T I M E and T H ERM O DYNAM I CS Kyle Kirkland, Ph.com TIME AND THERMODYNAMICS Copyright © 2007 by Kyle Kirkland, Ph. All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact: Facts On File, Inc.
An imprint of Infobase Publishing 132 West 31st Street New York NY 10001 ISBN-10: 0-8160-6113-0 ISBN-13: 978-0-8160-6113-6 Library of Congress Cataloging-in-Publication Data Kirkland, Kyle. Time and thermodynamics / Kyle Kirkland.—(Physics in our world) Includes bibliographical references and index. Space and time.7—dc22 2006016638 Facts On File books are available at special discounts when purchased in bulk quan- tities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at (212) 967-8800 or (800) 322-8755.
You can find Facts On File on the World Wide Web at http://www.com Text design by Kerry Casey Cover design by Dorothy M. Preston Illustrations by Richard Garratt Printed in the United States of America MP FOF 10 9 8 7 6 5 4 3 2 1 This book is printed on acid-free paper.com CONTENTS Preface v Acknowledgments vii Introduction ix 1 HEAT AND THE ENVIRONMENT 1 Temperature and Heat 2 Temperature and the Kinetic Energy of Molecules 4 The Flow of Energy 8 Cooling Down and Heating Up 14 Latent Heats and Heat Capacity 16 Seasons of the Year 19 Urban Heat Islands 23 Global Warming 26 2 HEAT AND BODY TEMPERATURE 31 Body Temperature 32 How People Sense Hot and Cold 35 Heat Conductors and Insulators 36 Warm-Blooded and Cold-Blooded Animals 39 The Comfort Zone: Maintaining the Right Temperature 42 Thermography 47 Extreme Temperatures and Life 49 3 HEAT AND TECHNOLOGY 55 Using Technology to Control Temperature 56 First Law of Thermodynamics 57 www.com Refrigerators and Air Conditioners 60 Second Law of Thermodynamics 62 Reversible Heat Pumps 65 Absolute Zero 67 4 HEAT ENGINES 71 Steam Power 72 The Carnot Engine 78 Car Engines 82 Racing Engines 88 Jet Engines and Gas Turbines 92 Heat Engines of the Future 96 5 TIME 101 Clocks 102 Pendulums and Periodicity 106 Time and the Laws of Physics 110 Entropy and Disorder 114 Second Law of Thermodynamics Revisited 117 Traveling in Time 118 The Beginning and the End of the Universe 122 CONCLUSION 125 SI Units and Conversions 129 Glossary 132 Further Reading and Web Sites 136 Index 141 www.com PREFACE T HE NUCLEAR BOMBS that ended World War II in 1945 were a convincing and frightening demonstration of the power of physics. A product of some of the best scientific minds in the world, the nuclear explosions devastated the Japanese cities of Hiroshima and Nagasaki, forcing Japan into an unconditional sur- render. But even though the atomic bomb was the most dramatic example, physics and physicists made their presence felt through- out World War II.
From dam-breaking bombs that skipped along the water to submerged mines that exploded when they magneti- cally sensed the presence of a ship’s hull, the war was as much a scientific struggle as anything else. World War II convinced everyone, including skeptical military leaders, that physics is an essential science. Yet the reach of this subject extends far beyond military applications. The principles of physics affect every part of the world and touch on all aspects of people's lives.
Hurricanes, lightning, automobile engines, eye- glasses, skyscrapers, footballs, and even the way people walk and run must follow the dictates of scientific laws. The relevance of physics in everyday life has often been over- shadowed by topics such as nuclear weapons or the latest theo- ries of how the universe began. Physics in Our World is a set of volumes that aims to explore the whole spectrum of applications, describing how physics influences technology and society, as well as helping people understand the nature and behavior of the uni- verse and all its many interacting parts. The set covers the major branches of physics and includes the following titles: ♦ Force and Motion ♦ Electricity and Magnetism v www.com vi Time and Thermodynamics ♦ Time and Thermodynamics ♦ Light and Optics ♦ Atoms and Materials ♦ Particles and the Universe Each volume explains the basic concepts of the subject and then discusses a variety of applications in which these concepts apply.
Although physics is a mathematical subject, the focus of these books is on the ideas rather than the mathematics. Only simple equations are included. The reader does not need any spe- cial knowledge of mathematics, although an understanding of elementary algebra would be helpful in a few cases. The number of possible topics for each volume is practically limitless, but there is only room for a sample; regrettably, interesting applications had to be omitted.
But each volume in the set explores a wide range of material, and all volumes contain a further reading and Web sites section that lists a selection of books and Web sites for continued exploration. This selection is also only a sample, offering sugges- tions of the many exploration opportunities available. I was once at a conference in which a young student asked a group of professors whether he needed the latest edition of a phys- ics textbook. One professor replied no, because the principles of physics “have not changed in years.” This is true for the most part, but it is a testament to the power of physics.
Another testament to physics is the astounding number of applications relying on these principles—and these applications continue to expand and change at an exceptionally rapid pace. Steam engines have yielded to the powerful internal combustion engines of race cars and fighter jets, and telephone wires are in the process of yielding to fiber optics, satellite communication, and cell phones. The goal of these books is to encourage the reader to see the relevance of physics in all directions and in every endeavor, at the present time as well as in the past and in the years to come.com ACKNOWLEDGMENTS T HANKS GO TO my teachers, many of whom did their best to put up with me and my undisciplined ways. Special thanks go to Drs.
George Gerstein, Larry Palmer, and Stanley Schmidt for helping me find my way when I got lost. I also much appreci- ate the contributions of Jodie Rhodes, who helped launch this project; executive editor Frank K. Darmstadt and the editorial and production teams who pushed it along, including copy editor Amy L. Conver; and the many scientists, educators, and writers who provided some of their time and insight.
Thanks most of all go to Elizabeth Kirkland, a super mom with extraordinary powers and a gift for using them wisely.com INTRODUCTION A LEGEND OF the ancient Greeks tells the story of a god called Prometheus, who taught people how to make fire. This gave a tremendous boost to humanity, and the other gods were furi- ous with Prometheus for allowing humans to wield such potency. Although the story of Prometheus is a myth, the ability to har- ness fire and heat did provide people with some of their earliest technology. Steam powered much of the Industrial Revolution, a period of time beginning in the late 18th century in which machines tremendously advanced the productivity of manufacturing and transportation.
But heat, temperature, and their relationships are much broader subjects than just steam-powered machines. Warmth is associated with life and activity; cold is associated with death and stillness. Some organisms rely on the environment to provide warmth, and some organisms can generate their own, but all living beings must adapt and interact in a world in which temperature is not constant. Time and Thermodynamics explores the physics of heat and temperature and their effects on people’s lives and technology.
The word thermo refers to heat, and the word dynamics gives an indication of motion, both of which are vital to the subject. Heat is energy that flows from warm objects to cooler ones. Nineteenth- century scientists and engineers such as Sadi Carnot, primarily motivated by the desire to understand and improve steam-pow- ered machines, discovered the principles of thermodynamics. Much to their surprise, they found that the physics of thermodynamics places strict limits on what machines can accomplish.
But the sub- ject also opened up vast areas of knowledge in habitats, biology, technology, engines, as well as a surprising amount of revelation ix www.com x Time and Thermodynamics on the topic of time. Time and Thermodynamics discusses thermo- dynamics principles related to each of these topics and how their application enables people to better understand the world and sometimes even improve it. Temperature is vital to the health and welfare of all animals, and Earth’s temperature varies considerably from place to place. Early humans could only live in warm areas such as the tropics, near the equator.
Although modern humans have the technology to keep their houses and offices warm even in cold environments, the growth and development of civilization has created uninten- tional effects. Cities are warmer than their surrounding regions, and on a global scale, Earth is experiencing rising temperatures. Thermodynamics offers an important tool to study these effects. Maintaining proper temperature is critical for life, and this need has a great influence on the form, function, and molecules of the bodies and organs of people and animals.
Reptiles bask in the sun for warmth, but humans generate a lot of heat on their own. These two methods of keeping warm differ in significant ways, yet both adhere to thermodynamic principles of heat generation and transfer. Heat naturally flows from warm to cold objects, but it is often desirable to get it to go in the opposite direction. Air condition- ers pump heat from the inside of a relatively cool house to the hot environment outside on a summer day.
The process requires energy, usually taken from electricity, and the reason why strikes at the heart of the laws of thermodynamics. Thermodynamics laws also put strict limits on the ability of engines to use heat to propel vehicles or raise heavy objects. Know- ing these limits prevents engineers from trying to design impos- sible machines, but it does not stop them from building impressive cars capable of roaring down a racetrack at 200 miles per hour (320 km/hr.), jet fighters that exceed the speed of sound by a fac- tor of two or three, and a new engine called a ramjet to accelerate an aircraft up to 7,000 miles per hour (11,200 km/hr. The final chapter explores time.
Although time would not seem at first to have strong ties with thermodynamics, the relationship is profound. Physics has much symmetry—the laws of physics are www.com Introduction xi often the same in a variety of circumstances. This includes time; physics formulas are usually the same whether time is increasing (going forward, into the future) or decreasing (going backward, into the past). Most of physics has no preference for either case, because its laws work equally well in both directions.
Yet people experience time as flowing in a single direction, from past to pres- ent and on into the future. Thermodynamics provides an ingenious explanation for this, because its laws are an exception to the rest of physics and breaks the symmetry in time. As a result, thermo- dynamics yields clues about the nature of time, the possibility of time travel, and the very beginning of time, at the creation of the universe.com 1 HEAT AND THE ENVIRONMENT A GIGANTIC ICEBERG floating in the ocean is frigid, yet it has a lot of thermal energy. The word thermal is derived from a Greek word meaning heat.
The iceberg is not hot, but it contains a lot of thermal energy. This strange-looking iceberg was floating in the Gerlache Strait near Antarctica in 1962. (NOAA/Rear Admiral Harley D.