David Malament's (1977) well-known result, which is often taken to show the uniqueness of the Poincare-Einstein convention for defining simultaneity, involves an unwarranted physical assumption: that any simultaneity relation must remain invariant under temporal reflections. Once that assumption is removed, his other criteria for defining simultaneity are also satisfied by membership in the same backward (forward) null cone of the family of such cones with vertices on an inertial path. What is then unique about the Poincare-Einstein convention is that it (...) is independent of the choice of inertial path in a given inertial frame, confirming a remark in Einstein 1905. Similarly, what is unique about the backward (forward) null cone definition is that it is independent of the state of motion of an observer at a point on the inertial path. (shrink)
After 1905, Einstein's miraculous year, physics would never be the same again. In those twelve months, Einstein shattered many cherished scientific beliefs with five extraordinary papers that would establish him as the world's leading physicist. This book brings those papers together in an accessible format. The best-known papers are the two that founded special relativity: On the Electrodynamics of Moving Bodies and Does the Inertia of a Body Depend on Its Energy Content? In the former, Einstein showed that absolute time (...) had to be replaced by a new absolute: the speed of light. In the second, he asserted the equivalence of mass and energy, which would lead to the famous formula E = mc 2 . The book also includes On a Heuristic Point of View Concerning the Production and Transformation of Light , in which Einstein challenged the wave theory of light, suggesting that light could also be regarded as a collection of particles. This helped to open the door to a whole new world--that of quantum physics. For ideas in this paper, he won the Nobel Prize in 1921. The fourth paper also led to a Nobel Prize, although for another scientist, Jean Perrin. On the Movement of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat concerns the Brownian motion of such particles. With profound insight, Einstein blended ideas from kinetic theory and classical hydrodynamics to derive an equation for the mean free path of such particles as a function of the time, which Perrin confirmed experimentally. The fifth paper, A New Determination of Molecular Dimensions , was Einstein's doctoral dissertation, and remains among his most cited articles. It shows how to calculate Avogadro's number and the size of molecules. These papers, presented in a modern English translation, are essential reading for any physicist, mathematician, or astrophysicist. Far more than just a collection of scientific articles, this book presents work that is among the high points of human achievement and marks a watershed in the history of science. Coinciding with the 100th anniversary of the miraculous year, this new paperback edition includes an introduction by John Stachel, which focuses on the personal aspects of Einstein's youth that facilitated and led up to the miraculous year. (shrink)
A discussion of the meaning of a physical concept cannot be separated from discussion of the conditions for its ideal measurement. We assert that quantization is no more than the invocation of the quantum of action in the explanation of some process or phenomenon, and does not imply an assertion of the fundamental nature of such a process. This leads to an ecumenical approach to the problem of quantization of the gravitational field. There can be many valid approaches, each of (...) which should be judged by the domain of its applicability to various phenomena. If two approaches have overlapping domains, the relation between them then itself becomes a subject of study. We advocate an approach to general relativity based on the unimodular group, which emphasizes the physical significance and measurability of the conformal and projective structures. A discussion of the method of matched asymptotic expansions, and of the weakness of terrestrial sources compared with astrophysical and cosmological sources, leads us to suggest theoretical studies of gravitational radiation based on retrodiction rather than prediction. (shrink)
The Nature of the Physical World is one of a series of semi-popular books, extremely popular and influential in the English-speaking world, that Arthur Eddington wrote between the 1920s and the 1950s. Not only were they masterful scientific expositions, but they included attempts to defend a definite philosophical position: dualism.
After introductory surveys of Poincaré’s role in the Dreyfus case and of his “Fourth Geometry,” I turn to the main question. The problem confronting both Poincaré and Einstein was how to reconcile the phenomena of electrodynamics, notably the optical principle of relativity, with the principles of Newtonian mechanics. I show that, on such questions as the existence and role of the ether and the relation between kinematics and dynamics, Poincaré and Einstein held diametrically opposed views. Poincaré did everything to preserve (...) the old viewpoint, while Einstein abandoned the absolute time and proposed a new mechanics. (shrink)
The dynamical equations for black-body radiation are derived from the vanishing of the stress-energy tensor and shown to imply a theorem which generalizes that of Tolman and Ehrenfest[Phys. Rev. 36,1791 (1930)]. A method for finding the general solution of these equations is given.
Towards the end of the career of many a distinguished scientist, or shortly after his or her death, an edition of the scientist's articles is published under the title: ‘The Collected Papers of…’. While not wishing to slight either the ceremonial importance or real utility of such collections, they must be clearly distinguished from the sort of editions on which the Collected Papers of Albert Einstein is modelled. The former are primarily intended to make the published papers of a great (...) scientist easily accessible to other scholars and students working in the same field as an aid to their research. The reader is provided with little or no help in understanding or evaluating the historical role these writings played in the development of this field, the circumstances leading to their creation, or how they fit into the life of their creator. (shrink)