Einstein’s 1935 derivation of mass—energy equivalence is philosophically important because it contains both a criticism of purported demonstrations that proceed by analogy and strong motivations for the definitions of the ‘new’ dynamical quantities. In this paper, I argue that Einstein’s criticism and insights are still relevant today by showing how his derivation goes beyond Friedman’s demonstration of this result in his Foundations of Spacetime ¹heories. Along the way, I isolate three distinct physical claims associated with Einstein’s famous equation that are (...) sometimes not clearly distinguished in philosophical discussions of spacetime theory. (shrink)

Collaboration on the First Edition of Spacetime Physics began in the mid-1960s when Edwin Taylor took a junior faculty sabbatical at Princeton University where John Wheeler was a professor. The resulting text emphasized the unity of spacetime and those quantities (such as proper time, proper distance, mass) that are invariant, the same for all observers, rather than those quantities (such as space and time separations) that are relative, different for different observers. The book has become a standard introduction to relativity. (...) The Second Edition of Spacetime Physics embodies what the authors have learned during an additional quarter century of teaching and research. They have updated the text to reflect the immense strides in physics during the same period and modernized and increased the number of exercises, for which the First Edition was famous. Enrichment boxes provide expanded coverage of intriguing topics. An enlarged final chapter on general relativity includes new material on gravity waves, black holes, and cosmology. The Second Edition of Spacetime Physics provides a new generation of readers with a deep and simple overview of the principles of relativity. (shrink)

The book opens with a description of the smooth transition from Newtonian to Einsteinian behaviour from electrons as their energy is progressively increased, ...

This book combines physics, history, and philosophy in a radical new approach to introducing the philosophy of physics.

It is known that Maxwell’s electrodynamics—as usually understood at the present time—when applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena. Take, for example, the reciprocal electrodynamic action of a magnet and a conductor. The observable phenomenon here depends only on the relative motion of the conductor and the magnet, whereas the customary view draws a sharp distinction between the two cases in which either the one or the other of these bodies (...) is in motion. For if the magnet is in motion and the conductor at rest, there arises in the neighbourhood of the magnet an electric field with a certain definite energy, producing a current at the places where parts of the conductor are situated. But if the magnet is stationary and the conductor in motion, no electric field arises in the neighbourhood of the magnet. In the conductor, however, we find an electromotive force, to which in itself there is no corresponding energy, but which gives rise—assuming equality of relative motion in the two cases discussed—to electric currents of the same path and intensity as those produced by the electric forces in the former case. Examples of this sort, together with the unsuccessful attempts to discover any motion of the earth relatively to the “light medium,” suggest that the phenomena of electrodynamics as well as of mechanics possess no properties corresponding to the idea of absolute rest. They suggest rather that, as has already been shown to the first order of small quantities, the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good.1 We will raise this conjecture (the purport of which will hereafter be called the “Principle of Relativity”) to the status of a postulate, and also introduce another postulate, which is only apparently irreconcilable with the former, namely, that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body.. (shrink)

It is argued that Minkowski space-time cannot serve as the deep structure within a ``constructive'' version of the special theory of relativity, contrary to widespread opinion in the philosophical community.

The purpose of this paper is to evaluate the `Lorentzian Pedagogy' defended by J.S. Bell in his essay ``How to teach special relativity'', and to explore its consistency with Einstein's thinking from 1905 to 1952. Some remarks are also made in this context on Weyl's philosophy of relativity and his 1918 gauge theory. Finally, it is argued that the Lorentzian pedagogy---which stresses the important connection between kinematics and dynamics---clarifies the role of rods and clocks in general relativity.

Bell’s spaceship ‘paradox’ [1] in special relativity is a particularly good one to examine with students, because although it deals with accelerated motions, it can be dissolved with elementary space–time diagrams. Furthermore, it forces us to be very clear about the relativity of simultaneity, proper length, and the ‘reality’ of the Lorentz contraction.

Appearance and Reality: An Introduction to the Philosophy of Physics addresses quantum mechanics and relativity and their philosophical implications, focusing on whether these theories of modern physics can help us know nature as it really is, or only as it appears to us. The author clearly explains the foundational concepts and principles of both quantum mechanics and relativity and then uses them to argue that we can know more than mere appearances, and that we can know to some extent the (...) way things really are. He argues that modern physics gives us reason to believe that we can know some things about the objective, real world, but he also acknowledges that we cannot know everything, which results in a position he calls realistic realism. This book is not a survey of possible philosophical interpretations of modern physics, nor does it leap from a caricature of the physics to some wildly alarming metaphysics. Instead, it is careful with the physics and true to the evidence in arriving at its own realistic conclusions. It presents the physics without mathematics, and makes extensive use of diagrams and analogies to explain important ideas. Engaging and accessible, Appearance and Reality serves as an ideal introduction for anyone interested in the intersection of philosophy and physics, including students in philosophy of physics and philosophy of science courses. (shrink)

Nobel Laureate's brilliant early treatise on Einstein's theory consists of his original 1921 text plus retrospective comments 35 years later.

Appearance and Reality: An Introduction to the Philosophy of Physics addresses quantum mechanics and relativity and their philosophical implications, focusing on whether these theories of modern physics can help us know nature as it really is, or only as it appears to us. The author clearly explains the foundational concepts and principles of both quantum mechanics and relativity and then uses them to argue that we can know more than mere appearances, and that we can know to some extent the (...) way things really are. He argues that modern physics gives us reason to believe that we can know some things about the objective, real world, but he also acknowledges that we cannot know everything, which results in a position he calls "realistic realism." This book is not a survey of possible philosophical interpretations of modern physics, nor does it leap from a caricature of the physics to some wildly alarming metaphysics. Instead, it is careful with the physics and true to the evidence in arriving at its own realistic conclusions. It presents the physics without mathematics, and makes extensive use of diagrams and analogies to explain important ideas. Engaging and accessible, Appearance and Reality serves as an ideal introduction for anyone interested in the intersection of philosophy and physics, including students in philosophy of physics and philosophy of science courses. (shrink)