Energy, the Subtle Concept: The discovery of Feynman's blocks from Leibniz to Einstein

441 Pages·2015·7.164 MB·English

by  Jennifer Coopersmith

ENERGY, THE SUBTLE CONCEPT
Nicolas Poussin, A Dance to the Music of Time, c. 1640 (By kind permission of the Trustees of the
Wallace Collection, London).
Energy, the
Subtle Concept
The discovery of Feynman’s blocks
from Leibniz to Einstein
JENNIFER COOPERSMITH
Revised Edition
1
1
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9780198716747-Coopersmith.indb 4 12/03/15 6:04 PM
To
Bertie Coopersmith
and
Murray Peake,
sages both

Preface to the Revised Edition
This book is both a history of the emergence of the concept of energy
and an explanation of energy through that history. As it is primarily a
book of explanation, the historical coverage is not exhaustive, and also
‘energy’ is brought in ahead of its final discovery, wherever an explan-
ation in modern terms would be an aid to understanding. The level is
popular science but hard thinking is required—we might call it serious
popular science. The facts do not, in general, speak for themselves, and
the aim is not only to explain, but, most of all, to imbue the reader with
a sense of awe—over these very facts, and the genius of their discoverers.
This second edition is more comprehensive in its coverage, especially
in Chapter 17, ‘A Forward Look’, but at the same time it is more stream-
lined in order to better bring out the logic of the arguments—argu-
ments that will lead to the concept of energy. The expertise gained while
researching The Lazy Universe: the Principle of Least Action Explained
(Oxford University Press, in preparation) has led to some changes in
Chapter 7, Part IV, and Chapter 13, ‘Hamilton’, and to some new ma-
terial in Chapter 18, ‘Impossible Things, Difficult Things’.
‘Energy’ is a huge topic, and to keep the book at a reasonable length,
and in one volume, energy in the current era has not been considered;
in fact, the aim has been to cover material, and to provide insights, not
easily found by a computer search. Likewise, the amount of biographical
detail is mostly in inverse proportion to the fame of the given scientist.
Some ‘housekeeping’:
Quotation marks appear all over the place, sometimes in thickets, and
with little attempt at consistency. This is because as new ideas arrive, new
words hover over them, and it takes a few decades for the right word to
land. (There are also many commas—this is the OUP house style.)
Mathematical notation: ‘height ∝ age’ means ‘height is proportional to
age’, ‘<x >’ means ‘the average value of x’, ‘Δx’ means ‘a small increment
in x’, ‘∫Edt’ is the ‘integral of E with respect to t’ or ‘the integral of E over
t’, or, less often, ‘the integral of E through t’, and is roughly equivalent to
a summation of the separate increments, E dt + E dt + E dt + . . . Vectors
1 2 3
are quantities that have a direction as well as a magnitude (a bit like an
arrow, of length 40 cm, pointing due west). They are indicated in bold;
viii Preface to the Revised Edition
for example v is velocity, whereas v is just the magnitude of velocity, also
known as speed.
The history has been given in roughly chronological order, but ‘heavy’
chapters on theoretical developments are interspersed with ‘lighter’
chapters on experiments and phenomenology. Chapters 7 (the last sec-
tion), 13, 17, and 18 assume some background knowledge in the physi-
cal sciences: readers with this background will enjoy the broad sweep
across the whole of physics (Chapter 17), and other readers should not
be discouraged as much knowledge can seep in by osmosis. Also, all
chapters contain gentle introductions, summaries, and occasional dis-
cursive sections (for example, on interactions between physicists, energy
in the public domain, and global warming). The summaries were vari-
ously called conclusions, summary, resumé, review, comments, remarks,
and so on, but the copy editor swept these aside and insisted on a uni-
form descriptor—‘overview’. Just one ‘Remarks’ has survived, in the
middle of Chapter 8 (the end of the section on Watt), as the remarks
really are . . . remarkable—there is even a mention of sex.
Acknowledgements
Six marvellous books have guided me and been my constant com-
panions: Donald Cardwell’s From Watt to Clausius: the Rise of Ther-
modynamics in the Early Industrial Age, Cornelius Lanczos’ The
Variational Principles of Mechanics, Richard Feynman’s Lectures on
Physics, Richard Westfall’s Force in Newton’s Physics, Charles Gillispie’s
The Edge of Objectivity, and Brian Pippard’s The Elements of Classical
Thermodynamics.
In the case of the last two books, I have been privileged to have a cor-
respondence with the authors. Both have been extremely enthusiastic
and encouraging (Professor Sir Brian Pippard died last year). Professor
Gillispie (Emeritus Professor at Princeton and founding father of the
discipline of the history of science) has read many of my draft chap-
ters and made invaluable suggestions. Professor Paul Davies (physicist,
science writer, and founder and director of ‘Beyond, Center for Funda-
mental Concepts in Science’), and Emeritus Professor Rod Home (De-
partment of History and Philosophy of Science, Melbourne University)
read some early draft chapters and were likewise very encouraging.
I would like to thank past colleagues and friends at King’s College
London, TRIUMF, UBC, Logica SDS, and the Open University. I
would especially like to thank the Open University students (London,
Winchester, and Oxford, 1986–96) who asked all those difficult-to-
answer questions.
My present colleagues at La Trobe University, Bendigo Campus, and
Swinburne University of Technology in Melbourne have been very sup-
portive. In particular, I would like to thank the late Rob Glaisher, Kath-
erine Legge, Glenys Shirley, John Schutz, Mal Haysom, Joe Petrolito,
John Russell, Glen Mackie, and Sarah Maddison. For special tasks: Mal
Haysom took the cover photos, Andrew Kilpatrick was tireless in draw-
ing diagrams, even randomizing the position of dot-molecules by hand
(mind you, I assisted with his marking-avoidance strategies), Sabine
Wilkens translated Euler and trawled through Helmholtz’s endless ac-
counts of indigestion, and Glenys Shirley helped with anything and eve-
rything, and with characteristic good humour.
I thank the University of La Trobe, Faculty of Science, Technology
and Engineering, Bendigo Campus, for providing me with an office,