The relation of the special and the general principle of relativity to the principle of covariance, the principle of equivalence and Mach's principle, is discussed. In particular, the connection between Lorentz covariance and the special principle of relativity is illustrated by giving Lorentz covariant formulations of laws that violate the special principle of relativity: Ohm's law and what we call “Aristotle's first and second laws.” An “Aristotelian” universe in which all motion is relative to “absolute space” is considered. The first (...) law: a free particle is at rest. The second law: force is proportional to velocity. Ohm's law: the current density is proportional to the electrical field strength. Neither of these laws fulfills the principle of relativity. The examples illustrate, in the context of Lorentz covariance and special relativity, Kretschmann's critique of founding Einstein's general principle of relativity on the principle of general covariance. A modification of the principle of covariance is suggested, which may serve as a restricted criterium for a physical law to satisfy Einstein's general principle of relativity. Other objections that have been raised to the validity of Einstein's general principle of relativity are based upon the preferred state of inertial frames in the general, as well as in the special theory, the existence of tidal effects in “true” gravitational fields, doubts as to the validity of Mach's principle, whether electromagnetic phenomena obey the principle, and, finally, the anisotropy of the cosmic background radiation. These objections are reviewed and discussed. (shrink)
The question is discussed whether the description of the gravitational Doppler effect as a simple energy effect is consistent with its general-relativistic description as a metric-time effect. The difference between a local description and a global one is stressed. In the local description one is permitted to ignore metric effects. The global description yields a position-dependent rate of proper time in a gravitational field, and the energy, or the frequency, of a “freely falling” photon is described as a constant of (...) motion. An experiment of nonlocal character measuring, simultaneously, the gravitational Doppler effect and the position-dependent rate of proper time may be performed by the use of a geostationary satellite. A simple general-relativistic treatment of the satellite experiment is obtained by transforming the Schwarzschild metric to a rotating frame, and describing the motion of free particles and the rates of standard clocks in the resulting metric. (shrink)
Using the time orthogonal spatial line element, which characterizes the spatial geometry inside a given reference frame in a coordinate-invariant way, the condition for uniform rotating motion without tangential strain is deduced. The results are the same as those previously found by Grunbaum and Janis using another method, and shows that my earlier criticism of their work is not valid.
This chapter examines Soren Kierkegaard's views about the concept of time and history. It suggests that while time and history do not figure prominently in the works of Kierkegaard, the implications of his key concepts can only be understood through the questions of time and history, particularly his ideas about selfhood, existence, and the ethical. The chapter also discusses the different notions of time and history, and considers how time and history come into play in the works of Kierkegaard.
"This book originates from a conference ... which took place at the Danish National Research Foundation's Center for Subjectivity Research, University of Copenhagen, on December 4-5, 2008... The articles collected ... are not proceedings but a selection of re-written texts from the conference including additional texts by authors invited to contribute to the book"--Page V.
A rotating disk with angular acceleration is given a relativistic description as observed from the rotating rest frameR of the disk. It is shown how a non-Euclidean intrinsic spatial geometry develops inR, as the disk gets an angular velocity. The explanation of this as given by anR-observer is discussed. A recent description of the geometry inR presented by Grünbaum and Janis is criticized. The motion of light as described by use of coordinate clocks inR is discussed in connection with some (...) recent work by R. C. Jennison and coworkers. The significance of the difference between directed signals and circular waves when clocks inR are to be synchronized by means of light emitted from the axis inR is made clear. (shrink)
This paper presents an introduction to Arne Grøn’s existential hermeneutics as a philosophical method, while also attempting to indicate how Grøn’s work contributes to and engages in a number of crucial topics in modern continental philosophy. The first section of the paper shows how Grøn draws on Paul Ricoeur and Michael Theunissen to rethink the concept of existence through a reading of Kierkegaard that uncouples this concept from the self-evident status it attained in twenty-century existentialism. The second section of the (...) paper argues that Grøn proposes an existential ethics that takes the Kierkegaardian notion that humans are inherently normative beings and uses this as a basis for a critique of ethics, as well as for establishing an ethics of vision inspired by Kierkegaard. The third section of the paper presents a reading of Grøn’s notion of religion as an inextricable part of human existence. (shrink)
It is shown that the equation deduced by Marinov for the gravitational frequency shift does not follow from his assumptions. The correct equation is deduced. It is pointed out that the result of Marinov's absolute spacetime theory concerning the gravitational frequency shift is contained in general relativity as an approximate description. The need for experiments testing the validity of Marinov's measurements is emphasized.
It is shown how a consistent kinematic resolution of Ehrenfest's paradox may be given in accordance with the special theory of relativity. Some statements by T. E. Phipps, Jr., connected with these matters, are commented upon. Problems connected with the relation between stress and strain are solved by a manifestly covariant formulation of Hooke's law.
In a recent article in this journal, Kingsley has tried to show that the postulates of special relativity contradict each other. Here we show that the arguments of Kingsley are invalid because of an erroneous appeal to symmetry in a non-symmetric situation. The consistency of the postulates of special relativity and the relativistic kinematics deduced from them is restated.
Using the Weyl-type canonical coordinates, an integration of Einstein's field equations in the cylindrosymmetric case considered by Kurşunoğlu is reexamined. It is made clear that the resulting metric is not describing the spacetime in a rotating frame, but in astatic cylindrical elastic medium. The conclusion of Kurşunoğlu that “for an observer on a rotating disk there is no way of escape from a curved spacetime” is therefore not valid. The metric in an empty rotating frame is found as a solution (...) of Einstein's field equations, and is not orthogonal. It is shown that the corresponding orthogonal solution represents spacetime in an inertial frame expressed in cylindrical coordinates. Introducing a noncoordinate basis, the metric in a rotating frame is given the static form of Kurşunoğlu's solution. The essential role played by the nonvanishing structure coefficients in this case is made clear. (shrink)
Einstein's gravitational field equations in empty space outside a massive plane with infinite extension give a class of solutions describing a field with flat spacetime giving neutral, freely moving particles an acceleration. This points to the necessity of defining the concept “gravitational field” not simply by the nonvanishing of the Riemann curvature tensor, but by the nonvanishing of certain elements of the Christoffel symbols, called the physical elements, or the nonvanishing of the Riemann curvature tensor. The tidal component of a (...) gravitational field is associated with a nonvanishing Riemann tensor, while the nontidal components are associated with nonvanishing physical elements of the Christoffel symbols. Spacetime in a nontidal gravitational field is flat. Such a field may be separated into a homogeneous and a rotational component. In order to exhibit the physical significance of these components in relation to their transformation properties, coordinate transformations inside a given reference frame are discussed. The mentioned solutions of Einstein's field equations lead to a metric identical to that obtained as a result of a transformation from an inertial frame to a uniformly accelerated frame. The validity of the strong principle of equivalence in extended regions for nontidal gravitational fields is made clear. An exact calculation of the weight of an extended body in a uniform gravitational field, from a global point of view, gives the result that its weight is independent of the position of the scale on the body. (shrink)
This volume offers the first English language collection of academic essays on the post-Holocaust thought of Jean Améry, a Jewish-Austrian-Belgian essayist, journalist and literary author. Comprehensive in scope and multi-disciplinary in orientation, contributors explore central aspects of Améry's philosophical and ethical position, including dignity, responsibility, resentment, and forgiveness.
The article addresses the question when the advocacy of forgiveness in the wake of political mass violence can be harmful and immoral. It engages with this question primarily by probing the value of different pictures of forgiveness, most importantly Rembrandt’s painting Return of the Prodigal Son and a photograph from post-genocide Rwanda. The critical examination of the value of particular pictures in the advocacy of forgiveness also involves attention to particularly problematic ‘pictures’ (in the sense of notions, imaginaries, representations) of (...) the unforgiving victim, of the choices available to societies responding to a violent past, and of unconditional forgiving. (shrink)
Einstein's second postulate (light-speed constancy) is modified in the following manner:(1) as to motion of light emitters, no modification is made;(2) as to motion of light absorbers, if the absorber moves with velocityv with respect to the observer, that observer will attribute to light the velocity (c+v). It is shown, with reference to the original Einstein train example, that such a modification of the second postulate restores to kinematics a concept of distant simultaneity. Thus is indicated the complicated (acausal) behavior (...) that must be attributed to light in order that the simple behavior earlier attributed (1) to matter (nonoccurrence of the Lorentz contraction) may be consistent with all known facts. A reply is made to Grøn's critique (2) of the earlier paper on metric standards. It is concluded that further experimental data are needed to decide the simple-light-complicated-matter versus complicated-light-simple-matter issue. (shrink)
Hegel's influence on post-Hegelian philosophy is as profound as it is ambiguous. Modern philosophy is philosophy after Hegel. Taking leave of Hegel's system appears to be a common feature of modern and post-modern thought. One could even argue that giving up Hegel's claim of totality defines philosophy after Hegel. Modern and post-modern philosophies are philosophies of finitude: Hegel's philosophy cannot be repeated. However, its status as a negative backdrop for modern and post-modern thought already shows its pervasive influence. Precisely in (...) its criticism of Hegel, modern thought is bound up with his thinking. (shrink)
It is argued that Grøn's criticism of our treatment of the rotating disk in special relativity is incorrect: Our results pertain to an acceleration program different from his but physically no less legitimate.
The complex gestures of artwork remain an under-explored theoretical topos in contemporary visual culture studies. In our turbulent mediasphere where images are constantly mobilized to enact symbolic forms of warfare and where they get entangled in all kinds of cultural conflicts and controversies, a turn to the gestural life of images promises a particularly pertinent avenue of intellectual inquiry. As both a cultural phenomenon and a philosophical concept, the notion of gesture straddles several disciplines, such as anthropology, linguistics, performance, theater, (...) film and visual studies. In this volume, contributors ask: How may one speak not only of the gestures of the body but also of the gestures of the image? What constitutes gesturality in the image and, more broadly, what are the gestures of the aesthetic itself? By thinking about images within this conceptual framework, this volume seeks to renew our understanding of the image. (shrink)
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