Ken Alder - The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World

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A LSO BY K EN A LDER

Engineering the Revolution

The White Bus: A Novel

THE FREE PRESS

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New York, NY 10020

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Copyright 2002 by Ken Alder

All rights reserved, including the right of reproduction in whole or in part in any form.

THE FREE PRESS and colophon are trademarks of Simon & Schuster, Inc.

Designed by Dana Sloan

Library of Congress Cataloging-in-Publication Data

Alder, Ken.

The measure of all things : the seven-year odyssey and hidden error that transformed the world / Ken Alder.

p. cm.

Includes bibliographical references and index. 1. Arc measuresHistory. 2. Meter (Unit)History. 3. Delambre, J. B. J. (Jean Baptiste Joseph), 17491822. 4. Mchain, Pierre, 17441804. I. Title.

QB291 .A43 2002

526'.1dc21

2002070267

ISBN 0-7432-1675-X

ISBN-13: 978-0-7432-4902-7 (eBook)

FOR B RONWYN AND M ADELEINE

It is the star to every wandering bark,

Whose worths unknown, although his height be taken.

The Leading Players

J EAN -B APTISTE -J OSEPH D ELAMBRE (17491822). Astronomer who led the northern portion of the meridian expedition in 1792-99. Delambre finished his career as Permanent Secretary of the Paris Academy of Sciences.

P IERRE -F RANOIS -A NDR M CHAIN (17441804). Astronomer who led the southern portion of the meridian expedition in 1792-99, with the assistance of the cartography engineer, J EAN -J OSEPH T RANCHOT . Mchain married B ARBE -T HRSE M ARJOU in 1777; their oldest son, J RME -I SAAC , served on Napoleons Egyptian expedition, and their younger son, A UGUSTIN , assisted Mchain on his second mission to Spain, from which he never returned.

J OSEPH -J RME L ALANDE (17321807). Astronomer and philosophe in the high Enlightenment tradition. An avid atheist, a friend of Voltaire, and the self-styled most famous astronomer in the universe, he was the matre of both Delambre and Mchain.

The Supporting Cast

J EAN -C HARLES DE B ORDA (173399). Veteran naval commander and Frances leading experimental physicist. He invented the repeating circle, the scientific instrument used by Delambre and Mchain.

J EAN -D OMINIQUE DE C ASSINI , known as Cassini IV (17481845). The fourth member of his family in succession to direct the Royal Observatory of Paris in the Ancien Rgime. Appointed to lead the meridian expedition, he withdrew as a protest against the Revolution.

M ARIE -J EAN -A NTOINE -N ICOLAS C ARITAT DE C ONDORCET (1743-94). Historys great optimist for human progress. He served as Permanent Secretary of the Academy of Sciences in the Ancien Rgime. An ardent Revolutionary, he touted the egalitarian virtues of the metric system. He committed suicide in 1794 to avoid execution at the hands of the Revolutionary police.

P IERRE -S IMON L APLACE (17491827). The leading mathematical physicist of his age. His crowning achievement, the System of the World, represented the eighteenth-century culmination of Newtonian physics. A crucial part of Laplaces theory concerned the shape of the earth. He was a leading proponent of the metric system.

A NTOINE -L AURENT L AVOISIER (174394). One of the principal founders of modern chemistry andthanks to his position as a royal tax collectorone of the wealthiest men in Ancien Rgime France. Despite welcoming the Revolution and serving as a powerful behind-the-scenes advocate of metric reform, he was executed in 1794 for his participation in the tax-gathering authority of the Ancien Rgime.

A DRIEN -M ARIE L EGENDRE (17521833). One of Frances leading mathematicians. He helped found modern statistics using the data gathered by Delambre and Mchain.

C LAUDE -A NTOINE P RIEUR -D UVERNOIS , known as Prieur de la Cte-dOr (17631832). A junior military engineer who became a codictator of France as a member of the Committee of Public Safety. He was a central force behind the adoption of the metric system.

E TIENNE L ENOIR (17441822). Frances premier instrument-maker. He fashioned the Borda repeating circle, as well as the definitive platinum meter bar of 1799.

I n June 1792in the dying days of the French monarchy, as the world began to revolve around a new promise of Revolutionary equalitytwo astronomers set out in opposite directions on an extraordinary quest. The erudite and cosmopolitan Jean-Baptiste-Joseph Delambre made his way north from Paris, while the cautious and scrupulous Pierre-Franois-Andr Mchain made his way south. Each man left the capital in a customized carriage stocked with the most advanced scientific instruments of the day and accompanied by a skilled assistant. Their mission was to measure the world, or at least that piece of the meridian arc which ran from Dunkerque through Paris to Barcelona. Their hope was that all the worlds peoples would henceforth use the globe as their common standard of measure. Their task was to establish this new measurethe meteras one ten-millionth of the distance from the North Pole to the equator.

The meter would be eternal because it had been taken from the earth, which was itself eternal. And the meter would belong equally to all the people of the world, just as the earth belonged equally to them all. In the words of their Revolutionary colleague Condorcetthe founder of mathematical social science and historys great optimistthe metric system was to be for all people, for all time.

We often hear that science is a revolutionary force that imposes radical new ideas on human history. But science also emerges from within human history, reshaping ordinary actions, some so habitual we hardly notice them. Measurement is one of our most ordinary actions. We speak its language whenever we exchange precise information or trade objects with exactitude. This very ubiquity, however, makes measurement invisible. To do their job, standards must operate as a set of shared assumptions, the unexamined background against which we strike agreements and make distinctions. So it is not surprising that we take measurement for granted and consider it banal. Yet the use a society makes of its measures expresses its sense of fair dealing. That is why the balance scale is a widespread symbol of justice. The admonition is found in the Old Testament: Ye shall do no unrighteousness in judgment, in meteyard, in weight, or in measure. Just balances, just weights, a just ephah, and a just hin, shall ye have. Our methods of measurement define who we are and what we value.