Self-conscious intelligent technological societies in the universe: a simple direct approach to probable astrosociological realistic scenarios

2021 ◽  
pp. 1-23
Author(s):  
L. A. L. da Silva
Keyword(s):  
Life Expectancy ◽  
Spiral Galaxy ◽  
Classification Scheme ◽  
Formation Rate ◽  
Observable Universe ◽  
Probable Number ◽  
Bottle Neck ◽  
Evolutionary Paths ◽  
The Universe ◽  
Alternative Equation

Abstract We present an alternative equation to estimate the probable number N of self-conscious intelligent technological societies (SCITSs) within the radius of the observable universe. This equation has only one poorly-known factor, Pc, the SCITS's formation probability, which can be estimated within an uncertainty by a factor of 102 (10−11 ≤ Pc ≤ 10−9) by applying the restriction imposed by Fermi's Paradox. The SCITS's formation rate for a typical spiral galaxy is then estimated as ≈1 civ Gyr−1. For a very optimistic maximum life expectancy ≈108 yr, the conclusion is that two civilizations never coexist in the same galaxy. Our estimated values for Pc are compatible with current biological and astrophysical evidences. We also propose an alternative astrosociological classification scheme which enables us to speculate about possible evolutionary paths for SCITSs in the universe. The so-called ‘Closed Bottle Neck’ (CBN) scenario suggests that civilizations are no exit evolutionary ways. We argue that simply there would not be interstellar travels nor Galaxy colonization or a Galactic Club. Thus Fermi's Paradox results eliminated, and the perspectives about the future of our own civilization may not be positive.

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

Gamma-Ray Bursts as Probes of the Universe

2011 ◽  
Author(s):  
Joshua S. Bloom
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Ongoing Study ◽  
Observable Universe ◽  
History Of ◽  
Expansion Of The Universe ◽  
The Universe

This chapter focuses on how gamma-ray bursts (GRBs) are emerging as unique tools in the study of broad areas of astronomy and physics by virtue of their special properties. The unassailable fact about GRBs that makes them such great probes is that they are fantastically bright and so can be seen to the farthest reaches of the observable Universe. In parallel with the ongoing study of GRB events and progenitors, new lines of inquiry have burgeoned: using GRBs as unique probes of the Universe in ways that are almost completely divorced from the nature of GRBs themselves. Topics discussed include studies of gas, dust, and galaxies; the history of star formation; measuring reionization and the first objects in the universe; neutrinos, gravitational waves, and cosmic rays; quantum gravity and the expansion of the universe; and the future of GRBs.

scholarly journals Black dwarf supernova in the far future

2020 ◽  
Vol 497 (4) ◽  
pp. 4357-4362
Author(s):  
M E Caplan
Keyword(s):  
White Dwarfs ◽  
High Mass ◽  
Observable Universe ◽  
Dwarf Stars ◽  
Low Mass ◽  
Chandrasekhar Limit ◽  
Ultimate Fate ◽  
Open Question ◽  
The Universe ◽  
Far Future

ABSTRACT In the far future, long after star formation has ceased, the universe will be populated by sparse degenerate remnants, mostly white dwarfs, though their ultimate fate is an open question. These white dwarfs will cool and freeze solid into black dwarfs while pycnonuclear fusion will slowly process their composition to iron-56. However, due to the declining electron fraction, the Chandrasekhar limit of these stars will be decreasing and will eventually be below that of the most massive black dwarfs. As such, isolated dwarf stars with masses greater than ∼1.2 M⊙ will collapse in the far future due to the slow accumulation of iron-56 in their cores. If proton decay does not occur, then this is the ultimate fate of about 1021 stars, approximately 1 percent of all stars in the observable universe. We present calculations of the internal structure of black dwarfs with iron cores as a model for progenitors. From pycnonuclear fusion rates, we estimate their lifetime and thus delay time to be 101100 yr. We speculate that high-mass black dwarf supernovae resemble accretion induced collapse of O/Ne/Mg white dwarfs while later low mass transients will be similar to stripped-envelope core-collapse supernova, and may be the last interesting astrophysical transients to occur prior to heat death.

scholarly journals Galactic ionizing photon budget during the epoch of reionization in the Cosmic Dawn II simulation

2020 ◽  
Vol 496 (4) ◽  
pp. 4342-4357 ◽  
Author(s):  
Joseph S W Lewis ◽  
Pierre Ocvirk ◽  
Dominique Aubert ◽  
Jenny G Sorce ◽  
Paul R Shapiro ◽  
...  
Keyword(s):  
Formation Rate ◽  
Mass Range ◽  
Mass Function ◽  
High Mass ◽  
Relative Contribution ◽  
Fully Coupled ◽  
The Universe ◽  
Lower Redshift ◽  
Galactic Haloes

ABSTRACT Cosmic Dawn II yields the first statistically meaningful determination of the relative contribution to reionization by galaxies of different halo mass, from a fully coupled radiation-hydrodynamics simulation of the epoch of reionization large enough (∼100 Mpc) to model global reionization while resolving the formation of all galactic haloes above ${\sim}10^8 \, {\rm M}_{\odot }$. Cell transmission inside haloes is bi-modal – ionized cells are transparent, while neutral cells absorb the photons their stars produce – and the halo escape fraction fesc reflects the balance of star formation rate (SFR) between these modes. The latter is increasingly prevalent at higher halo mass, driving down fesc (we provide analytical fits to our results), whereas halo escape luminosity, proportional to fesc × SFR, increases with mass. Haloes with dark matter masses within $6\times 10^{8} \, {\rm M}_{\odot }\lt M_{\rm halo}\lt 3 \times 10^{10} \, {\rm M}_{\odot }$ produce ∼80 per cent of the escaping photons at z = 7, when the universe is 50 per cent ionized, making them the main drivers of cosmic reionization. Less massive haloes, though more numerous, have low SFRs and contribute less than 10 per cent of the photon budget then, despite their high fesc. High-mass haloes are too few and too opaque, contributing <10 per cent despite their high SFRs. The dominant mass range is lower (higher) at higher (lower) redshift, as mass function and reionization advance together (e.g. at z = 8.5, xH i = 0.9, $M_{\rm halo}\lt 5\times 10^9 \, {\rm M}_{\odot }$ haloes contributed ∼80 per cent). Galaxies with UV magnitudes MAB1600 between −12 and −19 dominated reionization between z = 6 and 8.

scholarly journals The Cosmic Baryon and Metal Cycles

2020 ◽  
Vol 58 (1) ◽  
pp. 363-406 ◽  
Author(s):  
Céline Péroux ◽  
J. Christopher Howk
Keyword(s):  
Star Formation ◽  
Mass Density ◽  
Formation Rate ◽  
Cosmic Time ◽  
Dust Content ◽  
Star Formation History ◽  
Molecular Gas ◽  
Neutral Gas ◽  
Formation History ◽  
The Universe

Characterizing the relationship between stars, gas, and metals in galaxies is a critical component of understanding the cosmic baryon cycle. We compile contemporary censuses of the baryons in collapsed structures and their chemical makeup and dust content. We show the following: ▪  The [Formula: see text] mass density of the Universe is well determined to redshifts [Formula: see text] and shows minor evolution with time. New observations of molecular hydrogen reveal its evolution mirrors that of the global star-formation rate density, implying a universal cosmic molecular gas depletion timescale. The low-redshift decline of the star-formation history is thus driven by the lack of molecular gas supply due to a drop in net accretion rate related to the decreased growth of dark matter halos. ▪  The metal mass density in cold gas ([Formula: see text] K) contains virtually all the metals produced by stars for [Formula: see text]. At lower redshifts, the contributors to the total amount of metals are more diverse; at [Formula: see text], most of the observed metals are bound in stars. Overall, there is little evidence for a “missing metals problem” in modern censuses. ▪  We characterize the dust content of neutral gas over cosmic time, finding the dust-to-gas and dust-to-metals ratios fall with decreasing metallicity. We calculate the cosmological dust mass density in the neutral gas up to [Formula: see text]. There is good agreement between multiple tracers of the dust content of the Universe.

scholarly journals The Hα‐based Star Formation Rate Density of the Universe atz= 0.84

2008 ◽  
Vol 677 (1) ◽  
pp. 169-185 ◽  
Author(s):  
Víctor Villar ◽  
Jesús Gallego ◽  
Pablo G. Pérez‐González ◽  
Sergio Pascual ◽  
Kai Noeske ◽  
...  
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
The Universe

scholarly journals HOW MANY UNIVERSES DO THERE NEED TO BE?

2006 ◽  
Vol 15 (12) ◽  
pp. 2229-2233 ◽  
Author(s):  
DOUGLAS SCOTT ◽  
J. P. ZIBIN
Keyword(s):  
Cosmological Parameters ◽  
Current Data ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Spatial Curvature ◽  
Observable Universe ◽  
Particle Horizon ◽  
Knowing That ◽  
Density Perturbations ◽  
Best Fit ◽  
The Universe

In the simplest cosmological models consistent with General Relativity, the total volume of the Universe is either finite or infinite, depending on whether or not the spatial curvature is positive. Current data suggest that the curvature is very close to flat, implying that one can place a lower limit on the total volume. In a Universe of finite age, the "particle horizon" defines the patch of the Universe which is observable to us. Based on today's best-fit cosmological parameters it is possible to constrain the number of observable Universe sized patches, NU. Specifically, using the new Wilkinson Microwave Anisotropy Probe (WMAP) data, we can say that there are at least 21 patches out there the same volume as ours, at 95% confidence. Moreover, even if the precision of our cosmological measurements continues to increase, density perturbations at the particle horizon size limit us to never knowing that there are more than about 105 patches out there.

scholarly journals Explaining cosmological anisotropy: evidence for causal horizons from CMB data

2021 ◽  
Author(s):  
Pablo Fosalba ◽  
Enrique Gaztañaga
Keyword(s):  
Large Scale ◽  
Cosmological Parameter ◽  
Cosmic Acceleration ◽  
Statistical Fluctuation ◽  
Temperature Anisotropy ◽  
Microwave Background ◽  
Dark Energy Density ◽  
Observable Universe ◽  
Open Question ◽  
The Universe

Abstract The origin of power asymmetry and other measures of statistical anisotropy on the largest scales of the universe, as manifested in Cosmic Microwave Background (CMB) and large-scale structure data, is a long-standing open question in cosmology. In this paper we analyse the Planck Legacy temperature anisotropy data and find strong evidence for a violation of the Cosmological principle of isotropy, with a probability of being a statistical fluctuation of order ∼10−9. The detected anisotropy is related to large-scale directional ΛCDM cosmological parameter variations across the CMB sky, that are sourced by three distinct patches in the maps with circularly-averaged sizes between 40 to 70 degrees in radius. We discuss the robustness of our findings to different foreground separation methods and analysis choices, and find consistent results from WMAP data when limiting the analysis to the same scales. We argue that these well-defined regions within the cosmological parameter maps may reflect finite and casually disjoint horizons across the observable universe. In particular we show that the observed relation between horizon size and mean dark energy density within a given horizon is in good agreement with expectations from a recently proposed model of the universe that explains cosmic acceleration and cosmological parameter tensions between the high and low redshift universe from the existence of casual horizons within our universe.

scholarly journals Galaxy Interactions and Star Formation: Results of a Survey of Global Ha Emission in Spiral Galaxies in 8 Clusters

1990 ◽  
Vol 124 ◽  
pp. 327-330
Author(s):  
C. Moss
Keyword(s):  
Star Formation ◽  
Spiral Galaxy ◽  
Environmental Effects ◽  
Spiral Galaxies ◽  
Massive Stars ◽  
Formation Rate ◽  
High Dispersion ◽  
Galaxy Interactions ◽  
Excellent Quality ◽  
Objective Prism

Kennicutt & Kent (1983) have shown that the global Ha emission from a spiral galaxy is an indicator of the formation rate of massive stars. Moss, Whittle &: Irwin (1988) have surveyed two clusters (Abell 347 and 1367) for galaxies with Ha emission using a high dispersion objective prism technique. The purpose of the survey is to investigate environmental effects on star formation in spiral galaxies, and in particular to ascertain whether star formation is enhanced in cluster spirals. Approximately 20 % of CGCG galaxies were detected in emission. Two plates of excellent quality were obtained for each of the two clusters, and galaxies were only identified to have emission if this was detected on both plates of a plate pair. In this way, plate flaws and other spurious identifications of emission could be rejected, and weak emission confirmed.

scholarly journals Artificial versus biological intelligence in the Cosmos: clues from a stochastic analysis of the Drake equation

2020 ◽  
Vol 19 (5) ◽  
pp. 353-359
Author(s):  
Alex De Visscher
Keyword(s):  
Artificial Intelligence ◽  
Stochastic Analysis ◽  
Milky Way ◽  
Statistical Investigation ◽  
Observable Universe ◽  
Individual Result ◽  
The Galaxy ◽  
The Universe ◽  
Prevalent Form

AbstractThe Drake equation has been used many times to estimate the number of observable civilizations in the galaxy. However, the uncertainty of the outcome is so great that any individual result is of limited use, as predictions can range from a handful of observable civilizations in the observable universe to tens of millions per Milky Way-sized galaxy. A statistical investigation shows that the Drake equation, despite its uncertainties, delivers robust predictions of the likelihood that the prevalent form of intelligence in the universe is artificial rather than biological. The likelihood of artificial intelligence far exceeds the likelihood of biological intelligence in all cases investigated. This conclusion is contingent upon a limited number of plausible assumptions. The significance of this outcome for the Fermi paradox is discussed.

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