This book explores how researchers in a wide variety of fields determine the age of things.
The Age of Everything The Age of Everything how science explores the past Matthew Hedman The University of Chicago Press & is research associate in the Department of Astronomy at Cornell University. The University of Chicago Press, Chicago The University of Chicago Press, Ltd., London © by The University of Chicago All rights reserved. Published Printed in the United States of America -: ---- (cloth) -: --- (cloth) Library of Congress Cataloging-in-Publication Data Hedman, Matthew, – The age of everything : how science explores the past / Matthew Hedman. p. cm. Includes index. -: ---- (cloth : alk. paper) -: --- (cloth : alk. paper) . Archaeological dating. . Archaeology—Technological innovations. . Radiocarbon dating. . Earth—Age. . Solar system—Age. . Science—History. . Geochronometry. I. Title. CC.H .—dc The paper used in this publication meets the minimum require- ments of the American National Standard for Information Sciences— Permanence of Paper for Printed Library Materials, .-. contents Acknowledgments vii Introduction The Calendars of the Classic Maya Precession, Polaris, and the Age of the Pyramids The Physics of Carbon- Calibrating Carbon- Dates and the History of the Air Carbon- and the Peopling of the New World Potassium, Argon, DNA, and Walking Upright Molecular Dating and the Many Di erent Types of Mammals Meteorites and the Age of the Solar System Colors, Brightness, and the Age of Stars Distances, Redshifts, and the Age of the Universe Parameterizing the Age of the Universe Glossary Index To my Mom and Dad, and to Judy Burns, for helping me see this project through. acknowledgments Many people have helped me with this book over the years. Bruce Winstein and James Pilcher encouraged me to do the series of public lectures that formed the basis on this text. The people in the Enrico Fermi Institute and Kalvi Institute for Cosmological Physics, especially Nanci Carrothers, Char- lene Neal, and Dennis Gordon, helped with the practical matters of those lectures. I must also thank all the members of the CAPMAP collaboration, especially Dorothea Samtleben, who put up with me while I worked on the talks and even came to a few lectures. At the end of the lectures, both Bruce Winstein and Christie Henry of the University of Chicago Press convinced me to expand my notes into book form, and the people at Cornell University, especially J. A. Burns and P. D. Nicholson, have been very tolerant of my ef- forts to do so. In preparing this text, I bene ted from comments from Christie Henry, Michael Koplow, and several reviewers. Todd Telander provided many of the excellent illustrations for this nal book. My brother, Kevin, also read through the text and provided many use- ful suggestions for improving the prose. Throughout all this, my parents, Curt and Sally Hedman provided constant encouragement and support. The fol- lowing people either provided references and other information for this book or helped me to better understand some of the concepts discussed below: John Harris, the members of the Chicago Maya Society, K. E. Spence, John C. Whittaker, Wen-Hsiung Li, J. David Archibald, Robert Clayton, Stephen Simon, Andrey Kravstov, James Truran, David Cherno , Ira Wasserman, Stephan Meyer, Erin Sheldon, Rick Kline, and Wayne Hu. Of course, any errors in these pages are my responsibility alone. chapter one Introduction From our twenty- rst-century perspective, events from the past can often seem impossibly remote. With today’s complex technology and constantly shifting political and economic networks, it is sometimes hard to imagine what life was like even a hundred years ago, much less comprehend the vast stretches of time preceding the appearance of humans on this planet. How- ever, thanks to recent advances in the elds of history, archaeology, biology, chemistry, geology, physics, and astronomy, in some ways even the far distant past has never been closer to us. The elegantly carved symbols found deep in the rain forests of Central America, uninterpretable for centuries, now reveal the political machinations of Mayan lords. Fresh interdisciplinary studies of the Great Pyramids of Egypt are providing fascinating insights into exactly when and how these incredible structures were built. Meanwhile, the remains of humble trees are illuminating how the surface of the sun has changed over the past ten millennia. Other ancient bits of wood are helping us better un- derstand the lives of the rst inhabitants of the New World. Fossil remains, together with tissue samples from modern animals (including people) suggest that anthropologists may be close to solving the long-standing puzzle of when and how our ancestors started walking on two legs. Similar work might also help biologists uncover how a group of small, shrew-like creatures that lived in the shadow of the dinosaurs gave rise to creatures as diverse as cats, rab- bits, bats, horses and whales. The origins of the earth and the solar system are being explored in great detail thanks in part to the rocks that fall from the sky, while the history of the universe can be read in the light from distant stars. The cosmic static that appears on our television sets even allows cosmologists to look back to the very beginning of our universe.