns left

Inertia
G-force is caused by inertia. The law of inertia
says that moving objects try to travel straight at
a constant speed. When a car stops abruptly,
your body tries to keep going forward.

Water spills out to the right.

Label

Steering wheel
Because an F1 driver is
concentrating so hard on
winning a race and
because the space he is
in is so tight, all the
controls for the car
are on hand on his
steering wheel. He
has just two foot
pedals—the brake
and the accelerator.
These buttons fulfill all the driver’s
needs, from traction control to drinks
dispenser—drinks are pumped by tube
straight into the driver’s mouth. He
doesn’t worry about spilling HIS drink!

35

Including the driver, the minimum weight is 1,300 lb (600 kg).

Getting around

80 90 100
70
110
0
6
120
50
130
40

140
H 150
MP

30
20

10

Up to speed
Once you’re on the move, you naturally
want to go as fast as you can. But what
makes sports cars really fast and tankers
really slow? Speed isn’t just about raw
power—other factors are at work.

Speed, velocity, and
acceleration

Acceleration isn’t just
speeding up. Scientists also
use it to describe all
changes in velocity, like
slowing down and even
changing direction.

You measure speed by
dividing the distance
traveled by the time
it takes. Speed is
not the same as
velocity, which is a
measure of how fast
you are going in a
particular direction.
You feel acceleration
when you pedal your bike
really hard. Acceleration
measures how quickly your
velocity is changing.

Horsepower?
Engine power is still measured using a very old unit—the horsepower. It is
based on how many horses would be needed to provide the same amount
of pulling power. An average mid-sized car is equivalent to 135 horses.

36

How fast are electric cars?

Up to speed
Pulling power
If you have a powerful engine
you can accelerate very fast,
which is why a sports car will
always beat a lawnmower. But
if you give a ride to an elephant
your acceleration will suffer.
That is because it takes more
force to speed up heavy objects.
Milk tanker vs. Ariel Atom
Both have a 300 horsepower engine. A
full tanker can weigh as much as
110 tons (100 metric tons). The Atom
weighs half a ton. Even though they
have the same pulling power, the
weight of the milk means the tanker
takes 35 seconds to accelerate from
0 to 60 mph (97 km/h). The Atom
can do it in 2.7 seconds, making
it one of the fastest accelerating
road cars in the world.

Not such a drag
Nothing accelerates as fast as a dragster—not even the space shuttle.
Dragsters can go from 0 to 330 mph (530 km/h) in less than 4.5 seconds. They
use nitromethane as fuel, which provides twice as much power
as gas. The rear wheels have to be really big to
transfer the high power made by the enigne.

Superfast cars
If you want to go really fast and break records, then there’s only one solution—strap a
jet engine or two to your chassis. Jet engines don’t use pistons. Instead, they suck air
through the front of the engine, use it to burn fuel, and then blast the hot exhaust out
of the back. This pushes the car forward at speeds of up to 760 mph (1,230 km/h).

37

The Tesla Roadster can reach speeds of 130 mph (210 km/h).

Getting around

Powering up
Most cars are powered by gasoline
engines, but there are many other
ways to power a vehicle. In the future,
renewable forms of power that don’t
depend on fossil fuels such as gasoline
will become more important.
Solar car
The solar panels on a solar car use
sunlight to generate electricity.
The electricity powers an
Solar cars work best
electric motor that turns the
in very sunny places.
They tend to be flat
wheels. Solar cars are not
and very wide or long
to create room for the
powerful and so must be
large solar panels on
the roof.
very light and streamlined.

Electric car
Electric cars carry energy in
rechargeable batteries instead
of gas. The battery releases
energy as electricity, which
drives a motor that turns the
wheels. One problem is that
recharging can take hours.

The curved front and
flat body make the
car streamlined,
which reduces its
energy needs.

Electric motor

A solar panel is made
of lots of separate
units called cells.

38

When did the hybrid car go on sale?

Powering up
Biofuel
Many ordinary cars can run
on biofuels—fuels made from
plants. Biodiesel, for instance,
is a biofuel made from
vegetable oil. In some
countries, including Brazil
and the US, gasoline is diluted
with alcohol made from corn
or sugarcane. Using biofuels
reduces pollution, but biofuels
can harm the environment
because growing them uses
vast areas of land.

Corn is mixed with water
and left to ferment.

The sugar turns to alcohol,
which is added to gas.

Hydrogen power
Hydrogen-powered vehicles use liquid
hydrogen as a fuel instead of
gasoline. The hydrogen flows into a
device called a fuel cell, which
combines hydrogen with oxygen from
the air to make water and electricity.
The electricity drives the car’s motor
and wheels, just as in an electric car.

Fuel tank
Battery

Hybrid car

Gas engine. In some
hybrids, the engine
drives the wheels, but
in others it merely
charges the batteries.

Hybrid cars
Hybrid cars are powered by
a combination of gas and
electricity from batteries.
When the car stops, the
brakes capture energy and
use it to charge the batteries.
A computer switches between
the two forms of power to
make the best use of energy.

Electric motor

Air car
The air car works a bit like
a balloon. High pressure air
is stored in an air tank and
released through a valve
when the driver pushes the
accelerator. The jet of air
turns the engine.

39

In 1917.

Getting around

Trains and tracks
Most countries have a railroad system
where trains travel on steel tracks.
Trains are often powered by electricity
that runs through rails or cables.

This train’s cars
tilt to help it travel around
corners at high speed.

Diesel electric
Some electric trains
run on diesel fuel.
The diesel is burned
to make electricity.
This electricity
powers the motors
that make the
wheels turn and
the train move.

Engine and
generator unit

Electric third rail
Other trains use an electrified third rail. The train
picks up the electricity using a device called a shoe.

Most freight trains are
powered by diesel electrics.

Train
wheel

Shoe
Electrified
rails are
dangerous! You
can be killed if you
step on the third rail.

Overhead cables
There are trains that take electricity from overhead cables using
a metal arm. The cables carry high-voltage
electricity—around 25,000 volts.

The train’s metal arm is called
a pantograph.

40

What color lights do signals use?

Trains and tracks
Train travel

Signals
Signals tell the train
driver when it is safe
to move forward,
when to proceed
carefully to the next
section of track, and
when to stop.
You need wheels
Trains have metal wheels
with a rim, called a flange,
on the inside to stop them
slipping off the track. Usually
the flanges never touch the
rails, but if they do you hear
a squealing noise.

Trains are the most
efficient way to move
people and goods.
Freight trains carry
goods and can be more
than 4 miles (7 km) long.
Bullet trains in Japan
provided the world’s first
high-speed rail service.

Wheels are slightly
cone shaped.
Flanges

The French TGV is the
fastest train ever built. It
can go at 322 mph (515 km/h).
Rails

Eurostar travels between
England and France through
the Channel Tunnel.

Wheel centrally
placed on rail.

The Trans-Siberian Express
makes the longest trip—
5,857 miles (9,297 km).

Straight track

On the tracks
Railroad tracks guide trains from station to station. They
are made of steel and usually welded together to give a
smooth ride. Some rails are moveable. These are called
points. They help the train switch from one track to another.

The Qinghai–Tibet
railroad is the highest
anywhere—passengers
need to carry oxygen.

B

A
Points

C

The rail sits in
metal tie plates
that are bolted
onto the ties.

The rail is joined
to ties, which keep
the two rails the
right distance apart.

The track is laid on
ballast made from
broken stone.

Brakes
Metal wheels can slip
when the train engineer
brakes on icy rails. So
a small amount of sand is
dropped in front of them
to help them grip the rail.

Red, yellow, and green, like traffic lights.

Points

41

Gases and liquids

Gases and
liquids

Gas molecule

Air and water are
important examples
of two types of
substance—liquids
and gases. They behave
in different ways.

Gas
Air is a gas. The molecules in
a gas have a lot of energy and are
always moving and colliding. This
movement means they will fill up any
container you put them in. If there is
no container they will spread out as
far as possible. Because there is a
lot of empty space between gas
molecules, gases can be
squashed into small
spaces.

What’s a molecule?
Liquids and gases are made
of molecules. Molecules are so
tiny you can’t see them with
the naked eye. Molecules are
made of even tinier particles
called atoms. Everything in the
universe is made from atoms.

carbon dioxide

Feel the breeze
You can feel air molecules
moving when the wind blows.
Wind is simply air molecules
being pushed by a force we
call pressure.

42

oxygen

oxygen

carbon

oxygen

Air molecules
Air is made up of lots of
different atoms bonded
together in groups called
molecules. The main
molecules in air are nitrogen,
oxygen, and carbon dioxide.

nitrogen

What do we call materials in which the atoms cannot move?

Gases and liquids
Curiosity quiz
Scientists call
water molecules
H2O (H stands for
hydrogen and
O stands for
oxygen).

Look through the “Gases
and liquids” pages and
see if you can identify
the picture clues below.

Liquid

Liquids always take on the
shape of their container. The
molecules in a liquid are closer
together than in a gas, but have less
energy to move around. Special
forces hold the liquid molecules
together. It is very difficult to
squash a liquid into a
Water
smaller space.
molecule

oxygen

Solids.

hydrogen

Water molecules
Water molecules are
made of two hydrogen
atoms bonded to one
oxygen atom. Water
molecules are so sticky
they clump together to
form drops.

Become
an expert...
on how ships float,
46–47
on how airplanes
fly, 52–53

43

Gases and liquids

How fluids work
Gases (such as air) and liquids
(such as water) are known as
“fluids.” This is because they move
in a similar way and can flow
around corners and fill containers.
Fluid motion
Fluids flow smoothly
over curved
(streamlined) objects.
They do not flow
smoothly over shapes
that have corners and
bumps. These slow
fluids down, causing
a force called drag.

Smooth sides mean a fluid only has to
travel a short distance around an object.
This produces little or no drag.

Smooth
shape

Fluid flow

Block shapes with flat edges split the
fluid’s flow into different streams. Some
pass over an object. Some pass around it.
Others twist and turn back, creating areas
of drag known as eddies.

Fluid flow

Sir Isaac Newton
discovered gravity
when an apple fell
from a tree.

44

Streamlined car
A car is designed to be as
streamlined as possible, so air
can pass over it smoothly.

Block
shape

Eddy

Gravity and weight
Gravity is the force that keeps you
stuck to the ground. It also keeps
the Moon in orbit around the Earth,
and keeps the Earth traveling
around the Sun. Gravity gives
everything weight. Without it you
would simply float away as if you
were in space.

What is more dense—water or air?

How fluids work
How dense?
The weight of an object also depends
on its mass—the amount of tiny
particles (called atoms) it contains.
Some substances pack more atoms
into a space than others. The more
closely packed the atoms are, the
more dense the substance is. All
substances have different densities.

A kilogram (2 1/5 lb) of
bricks weighs the same as
a kilogram of oranges, but
the oranges take up more
space. Because the mass
of the bricks is packed into
a smaller space, we say
the bricks have a higher
density than the oranges.

Moving through fluids
When objects move through a fluid they either float or sink, depending
on their density.
An object will float in air if it is less
dense than air.

An object will float in water if it is less
dense than water.

The gas inside the balloon is lighter than
the air around it, so it rises slowly.

Boats float because they are mainly filled
with air, which is less dense than water.

An object will sink in air if it is more
dense than air.

An object will sink in water if it is more
dense than water.

Apples are denser than air so they drop
from trees.

Brick molecules are very close together,
making bricks dense, so they sink.

45

Water is 1,000 times more dense than air.

Gases and liquids

Float that boat
How do ships float, and why
do they sometimes sink? It’s
all about buoyancy.
Setting sail
A ship is very heavy, especially when
it’s loaded with crew, passengers, and
cargo. But the ship still floats because as
it pushes down, it displaces water, and
the displaced water pushes upward.
If the ship weighs less than the
displaced water, it will
float. (See page 45.)

Floating beach ball

Buoyancy
When an object
weighs less than the
amount of water it
displaces, it floats (or
is “buoyant”). If it
weighs more, it sinks.

The weight of the ship is
spread out across the hull.

Gravity
Balancing act
While buoyancy pushes the
boat upward, gravity pulls it
downward. These two forces
balance each other out, so a
ship can float on the water.

46

Buoyancy

What’s the longest ship in the world?

Sinking
golf ball

If one compartment starts to
leak, the bulkheads stop the
water from flooding the ship.

Bulkheads

Safety systems
A ship may sink if it takes
on water. To prevent this,
ships have safety features
such as bulkheads—walls
that divide large areas into
smaller ones.

Double hull
A big ship usually
has a double hull,
which is like a tire
with an inner tube. It
gives extra protection
if the ship collides with
rocks or icebergs.

Hull

Double hull

The steel hull is full of air,
which is very light and keeps
the ship afloat.

That sinking feeling
The air inside a ship’s hull
makes the ship less dense
than the water around it.
If the ship hits a rock and
rips a hole in its hull, water
pours in and replaces the
air. This makes the ship
more dense and it sinks.

Float that boat
Going down
Submarines
are not like
other boats—
they have to
be able to sink or float
on command. They do this
by filling and emptying
their ballast tanks with
air or water.
Periscope
The weight of a
submarine’s hull Compressed
helps it to sink, air tank
Valve
but it can’t sink when
there is air in the ballast
tanks. Most of the air is
let out through a valve.
Some air is compressed
Interior
(squashed) into a small
holding tank. Water is
then pumped into the
tanks and the sub sinks.
Ballast
Water is
tank
taken in

1

2

Air flows
into the
ballast tanks.

When the sub is
underwater, air is pumped
back into the ballast tanks
until the density of the sub
matches that of the water
around it. The sub can
stay at one level as it
moves through the water.

Water is forced out.
When it’s time
to surface, more
air is pumped
into the tanks, pushing
the water out. Once it’s
at the surface, air is
sucked in to fill the ballast
tanks and the sub floats.

3

This ship is taking on water
and has started to sink.

and the
sub sinks.

Air fills the
tanks and
the sub rises.

Water is forced out.

47

An oil tanker called Knock Nevis. It’s 1,504 ft (458.4 m) long.

Gases and liquids

Floating balloons
Why do some balloons rise up into the
air and others drop to the floor? To
understand this you have
to look at the gases
inside them.
alloons
b
y
t
ar
a
He

wit
h he
l
i
u
m

Helium
This balloon is
filled with a gas
called helium.
Helium is lighter
than air, so this
balloon floats.

d
fille
re

P

An airship can rise over 6,500 feet
(2,000 meters). That’s lower than an
airplane’s usual cruising height of
29,000 feet (8,800 meters).

g
a
s.
At parties, helium
balloons are tied
down so they
don’t float off!

48

Heavy air
When a balloon is
filled with a gas that
is lighter than air it
floats. When it is
filled with a gas that
is heavier than air,
it sinks.
CO2

Carbon dioxide
When you breathe out (into a
balloon) the air contains more
carbon dioxide than normal
air, making it heavier. So a
balloon you blow up with
your breath will sink.

Helium facts
Helium gas has no
smell. It makes up about
7 percent of natural gas.
Deep-sea divers breathe
in a mixture of helium and
oxygen.
Helium boils at a very
low temperature, -452˚F
(-269˚C), and turns to gas.
Helium, found in stars, is
named after the Greek word
for the Sun—helios.
Liquid helium is colorless,
and very cold. It helps
launch space rockets.

What is the only element to be discovered in space before it was found on Earth?

Floating balloons
Flying ships of air
An airship is known as a lighter-than-air
(LTA) craft. Airships have a main heliumfilled balloon and two other large internal
balloons called ballonets. To control how
high an airship floats, the ballonets take in
or release air.

How airships rise and fall
Airship
rising

Ballonets deflate
to go higher

Air expelled
through air
valves

To rise, the ballonets are closed
and deflated. The helium makes
the airship float upward.

Cold air weighs
more because
its molecules
are closer
together.

Hot air is
lighter
because its
molecules are
farther apart.

The balloon
holds the hot
air. Its shape
makes it hard
for the hot air
to escape.

Skirt
Propane tanks

Helium.

How hot-air balloons work
Hot-air balloons float upward
when the air inside them is
heated. This gives the air
molecules more energy and
they move farther apart,
which makes the air lighter.

Airship
falling

Helium

Air inflating
ballonets

Air taken in
filling the
ballonets

To descend back down to Earth,
the ballonets are filled with the
heavier air, making the airship sink.

A flap at the top of
the balloon allows hot
air to escape and
controls how quickly
the balloon sinks.

Fabric panels are sewn
together sideways and
lengthwise to give the
balloon strength.
Burners use propane
gas to produce a hot
flame, which heats the
air inside the balloon.

49

Gases and liquids

Roller coaster

These rip-roaring rides are powered
by gravity itself. They slingshot
thrill-seeking passengers along
at breathtaking speeds.
Going up...

Over the top
At the top of a hill,
roller-coaster cars have
high potential energy.
This becomes kinetic
energy as the
roller coaster rolls
down the slope.
arg

hhh

As the roller coaster goes
up the first, tallest hill
(called the lift hill), it’s
gradually building
up potential energy.

There is maximum
potential energy at
the top of the hill.

Some older roller coasters run on intricate
wooden scaffolding.

Rushing down a steep
slope can make you
feel almost weightless,
which may be quite
uncomfortable!

Chain reaction
Roller-coaster cars don’t
have motors. They’re
pulled to the top of the
first hill by a chain
connected to a motor
at the top.

50

Where was the world’s first roller coaster?

The cars gain speed
as they roll down
the hill.

Roller coaster
Wheeeeeeee!
Lots of different things
affect the way you feel
when you’re whizzing
around a roller coaster.

Flexible metal
The tracks and supports
of most roller coasters are
made from hollow steel.
This can be shaped into
loops and corkscrews.

Shoulder
harness

Acceleration force
Apparent weight
Gravity (weight)

Safety first
All riders are protected by a
safety harness. Brakes are built
into the track, not the cars—
they are used at the end
of the ride, or in emergencies.
After coming down the
first hill, the cars have
enough speed to send them
around the next loop. This
creates “g-force,” which
makes the passengers
feel much heavier.

Cars lose momentum
throughout the ride,
so the hills have to
get smaller.
There is maximum
kinetic energy at the
bottom of the hill.

Focus the force
The roller coaster track acts as a channel for
gravity. When the track slopes down, the
car fronts go faster—when it tilts up, the
car backs are pulled
down, and they
go slower.

Ultimate experience
Thrill seekers in Florida can enjoy the new
Rip Ride Rockit roller coaster. It’s very short
and powerful, so it can pivot like a
skateboard and climb straight uphill.
Passengers can choose
the music they hear
while they’re terrified.

Steel track
Load wheels
Guide wheels
Upstop wheels
Roller-coaster cars are
clamped securely to the
rails by three sets of wheels.

51

The very first coaster was an elaborate ice slide built in Russia during the 1600s.

Gases and liquids

How do planes fly?
Hugge,, heavy
y machines seem to defy
y gravity
y by
y stay
yingg up
p
in the air! Yet airplanes fly around the world every day.
It’s because they
y can create the forces they
y need to fly.
The forces of flight
“Aerodynamics” means “the way air moves.” There
are four aerodynamic forces—thrust and drag, and
lift and weight. Airplanes need to
balance them out in order to fly.
Thrusting forward
Planes need to create
thrust to balance out
drag. This plane has
a propeller to create
thrust. As the
propeller turns, it
draws air past the
blades, pulling the
plane forward.

Engine

Thrust

Level of plane

Cooler air

52

Cockpit

Warmer air rises
faster, “bumping”
the plane upward

Propeller

A bumpy ride
Just like boats bounce
over waves, planes
can bounce up and
down in the air.
Called turbulence,
this happens when
pockets of air move
at different speeds.
It can be caused by
strong winds, storms,
or when cold and
warm air meet.

The biggest jumbo
The world’s largest plane is the
Airbus A380. At 239½ ft (73 m)
long, this jumbo jet can carry up
to 853 passengers. It’s 10 times
longer than the four-seater
Cessna 400.
Cessna 400
Airbus A380

What was the first airplane to stay up in the air successfully?

How do planes fly?
Lifting up
Lift is the opposite force
to weight. A plane
creates most of its lift
with its wings.
Lift

As the plane moves,
air flows over its
wings. The top of
the wing is curved,
making the air
above the wing
move faster than the
air under the wing.

What does that part do?
Every part of a plane has a
job to do, from the streamlined
nose to the tail fin that keeps
the plane steady in the sky.
Flaps that come down from the
wings are used to increase lift
during takeoff and landing.

The slow-moving air
under the wing pushes
up more than the
fast-moving air above
the wing pushes down.
This creates lift.

Airflow

Ailerons on the back edge
of the wings are used to
“roll” the plane, to make it
turn or keep it level.

Tail fin
Aileron

Fuselage

Rudder

Weight

Wing

Flap

Elevator

A rudder in the plane’s tail turns
the plane left or right.

Drag

Weighing down
Weight is caused by
gravity pulling down on
an object. Everything
has weight, even air.
The Airbus A380 needs
to create a lot of lift to
balance out its weight—
it’s a whopping 617 tons
(560 metric tons).

Dragging back
Drag is the opposite force
from thrust—it slows things
down. Imagine trailing your
hand in water as you sail
along in a boat. You can feel
the water push back, or
drag, against your hand. Air
has the same effect on planes
(and anything else that
moves). A plane’s smooth
surface and streamlined
shape help to reduce drag.

Elevators in the tail move up and
down to balance the position of
the nose, keeping the plane level.

53

The Wright Flyer. On its first outing in 1903, it flew for 12 seconds!

Gases and liquids

Blastoff!
Nose cone

Space is the final frontier. So far,
man has explored only a tiny part
of our galaxy, and this has
been very difficult, dangerous,
and expensive to do.

Command module
Service module
Rocket stage containing lunar
module
Instrument unit
Rocket stage
containing fuel

What makes rockets go?

Engine

Most rockets need two different
chemicals: a fuel and an oxidizer.
When they’re mixed together, they
cause a fierce but smooth burn—this is
funneled downward, propelling the rocket
up. Clamps hold it down while the power
builds, so it doesn’t go end over end and
crash. At the word “blastoff,” the
clamps are removed and the rocket is on
its way. Good luck!

Rocket stage
containing fuel

Engines

Gravity

Thrust

Rocket stage

54

When the Apollo lunar-mission
crew returned to Earth, they
landed in the Pacific Ocean and
were rescued by Navy personnel.

When was the first liquid-fueled rocket made?

Blastoff!
Shuttle spacecraft
have a winged
orbiter, a huge
fuel tank
underneath, and
two rocket
boosters that
send them into
orbit.

Space journey
After rockets are launched, they use huge amounts
of fuel to get into Earth’s orbit. They then release
several rocket stages containing fuel so that only
the much smaller capsule actually goes into orbit.

Or

bit

3
The engines have
boosted the capsule
into orbit.

2
As the fuel is
used up, the
fuel tanks are
released.

Rocket blasts
off from
launch pad.

Command module
parachutes into
the ocean.

1

7

Command
module positions
itself to reenter
Earth’s atmosphere.

5
Command module
separates from
service module.

Space junk
Experts believe there are more
than 150,000 objects orbiting the
Earth—pieces off satellites, bags of
garbage, and dropped tools.

March 1926, by Dr. Robert H. Goddard in Massachusetts.

6

4
Capsule circles
the Earth in
orbit.

55

What is energy?

What is energy?
Energy is what makes everything happen. It is involved in
every action that we make. It powers your muscles, runs
your car, and lights your home. Without energy you could
not ride a bike, watch television, or fly in an airplane.
Different types of energy
Energy can’t be made, just changed from one type
to another. Here are some of the main types.
Light
is a form of energy that we can see.
Most of the energy on Earth comes
from the Sun as light.

Heat energy
is the energy of atoms or molecules
vibrating. The hotter an object
gets, the faster and more violently
the atoms or molecules vibrate.

Atoms vibrate
as they get hotter.

Nuclear energy
is stored in atoms. Nuclear energy is
used to run power plants that
generate electricity.

Electromagnetic energy
is carried by X-rays, radio
waves, and microwaves.

56

Everything is made up of atoms—but what are they?

What is energy?
Curiosity quiz
Look through the “What
is energy?” pages and
see if you can identify
the picture clues below.

Gravitational energy
is the stored energy in an object that has been lifted but is
not allowed to fall. Dams can turn gravitational energy
into electrical energy.
Kinetic energy
is the energy a moving object has.
The faster a car moves, the more
kinetic energy
it has.

Electrical energy
can travel easily
through wires. It
is the energy we
use to power
devices in our
homes.

Become
an expert...
on power plants,
pages 62–63
on gravity,
pages 44–45

57

The smallest particles that something can be broken down into.

What is energy?

It’s electric!
If you flip a switch to make something
work, it probably runs on electricity.
Most of the energy we use every day
is electric.
What is electricity?

W Electrical energy

This magical power source comes
from electrons—tiny charged
particles on the outside of atoms.
They move from atom to atom
creating electrical energy, and this
energy travels on a circuit.

travels very quickly, at
125,000 miles (200,000
km) per second. That’s
two-thirds as fast as the
fastest thing ever—
light!

Electric sockets are live. You
should never put your finger
or an object (other than a
plug) into a socket—you
might get an electric shock.

Electricity passes freely
from the socket to the
lamp through the wiring.

Electrons

Starting small
To understand electricity, you
have to look at the teeny tiny
building blocks that everything
is made from—atoms.

or wha
t
?

d
e ir

Plugs have
metal prongs
that connect
with the power
supply wired
into the wall.

r
car

Atom

n
ya

Elect

Electrons

ricity
flow
y
s wa
s thi

58

ele

c tr
ical
charge.

Electricity is passed along
wires by electrons. When you
supply energy to the wire, it
makes the electrons move
along it, carrying electric
charge with them.

Who made the first battery?

When you
switch on a lamp,
electric current
flows along the
flex to the bulb,
lighting it up.

It’s electric!
Electricity

Simple circuit
A flashlight works using a simple electrical circuit.
Batteries produce electricity, which flows around
the circuit to power the bulb so it lights up.

When we talk about
electricity, we use the
same words over and
over again.

When the switch is on
“off,” the circuit is broken
and the bulb goes out.

Lamp filament

Conductor—a material
that allows electricity to
flow through it easily.

Broken
circuit

Circuit—a path that an
electrical current can
flow along.

Plastic
case

On

Off

Batteries

To turn off the
flashlight the
circuit is broken.

A

Ampere—a basic unit of
electrical current.
Current—a flow of
electricity through a
conductor.

Power masts
Electricity travels from power
plants along thick cables often
strung between big metal towers.
The cables carry very high levels of
electricity—enough to kill an adult
man if they fell on him.

Slide switch

When the switch slides to
“on,” the circuit is complete
and current flows all the way
to the bulb, which lights up.

V

Voltage—a measure
of electrical strength.

Off

Metal switch
contacts

Metal spring

Electricity flows from the batteries
and along the metal wire.

Birds don’t complete an electrical
circuit with the ground like people
do, so they can sit on cables
without being harmed.

59

An Italian named Alessandro Volta made the first battery in 1800.

What is energy?

The power of magnets
BEWARE:

Magnets create an invisible force known as
magnetism that repels and attracts certain
substances, like iron. Electricity and
!
magnetism have a close relationship.

ELECTRICAL CHARGE

Can you field the force?
A magnetic field is the
space around a magnet
where its force can be felt.
The force gets weaker as
the field gets farther from
the magnet. It is strongest
at the two poles.

Iron filings reveal the magnetic field around a magnet

Poles

N

S

N

Opposite poles attract

Magnetic Earth

S

The Earth acts like a gigantic
magnet. It has a magnetic north
and south pole, although they
aren’t in the same place as the
geographical poles, but are very
close. Over the Earth’s lifetime
the magnetic poles have
switched around a few times.

Magnets have two points where their field is
strongest, known as poles. Each magnet has
a north and south pole. These can attract
and repel other magnets. Similar poles repel
and opposites attract.

S

Similar poles repel

Super magnets
These are really sticky
magnets. They can be
natural magnets or
electromagnets.
The maglev train uses an
electromagnet.

N
E

N

W
S

S
60

S

A compass uses a
magnet as a “needle.”
The needle is attracted
and points to the
magnetic north pole.

Which elements are attracted to magnets?

Electromagnets
A magnet can produce
electricity and electricity can
create magnetism. An iron
bar can become magnetic
when an electric wire is
wound around it in a coil.
A moving magnet can also
make an electric current in a
coil of wire. Electromagnetic
generators are used to create
electricity at power plants.

The power of magnets
Everyday magnets
Magnets are used in many everyday items,
such as:
Audio speakers use
electromagnets to make
sound vibrations.
Some handbags
close with magnetic
clasps.

Credit cards use a
magnetic strip to store
your information.
Central locking in a
car uses a series of
electromagnets to lock up.

The wheel has to keep turning for
the dynamo to light the bulb.

Wheel power
A simple example of an electromagnetic generator is
a bicycle dynamo. It uses the kinetic energy produced
by the spinning wheel to turn the magnet past a coil
of wire. The movement of the magnetic field produces
enough electric current to light a bicycle light.
Electric current runs up the
wire to power the light bulb.
Wheel

spins

The dynamo turns
as the wheel spins.

The magnet
rotates.
Iron core

Coil of insulated
wire surrounds
the iron core.

Electrical output

rd
wei

or what?

Lodestone is a naturally
occurring magnet thought to
be made when lightning strikes.
In 500 BCE Thales of Miletus
noticed it because the iron
nails in his sandals
stuck to it.

The insulated wire stops the
current from taking a shortcut
from loop to loop and keeps
it flowing around the core.

61

Iron (Fe), Nickel (Ni), and Cobalt (Co) are all attracted to magnets.

What is energy?

Power plants

There are two kinds of energy—
renewable and nonrenewable.
Earth will run out of nonrenewable fuels, but renewable
energy comes from endless
resources such as wind and sun.

In Shanghai, China, vast quantities of coal are loaded
on a conveyor belt.

Burn, burn, burn
Most power plants burn nonrenewable
fossil fuels like coal, oil, and natural gas.
These are formed from fossilized plankton
or plants that lived millions of years ago.
Fossil fuels release energy from these plants
when they’re burned.

Smoke and hot
gases escape from
the chimney.

Heat from burning
coal turns water
in the pipe into
steam. Ash collects
underneath.

The steam drives
the turbine.

Flow of
steam

The turbines produce
electricity by turning a
magnet inside a large
coil of wire.

Cooling
water out

Pump

The steam
passes into
a condenser.
Crushed coal
and hot air

Pump brings
in cooling
water.

Ash
As the steam
condenses to
water, it collects
in this tank.

Flow of water

62

How far does power travel?

Cold water in
the pipe cools
the steam so
it condenses.

Power plants
Dangerous power
Nuclear power plants create energy by splitting uranium
atoms, which release heat to run the generators that
make electricity. Nuclear power is nonrenewable
because there is a limited supply of nuclear fuels. The
waste from these fuels is radioactive, so they may
damage cells and cause cancer.

Green power
Renewable energy sources
will always be there—
and they’re less harmful
to the environment than
fossil fuels.

On April 26, 1986, at
1:23 a.m., Reactor Four
at Chernobyl Nuclear
Power Plant in Ukraine
exploded. Over 20 years
later, an inspector checks
the interior (left).

Solar power comes from
the Sun. In theory, it could
provide all our energy.
Hydroelectric power is
created by falling water,
like a dam or waterfall.

Become
an
expert...

Wind power is generated
by turbines. Lots of them
together make a wind farm.

on renewable
energy,
pages 66-67

Transformer
“steps up” the
voltage.

Tidal power uses water in
the form of waves rather
than waterfalls.
Biofuels (like corn oil) are
made from growing things,
so they’re renewable.

Stretched between
towers, cables carry
high currents.

Power masts are huge
steel towers. They
have extra wires
running along the top
to ground lightning.

Geothermal power comes
from heat deep, deep down
toward the Earth’s core.

Substations reduce
voltage and send power
in different directions.

On the
way...
All over the
world, rows of
masts march across
the landscape. They
support the high-tension
cables that carry electricity
from power plants to homes
and offices.

Electricity is wired
to power points in
your home. It
connects with
equipment through
a plug.

Local grid

Cables below
ground

63

Power can travel up to 300 miles (480 km) to your home.

What is energy?

Running out

What can you do
to save energy?

Most of the energy we use comes
from burning fossil fuels. But these
fuel sources won’t last forever, so we
need to start thinking about how we
can use less energy, and try to find
other ways of providing it.

Turbines in a coal-fired power plant
without their metal covers.

Steam power
Electricity that comes
from coal is relatively
inexpensive to make. In a
machine called a pulverizer,
the coal is broken down into
a fine powder, then burned
in a furnace. The furnace
heats a boiler to produce
steam. The steam powers
turbines that run generators
to create electricity.
Tall pipes are used to
drill oil from the
ocean floor.

Oil and gas
We get oil by drilling
under the ground—
from dry land, or from
the ocean floor. Today,
we use oil for 38
percent of our energy,
either as fuel for
heating, or turned into
gasoline for cars and
planes. Experts think
oil reserves will run
out in about 40 years.

64

Grow your own fruit and
vegetables. Try to eat food
that is produced locally.
Don’t waste heat. Ask
your parents to make sure
your home is insulated.
Save gasoline. When you
can, walk instead of
asking for a ride.
Turn off your television
and computer. Don’t leave
them on standby!
Switch off lights when
you leave a room, and use
energy-saving light bulbs.
Dry laundry outside
instead of using a dryer.

Recycle and reuse items
such as glass, plastic,
and paper.
Oil rig

Oil reservoir

Marine life that
has decayed.

How much oil can the largest oil rig store?

A layer of rock traps the
decaying remains, which
turn into oil.

Running out

rd
i
e
w

Compressed lignite
turns into coal.
Compressed peat
becomes lignite.
Decaying plants
form peat.

Peat is the earliest
stage in the
formation of coal.

Underground gas
Natural gas is also a fossil
fuel. It comes from coal beds,
marshes, bogs, and oil reserves.
The largest reserves of natural
gas are shared between Iran and
Qatar, although Russia is the
world’s biggest gas producer.
Natural gas is likely to run out
in about 100 years. At the
moment, it provides 23 percent
of our energy.

or what
?

In the US, about
half of all the
electricity used comes
from coal-burning
power plants.

Black diamonds
Like diamonds, coal is a form of
carbon. Excavated from the
ground through deep mines or open
pits, it provides 25 percent of the
world’s energy supply. If we
continue digging coal at the
current rate, we have about a 250
years’ supply left in the Earth.

Gas facts
Easily piped into
homes, natural gas is
completely clear and odorless.
When it burns, it releases lots of
energy, which makes it suitable
for use in cooking, heating, and
cooling. It also gives off fewer
harmful substances than
other fossil fuels, so it’s
slightly greener.

65

The Hibernia platform in the Atlantic Ocean can hold 1.3 million barrels of crude oil.

What is energy?

Become
an
expert...

Renewable energy
Energy made from fossil fuels will
eventually run out, but certain
types of energy are renewable,
which means that we can go on
using them forever.

on energy-efficient
homes, 72–73
Anemometer
Low-speed
shaft
Controller

Gear box
The wind
blows the
blades
around.

df

oul

le c

eop

dp

dre

Electricity is wired
to power points in
your home.

High-speed
shaft

un

Blade

eh

Wind farms are where lots of turbines are
installed in a field or in the sea.

Generator

On

Brake

no

it o

Substations divide
power so it can travel
in different directions.

The transformer
sends alternating
currents into
power lines.

Wind power
Wind turbines use the power of moving
air currents to spin their propellers. These
are huge windmill-like blades on top of a
tall tower. As they spin, generators inside
the turbines make electricity, which is
sent via cables underground.
The electricity travels underground
to a transformer station.

When was the first geothermal plant built?

de.

bla

Cables carry high
currents between
masts.

66

ne

Local grid

Wind moves
faster the
higher up
you go from
the ground.
Taller towers
generate
more
electricity.
Underground

Renewable energy

The spillway of a dam
is used to control the
flow of water.

Water from
a reservoir
flows down
a pipe to a
turbine.

Hydroelectric power
A fifth of the world’s electricity comes from
hydroelectric power plants. Usually a dam is
built to trap a river and create a lake. Water is
released at a controlled rate and allowed to
flow through a spinning machine called a
turbine, which drives an electricity generator.
Solar energy
Huge glass panels are put on the
roofs of buildings to capture energy
from the Sun and convert it into
electricity. The stronger
the sunlight, the more
electricity they make.

Electricity
generator

Turbine

Geothermal energy
The Earth’s crust is a hot
place! Some rocks can be as
hot as 1,800 ºF (1,000 ºC).
Geothermal energy uses
the heat from these rocks
to generate electricity
and heat water.

When sunlight lands
on a cell, electrons
are pushed from
one layer to the
other creating an
electric current.

Solar panel
Photovoltaic
cell
Pure silicon doesn’t conduct electricity
well. Each cell contains silicon doped
(made impure) with phosphorus,
which produces free electrons.
Silicon doped with boron makes “holes”
where electrons are missing in the cell.

One of the biggest
geothermal areas in the
world is Iceland. People
can swim next door to
this geothermal plant in
Iceland since the water
is so warm.

Biofuels
Biofuels come from fast-growing crops,
such as corn, sugar cane, and palm oil.
These fuels can add to or replace fossil
fuels such as diesel or gas. Biofuels have
been criticized for taking up land that
could be used to grow food.

67

The first plant was built in 1904 in Ladarello, Italy.

What is energy?

What’s cooking?
The stove is probably the most important
piece of equipment in the kitchen. Without
it, you’d have to eat all your food raw.
The oven
Heat is a form
of energy. It
comes from the
movement of
atoms and
molecules.
The faster the
molecules move
around, the
higher the
temperature.

Inside an electric oven are large coils of wire called
heating elements. These heat up when electricity
travels through them. They are controlled by
a thermostat that keeps
the temperature
inside constant.
On a burner, the
element is in direct
contact with the
saucepan, which
passes the heat
through to
the food.

Dial controlling
the thermostat.

Because the broiler
element is much closer to
the food and gets hotter
than the one in the oven,
the food cooks quickly.

Convection ovens
have fans that blow
air around and keep
the whole oven at the
same temperature.
Food cooks faster in
a convection oven.

The oven works by
surrounding the food
with hot air. Since hot air
rises, the top of the oven
is slightly hotter than the
bottom. When the oven
gets too hot, the
thermostat turns the
heating elements off. It
turns them back on again
when the oven cools.

68

Can you cook ice cream in an oven without melting it?

What’s cooking?
Heat’s effect on food
Heat changes food, and different foods react to it differently.
Cooking is simply delicious experiments in chemistry and physics.
Cooking eggs
Egg whites and yolks are
made of stringy chains of
protein floating in water.

Chains of
protein

Each individual chain
is twisted and curled up.
When you add heat, the
chains uncurl and start
to link together.

Chains of
protein
unravel and
join up.

Baking bread
A basic bread mixture includes
flour, water, and yeast. Yeast
is a live, single-celled fungus.
Flour, when it mixes with
water, releases stretchy gluten.

+

Sweet treats
Many candies are made
by simply adding sugar
to water and heating the
mixture to very high
temperatures.

+

+

Yeast is inactive until it comes
into contact with warm water.
When the bread mix is left in
a warm place, the yeast starts
feeding on the sugars in flour
and releases carbon dioxide gas.

As you cook it, the water
boils away, leaving a much
stronger solution of sugar.
Very strong solutions make
toffee or hard tack candy.

Water
boils out
of the
sugar.

Gas is
released.

The chains form a mesh
that traps the water they
floated in. The egg
is now cooked.

The gumlike gluten fills with
thousands of gas bubbles and
the bread rises. Cooking traps
the bubbles in the bread.

If you stir the mixture as it
cools, it forms crystals. This
is how you make fudge, but
you leave hard candy to set
without stirring.

The chains
form a mesh.

69

Yes, if you make baked Alaska—ice cream covered in meringue.!

What is energy?

Keeping cool
We keep food cool so it stays fresh,
and we keep liquids cool so they’re
refreshing to drink. Electricity
makes all this possible.
45ºF
(7ºC) and
above

Some foods don’t need to be
chilled to stay fresh.

Let cheese
warm up
before you
eat it.

32–45ºF
(0–7ºC)

32ºF
(0ºC) and
below

70

Some treats and
desserts are
served frozen.

Eggs are usually stored in
the refrigerator door,
which is a few degrees
warmer than the shelves.

Room temperature
Dry foods such as beans
and pasta keep very well
at room temperature.
Root vegetables like
potatoes don’t need to
be refrigerated, but they
keep best in a cool
place rather than a
warm one.
Refrigerator
The temperature inside
a refrigerator is cold
enough to slow down
the growth of bacteria
(germs) in our food, so it
stays fresh longer. Dairy
products, meat, and
fish should always be
stored here.
Freezer
Freezers are cold enough
to make your skin freeze!
Bacteria can’t multiply
in these temperatures,
so food stays fresh for
months or even years.
Most foods are thawed
or warmed before you
eat them.

Lettuce and other
salad vegetables go
in the door, or in a
drawer at the bottom
of the refrigerator.

Cool coil
A long coiled
pipe is set into
the refrigerator
walls. Inside is a
gas called
tetrafluoroethane,
which travels
around the fridge
soaking up heat.
This heat travels
to a compressor,
and is then
released at the Gas
coolant
back, which
is why it feels circulating
around
fridge
warm there.

How quickly do bacteria grow at room temperature?

Keeping cool
Adjustable
temperature
control

Warmed
coolant

Compressor

Control
electronics

Compressor

71

In just four hours, one bacterium can turn into more than 1,000!

What is energy?

Energy efficiency
Every home needs energy for heating, lighting, cooking,
and lots of other things. It’s important not to waste this
power—not only because you have to pay for it, but also
because the sources of this power may one day run out.
Eco living

Triple-paned windows have
three panes of glass with a
layer of air between them.
The air stops heat from
escaping, so you need less
energy to heat the house.

The windcatcher
channels air into
the house, providing
ventilation. The
aluminum tubing
reflects light inside.

Sustainable homes are
designed to be better for
the environment. They
have lots of features that
save energy and water.
They produce fewer
carbon emissions and
are also cheaper to run.
The outside of the roof is
covered in photo-voltaic and
solar panels. These generate
electricity for the whole house.

72

The “Lighthouse” is
built with materials
that absorb heat
during the day and
give it out at night.

A biomass boiler burns wood
pellets for heating and hot
water during the winter.

What are carbon emissions?

Energy efficiency
Batteries

In your home
We can all do things to
make our homes more energy
efficient. A lot of energy is used
to heat a house. Ask your
parents to lag your attic with
insulation to keep heat in. You
can also insulate walls and
floors, plug gaps around doors
and windows, and install
double-paned windows.
Thermograms are
pictures that show
hot things as white
and yellow and
cold things as blue.
The hottest part of
this house is its
windows, because
heat is escaping
through them.

When rain hits the roof,
it collects in a gutter and
runs down a pipe into a
recycling tank. The water is
used in a washing machine.

Every household uses
batteries to power all
kinds of things—but
batteries eventually run
out. So how should you
dispose of them?
Change old batteries
right away. Batteries
contain chemicals that may
leak and ruin the gadget.

Insulating a loft

Become
an expert...

Don’t trash batteries.
Recycle them instead—it’s
better for the environment.
Batteries should never
be thrown onto a fire—
they might explode.

on saving energy,
pages 64–65
on renewable energy,
pages 66–67

When things break…
However energy-efficient you are, electrical
goods will eventually wear out. But some
items are simply too dangerous to throw
away. Old refrigerators contain gases that
are harmful if they leak. The safest way to
get rid of a broken refrigerator is to contact
your local recycling center.

Broken fridges
must be taken
apart carefully
so they don’t
release harmful
gases.

Make a difference
If you get a new computer or cell
phone but there’s nothing wrong
with the one you had, you can
donate the old one to charity. Go
online to find charities, schools,
and groups that can make good
use of your unwanted equipment.

73

Gases containing carbon that are released into the air and may cause global warming.

Light and sound

Light and sound

of

What is light?
Light is a type of energy called
electromagnetic radiation, or EMR.
“Electromagnetic” means it’s made up
of electrical and magnetic energy, and
“radiation” means it spreads out from
a source. Atoms—the tiny particles
that make up everything around us—
are that source. Atoms that have too
much energy can get rid of it
in the form of light.

’s
n
u

give out l
s
m
o ts
ato

See the light
Light is made up of different
colors, but light cannot be
seen unless it hits our eyes.
Light travels in straight lines,
but it can change direction.
When light passes through a
prism (usually a threedimensional glass triangle),
it bounces off the sides of
the prism and bends. Some
colors in light bend more
than others, so they spread
out and you can see the
different colors.

Th
e
S

A glass prism splits the light into colors.

Most of what we know about the
world we learn by seeing and hearing.
Everything we see needs light, and
everything we hear involves sound.
They can both reach us by traveling
in waves.
t.
h
lig

The speed of light
Light travels in waves, a bit like waves that travel through
water. Light travels faster than anything else in the universe—
an amazing 186,000 miles per second (300,000 km per second)!
It takes just eight minutes for light from the Sun to reach Earth.

74

What is refraction?

Light doesn’t always behave like a wave.
Sometimes it behaves like it’s made up
of particles, so it spreads out more like
a spray of water from a hose than
waves in the sea.

Secrets of sound

Light and sound
Curiosity quiz

When something vibrates, it
squeezes and stretches the air
around it, sending out waves
that we hear as sound.

Look through the “Light
and sound” pages and
see if you can identify
the picture clues below.

Echolocation
Some animals use sound
to find their way around.
This is called echolocation.
Bats send out high-pitched
squeaks that bounce off their
surroundings. If their echo
comes back quickly, it means
there’s something nearby.

Cymbals make
large waves,
which means
a loud sound!

The speed of sound
Sound travels more slowly than light, at 1,125 ft per second
(343 meters per second) in air. But the speed changes,
depending on what the waves are traveling through.
They can move four times faster in water than in air.
Become

an expert...

on visible light,
pages 76–77
on how ears hear,
pages 90–91

75

Refraction is when light waves bend, such as in a prism.

Light and sound

Now you see it…
Light waves (or electromagnetic
waves) are all different
lengths, but each length
travels at the same speed.
Some light waves are too short
or too long for us to see.
The light we can see is called
“visible spectrum” light.

Blue

Cyan

Green

Red

... And now you don’t
Our eyes can see only light waves of
a certain size—if they’re longer or
shorter, they’re invisible. We use
invisible electromagnetic waves in
our lives every day.

Radio waves

Radio waves carry sound and images
through the air. Radios, televisions, and
cell phones all use radio waves. The longest
radio waves can be 100,000 times longer
than the shortest ones.

76

Light of many colors
Visible light is made up of waves of
different lengths. Each length appears
as a separate color. For example, red
waves are long and blue rays are
short. Light contains an endless
amount of colors. The only limit is
on how well your eye and brain can
tell one wavelength from another.

Microwaves

Microwaves heat water molecules in
food and liquid, but they pass straight
through glass and plastic. So when you
heat soup in a microwave oven, it’s not
the microwaves that make the bowl hot,
it’s the hot soup inside.

What is white light?

Infrared waves

Infrared waves carry heat. We can see
infrared waves with night-vision goggles
or special cameras, both of which are
designed to pick up heat rather than
light. When you get near something hot,
it’s infrared rays you feel on your skin.

Prisms and rainbows
Light bends when it
passes through a prism.
Each color bends at a
different angle, so they
separate out and form
a rainbow.

I can see a rainbow
When it’s raining or misty, the tiny droplets of water
in the air act like hundreds of prisms, breaking down
sunlight into its different wavelengths. Each drop of
water, depending on where it is, bounces a particular
color into your eyes. You see these colors as the bands
in a rainbow.

Visible

Everything we see can
be seen because visible
light waves bounce off
objects. Light waves
can come from the Sun
and from light bulbs.

Ultraviolet (UV) rays

Ultraviolet waves come straight from the
Sun. Some UV waves can burn your skin
and, over time, cause wrinkles and cancer.
That’s why it’s wise to cover up when you
go outside in summer and put sunscreen
on your skin to block out harmful rays.

A well-cut diamond is the best
prism there is. Because it has
so many different surfaces, light
bounces around inside, creating
bright, sparkly colors.

X-rays

X-ray waves pass through most
things, but not bones, teeth, or
metal. When doctors want to
look at your bones, they take
X-ray pictures to see if anything
is out of place or broken.

Gamma rays

Gamma rays can bore through
solid objects and kill living cells.
Doctors use them in radiation
treatments to destroy cancer cells.
Gamma rays are also released
when nuclear bombs explode.

All the colors of visible light appearing together.

Visible spectrum

Now you see it...

77

Light and sound

Light and bubbles
When light hits the surface of a bubble,
it reflects off both the outside AND the
inside of its skin, producing the effect
of swirling, shimmering colors.
Bubble colors
There are different colors in a bubble
(purple, yellow, and blue) from those in
a rainbow (green, blue, and red). This
is because a rainbow splits white light
into separate colors, but a bubble
subtracts colors from light. If red is
subtracted, you see the greeny-blue
that is left behind.

Hands On
Make your own
bubble solution by mixing
half a cup of dishwashing
liquid with four cups
of water and four
tablespoons
of glycerine.

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These bubbles are on the surface of a soap and water solution.

Color secrets
You can tell how thick a bubble is by the
colors it reflects. The blue pa