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)

In this paper we describe a propagation experiment to measure the one-way velocity of electromagnetic radiation. The experiment utilizes the rotation of the earth to interchange the positions of two rubidium vapor frequency standards over12 h, thereby canceling initial clock phase differences. It is demonstrated that although the drift characteristics of modern rubidium atomic clocks may be large for long-term absolute timing requirements, the short-term random fluctuations are small. It is found that over a24-h period, the long-term drift can be (...) accurately parameterized in retrospect and removed, thereby permitting the detection of temporal variations less than1 nsec in magnitude. With coherent summing techniques this value may be significantly reduced, and it becomes realistic to consider an experiment where the clocks are separated by distances of the order of several hundreds of meters in order to detect velocities of the order of that of the solar system with respect to the center of the galaxy(≈10 5 m sec −1 ), thus ensuring that the rotational motion of the earth has a negligible effect in altering the relative inertial characteristics of the reference frames of each clock. It is demonstrated that under such conditions the measurement of the one-way speed of propagation of electromagnetic radiation is not only meaningful, but can be simply implemented with commercially available instrumentation. (shrink)

This collection of original papers on the special and general theories of relativity constitutes an indispensable part of a library on relativity. Here are the 11 papers that forged the general and special theories of relativity: seven papers by Einstein, plus two papers by Lorentz and one each by Minkowski and Weyl.

After describing a new method of synchronizing spatially separated clocks by means of clock transport, this paper discusses the philosophical import of the existence of such methods, including those of Ellis and Bowman and of Bridgman, with special reference to the Ellis-Bowman claim that "the thesis of the coventionality of distant simultaneity... is thus either trivialized or refuted." I argue that the physical facts do not support this philosophical conclusion, and that a substantial part of their argument against Reichenbach, in (...) particular, is misdirected. Finally, I suggest that Ellis and Bowman employ seriously unclear notions of triviality and "good physical reasons" that tend to obscure rather than clarify the basic philosophical issues. An objective criterion of nontriviality of conventions is advanced. (shrink)

The paper defends the thesis of conventionality in distant simultaneity within the special theory of relativity. The thesis can be expressed in the following way: There is no method independent of standard synchronization by which the one-way velocity of light can be measured if all empirical consequences of the special theory of relativity are to be accepted. Three methods which have recently been suggested are investigated. It is shown that they all depend on the method of standard synchronization. It is (...) finally claimed that nobody has suggested a method which cannot be shown to depend on the method of standard synchronization. (shrink)

The Conventionality of Simultaneity espoused by Reichenbach, Grunbaum, Edwards, and Winnie is herein extended to mechanics and electrodynamics. The extension is seen to be a special case of a generally covariant formulation of physics, and therefore consistent with Special Relativity as the geometry of flat space-time. Many of the quantities of classical physics, such as mass, charge density, and force, are found to be synchronization dependent in this formulation and, therefore, in Reichenbach's terminology, "metrogenic." The relationship of these quantities to (...) 4-vectors and their physical significance is discussed. (shrink)

The most recent attempt at factually establishing a "true" value for the one-way velocity of light is shown to be faulty. The proposal consists of two round-trip photons travelling first in vacuo and then through a medium of refractive index n before returning to their common point of origin. It is shown that this proposal, as well as a similar one considered by Salmon (1977), presupposes that the one-way velocities of light are equal to the round-trip value. Furthermore, experiments of (...) this type, involving regions of space with varying refractive indices, cannot "single out" any factual value for the Reichenbach-Grünbaum ε factor thus posing no threat to the conventionalist thesis. (shrink)

The Law of Inertia plays a key role in the scheme of constructive axioms for the General Theory of Relativity. A new formulation of this law which avoids the circularity problems inherent in previous formulations is presented. The empirical status of this law and the manner in which it provides a non-conventional foundation for the Law of Motion and the definition of physical forces is established. First, quite general path structures are discussed which are not defined at the outset in (...) terms of geodesic paths and which require for their description only the local differential topological structure. Secondly, a number of theorems are presented which serve as purely local differential topological criteria for singling out from among the general path structures the geodesic ones that represent the inertial structure of spacetime. (shrink)