Ernest Rutherford And the Explosion of Atoms Image Not Available Owen Gingerich General Editor Ernest Rutherford And the Explosion of Atoms J. L. Heilbron 1 Oxford New York Auckland Bangkok Buenos Aires Cape Town Chennai Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi São Paulo Shanghai Singapore Taipei Tokyo Toronto Copyright © 2003 by John L. Heilbron Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup-usa.org Oxford is a registered trademark of Oxford University Press All rights reserved. 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 permission of Oxford University Press. Design: Design Oasis Layout: Lenny Levitsky Library of Congress Cataloging-in-Publication Data Heilbron, J. L. Ernest Rutherford : and the explosion of atoms / John L. Heilbron. p. cm.—(Oxford portraits in science) Summary: A biography of the scientist considered to be the father of nuclear physics for his development of the nuclear theory of the atom in 1911 and discovery of alpha and beta rays. Includes bibliographical references and index. ISBN 0-19-512378-6 (acid-free paper) 1. Rutherford, Ernest, 1871-1937--Juvenile literature. 2. Physicists-New Zealand- Biography-Juvenile literature. 3. Nuclear physics-History-Juvenile literature. [1. Rutherford, Ernest, 1871-1937. 2. Physicists. 3. Scientists. 4. Nuclear physics- History. 5. Nobel Prizes-Biography.] I. Title. II. Series. QC16.R8 H45 2003 539.7'092--dc21 2002155600 Printing number: 9 8 7 6 5 4 3 2 1 Printed in the United States of America on acid-free paper On the cover: Ernest Rutherford; inset: Rutherford works in his basement on the megnetization of iron. Frontispiece:A 1932 portrait of Rutherford by Oswald Birley. Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Chapter 1: Cambridge and Ray Physics . . . . . . . . . . . . . . . . . .10 Sidebar: Cathode Ray Tubes . . . . . . . . . . . . . . . . . . . . . . . .19 Sidebar: Measuring the e/m of the Corpuscle . . . . . . . . . .28 Chapter 2: McGill and the Explosion of Atoms . . . . . . . . . . .32 Sidebar: The Bending of Alpha Particles . . . . . . . . . . . . . . .43 Sidebar: The Periodic Table of the Elements . . . . . . . . . . .46 Chapter 3: Manchester and the Structure of Atoms . . . . . . .57 Sidebar: Helium from Alpha Particles . . . . . . . . . . . . . . . . .63 Sidebar: Bohr’s Atomic Theory . . . . . . . . . . . . . . . . . . . . . .72 Sidebar: Isotopes and Transformations . . . . . . . . . . . . . . . .78 Chapter 4: War and the Promotion of Science . . . . . . . . . . .83 Sidebar: Acoustical Detection . . . . . . . . . . . . . . . . . . . . . . .93 Chapter 5: The Center of Physics . . . . . . . . . . . . . . . . . . . . . .98 Sidebar: Neutron Absorption . . . . . . . . . . . . . . . . . . . . . .112 Sidebar: The Linac and the Cyclotron . . . . . . . . . . . . . . .116 Chronology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130 Periodic Table of the Elements . . . . . . . . . . . . . . . . . . . . . . . .133 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 This page intentionally left blank Charles Babbage Alexander Graham Bell Nicolaus Copernicus Francis Crick & James Watson Marie Curie Charles Darwin Thomas Edison Albert Einstein Michael Faraday Enrico Fermi Sigmund Freud Galileo Galilei William Harvey Joseph Henry Edward Jenner Johannes Kepler Othniel Charles Marsh & Edward Drinker Cope Margaret Mead Gregor Mendel Isaac Newton Louis Pasteur Linus Pauling Ivan Pavlov Ernest Rutherford Ernest Rutherford Introduction The earth’s crust and atmosphere have been radioactive since their creation. Human beings knew nothing about the radiations in which they bathed, however, until a hundred years ago, around 1900, when they first made conscious contact with rays from uranium, discovered the apparently inexhaustible radiator known as radium, and invented the concept of radioactivity. Twenty-five hundred years ago a few Greek philoso- phers decided that the material world was composed of hard, indestructible particles they called atoms. Their theory, revived in Europe 2,000 years later, set the crucial question for chemistry and physics: Do atoms exist? Radioactivity helped to confirm both their existence and their non-exis- tence by showing that although the atoms that figured in the theories of physics and chemistry did indeed exist, they were not indestructible. Five hundred years ago western Europe was alive with alchemists, people who believed that base metals could be transmuted into gold. Much time and money were transmut- ed into nothing in the attempt to demonstrate the theory. The alchemists failed, not because their aims were frivolous, but because transmutation requires much more powerful methods than they had at their disposal. Their failure made “alchemist” a synonym for “imposter.” In radioactivity, how- ever, nature itself regularly transmutes one sort of chemical atom into another. 8 Introduction The man who discovered nature’s transmutations and the structure of the atom was Ernest Rutherford, whose career is as interesting as the science he advanced. Born the Rutherford became a life son of a flax farmer in the most remote part of the English- peer in 1931. He took as speaking world, he ended up a British baron and the chief his baronial crest a professor at the center of the universe of physics. His jour- design indicating his achievements in science ney ran from the margin to the interior, from New Zealand (the crossing curves on to Cambridge, through unexplored worlds where only he the shield) and his origins could see the direction of advance. Fortunately, the record in New Zealand (the kiwi of his path breaking is intelligible as well as inspirational. bird on the left and the Rutherford’s science was not mysterious and mathematical Maori warrior on the like Einstein’s or burdened with details like Marie Curie’s. right). The sage on the It consisted of bold inferences from apt experiments, disci- left, Hermes Trismegistus, represents ancient alche- plined common sense, and inspired neglect of what other my; the Latin slogan, “to people thought important. inquire into the founda- When, late in life, down-to-earth “Ern” Rutherford tions of things,” states the transmuted into Lord Rutherford of Nelson, he did not for- enduring quest of physics. get his origins. He designed a shield displaying items seldom sighted in the British Isles: a kiwi bird and a Maori warrior. These creatures, intended to refer to the exotic place of his birth, may also be read as indi- cators of prominent traits in his character. Like the wingless kiwi, Rutherford, a no-non- Image Not Available sense, robust, commonsensical man, had his feet fixed firmly on the ground. Like the Maori warrior, he was always pre- pared for action against anyone foolish enough to oppose him. 9