A Tale of Two Twins: The Langevin Experiment of a Traveler to a Star

Description

The thought experiment proposed by Langevin in 1911, known under the popular names, 'Clock Paradox' or 'Twin Paradox', is the most surprising result of the theory of Relativity: A twin who travels to a star at nearly the velocity of light comes back to Earth and finds his twin brother much older. In over a century, several thousands of published articles debated both in favor of and against this result. Unique to the physics of Relativity, this baffling phenomenon is analyzed as a main goal of this book.Among an incredible number of solutions, is there one of simplicity and clarity which may be accepted unanimously by all of the physics community? The answer is yes and this solution, which has its origin in Einstein himself, is developed in the framework of the Special Theory of Relativity. In detailing this solution, it is shown that the essential ingredient to understand the theory is the acceleration of the twins. All the models which do not include acceleration are incompatible with the original idea of Langevin. If one considers this phenomenon, several questions come to mind. Why did physicists debate excessively on the paradox and struggle to reach an agreement? Why was there resistance to integrate acceleration into their studies? Why is the solution developed in this book known only by a minority of scientists?Written for physicists, historians and philosophers of science, this book seeks to answer these questions based on (1) the psychological difficulty to accept the theoretical results, and (2) the fact that scientific knowledge is not uniformly distributed among scientists. Contents Preface 1. Introduction Part I: Langevin 2. The Story in Short 2.1. The Langevin Article 2.2. Einstein in Paris: The Meeting with Bergson 2.3. The First Reactions 2.4. The Deluge of Solutions After 1950 2.5. The Solution of Møller (1952) 2.6. The Dingle and Sachs Controversies 2.7. The Deniers 2.8. The Article 3. The Article of Langevin Part II: Physics 4. The Clock or The Twin Paradox 4.1. Inertial Frames 4.2. The Lorentz Transformation 4.2.1. Application of the Lorentz transformation 4.2.2. Simultaneity and length contraction 4.3. Dynamics 4.4. The Formulation 4.5. When a Frame Stops Its Motion 4.6. A Graphical Solution 4.7. The Two Aspects of the Concept of Mass 4.8. The Gravitation–Acceleration Equivalence 4.9. The Time in a Non-inertial Frame 4.10. The Langevin Problem 5. The First Solutions 5.1. The First Einstein Argument 5.2. The Lorentz Solution 5.3. The Langevin Solution 5.4. The Einstein Solution 5.5. The Born Solution 6. The Einstein-Møller Solution 6.1. Determination of the Travel Times 6.1.1. The point of view of the observer on the earth 6.1.2. The point of view of the traveler 6.2. Analysis of the Travel Times 6.3. The Hafele–Keating Experiment 6.4. The Precursor and the Followers 7. The Disappearance of the Acceleration and the Symmetry Breaking 7.1. How to Clear the Acceleration? 7.2. The Symmetry Breaking 7.3. The Exchange of Signals 7.4. The Three-Frame Model 7.4.1. Solution of the three-frame model Summary of Part II Part III: Discussions 8. Physicists Out of the Mainstream 8.1. The Dingle Controversy 8.2. The Sachs Controversy 8.3. Dingle Versus Sachs 9. Questions With and Without Answers 9.1. The Time Dilation and the Time Reciprocity 9.2. Forgetting Reciprocity 9.3. The Acceleration 9.4. The Multiplicity of Solutions 9.5. Concluding Remarks 10. Bergson and the Relativity 10.1. The Philosopher Bergson 10.2. The Content of “Duration and Simultaneity” 10.3. Debates and Critics 10.4. The Journey of the Projectile (The Clock Paradox) 11. The Langevin Effect Bibliography Index