The Science of Energy

SCIENCE FUNDAMENTALS

ENERGY THE SCIENCE OF

AUTHOR: MASON CREST

mason cresT

mason crest 450 Parkway Drive, Suite D Broomall, PA 19008 (866) MCP-BOOK (toll free) www.masoncrest.com

©2016 by Mason Crest, an imprint of National Highlights, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, taping, or any information storage and retrieval system, without permission from the publisher. Printed and bound in the United States of America. First printing 1 3 5 7 9 8 6 4 2 Library of Congress Cataloging-in-Publication Data The science of energy. pages cm. — (Science fundamentals) Includes bibliographical references and index. ISBN 978-1-4222-3513-3 (hc) — ISBN 978-1-4222-8333-2 (ebook)

1. Force and energy—Juvenile literature. 2. Dynamics—Juvenile literature. 3. Physics—Juvenile literature. QC73.4.S35 2017

531.6—dc23 2015035337 Science Fundamentals Series ISBN: 978-1-4222-3512-6

SCIENCE FUNDAMENTALS

THE SCIENCE OF ENERGY THE SCIENCE OF LIFE THE SCIENCE OF SPACE THE SCIENCE OF TIME PICTURE CREDITS Page:

5: Pat Corkery, United Launch Alliance, 6, 8, 10, 12, 14, 16, 18, 22, 32, 33, 34, 38, 44: Used under license from Shutterstock, Inc.; 9, 13, 17, 18, 23, 24, 25, 28, 29, 33, 34, 35: Wellcome Library, London; 18: Everett Historical; 30: Wikimedia Commons; 39, 42: Library of Congress; 41: NASA/SDO; 43: U.S. Department of Energy Vector Illustrations: 7,11,15,21,27,31,36,40,45: rzarek/Shutterstock.com Background Images: 2, 13, 30: Hyena Reality/Shutterstock.com; 8, 14, 20, 26, 28, 34, 38, 40: Digital_Art/Shutterstock.com; 10, 16: BackgroundStore/Shutterstock.com; 16: vlastas/Shutterstock.com; 24: TairA/Shutterstock.com

Table of Contents

Chapter One: Making it Work Chapter Two: Cosmic Mind Chapter Three: Living Energy Chapter Four: Letting in Light Chapter Five: Making Connections Chapter Seven: Steaming Ahead Chapter Eight: Packets of Energy Chapter Nine: Enter Einstein Chapter Six: Liquid Fire

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12 16 22 28 32 37 41 46 47 47 48

Series Glossary of Key Terms

Further Reading Internet Resources

Index

3.

The search for an understanding of energy, the stuff that drives the Universe, has fascinated people for centuries. Have you ever felt full of energy? When you do you feel that you can make all sorts of things happen. You can work hard if you want to, or you can play for hours. If this is what you mean by energy then you are very close to what a scientist means by it. The word itself comes from the Greek word energeia , which means “in work.” Energy can make things happen. Energy makes things warmer, energy can move things, energy can make things brighter and energy can help living things grow. The more energy there is the more it can do, just as you can do more when you have lots of energy. If a scientist describes an object as “energetic,” he or she means that the object can do things. For instance, if you see a ball on the ground it should be pretty obvious that it doesn’t have much energy. It isn’t doing anything just lying there. However, if you give it some energy by kicking it, it will be able to do things, such as breaking a window if you’re careless about the direction you kick it in! The ball didn’t suddenly get its energy from nowhere. You had to give it the energy it needed to leave the ground and move through the air. DI FFERENT FORMS OF ENERGY As we shall see, scientists believe that the amount of energy in the Universe always stays the same. It is impossible to make new energy. This means that if you want to make something happen you have to transfer energy from somewhere else. When you kick a ball, you use chemical energy in your muscles to move your leg and give the ball movement energy . The chemical energy in your muscles comes from chemical energy in your food. 4. Chapter MAKING IT WORK

An enormous amount of energy is required to fire a rocket into orbit around the Earth. During the launch, the chemical energy stored in the rocket’s fuel is converted in a controlled way into the movement energy needed for lift-off.

When you play a sport such as basketball, food energy stored in your muscles is constantly being converted into the movement energy you need to run and to throw the ball. You pass some of that energy on to the ball when you shoot, while some of the energy is lost from your body as heat.

Energy comes in different forms and can be switched from one form to another. Two forms have been mentioned already, chemical energy—part of what is called internal energy —stored in substances, and movement energy. How many more can you think of? Light, sound, heat and electricity are all forms of energy. The string of a bow pulled tight is storing energy, called potential energy , which is converted to movement energy in the arrow when the string is released.

The peoples of the ancient world didn’t think in terms of abstract ideas like energy when they thought about the way the world worked. They used gods and other mythical beings to explain why things behave as they do. The word energy , in the sense we understand it now, was first used in the 1840s by William Thomson. We will be meeting him later in the story. However, the early Greek philosophers had some interesting ideas and we turn to them first to begin our exploration of energy.

When the archer pulls back the bowstring chemical energy stored in the archer’s arm muscles is converted into potential energy in the stretched string. When the archer lets go of the string the potential energy is suddenly changed into movement energy, which is passed on to the arrow, making it fly towards the target.

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WORDS TO UNDERSTAND

chemical energy —energy stored in the links that hold atoms together when they join to form groups of atoms, called molecules.

internal energy —the total heat energy and chemical energy within an object.

movement energy —the energy an object has in motion. Also called kinetic energy.

potential energy —energy stored in an object, such as the energy stored in a coiled spring which is released as kinetic energy when the spring unwinds.

work —a measure of the energy transferred to or from an object or a system. Work involves the action of a force on the object or system and is measured in joules.

RESEARCH PROJECT The famed physicist Richard Feynman, sometimes known as the “great explainer,” discusses the nature of energy and light waves in a short video, available at https://www.youtube.com/watch?v=FjHJ7FmV0M4.

TEXT-DEPENDENT QUESTIONS

1. Is it possible to create more energy? 2. What are two forms of energy?

7.

Chapter COSMIC MIND

Our scientific understanding of matter and of how energy can change it owes much to the theories of ancient Greek thinkers. Anaxagoras (c.500–428 bce ) was one of the first people we know about who thought seriously about the nature of the Universe and the way it worked. He wanted to explain why matter behaves as it does, for example why it moves and changes in certain ways. He wasn’t satisfied with the explanation that was usually given at the time, which was that matter behaves as it does because it is in its nature to do so. Anaxagoras was looking for something—some sort of force —that would link the seemingly infinite variety of matter and all the changes and interactions that could possibly be produced in it. Whatever this link or guiding force was, Anaxagoras was certain of one thing. It must have no mythical character or have anything to do with gods. It had to be

absolutely logical and rational and be able to account for everything he saw in the Universe. Anaxagoras gave his force the name nous , which means “mind” or “reason.”He believed that the Universe came into being through the action of nous on an infinite number of “seeds.” The huge amount of energy released during a lightning flash can join together particles of different chemicals in the air to produce new ones. This is rather like the idea of a cosmic force acting on “seeds,” proposed by the Greek scientist Anaxagoras.

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This Medieval manuscript illustration represents three of the greatest ancient Greek scientists: Plato, Anaxagoras, and Democritus. Anaxagoras believed that the Universe came about through the action of a cosmic mind, or nous , on an infinite number of particles, or “seeds.” Democritus was the first person to say that matter consisted of particles that could not be divided into smaller parts. He called these particles atoms .

THE COSMIC MIND AT WORK Anaxagoras’s seeds were similar to what we would think of today as atoms. The idea that everything was made up of tiny particles too small to see had been put forward by another Greek, Leucippus, who lived around the same time as Anaxagoras. Our word “atom” comes from the Greek atomein , which means “cannot be divided.” Anaxagoras’s seeds, however, could be divided an infinite number of times. The idea that atoms could not be divided came from Leucippus’s pupil Democritus (470–380 bce ). All the order and forms around us came into being, Anaxagoras believed, by the action of nous , the cosmic mind, shaping the substance of the Universe. “Mind rules the world and has brought order out of confusion,” he said. If Anaxagoras’s seeds can be seen as atoms then perhaps we might also think of his nous as being like energy. It was the force that moved the Universe and determined its shape. 9.

This has some similarity to our current ideas about the origin of the Universe. Most scientists now believe that it started with a colossal explosion of energy, which has been called the big bang . For a while the Universe was pure energy, but after a time particles of matter formed out of it. These particles came together to produce all the matter in the Universe today. If you substitute nous for “energy” and seeds for “particles of matter” in those sentences, it sounds very similar to Anaxagoras’s idea, doesn’t it? Anaxagoras’s ideas were not very popular. In fact, he was put on trial for his beliefs. Later Greek thinkers, such as Aristotle (384–322 bce ), had a greater influence. He founded the Lyceum, a school of study in Athens, around 335 bce . Aristotle put the emphasis on collecting information and on sorting and classifying everything. Yet Aristotle did not believe in experiment, only in observation. He called his study physics. He believed that things had certain “causes.” The aim of Aristotle’s physics was to discover the nature of things. Everything had a “final cause,” which was the object’s purpose for existence. Because everything was seen as having a purpose the Universe came to be viewed as rather like a living thing. There was no point in looking for the force or energy that moved things; they were simply fulfilling their purpose. Aristotle did try to put together laws that would explain why things moved, but these simply came down to saying that, for example, objects fall because that is the natural thing for them to do. He never tried to back up his ideas by experiment. Aristotle’s view of the world dominated thinking for the next thousand years.

Aristotle believed that everything had a purpose, or “final cause,” and that an object would behave according to its purpose. He did not attempt to test his ideas by experiment, however.

WORDS TO UNDERSTAND

big bang —the name given to the theory that all the matter and energy in the Universe originated in a sudden explosion outwards from a single point, about 15 billion years ago.

force —a power or agency that affects the movement or behavior of an object.

nous —the name the Greek philosopher Anaxagoras gave to the force he believed guided and ordered the behavior of the Universe.

physics —the study of the laws, or rules, that determine the behavior of the matter and energy in the Universe.

RESEARCH PROJECT

Using the Internet or your school library, do some research on one of the following ancient Greek scientists: Anaxagoras, Leucippus, Democritus,

TEXT-DEPENDENT QUESTIONS

1. What name did Anaxagoras give to the force that he believed would cause matter to move and change in certain ways? 2. What was the aim of Aristotle’s science of physics?

Plato, or Aristotle. Write a two-page

report on this person’s accomplishments, and present it to your class.

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Chapter LIVING ENERGY

Seventeenth-century scientists performed experiments that gave a better understanding of the energy changes that take place when an object moves. The first real experiments into the behavior of moving objects were conducted by Galileo Galilei (1564–1642), the Italian astronomer and physicist. Although Galileo could not have understood energy as we understand it today, he seems to have had an awareness that the energy of an object thrown vertically upwards, a ball say, does not gradually disappear as it reaches the top of its flight. The energy is, in fact, changing from one form into another, from energy of movement into energy of position. We now call these ideas kinetic energy and potential energy. As the object reaches its highest point all of its kinetic energy has become potential energy and for a split second the ball stops moving. As it starts to fall, the ball’s potential energy is changed back again into kinetic energy so that when it reaches the ground it has just as much kinetic energy as it had when it was first thrown up. Aristotle had said that in order to keep

moving a body had to have a force applied to it continuously. This was supposedly provided by air rushing in to fill the space left by the moving object. Later, others pointed out that if this was true then moving objects should travel faster and faster. Galileo showed that this point of view was the correct one. He measured the velocities of objects moving on slopes, on level surfaces and falling freely. He showed that an object moving down a slope or falling freely accelerates, that is, its velocity increases, but on a flat surface

A ball is given kinetic energy when it is thrown into the air. At its highest point it has no kinetic energy, but it has maximum potential energy.

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its velocity stays the same. The increase in velocity of a falling object is caused by the constant pull of the Earth. VELOCI TY AND MOMENTUM Every moving object has a quality called momentum . This is found by multiplying the mass of the object, which is the amount of material it contains, by its velocity (written as v). the more massive an object is and the faster it is travelling, the more momentum it will have. How does the object gain momentum? To get something moving you have to apply a force to it, perhaps by pushing it or firing it from a gun. Whatever you do you are turning one form of energy into movement energy. The amount of energy a moving object has

Galileo was the first scientist to measure the velocities of moving objects. He determined that a ball will remain stationary until a force acts upon it to move it.

can be worked out from the force needed to get it moving at a certain velocity. If we do this we find that the amount of energy in a moving object is equal to a half times its mass (written as m), multiplied by its velocity squared, a definition first given by the Frenchman Gaspard de Coriolis (1792–1843). This fundamental law can be written simply as: kinetic energy = 1/2 mv 2 . Galileo’s work on moving objects was continued by Christian Huygens (1629– 1795), a Dutch scientist. Huygens showed that the momentum of moving objects is always conserved. That is to say, it cannot be created or destroyed, only exchanged between different objects. If two objects collide head on, one with a momentum of x, say, and the other with a momentum of y, then the total momentum at the time of the collision is x plus y. Measuring the speed and direction of the objects after the collision shows that the total momentum is still x plus y. This was the first step along the path to showing that energy was conserved, a principle that would be demonstrated by Hermann Helmholtz 150 years later. VIS VIVA—THE L IVING FORCE In 1686 the German mathematician Gottfried Leibniz (1646–1716) introduced the Latin term vis viva , which means living force. This concept was very similar to the idea of kinetic energy worked out much later, in the nineteenth century, 13.

in that the vis viva of an object depended on both its mass and on its velocity. Several scientists, including the Dutchman Willem s’Gravesande (1688–1742) and the Marquise du Châtelet, Gabrielle de Breteuil (c.1700–1749), were impressed by Leibniz’s idea and carried out experiments to test it.

S’Gravesande built a variety of machines to experiment with motion, such as one in which a moving metal ball on a thread was made to strike a stationary similar ball. By knowing the masses of the balls and their velocities before and after the collision, s’Gravesande could calculate how much vis viva was in each ball. It seemed that the vis viva could be transferred almost entirely from the moving ball to the stationary one. One of the most famous English scientists, Isaac Newton (1642–1727), made many

An object accelerates rapidly when it is free to fall. Galileo found that, whatever the

contributions to the study of energy and forces. Among Newton’s greatest contributions were his laws of motion , describing the way objects move. In mass of the object, it always accelerates at the same rate.

doing so he built on work done by Galileo over a hundred years earlier. The science of moving objects was brought to a peak by Newton, whose laws could be used to explain everything from an arrow travelling towards its target to the motion of the Moon around the Earth.

Find out about a device known as “Newton’s cradle.” How does it work, and what does this device demonstrate about momentum and energy? RESEARCH PROJECT

S’Gravesande investigated the amount of vis viva that could be passed on when one ball collided with another.

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