This volume is the first systematic presentation of the work of Albert Einstein, comprising fourteen essays by leading historians and philosophers of science that introduce readers to his work. Following an introduction that places Einstein's work in the context of his life and times, the book opens with essays on the papers of Einstein's 'miracle year', 1905, covering Brownian motion, light quanta, and special relativity, as well as his contributions to early quantum theory and the opposition to his light quantum (...) hypothesis. Further essays relate Einstein's path to the general theory of relativity (1915) and the beginnings of two fields it spawned, relativistic cosmology and gravitational waves. Essays on Einstein's later years examine his unified field theory program and his critique of quantum mechanics. The closing essays explore the relation between Einstein's work and twentieth-century philosophy, as well as his political writings. (shrink)

Before the discovery of the expanding universe, one of the challenges faced in early relativistic cosmology was the determination of the finite and constant curvature radius of space-time by using astronomical observations. Great interest in this specific question was shown by de Sitter, Silberstein, and Lundmark. Their ideas and methods for measuring the cosmic curvature radius, at that time interpreted as equivalent to the size of the universe, contributed to the development of the empirical approach to relativistic (...) cosmology. Their works are a noteworthy example of the efforts made by modern cosmologists toward the understanding of the universe as a whole, its properties, and its content. (shrink)

Among the many controversial contributions of E. A. Milne to cosmology, the only one which is taken seriously today (to the extent that it has been absorbed as a premise in most scientific approaches to the problem of the universe as a totality) is his early suggestion that a formal equivalence may be made between Newtonian and Relativistic cosmology. My own paper suggests that, over and above any logical validity in the alleged equivalence, the actual way in (...) which it has subtly insinuated itself into nearly all contemporary speculation reveals as few things could some of the epistemological foundations that underlie the current assumptions in cosmological science. (shrink)

In this article it is argued that a continuity exists between Karl Schwarzschild's work on foundational problems on the borderline of physics and astronomy and his later occupation with general relativity. Based on an analysis of Schwarzschild's published works as well as formerly neglected unpublished notes it is shown that, long before the rise of general relativity, Schwarzschild was concerned with problems that later became associated with that theory. In particular he considered non-Euclidean cosmologies, linked the phenomena of gravitation and (...) inertia to the problem of the precession of Mercury's perihelion, and entertained the possibility of inertial frames rotating with respect to one another. It is argued that these earlier considerations, which reflect his interdisciplinary outlook on the foundations of the exact sciences, enabled Schwarzschild to recognize the significance of general relativity for astronomy, astrophysics, and cosmology earlier than most of his collegues and shaped his contributions to this theory. (shrink)

What is the link between the discovery of the relativistic expanding Universe and British imperialism? A public panel debate in the early days of relativistic cosmology shows how fundamental scientific research, whether there are obvious political stakeholders (like biosecurity and climate) or not, runs real-time risks of being repurposed for political ends.

This essay aims to provide a self-contained introduction to time in relativistic cosmology that clarifies both how questions about the nature of time should be posed in this setting and the extent to which they have been or can be answered empirically. The first section below recounts the loss of Newtonian absolute time with the advent of special and general relativity, and the partial recovery of absolute time in the form of cosmic time in some cosmological models. Section (...) II considers the beginning and end of time in a broader class of models in which there is not an analog of Newtonian absolute time. As we will see, reasonable physical assumptions imply that the universe is finite to the past, and Section III turns to consideration of the “beginning” itself. We critically review conventional wisdom that a “singularity” reveals flaws in general relativity and briefly assess ways of avoiding the singularity. (shrink)

This chapter provides a self‐contained introduction to time in relativistic cosmology that clarifies how questions about the nature of time should be posed and the extent to which they have been or can be answered empirically. The first section of the chapter recounts the loss of Newtonian absolute time with the advent of special and general relativity, and the partial recovery of absolute time in the form of cosmic time in cosmological models. The second considers the beginning and (...) end of time in a broader class of models in which there is not an analog of Newtonian absolute time. Reasonable physical assumptions imply that the universe is finite to the past, and the third section considers the “beginning” itself. The fourth section discusses the ramifications of the two recent debates of cosmology. The final section takes up the source of the asymmetry in people's experience of time. (shrink)

Readers familiar with the workhorse of cosmology, the hot big bang model, may think that cosmology raises little of interest about time. As cosmological models are just relativistic spacetimes, time is understood just as it is in relativity theory, and all cosmology adds is a few bells and whistles such as inflation and the big bang and no more. The aim of this chapter is to show that this opinion is not completely right...and may well be (...) dead wrong. In our survey, we show how the hot big bang model invites deep questions about the nature of time, how inflationary cosmology has led to interesting new perspectives on time, and how cosmological speculation continues to entertain dramatically different models of time altogether. Together these issues indicate that the philosopher interested in the nature of time would do well to know a little about modern cosmology. (shrink)

With the discovery that the universe is expanding at an accelerating rate, Einstein’s cosmological constant, which he once supposedly called his biggest blunder, is making a remarkable comeback. Einstein’s introduction of this constant had little to do with cosmology. It was part of yet another failed attempt to eliminate absolute space from physics. It took the Dutch astronomer Willem de Sitter only a few days to blow the idea out of the water. It took Einstein over a year to (...) concede the point. In the process Einstein and De Sitter produced the first two models of relativistic cosmology, the Einstein cylinder universe and the De Sitter hyperboloid universe. (shrink)

The various cosmological proposals by Einsteinian relativists seek to show the structure of the world as a consequence of the basic notions of relativity. In particular, the irrelevance of the state of motion of an observer to his description of the fundamental laws of nature is to be maintained. Furthermore, gravity is understood as being a description of the fact that particles move along certain minimal paths in non-Euclidean space. In this theory, the effect of one material particle on another (...) particle in the old-fashioned sense of gravitational attraction becomes indirect; that is, a particle moves on a minimal path in a space having a degree of curvature dependent on the material entities which exist in it, rather than having its path bent by the attraction between it and other material bodies, all of them existing in an absolute or receptacle-like space. (shrink)

Isaac Newton's Scientific Method examines Newton's argument for universal gravity and his application of it to resolve the problem of deciding between geocentric and heliocentric world systems by measuring masses of the sun and planets. William L. Harper suggests that Newton's inferences from phenomena realize an ideal of empirical success that is richer than prediction. Any theory that can achieve this rich sort of empirical success must not only be able to predict the phenomena it purports to explain, but also (...) have those phenomena accurately measure the parameters which explain them. Harper explores the ways in which Newton's method aims to turn theoretical questions into ones which can be answered empirically by measurement from phenomena, and to establish that propositions inferred from phenomena are provisionally accepted as guides to further research. This methodology, guided by its rich ideal of empirical success, supports a conception of scientific progress that does not require construing it as progress toward Laplace's ideal limit of a final theory of everything, and is not threatened by the classic argument against convergent realism. Newton's method endorses the radical theoretical transformation from his theory to Einstein's. Harper argues that it is strikingly realized in the development and application of testing frameworks for relativistic theories of gravity, and very much at work in cosmology today. (shrink)

The articles included in this Volume represent a broad and highly qualified view on the present state of general relativity, quantum gravity, and their cosmological and astrophysical implications. As such, it may serve as a valuable source of knowledge and inspiration for experts in these fields, as well as an advanced source of information for young researchers. The occasion to gather together so many leading experts in the field was to celebrate the centenary of Einstein's stay in Prague in 1911-1912. (...) It was in fact during his stay in Prague that Einstein started in earnest to develop his ideas about general relativity that fully developed in his paper in 1915. Approaching soon the centenary of his famous paper, this volume offers a precious overview of the path done by the scientific community in this intriguing and vibrant field in the last century, defining the challenges of the next 100 years. The content is divided into four broad parts: (i) Gravity and Prague, (ii) Classical General Relativity, (iii) Cosmology and Quantum Gravity, and (iv) Numerical Relativity and Relativistic Astrophysics. (shrink)

Accelerating Expansion explores some of the philosophical implications of modern cosmology, focused on the significance that the discovery of the accelerating expansion of the Universe has for our understanding of time, geometry, and physics. The appearance of the cosmological constant in the equations of general relativity allows one to model universes in which space has an inherent tendency towards expansion. This constant, introduced by Einstein but subsequently abandoned by him, returned to centre stage with the discovery of the accelerating (...) expansion. This pedagogically-oriented essay begins with a study of the most basic and elegant relativistic world that involves a positive cosmological constant, de Sitter spacetime. It then turns to the relatives of de Sitter spacetime that dominate modern relativistic cosmology. Some of the topics considered include: the nature of time and simultaneity in de Sitter worlds; the sense in which de Sitter spacetime is a powerful dynamical attractor; the limited extent to which observation can give us information about the topology of space in a world undergoing accelerated expansion; and cosmologists' favourite sceptical worry about the reliability of evidence and the possibility of knowledge, the problem of Boltzmann brains. (shrink)

One of the more important cosmological consequences of Einstein's general theory of relativity is the hypothesis that our universe may either expand or contract with time. Relativistic cosmogony is concerned with those phases of this process which belong to the past. We begin with a digest of cosmogonic developments.

The extension of the method of science to the study of the astronomical universe as a whole is an impressive and important feature of recent intellectual history. In a field where previously myth and metaphysics ranged at will with speculative abandon but with little in the way of progressively cumulative information or insight, by contrast, scientific cosmology has already produced significant results of an observational sort and opened up vistas of disciplined theoretical vision that are a token of even (...) more extensive disclosures to come. With the aid of high-powered telescopes, observationally grounded descriptive generalizations have been established about the structure, distribution and motions of the bodies constituting the basic astronomical units out of which the universe is composed. Such units are, in contemporary investigations, identified as the extragalactic nebulae. Preliminary surveys revealed a uniformity of distribution of these nebulae throughout space and in all directions. Also original surveys, accomplished primarily by Hubble, suggested an empirical law stating a linear proportionality between the distances to nebulae and the red-shift in their spectra. If such red-shift is interpreted as a velocity effect, it may be taken as marking a mutual recession of nebulae from one another, and leads thereby to the general idea of an “expanding universe.' Meanwhile, theoretical cosmology in the hands of the mathematical physicists has kept pace with observational advances by offering a variety of ”models” or explanatory theoretical devices for the systematic ordering and incorporation of the fruits of observation. Beginning with the ground-breaking paper by Einstein in 1917 where an extension was made of relativistic principles to the cosmologic domain, a variety of further attempts were made along classical relativistic lines by Einstein himself, de Sitter, Robertson, Tolman and Lamaître while somewhat different modes of approach were subsequently opened in several directions by Milne, Eddington, Hoyle, and others. While nothing in the way of a stable or wholly acceptable theory has yet made its appearance, nevertheless fruitful and promising lines of research have thus been inaugurated. (shrink)

It will be argued that Minkowski's implementation of distances is inconsistent. An alternative implementation will be proposed. In the new model the proper time of an object is taken as its fourth coordinate. Distances will be measured according to a four dimensional Euclidean metric. In the present approach mass is a constant of motion. A mass can therefore be ascribed to photons and neutrinos. Mechanics and dynamics will be reformulated in close correspondence with classical physics. Of particular interest is the (...) equation of motion for the proper time momentum. In the classical limit it reduces to the classical law of conservation of (kinetic+potential) energy. In the relativistic limit it is similar to the conservation of energy of the theory of relativity. The conservation of proper time momentum allows for an alternative explanation for Compton scattering and pair annihilation. On the basis of the proper time formulation of electrodynamics also an alternative explanation will be offered for the spectra of hydrogenic atoms. The proper time formulation of gravitational dynamics leads to the correct predictions of gravitational time dilation, the deflection of light and the precession of the perihelia of planets. For this no curvature will be needed. That is, spacetime is flat everywhere, even in the presence of sources of gravitation. Some cosmological consequences will be discussed. The present approach gives a new notion to energy, antiparticles and the structure of spacetime. The contents of the present paper will have important implications for the foundations of physics in general. (shrink)

Today the issue of ethics and most importantly moral values are being seen as merely based upon opinions and emotions. This has led towards a relativisation of moral values and thus towards the erosion of values amongst societies. This paper would analyze and suggest ways of preserving values for the structuring of developmental ideas for thinkers in developing countries. Coming from an Islamic standpoint the ideas of virtues have to be rooted within the transcendent or the Absolute. Such defense of (...) virtues are definitely beyond the grasp of usual western philosophy as the philosophy that is propagated by Islam is not a mere intellectual exercise but a transformative exercise which connects the profane to the sacred, the outer to the inner and the physical world to the spiritual world. The loci or the focus point is the human being thus developing the idea of being human via the inculcation of and preservation of virtues is of utmost importance. The virtues most important in Islam such as justice, moderation or temperance have been discussed by various muslim philosophers. These virtues are rooted in the Absolute and through His presence in the various levels of existences are they known. For Using ideas from malay cosmology and soteriology based upon the writings of Malay scholars, this paper would highlight ways to preserve and ensure Malay society does not fall under the threat of relativism of moral values. (shrink)

I argue that quantum decoherence—understood as a dynamical process entailed by the standard formalism alone—carries us beyond conceptual aspects of non-relativistic quantum mechanics deemed insurmountable by many contributors to the recent quantum gravity and cosmology literature. These aspects include various incarnations of the measurement problem and of the quantum -to-classical puzzle. Not only can such problems be largely bypassed or dissolved without default to a particular interpretation, but theoretical work in relativistic arenas stands to gain substantial physical (...) and philosophical insight by incorporating decoherence phenomena. (shrink)

Isaac Newton's Scientific Method examines Newton's argument for universal gravity and his application of it to resolve the problem of deciding between geocentric and heliocentric world systems by measuring masses of the sun and planets. William L. Harper suggests that Newton's inferences from phenomena realize an ideal of empirical success that is richer than prediction. Any theory that can achieve this rich sort of empirical success must not only be able to predict the phenomena it purports to explain, but also (...) have those phenomena accurately measure the parameters which explain them. Harper explores the ways in which Newton's method aims to turn theoretical questions into ones which can be answered empirically, by measurement from phenomena, and to establish that propositions inferred from phenomena are provisionally accepted as guides to further research. This methodology, guided by its rich ideal of empirical success, supports a conception of scientific progress that does not require construing it as progress toward Laplace's ideal limit of a final theory of everything, and is not threatened by the classic argument against convergent realism. Newton's method endorses the radical theoretical transformation from his theory to Einstein's. Harper argues that it is strikingly realized in the development and application of testing frameworks for relativistic theories of gravity, and very much at work in cosmology today. (shrink)

§1 To many in or on the edges of the Academy, ”Relativism” is a word with overtones of sinister iconoclasm, representing a kind of intellectual and ethical free-for-all in which the traditional investigative virtues of clarity, rigour, objectivity, consistency and the unbiased pursuit of truth are dismissed as illusory and the great scientific constructions of the last two hundred years, together with our deepest moral convictions, rated merely as ‘our way of seeing’ the world, more elaborate and organised but otherwise (...) on all fours with the cosmology and customs of primitive tribes. In his short book, Paul Boghossian aims to address, and to expose as bankrupt, the idea that there is even a coherent, let alone defensible philosophical stance about truth and knowledge that can underwrite these ‘pluralist’, or ‘postmodernist’ tendencies. But since it is crucial to his project that his style of discussion make it available to non-specialists, much of the recent more technical, less emotional debate within analytical philosophy about relativism’s renaissance as a particular form of semantic theory is passed over unmentioned. Part of my aim in what follows is to illustrate how Boghossian's discussion connects quite straightforwardly with relativism in its contemporary analytical philosophical livery—what I have elsewhere called New Age relativism1— and how some of his critical arguments may be presented in that setting. My main contentions will be, first, that when relativism about epistemic justification, and about morals, are couched in the currently canonical sort of form, they still remain in range of artillery that Boghossian positions in chapter 6 of his book; second, that there is evasive action that they can.. (shrink)

This article looks at Vesto Slipher’s work on nebular spectroscopy between 1912 and 1922as well as related research by other astronomers of the period, and it examines the dissem-ination of their results more widely. Slipher’s observations are viewed as marking the di-viding line between speculation about the universe in traditional astronomy and theadvent of modern cosmology and the theory of an expanding universe. The intent is todocument the dissemination of Slipher’s results in the period leading up to the publicationof (...) studies of relativistic cosmology by Willem de Sitter in 1917 and Alexander Friedmannin 1922. Themes touched on in the article include the unprecedented character ofSlipher’sfindings and the interaction of observation and theory in modern cosmology.A prominent concern is the role of technology in astronomical science over the past cen-tury and a half. Here reference is made to the writings of Paul Forman on historical shiftsthat have taken place in our understanding of the relationship of science and technology. (shrink)

The paper is inspired by the arguments raised recently by Grunbaum criticizing the current approaches of many cosmologists to the problem of spacetime singularity, matter creation and the origin of the universe. While agreeing with him that the currently favored cosmological ideas do not indicate the biblical notion of divine creation ex nihilo, I present my viewpoint on the same issues, which differs considerably from Grunbaum's. First I show that the symmetry principle which leads to the conservation law of energy (...) is violated when the time axis is terminated at t = 0. Next I discuss why this epoch (t = 0) is more a mathematical artifact whose supposed significance may disappear when one goes beyond the classical relativistic cosmology. This is illustrated by the example of quantum cosmology. (shrink)

Relativistic models of an expanding universe followed by contraction, or a big bang followed by a big crunch, were first proposed by A. Friedmann in 1922 and nine years later by A. Einstein. In the period ca. 1922–1960, the more speculative idea of a large and possibly infinite number of cycles was discussed by R. Tolman in particular. To some cosmologists, the idea was philosophically appealing because it seemed to justify an eternal yet dynamic universe without an absolute beginning (...) in time. During the 1950s models of this kind, sometimes known as Phoenix models, were investigated by a few cosmologists of whom the most important were A. Dauvillier, W. Bonnor, and H. Zanstra. (shrink)

The genesis of classical science was accompanied by a transition from logical to mathematical analysis. This change did not mean a rejection of Aristotle's canons of logic; it was simply that these canons became inadequate. They underwent a certain generalization and, in the course of this, came closely to approximate mathematical analysis, the foundations of the calculus of the infinitesimal. Classical science no longer took as its point of departure the notion of motion from "something" into "something," as did Peripatetic (...) physics and cosmology . The initial concept is motion, considered from point to point and instant to instant. This kind of differential notion of motion was clearly expressed by Kepler when he wrote: "Where Aristotle sees direct oppositeness between two things, with no mediating links, there I, looking at geometry philosophically, find a mediated opposition; so that where Aristotle employs a single term, ‘other,’ I use two: ‘larger’ and ‘smaller.’". (shrink)

Recently the neglected issue of the causal structure in the flat space-time approach to Einstein's theory of gravity has been substantially resolved. Consistency requires that the flat metric's null cone be respected by the null cone of the effective curved metric. While consistency is not automatic, thoughtful use of the naive gauge freedom resolves the problem. After briefly recapitulating how consistent causality is achieved, we consider the flat Robertson–Walker Big Bang model. The Big Bang singularity in the spatially flat Robertson–Walker (...) cosmological model is banished to past infinity in Minkowski space-time. A modified notion of singularity is proposed to fit the special relativistic approach, so that the Big Bang becomes nonsingular. (shrink)

A solution of the sourceless Einstein's equation with an infinite value for the cosmological constant Λ is discussed by using Inönü–Wigner contractions of the de Sitter groups and spaces. When Λ→∞, spacetime becomes a four-dimensional cone, dual to Minkowski space by a spacetime inversion. This inversion relates the four-cone vertex to the infinity of Minkowski space, and the four-cone infinity to the Minkowski light-cone. The non-relativistic limit c→∞ is further considered, the kinematical group in this case being a modified (...) Galilei group in which the space and time translations are replaced by the non-relativistic limits of the corresponding proper conformal transformations. This group presents the same abstract Lie algebra as the Galilei group and can be named the conformal Galilei group. The results may be of interest to the early Universe Cosmology. (shrink)

This book provides a compilation of in-depth articles and reviews on key topics within gravitation, cosmology and related issues. It is a celebratory volume dedicated to Prof. Thanu Padmanabhan ("Paddy"), the renowned relativist and cosmologist from IUCAA, India, on the occasion of his 60th birthday. The authors, many of them leaders of their fields, are all colleagues, collaborators and former students of Paddy, who have worked with him over a research career spanning more than four decades. Paddy is a (...) scientist of diverse interests, who attaches great importance to teaching. With this in mind, the aim of this compilation is to provide an accessible pedagogic introduction to, and overview of, various important topics in cosmology, gravitation and astrophysics. As such it will be an invaluable resource for scientists, graduate students and also advanced undergraduates seeking to broaden their horizons. (shrink)

There exists a growing literature on the so-called physical Church-Turing thesis in a relativistic spacetime setting. The physical Church-Turing thesis is the conjecture that no computing device that is physically realizable can exceed the computational barriers of a Turing machine. By suggesting a concrete implementation of a beyond-Turing computer in a spacetime setting, Istvan Nemeti and Gyula David have shown how an appreciation of the physical Church-Turing thesis necessitates the confluence of mathematical, computational, physical, and indeed cosmological ideas. In (...) this essay, I will honour Istvan's seventieth birthday, as well as his longstanding interest in, and his seminal contributions to, this field going back to as early as 1987 by modestly proposing how the concrete implementation in Nemeti and D\'avid might be complemented by a quantum-information-theoretic communication protocol between the computing device and the logician who sets the beyond-Turing computer a task such as determining the consistency of Zermelo-Fraenkel set theory. This suggests that even the foundations of quantum theory and, ultimately, quantum gravity may play an important role in determining the validity of the physical Church-Turing thesis. (shrink)

This paper looks at Kurt Gödel's causally‐pathological cosmological models (derived from general relativity), in the light of anthropic explanations. If a Gödelian world is a possible world, could anthropic reasoning shed any light on whether or not our world is Gödelian? This paper argues that while there are some good anthropic reasons why our world ought to be Gödelian, too many observations suggest that our world can’t possibly be Gödelian in fact. If Gödel's world is a possible one, anthropic teleology (...) alone cannot explain why it isn’t the world we inhabit. Furthermore, if our world were Gödelian, anthropic arguments against the existence of extraterrestrial intelligences would imply a bleak human future. En route, some general objections to relativistic causal pathologies are addressed and some anthropic arguments to the effect that Gödelian worlds couldn’t sustain life are also addressed and dismissed. (shrink)

This paper deals with two important English scientists of the first half of the twentieth century: Edward Arthur Milne and James Hopwood Jeans. It examines the philosophical reasons that, in 1932, induced Milne to devote himself to the newborn modern cosmology. Among those reasons, it is argued that the most important ones were some of Jeans’ philosophical statements regarding the new relativistic view of the expanding universe. In particular, Milne reacted to some confusing idealist opinions expressed by Jeans (...) in the London newspaper The Times, in May 1932, in a debate on the expansion of the universe. Actually, as it will be shown, Jeans received many criticisms about the philosophical reasonings present in all of his popularizing works. (shrink)

Inspired by possible connections between gravity and foundational question in quantum theory, we consider an approach for the adaptation of objective collapse models to a general relativistic context. We apply these ideas to a list of open problems in cosmology and quantum gravity, such as the emergence of seeds of cosmic structure, the black hole information issue, the problem of time in quantum gravity and, in a more speculative manner, to the nature of dark energy and the origin (...) of the very special initial state of the universe. We conclude that objective collapse models offer a rather promising path to deal with all of these issues. (shrink)

The aim of this paper is not only to deal with the concept of infinity, but also to develop some considerations about the epistemological status of cosmology. These problems are connected because from an epistemological point of view, cosmology, meant as the study of the universe as a whole, is not merely a physical (or empirical) science. On the contrary it has an unavoidable metaphysical character which can be found in questions like “why is there this universe (or (...) a universe at all)?”. As a consequence, questions concerning the infinity of the universe in space and time can correctly arise only taking into account this metaphysical character of cosmology. Accordingly, in the following paper it will be shown that two different concepts of physical infinity of the universe (the relativistic one and the inflationary one) rely on two different ways of solution of a metaphysical problem. The difference between these concepts cannot be analysed using the classical distinctions between actual/potential infinity or numerable/continuum infinity, but the introduction of a new “modal” distinction will be necessary. Finally, it will be illustrated the role of a philosophical concept of infinity of the universe. (shrink)

The Mössbauer rotor effect recently gained a renewed interest due to the discovery and explanation of an additional effect of clock synchronization which has been missed for about 50 years, i.e. starting from a famous book of Pauli, till some recent experimental analyses. The theoretical explanation of such an additional effect is due to some recent papers in both the general relativistic and the special relativistic frameworks. In the first case the key point of the approach is the (...) Einstein’s equivalence principle, which, in the words of the same Einstein, enables “the point of view to interpret the rotating system K’ as at rest, and the centrifugal field as a gravitational field”. In this paper, we analyse both the history of the Mössbauer rotor effect and its interpretation from the point of view of Einstein’s general theory of relativity by adding some new insight. In particular, it will be shown that, if on one hand the “traditional” effect of redshift has a strong analogy with the gravitational redshift, on the other hand the additional effect of clock synchronization has an intriguing analogy with the cosmological redshift. Finally, we show that a recent claim in the literature that the second effect of clock synchronization does not exist is not correct. (shrink)

This paper reviews recent applications of the Einstein- Rosen type space-times to some problems of modern cosmology. An extensive overview of inhomogeneous universes filled with gravitational waves, classical fields, and relativistic fluids is given. The dynamics of primordial inhomogeneities, such as gravitational and matter waves and shocks, their interactions, and the global evolution of the models considered, is presented in detail.

Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The (...) Poincaré gauge theory of gravity, like gauge theories of internal groups, has no automatic conservation in the sense defined above. This does not lead to any difficulties in principle. Analogies to 3-dimensional continuum mechanics are stressed throughout the article. (shrink)

This paper proposes a parallel in the forms of Aristotle’s and Einstein’s physics. It’s an exercise on conceptual analysis rather than history. The possible similarity between Aristotle’s world and the form (global geometry) of Einstein’s universe is discussed. The correlation between kinematics, dynamics and gravity in their respective theories is also studied. Finally, Aristotle’s ontology of space is compared to the relativistic ontology spacetime.

This paper proposes a parallel in the forms of Aristotle’s and Einstein’s physics. It’s an exercise on conceptual analysis rather than history. The possible similarity between Aristotle’s world and the form (global geometry) of Einstein’s universe is discussed. The correlation between kinematics, dynamics and gravity in their respective theories is also studied. Finally, Aristotle’s ontology of space is compared to the relativistic ontology spacetime.