Don S. Lemons - Thermodynamic Weirdness: From Fahrenheit to Clausius

2019 The Massachusetts Institute of Technology

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This book was set in ITC Stone Serif Std by Toppan Best-set Premedia Limited. Printed and bound in the United States of America.

Library of Congress Cataloging-in-Publication Data

Names: Lemons, Don S. (Don Stephen), 1949 author.

Title: Thermodynamic weirdness : from Fahrenheit to Clausius / Don S. Lemons.

Description: Cambridge, MA : The MIT Press, [2019] | Includes bibliographical references and index.

Identifiers: LCCN 2018020782 | ISBN 9780262039390 (hardcover : alk. paper)

eISBN 9780262351317

Subjects: LCSH: ThermodynamicsHistory.

Classification: LCC TJ265 .L38375 2019 | DDC 536/.7dc23 LC record available at https://lccn.loc.gov/2018020782

ePub Version 1.0

d_r0

1. Chapter 1
2. Chapter 3
3. Chapter 4
4. Chapter 5
5. Chapter 6
6. Chapter 7
7. Chapter 8
8. Chapter 9
9. Chapter 10
10. Chapter 11

Physics, chemistry, and engineering students are taught the methods of classical thermodynamics, but its principles are not often scrutinized. As a result, heat is sometimes thought to be a form of motion, and the second law of thermodynamics is often, I maintain, misidentified as the law of increase of entropy.

These missteps are quite understandable. After all, those who write thermodynamics textbooks (a group that includes me) feel, above all else, the burden of preparing students to perform well on assigned problems. These books aim at analytical prowess and problem-solving skillsnot at precise verbalizations of the laws and concepts of thermodynamics.

This problem-solving-first approach to thermodynamics works well for a certain group of students and teachers. After all, a verbal understanding of the laws and important concepts of classical thermodynamics can always be extracted from their mathematical formulation and applicationif one takes the time to do so. And such is an excellent exerciseif attempted. Yet the conceptual structure of classical thermodynamics remains elusive for many, even for many of those who can apply its laws adeptly.

One difficulty is that thermodynamics emerged in the mid-nineteenth century not out of the earlier Newtonian synthesis but from a then more recent understanding of the limitations on heat flow and the newly discovered convertibility of work and heat. Sadi Carnot, Robert von Mayer, and James Joule established these understandings, while Rudolf Clausius and William Thomson (known late in life as Lord Kelvin) harmonized and expressed them in mathematical form. In this way, thermodynamics overthrew the hegemony of Newtonian concepts.

Because beginning physical science and engineering students, now as well as then, invest great effort in mastering Newtonian mechanics, they naturally attempt to incorporate all other subjects into its structure. Yet classical thermodynamics resists this incorporation. Thermodynamic weirdness predates quantum weirdness by at least a half century.

One pedagogical response to thermodynamic weirdness is the creation of thermal physics, an approach that interprets the laws and concepts of thermodynamics in terms of the Newtonian and quantum mechanics of particles as mediated through the statistics of large numbers, that is, through statistical mechanics. This approach is successful in many ways, but it has further marginalized the patterns of thought that brought thermodynamics into being.

Thermodynamic Weirdness responds to the problem-solving-first approach to thermodynamics and thermodynamic weirdness itself in another way: by focusing on the ideas of classical thermodynamics and their relationships, one to another, verbally expressed. Hence, this book avoids reference to developments that follow and add content to classical thermodynamics, in particular, the existence of atoms and molecules, statistical methods, and the ideas of quantum mechanics. Neither does the book develop mathematical methods. While this focus may limit the interest of some, I hope the resulting emphasis on concepts and intellectual structure attracts others. I have two kinds of readers in mind: teachers and students of thermodynamics who want to deepen their understanding of its classical formation and general readers who desire an introduction to its foundational ideas.

The history of thermodynamics is singularly helpful in this authorial and readerly taskmore so, for instance, than, I think, the history of mechanics or the history of electromagnetism would be in parallel tasks. For this reason, the ideas in Thermodynamic Weirdness are chronologically as well as logically ordered, and primary sources that confirm and contextualize these ideas append most chapters. Included among the ideas explored and ordered are those, like the caloric or Thomsons 1848 definition of absolute temperature, that have in the fullness of time been found wanting, for the rise and fall of these ideas and others illumine, as no other light can, the more successful ideas that have taken their place.

Thermodynamic Weirdness also reflects my interest in the earliest versions of the second law of thermodynamics. While Carnot was the first, in 1824, to use a version of the second law, it was not until thirty years later, in 1854, that Clausius proved that the state variable we now call entropy must exist. Thus, postulating the second law of thermodynamics in terms of entropy, as is often done, obscures the development and possibly the meaning of these laws and concepts.

Even so, Thermodynamic Weirdness is not a history of thermodynamics. After all, I am a physicist and physics teacher, not a historian of science. A proper history of thermodynamics would do more to avoid Whig history, a term of opprobrium invented by Herbert Butterfield to describe an approach to intellectual history in which ideas are either emphasized or ignored according to how well they remain currenta sin of which the history of science is especially prone. Whig history allows the present to distort the past.

My aim in writing Thermodynamic Weirdness is, rather, to allow the past to enlighten the present and help readers appreciate the simplicity and coherence of classical thermodynamics, attractive features that have been obscured by its non-Newtonian origin and the current slant of pedagogical practice.

Thermodynamic Weirdness originated in my response to an anthology of primary sources on heat put together by Howard Fisher for his students at St. Johns College, Santa Fe, New Mexico. Reading the words of Daniel Fahrenheit, Joseph Black, Antoine Lavoisier, Count Rumford, Sadi Carnot, Lord Kelvin, Robert Mayer, James Joule, and Rudolf Clausius gave me a new sense of their accomplishment and deepened my appreciation for and understanding of classical thermodynamics. These luminaries are still excellent teachers.

Howard Fisher also critically reviewed initial drafts of the text, as did Rick Shanahan, Joel Krehbiel, Galen Gisler, Reuben Hersh, and Harvey Leff. Kenneth Caneva offered a historians perspective. Jesse Graber produced the figures. Blakely Mechau graciously translated, from the Latin, the excerpt from Daniel Fahrenheits paper on the freezing of water.