Brownian Motion and Molecular Reality

by George E. Smith, Raghav Seth

Overview

Between 1905 and 1913, French physicist Jean Perrin's experiments on Brownian motion ostensibly put a definitive end to the long debate regarding the real existence of molecules, proving the atomic theory of matter. While Perrin's results had a significant impact at the time, later examination of his experiments questioned whether he really gained experimental access to the molecular realm. The experiments were successful in determining the mean kinetic energy of the granules of Brownian motion; however, the values for molecular magnitudes Perrin inferred from them simply presupposed that the granule mean kinetic energy was the same as the mean molecular kinetic energy in the fluid in which the granules move. This stipulation became increasingly questionable in the years between 1908 and 1913, as significantly lower values for these magnitudes were obtained from other experimental results like alpha-particle emissions, ionization, and Planck's blackbody radiation equation. In this case study in the history and philosophy of science, George E. Smith and Raghav Seth here argue that despite doubts, Perrin's measurements were nevertheless exemplars of theory-mediated measurement-the practice of obtaining values for an inaccessible quantity by inferring them from an accessible proxy via theoretical relationships between them. They argue that it was actually Perrin more than any of his contemporaries who championed this approach during the years in question. The practice of theory-mediated measurement in physics had a long history before 1900, but the concerted efforts of Perrin, Rutherford, Millikan, Planck, and their colleagues led to the central role this form of evidence has had in microphysical research ever since. Seth and Smith's study thus replaces an untenable legend with an account that is not only tenable, but more instructive about what the evidence did and did not show.

Product Details

ISBN-13:	9780190098049
Publisher:	Oxford University Press
Publication date:	08/14/2020
Series:	Oxford Studies in Philosophy of Science
Sold by:	Barnes & Noble
Format:	eBook
Pages:	288
File size:	3 MB

About the Author

George E. Smith, Professor of Philosophy, Tufts University, Raghav Seth, Anesthesiology Resident, Beth Israel Deaconess Medical Center George E. Smith joined the Philosophy Department of Tufts University in 1977. He specializes in the critical assessment of evidence in the physical sciences especially during historical transitions in which areas of research go from struggling to extract high quality evidence out of data to becoming exceptionally effective in doing so. He served as Acting Director of the Dibner Institute for the History of Science and Technology at MIT from 2001 until 2006 and has twice been a Distinguished Visiting Professor in the Philosophy Department of Stanford University. Raghav Seth graduated from Tufts University in 2012 with a B.A. in Philosophy. After college, he worked as a research assistant at the McGovern Institute for Brain Research at MIT and then as an EMT in Essex County before transitioning to medical school at the Tufts University School of Medicine from which he graduated in 2018. He is currently an anesthesiology resident at Beth Israel Deaconess Medical Center.

Table of Contents

Preface Bibliographical Notice Chapter 1. Introduction 1.1 Brownian Motion and Molecular Reality: The "Lore" 1.2 Two Issues 1.3 Challenges to Our Second Issue 1.4 Why the Focus So Narrowly on Perrin? 1.5 Organization of the Monograph Chapter 2. The Historical Background: Molecular Theory as of 1900 2.1 On the "Hypothetical" Status of the Molecular Hypothesis 2.2 Kinetic Theory as a Means of Gaining Access to Molecules 2.3 The Problem Posed by the Specific Heats of Gases 2.4 Ostwald on How a Hypothesis Can Become Something More 2.5 A Further Dimension of the Dispute over Molecular-Kinetic Theory 2.6 A Major Development in Support of the Molecular Hypothesis 2.7 Ions in Solutions: van't Hoff, Arrhenius, Ostwald, and Nernst 2.8 By What Authority Still Only a Hypothesis? Chapter 3. The Historical Bakcground: Brownian Motion 3.1 The Promise of Brownian Motion 3.2 Granular Velocity Measurement: A Failure in Experimentation 3.3 Explaining Granular Velocities: A Failure in Theory-Mediation 3.4 The Problem Reconsidered; The Promise Delivered 3.5 The History in Retrospect Chapter 4. Perrin's Brownian Motion Experiments 4.1 Some Preliminaries 4.2 Perrin's Vertical-Gradient Experiments 4.3 Perrin's Vertical-Gradient Results Re-Examined 4.4 Perrin's Granule-Displacement Experiments: The Two Measures 4.5 Perrin's Granule-Displacement Experiments: Displacement Results 4.6 Perrin's Granule-Displacement Experiments: Diffusion Results 4.7 Perrin's Granule Rotation Experiments 4.8 The Three Different Types of Experiment, Taken Together 4.9 Some Remarks about "Well-Behaved" Theory-Mediated Measurements 4.10 A Critical Assessment of Perrin's Results at the Time Chapter 5. Implications for Molecular-Kinetic Theory 5.1 Testing Molecular-Kinetic Theory: The Kinetic Energy "Test" 5.2 Testing Molecular-Kinetic Theory: Other "Tests" 5.3 Grounding Molecular-Kinetic Theory 5.4 Parallels with Molecular-Kinetic Theory 5.5 Continuity with Molecular-Kinetic Theory 5.6 Continuity from Granule to Liquid Substrate 5.7 A Brief Recap Chapter 6. Converging Values of Avogadro's Number: Perrin's Comparisons 6.1 Some Historical Background 6.2 What Agreeing Measurements? 6.3 Perrin's Comparisons, Individually 6.4 Perrin on the Values # 62 x 1022 6.5 Perrin's Comparisons, Collectively 6.6 "Les Preuves de la Réalité Moléculaire"? 6.7 On Eliminating All Reference to the Invisible 6.8 A Parting Comment, re réalité moléculaire Chapter 7. Our Initial Issues, Revisited 7.1 Conclusions Established About Brownian Motion 7.2 Perrin's Contribution to the New Standing 7.3 The New Standing of Molecular Theory: Ostwald's "Conversion" 7.4 The New Standing of Molecular Theory: In the Aftermath of Solvay 7.5 On the Standing of Hypotheses 7.6 1905-1913 Within the History of Theory-Mediated Measurement Postcript on the Realism-Instrumentalism Debate 1. On the Scientific Literature 2. On Some Key Distinctions 3. On What Has Claim to Being Permanent Appendix: On Ostwald (1889-90), Nernst (1893), and Meyer (1899) Glossary Scientific Terminology Theory-mediated Measurement Terminology Bibliography

Editorial Reviews

"Any philosopher hitherto who wishes to take a stand on the relevance of Perrin's studies to the debate about realism will need to take heed of the findings here. All of the publications on the matter that preceded its publication will need to be reconsidered, my own included." — Alan Chalmers, Philosophy of Science

"...an exceptional study..." — Enric Pérez, Metascience

"...excellent...Summing Up: Recommended. Graduate students, faculty, and professionals." — F. Potter, CHOICE

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