Robert W. Brehme

Bio: Robert W. Brehme is an academic researcher. The author has contributed to research in topics: Velocity-addition formula & Lorentz transformation. The author has an hindex of 9, co-authored 15 publications receiving 215 citations.

The Advantage of Teaching Relativity with Four-Vectors

Abstract: An argument is given that teaching relativity from the beginning using four-vectors provides a powerful and correct way of thinking that also conforms to everyday methods of making measurements. In particular, it is pointed out that the emphasis on the relativistic mass is both undeserved and misleading.

Inside the black hole

Abstract: The simplest model of a black hole, the massive point source generating a static spherically symmetric gravitational field, is examined using the Schwarzschild coordinate frame. A brief review is given of this coordinate frame external to the Schwarzschild surface. Greater attention is paid to an interpretation of this frame inside the Schwarzschild surface. Here the roles of space and time are reversed in the sense that the external radial coordinate becomes an internal temporal coordinate, and the external temporal coordinate becomes an internal spatial coordinate. An internal universe is constructed from this frame, and a few simple kinematic phenomena are described in terms of it. The internal and external coordinates are connected graphically by using Kruskal coordinates and physically by considering the world lines of photons and freely moving particles which transit the Schwarzschild surface.

A Geometric Representation of Galilean and Lorentz Transformations

Abstract: The kinematic concepts of special relativity seem best understood by the beginning student if they are presented in purely geometric form. The description of events in space-time is given geometrically as viewed from different coordinate systems in relative motion with one another, both from the classical and relativistic points of view. These geometric representations differ somewhat from those usually seen. Some justification is given the Lorentz transformation by requiring that the velocity of light be the same for all observers and that in the limit of small velocities, the Lorentz transformation reduce to the Galilean transformation. The relativistic contraction of lengths and the dilation of time intervals are deduced.

On the physical reality of the isotropic speed of light

Abstract: It was suggested by Einstein and later greatly elaborated on by others that the methods used to synchronize distant clocks are a matter of convention. The standard method, in which it is assumed that the speed of light is isotropic, obviously yields an isotropic light speed when such clocks are involved in determining the speed of light. Another method, in which clocks travel symmetrically but otherwise arbitrarily in opposite directions, may also be used to synchronize distant clocks. This method establishes whether or not the clocks are synchronized in a physically significant way in the sense that it allows a distinction to be made between a contrived anisotropic light speed and an anisotropic speed that is physically significant or real. Specifically, a contrived anisotropic light speed results in laws of physics that are not symmetric, whereas a true anisotropic light speed does not affect the symmetry of physical laws. Furthermore, when invariance in the speed of light is imposed, the invariant inte...

Drawing the line between kinematics and dynamics in special relativity

Abstract: In his book, Physical Relativity, Harvey Brown challenges the orthodox view that special relativity is preferable to those parts of Lorentz’s classical ether theory it replaced because it revealed various phenomena that were given a dynamical explanation in Lorentz’s theory to be purely kinematical. I want to defend this orthodoxy. The phenomena most commonly discussed in this context in the philosophical literature are length contraction and time dilation. I consider three other phenomena of this kind that played a role in the early reception of special relativity in the physics literature: the Fresnel drag eect in the Fizeau experiment, the velocity dependence of electron mass in -ray deflection experiments by Kaufmann and others, and the delicately balanced torques on a moving charged capacitor in the Trouton-Noble experiment. I oer historical sketches of how Lorentz’s dynamical explanations of

One hundred third critical bibliography of the history of science and its cultural influences (to January 1978).

Abstract: The present CriticalTBibliography,* which includes 2636 citations, is the twenty-fourth to be classified according to the system established in 1953. The main purpose of the classification has always been, in the words of its founder, George Sarton, "to satisfy the needs of historians of science in general rather than those of historians of particular sciences". While the classification is both chronological and by subject, preference is given to the former. The reader who wishes to find all references to a particular subject, therefore, must examine several sections of the bibliography.

Thomas precession: Its underlying gyrogroup axioms and their use in hyperbolic geometry and relativistic physics

Abstract: Gyrogroup theory and its applications is introduced and explored, exposing the fascinating interplay between Thomas precession of special relativity theory and hyperbolic geometry. The abstract Thomas precession, called Thomas gyration, gives rise to grouplike objects called gyrogroups [A, A. Ungar, Am. J. Phys.59, 824 (1991)] the underlying axions of which are presented. The prefix gyro extensively used in terms like gyrogroups, gyroassociative and gyrocommutative laws, gyroautomorphisms, and gyrosemidirect products, stems from their underlying abstract Thomas gyration. Thomas gyration is tailor made for hyperbolic geometry. In a similar way that commutative groups underlie vector spaces, gyrocommutative gyrogroups underlie gyrovector spaces. Gyrovector spaces, in turn, provide a most natural setting for hyperbolic geometry in full analogy with vector spaces that provide the setting for Euclidean geometry. As such, their applicability to relativistic physics and its spacetime geometry is obvious.