Showing papers on "Cosmology published in 1969"
TL;DR: Powerful emissions from the centres of nearby galaxies may represent dead quasars as mentioned in this paper, which may represent the end of the universe as we know it. But this is not always the case.
Abstract: Powerful emissions from the centres of nearby galaxies may represent dead quasars.
1,268 citations
TL;DR: In this article, it was shown that any injection of energy att>1010 sec (red shiftz <105) leads to deviation from an equilibrium spectrum, and that a period of neutral hydrogen in the evolution of the universe is unavoidable.
Abstract: In this paper we continue the investigation initiated by Weymann as to the reason why the spectrum of the residual radiation deviates from a Planck curve. We shall consider the distortions of the spectrum resulting from radiation during the recombination of a primeval plasma. Analytical expressions are obtained for the deviation from an equilibrium spectrum due to Compton scattering by hot electrons. On the basis of the observational data it is concluded that a period of neutral hydrogen in the evolution of the universe is unavoidable. It is shown that any injection of energy att>1010 sec (red shiftz<105) leads to deviation from an equilibrium spectrum.
722 citations
186 citations
TL;DR: The 3 K background radiation was found to be highly isotropic as discussed by the authors, which supports the hypothesis that the radiation was produced at an early stage in the expansion of the universe.
Abstract: THE discovery of the 3 K background radiation has provided a new tool for studying the universe. The radiation exhibits a black-body spectrum over a frequency range of 280 to 1 (ref. 1) and is highly isotropic2–4, which supports the hypothesis that the radiation was produced at an early stage in the expansion of the universe. If this is correct, the radiation defines an extremely distant reference frame—that of the matter which last scattered it5. If the Earth has a total velocity v with respect to this frame, there will be an apparent excess of radiation in the direction of motion6 of magnitude (v/c) cos θ. Preliminary experimental results at Stanford show a definite excess with this kind of angular variation. Assuming that intrinsic anisotropy of this type is negligible, a large value for the Earth's motion is indicated in addition to rotation around the galaxy.
135 citations
TL;DR: In this paper, it was shown that stable causality is the necessary and sufficient condition that there should exist a cosmic time function which increases along every future directed timelike or null curve.
Abstract: It is shown that stable causality is the necessary and sufficient condition that there should exist a cosmic time function which increases along every future directed timelike or null curve. Stable causality means that there are no closed timelike or null curves in any Lorentz metric that is sufficiently close to the space-time metric.
129 citations
TL;DR: In this article, it is assumed that a very hot, dense plasma was present during the early stages of the universe, and interaction of photons and electrons leads inevitably to an equilibrium (blackbody) spectrum.
Abstract: THE discovery of cosmic blackbody radiation with a temperature of 2.7 K is widely considered as powerful evidence for the hot, big-bang model of the universe. As first discussed by Gamow, it is assumed that a very hot, dense plasma was present during the early stages of the universe, and interaction of photons and electrons leads inevitably to an equilibrium (blackbody) spectrum. The shape of the equilibrium spectrum is preserved during the subsequent expansion and cooling, although the radiation temperature decreases to the value of 2.7 K observed today.
68 citations
TL;DR: Finite rotating universe model construction not possessing Goedel cosmos pathological properties, discussing relation to Mach principle as discussed by the authors, and discussing relation between Mach principle and infinite rotating universe models construction.
62 citations
TL;DR: In this paper, the formation of gravitationally bound systems from primordial gas is studied by means of Tolman's solution for dust-like matter, and the critical values of density contrast and its growth rate at an initial epoch are derived, which are necessary for an inhomogeneity to condense into a bound system before the appearance of the oldest stars.
Abstract: The formation of gravitationally bound systems from primordial gas is studied by . means of Tolman's solution for dust-like matter. The critical values of density contrast and its growth rate at an initial epoch are derived, which are necessary for an inhomogeneity to condense into a bound system before the appearance of the oldest stars. The matter distributions in an . isolated inhomogeneity and an inhomogeneity included in a larger one (which will be a cluster of gas clouds) are followed with time by assuming simple models for inhomogeneities, and it is shown how the bound region spreads outwards. Moreover, the minimum mass of fragments into which the gas clouds may break up is examined. The formation of galaxies which are dispersed everywhere at present in the universe has been studied by many authors. Some of them have assumed that small density fluctuations in an early stage of cosmic evolution grow owing to gravitational instability, until they condense into protogalaxies. However, on Lifshitz's assumption!) that the early stage was very quiet and the fluctua tions were statistical, gravitational instability was not effective. This is because the density contrasts of the statistical fluctuations corresponding to galaxies are too small (r-J 10- 34 ) to grow to gravitationally bound systems within the cosmic age. The linearized theories were sufficient for the description of such small fluctuations. After Lifshitz, the behavior of the fluctuations has been studied successively in the linear approximation,2) while Lifshitz's assumption was not always used. On the other hand, it has been assumed that an early stage of the UnIverse was very turbulent and density fluctuations were not small. S ) At the stage when radiation density was larger than matter density and matter was wholly ionized, matter was strongly kicked by photon particles and hindered from condensing. But, once matter was neutrarized, density fluctuations condensed promptly into bound systems. However, we do not know at present how quiet or turbulent the early stages were. Accordingly, still we could assume the existence of fluctuations with vari ous amplitudes. In the process of their condensation, gravitation would have played the main role, and, as the density contrasts increased to the order o£
36 citations
TL;DR: Isotropic cosmic X-rays in the I keV-I MeV range may be due to the Compton-blackbody process acting in remote radio galaxies or quasars as mentioned in this paper.
Abstract: Isotropic cosmic X-rays in the I keV–I MeV range may be due to the Compton-blackbody process acting in remote radio galaxies or quasars. The break in the X-ray spectrum then poses a stringent condition on theories of radio source evolution and distribution.
Book•
[...]
01 Jan 1969
TL;DR: In this paper, the authors present a summary of selected recent results in the field of classical astronomy and cosmogony and cosmology, as well as a survey of the current state of the art.
Abstract: I. Classical Astronomy.- II. Sun and Stars Astrophysics of Individual Stars.- III. Stellar Systems Milky Way and Galaxies Cosmogony and Cosmology.- IV. A Summary of Selected Recent Results.- Physical Constants and Astronomical Quantities.- Figure Acknowledgments.
Journal Article•
TL;DR: In this article, the effect of magnetic fields on the β decay rate of a neutron was examined, which is a fundamental process in many astrophysical phenomena and in particular in a problem of current interest, that is, the production of He in the big-bang expansion of the universe.
Abstract: RECENT advances in the production of large magnetic fields in the laboratory1,2 have generated interest in the effect of intense magnetic fields on various phenomena3,4. The largest field that can be produced in the laboratory1,2 at present is about 106 G, which is considerably lower than the quantum critical field value5 of Hc = m2c3/eV = 4.4 × 1013 G; but the “cosmic laboratory” may be a source of much stronger fields and it has been suggested6 that magnetic fields as large as 1014−1016 G may exist in neutron stars. Hoyle7 has cited the possibility of a large primordial magnetic field, and Brownell and Callaway8 speculate that neutron stars and the dense early universe may be ferromagnetic. One of us (R. F. O.) has examined9 various effects of a large magnetic field and has indicated an effect of magnetic fields which has been often ignored in astrophysical investigations, namely, that the rates of all elementary particle processes will be affected. Pursuing this idea, we examine here the effect of a magnetic field on the β decay rate of a neutron. This is a fundamental process in many astrophysical phenomena and in particular it is very important10 in a problem of current interest, that is, the production of He in the “big-bang” expansion of the universe11. In addition, our calculations should be applicable to other elementary particle processes. We present here only the main ideas ; the calculation details will be published elsewhere12.
TL;DR: In this paper, Lemaitre universe and galaxy formation effect on stability of quasi-static epoch, deriving limits for red shift, cosmic ray and electromagnetic fluxes, were analyzed. But the results were limited.
Abstract: Lemaitre universe and galaxy formation effect on stability of quasi-static epoch, deriving limits for red shift, cosmic ray and electromagnetic fluxes
TL;DR: In this paper, it is shown that some power laws σ∼T mερετρε mετε σ for the cross-section σ lead to collisionless behavior near the initial singularity in a "big bang" model.
Abstract: The Einstein Field Equations for homogeneous cosmologies are considered within the viscosity approximation. It is shown that some power laws σ∼T
m
(whereT is the temperature) for the cross-section σ lead to collisionless behavior near the initial singularity in a ‘big bang’ model. Under some circumstances one may have two viscous phases, as the cosmic fluid passes from collisionless to collisional to collisionless again, while the universe expands.
TL;DR: Deceleration parameter lower and upper limits for zero pressure big bang cosmological Friedmann models imposed by density parameter, Hubble constant and universe age are given in this article for zero-pressure big-bang cosmologies.
Abstract: Deceleration parameter lower and upper limits for zero pressure big bang cosmological Friedmann models imposed by density parameter, Hubble constant and universe age
TL;DR: In all of the observations, however, there has been no direct evidence for or against continuous creation as discussed by the authors, and the theoretical successes of steady-state cosmology have survived the tests of observation.
Abstract: TWENTY years have passed since Bondi and Gold1 introduced the steady-state theory of the universe and the attendant concept of continuous creation. Thus far, the theoretical successes of steady-state cosmology have survived the tests of observation2. In all of the observations, however, there has been no direct evidence for or against continuous creation.
TL;DR: The Friedman-Lemaitre cosmological models are based on a very simple world picture, and it is unfortunate that the standard approach to the models brings to bear theoretical machinery much more complicated than this world picture as mentioned in this paper.
Abstract: The Friedman-Lemaitre cosmological models are based on a very simple world picture, and it is unfortunate that the standard approach to the models brings to bear theoretical machinery much more complicated than this world picture. The purpose of this paper is to give an alternative and perhaps more illuminating approach to the model results from a discussion of how a local observer would describe the expansion of the universe. This treatment of the models is rigorous, according to the theory of general relativity, but hopefully simpler than the standard one, because it deals with quantities that are in principle directly observable.
TL;DR: In this article, the authors arrive at the two fundamental "megaphysical" equations (I, II)0Π+c2=0,0ϕ=0 where 0Π is the scalar gravitational potential due to the smoothed-out universe, 0ϕ is its electrostatic potential andc denotes the light velocity in vacuo.
Abstract: Starting with the idea that the inertia of bodies is a general property of all kinds of their potential energy, the author arrives at the two fundamental “megaphysical” equations (I, II)0Π+c2=0,0ϕ=0 where0Π is the scalar gravitational potential due to the smoothed-out universe,0ϕ is its electrostatic potential andc denotes the light velocity in vacuo.
TL;DR: In this paper, the authors compare theoretical and observational apparent magnitude-redshift relations, the rates of galaxy evolution required to force coincidence of these relations in visual light are deduced for each model and also predict the slope of the bright end of the luminosity function of elliptical galaxies.
Abstract: It is assumed that the universe can be represented by low density Friedmann models with non-zero cosmological constant and long ages. By comparing theoretical and observational apparent magnitude-redshift relations, the rates of galaxy evolution required to force coincidence of these relations in visual light are deduced for each model. These rates are compared with various recent estimates of this effect and are also used to predict the slope of the bright end of the luminosity function of elliptical galaxies. Both the comparison and the prediction indicate that, unless the slope of the bright end of the luminosity function is considerably flatter than that produced by extrapolation, it is impossible to assign all of the difference between theory and present observations to evolutionary effects. Such an assignment could, however, be made if a dispersion in the luminosities of the most distant galaxies is found.