Earth Magnetism A Guided Tour through Magnetic Fields This Page Intentionally Left Blank Complementary Science Series [m 2000/2001 The Physical Basis of Chemistry, 2nd Edition Warren S. Warren Physics in Biology and Medicine, 2nd Edition Paul Davidovits Introduction to Relativity John Kogut The Human Genome, 2nd Edition R. Scott Hawley I~ Julia Richards I~ Catherine Mori 1999 Chemistry Connections Kerry Karukstis I~ Gerald Van Hecke Mathematics for Physical Chemistry, 2nd Edition Robert Mortimer Fundamentals of Quantum Mechanics J.E. House www.harcourt-ap.com This Page Intentionally Left Blank Earth Magnetism A Guided Tour through Magnetic Fields Wallace Hall Campbell Boulder, Colorado [I/ ................... A Harcourt Science and Technology Company San Diego San Francisco New York Boston London Sydney Tokyo Sponsoring Editor Jeremy Hayhurst Production Managers Joanna Dinsmore and Andre Cuello Editorial Coordinator Nora Donaghy Marketing Manager Marianne Rutter Cover Design G. B. D. Smith Copyeditor Julie Nemer Proofreader Cheryl Uppling Preproduction Supplinc Composition Archetype Publishing, Inc. Printer Bertelsmann Industry Services, Inc. Series logo: Images (cid:14)9 2000 PhotoDisc, Inc. This book is printed on acid-free paper. (~ Copyright (cid:14)9 2001 by HARCOURT/ACADEMIC PRESS All Rights Reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt, Inc., 6277 Sea Harbor Drive, Orlando Florida 32887-6777 Academic Press A Harcourt Science and Technology Company 525 B Street, Suite 1900, San Diego, California 92101-4495, U.S.A. http://www.academicpress.com Academic Press Harcourt Place, 32 Jamestown Road, London NW 1 7BY, UK http://www.academicpress.com Harcourt/Academic Press A Harcourt Science and Technology Company 200 Wheeler Road, Burlington, Massachusetts 01803 http://www.harcourt-ap.com Library of Congress Catalog Card Number: 00-108261 Intemational Standard Book Number: 0-12-158164-0 PRINTED IN THE UNITED STATES OF AMERICA 00 01 02 03 04 05 BS 9 8 7 6 5 4 3 2 1 A wonder of such nature I experienced as a child of 4 or 5 years, when my father showed me a compass. That this needle behaved in such a determined way did not at all fit into the nature of events, which could find a place in the unconscious world of concepts (effect connected with direct 'touch'). I can still remember--or at least I believe I can remember--that this experience made a deep and lasting impression upon me. Something deeply hidden had to be behind things. Albert Einstein This Page Intentionally Left Blank Contents Foreword xiii Preface xv Acknowledgments xxi 1 Nature's Magnetism 1 1.1 Finding the Fields . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Historical Tour Markers . . . . . . . . . . . . . . . . . . . . 2 1.2.1 Compass Origin . . . . . . . . . . . . . . . . . . . . . 2 1.2.2 Global Explorations . . . . . . . . . . . . . . . . . . . 3 1.2.3 Geomagnetism Patriarchs . . . . . . . . . . . . . . . . . 5 Gilbert . . . . . . . . . . . . . . . . . . . . . . . . 5 Halley . . . . . . . . . . . . . . . . . . . . . . . . 7 Faraday . . . . . . . . . . . . . . . . . . . . . . . 5 Gauss . . . . . . . . . . . . . . . . . . . . . . . . 7 Maxwell . . . . . . . . . . . . . . . . . . . . . . . 7 Chapman . . . . . . . . . . . . . . . . . . . . . . 11 1.3 Local Language Dictionary . . . . . . . . . . . . . . . . . . 7 1.3.1 Earth Fields, Steady and Changing . . . . . . . . . . . . 11 1.3.2 Forces at Work . . . . . . . . . . . . . . . . . . . . . 13 1.3.3 Measuring Scales . . . . . . . . . . . . . . . . . . . . 15 1.3.4 Locating the Fields . . . . . . . . . . . . . . . . . . . . 17 1.3.5 Nature's Basic Particles . . . . . . . . . . . . . . . . . 18 Atoms . . . . . . . . . . . . . . . . . . . . . . . . 18 ix
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