Seduced by Logic Emilie Du Chatelet, Mary Somerville and the Newtonian Revolution

345 Pages·2012·1.069 MB·English

by  Arianrhod, Robyn

SEDUCED BY LOGIC
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SEDUCED BY LOGIC
Émilie Du Châtelet, Mary Somerville
and the Newtonian Revolution
Robyn Arianrhod
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1
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© Robyn Arianrhod 2012
First published in Australia in 2011 by University of Queensland Press.
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Library of Congress Cataloging-in-Publication Data
Arianrhod, Robyn.
Seduced by logic : Émilie Du Châtelet, Mary Somerville,
and the Newtonian revolution / Robyn Arianrhod.
p. cm.
ISBN 978-0-19-993161-3
1. Du Châtelet, Gabrielle Émilie Le Tonnelier de Breteuil, marquise, 1706-1749.
2. Somerville, Mary, 1780-1872. 3. Women scientists—France—Biography. 4. Women
scientists—Great Britain—Biography. 5. Scientists—France—Biography. 6. Scientists—
Great Britain—Biography. 7. Women—France—Intellectual life—18th century.
8. Women—Great Britain—Intellectual life—19th century. I. Title.
Q141.A725 2012
510.92—dc23[B] 2012006294
1 3 5 7 9 8 6 4 2
Typeset in Janson Text
Printed in the United States of America
on acid-free paper
CONTENTS
Introduction 1
1 Madame Newton du Châtelet 6
2 Creating the theory of gravity: the Newtonian controversy 12
3 Learning mathematics and fighting for freedom 20
4 Émilie and Voltaire’s Academy of Free Thought 37
5 Testing Newton: the ‘New Argonauts’ 56
6 The danger in Newton: life, love and politics 67
7 The nature of light: Émilie takes on Newton 80
8 Searching for ‘energy’: Émilie discovers Leibniz 97
9 Mathematics and free will 114
10 The re-emergence of Madame Newton du Châtelet 132
11 Love letters to Saint-Lambert 147
12 Mourning Émilie 155
13 Mary Fairfax Somerville 161
14 The long road to fame 175
15Mechanism of the Heavens 197
16 Mary’s second book: popular science in the nineteenth
century 214
17 Finding light waves: the ‘Newtonian Revolution’ comes
of age 227
18 Mary Somerville: a fortunate life 244
Epilogue: Declaring a point of view 252
Appendix 258
Notes and Sources 286
Bibliography 318
Acknowledgments 328
Index 329
INTRODUCTION
Two of my favourite women in history are the wonderfully outra-
geous Émilie du Châtelet and the charmingly subversive Mary
Somerville. Against great odds, Émilie and Mary taught themselves
mathematics, and they did it so well that they each became a world
authority on Newtonian mathematical physics. When I started out
studying higher mathematics, the very existence of these women
was enough to encourage me to believe that I, too, could succeed.
But this book took shape much more recently, when I discovered a
new connection with my heroines.
I was in Paris, researching Émilie’s life and work, and just as I
had hoped, it was both moving and exciting to be able to build a
deeper kinship with her–walking the streets she walked, reading
her poignant, passionate letters, and best of all, reading her painstak-
ingly handwritten manuscript of her French translation of Newton’s
monumental Principia. But this last experience led me to something
entirely unexpected: a deeper appreciation of Newton himself, and
of the importance of his work not only in science, but also in our
cultural history. Of course, I already admired Newton immensely: in
the Principia (the full title of which is Philosophiae Naturalis Principia
Mathematica or Mathematical Principles of Natural Philosophy), he
published his famous theory of gravity, and in so doing, he created
the very discipline of theoretical physics. But modern students and
researchers generally study modern textbooks and current research
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Seduced by Logic
papers, not fusty original sources, so it was through reading Émilie’s
translation of the Principia that I first seriously engaged with this
magnificent book.
In fact, I became so entranced by Newton’s awesome scope and style
that, in order to appreciate it more fully, I began reading the Principia
in English, and for many weeks I couldn’t put it down. Predictably,
I wrestled with the archaic and sometimes anarchic parts of it, but
the underlying conception was bold and modern. I was astonished
at Newton’s extraordinary attention to detail, and I marvelled that
one man was able to tie together, in one profoundly satisfying whole,
all the astronomical knowledge of his forbears, as well as his own
remarkable discoveries. And suddenly, I felt what Émilie must have
felt 260 years earlier when she began her translation, because I, too,
was in thrall to Newton’s brilliance. Before then, my appreciation
had been relatively academic, based on the fact that so much had
flowed from Newton’s work, including Einstein’s theory of general
relativity (which is my own area of research); but as I began to read
thePrincipia more closely, I watched with awe and delight as the first
comprehensive scientific theory in history took shape before my eyes.
We take the idea of universal gravity for granted today, so it is easy
to forget that once it was actually considered contentious. However,
in using his theory to solve the ancient mystery of why the planets
move through the sky, Newton had wrenched humanity once and for
all from its age-old place at the centre of the universe. Moreover, he
had done it not with the traditional tools of theology or philosophy,
but with the seductive logic of mathematics. Newton’s mathematics
was so seductive, in fact, that most of his late seventeenth-century
Continental peers were both dazzled and suspicious, because the
theory of gravity had been built solely on physical observation and
mathematical insight, with no recourse to the usual religious or meta-
physical hypotheses about the nature of reality.
But Émilie and some of her early eighteenth-century
Enlightenment colleagues–including her lover, Voltaire–real-
ised the Principia had changed not only the way we see the world,
but also the way we do science. Newton had created a method for
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Introduction
constructing and then testing theories, so the Principia provided the
first truly modern blueprint for theoretical science as both a predic-
tive, quantitative discipline–Newton eschewed qualitative, unproven
metaphysical speculations–and a secular discipline, separate from
religion, although by no means inherently opposed to it. Since then,
this style of mathematical physics has had such a phenomenal impact
on the way we live and the way we see ourselves in the universe that
Newton is probably the most important scientist of all time, and
Émilie was one of the first Continental scholars to actively promote
his radical new way of thinking. In the late 1740s, she also made what
is still the authoritative French translation of Newton’s 510-page
masterpiece, and she added a detailed ‘commentary’ that summarised
both Newton’s work and that of his earliest Continental followers.
Almost a century later, the Scottish-born Mary Somerville became
a world authority on nineteenth-century Newtonian mathemati-
cal physics. There is an interesting symmetry in the fact that, while
Émilie helped bring Newton’s ideas from Britain to France in the
first place, Mary helped take back to Britain the extraordinary
Continental development of Newton’s work that had taken place
since then. In particular, while Émilie had translated the Principia
into French, Mary translated into English the work of Pierre Simon
Laplace, Newton’s famous French disciple.
Laplace’s exhaustive five-volume Mécanique Céleste (Celestial
Mechanics) summed up the then-current state of gravitational mathe-
matics. It was widely acclaimed as the greatest intellectual achievement
since the Principia, and Mary Somerville was considered to be one of
the few people capable of bringing it to an English-speaking audi-
ence. Her book was not a literal translation but an expanded version
of Laplace’s first two volumes, so it is a stand-alone exposition of the
mathematics needed to explain what she called, in the title of her
book, the underlying ‘mechanism of the heavens’.
Mechanism of the Heavens became a standard text at Cambridge
University for the next hundred years. And recently, it introduced
me to Laplace’s great work, although I am not interested in Mary and
Émilie solely because they make accessible two of history’s greatest
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