Interpretations of Cosmic Expansion: Anchoring Conceptions and Misconceptions
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The Reionization of Cosmic Hydrogen by the First Galaxies Abstract 1
David Goodstein’s Cosmology Book The Reionization of Cosmic Hydrogen by the First Galaxies Abraham Loeb Department of Astronomy, Harvard University, 60 Garden St., Cambridge MA, 02138 Abstract Cosmology is by now a mature experimental science. We are privileged to live at a time when the story of genesis (how the Universe started and developed) can be critically explored by direct observations. Looking deep into the Universe through powerful telescopes, we can see images of the Universe when it was younger because of the finite time it takes light to travel to us from distant sources. Existing data sets include an image of the Universe when it was 0.4 million years old (in the form of the cosmic microwave background), as well as images of individual galaxies when the Universe was older than a billion years. But there is a serious challenge: in between these two epochs was a period when the Universe was dark, stars had not yet formed, and the cosmic microwave background no longer traced the distribution of matter. And this is precisely the most interesting period, when the primordial soup evolved into the rich zoo of objects we now see. The observers are moving ahead along several fronts. The first involves the construction of large infrared telescopes on the ground and in space, that will provide us with new photos of the first galaxies. Current plans include ground-based telescopes which are 24-42 meter in diameter, and NASA’s successor to the Hubble Space Telescope, called the James Webb Space Telescope. In addition, several observational groups around the globe are constructing radio arrays that will be capable of mapping the three-dimensional distribution of cosmic hydrogen in the infant Universe. -
General Relativity and Cosmology: Unsolved Questions and Future Directions
Article General Relativity and Cosmology: Unsolved Questions and Future Directions Ivan Debono 1,∗,† and George F. Smoot 1,2,3,† 1 Paris Centre for Cosmological Physics, APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/lrfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, 75205 Paris CEDEX 13, France; [email protected] 2 Physics Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, 94720 CA, USA 3 Helmut and Anna Pao Sohmen Professor-at-Large, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077 Hong Kong, China * Correspondence: [email protected]; Tel.: +33-1-57276991 † These authors contributed equally to this work. Academic Editors: Lorenzo Iorio and Elias C. Vagenas Received: 21 August 2016; Accepted: 14 September 2016; Published: 28 September 2016 Abstract: For the last 100 years, General Relativity (GR) has taken over the gravitational theory mantle held by Newtonian Gravity for the previous 200 years. This article reviews the status of GR in terms of its self-consistency, completeness, and the evidence provided by observations, which have allowed GR to remain the champion of gravitational theories against several other classes of competing theories. We pay particular attention to the role of GR and gravity in cosmology, one of the areas in which one gravity dominates and new phenomena and effects challenge the orthodoxy. We also review other areas where there are likely conflicts pointing to the need to replace or revise GR to represent correctly observations and consistent theoretical framework. Observations have long been key both to the theoretical liveliness and viability of GR. -
The Age of the Universe, the Hubble Constant, the Accelerated Expansion and the Hubble Effect
The age of the universe, the Hubble constant, the accelerated expansion and the Hubble effect Domingos Soares∗ Departamento de F´ısica,ICEx, UFMG | C.P. 702 30123-970, Belo Horizonte | Brazil October 25, 2018 Abstract The idea of an accelerating universe comes almost simultaneously with the determination of Hubble's constant by one of the Hubble Space Tele- scope Key Projects. The age of the universe dilemma is probably the link between these two issues. In an appendix, I claim that \Hubble's law" might yet to be investigated for its ultimate cause, and suggest the \Hubble effect” as the searched candidate. 1 The age dilemma The age of the universe is calculated by two different ways. Firstly, a lower limit is given by the age of the presumably oldest objects in the Milky Way, e.g., globular clusters. Their ages are calculated with the aid of stellar evolu- tion models which yield 14 Gyr and 10% uncertainty. These are fairly confident figures since the basics of stellar evolution are quite solid. Secondly, a cosmo- logical age based on the Standard Cosmology Model derived from the Theory of General Relativity. The three basic models of relativistic cosmology are given by the Friedmann's solutions of Einstein's field equations. The models are char- acterized by a decelerated expansion from a spatial singularity at cosmic time t = 0, and whose magnitude is quantified by the density parameter Ω◦, the present ratio of the mass density in the universe to the so-called critical mass arXiv:0908.1864v8 [physics.gen-ph] 28 Jul 2015 density. -
Pre-Big Bang, Space-Time Structure, Asymptotic Universe
EPJ Web of Conferences 71, 0 0 063 (2 014 ) DOI: 10.1051/epjconf/20147100063 C Owned by the authors, published by EDP Sciences, 2014 Pre-Big Bang, space-time structure, asymptotic Universe Spinorial space-time and a new approach to Friedmann-like equations Luis Gonzalez-Mestres1,a 1Megatrend Cosmology Laboratory, Megatrend University, Belgrade and Paris Goce Delceva 8, 11070 Novi Beograd, Serbia Abstract. Planck and other recent data in Cosmology and Particle Physics can open the way to controversial analyses concerning the early Universe and its possible ultimate origin. Alternatives to standard cosmology include pre-Big Bang approaches, new space- time geometries and new ultimate constituents of matter. Basic issues related to a possible new cosmology along these lines clearly deserve further exploration. The Planck collab- oration reports an age of the Universe t close to 13.8 Gyr and a present ratio H between relative speeds and distances at cosmic scale around 67.3 km/s/Mpc. The product of these two measured quantities is then slightly below 1 (about 0.95), while it can be exactly 1 in the absence of matter and cosmological constant in patterns based on the spinorial space- time we have considered in previous papers. In this description of space-time we first suggested in 1996-97, the cosmic time t is given by the modulus of a SU(2) spinor and the Lundmark-Lemaître-Hubble (LLH) expansion law turns out to be of purely geometric origin previous to any introduction of standard matter and relativity. Such a fundamen- tal geometry, inspired by the role of half-integer spin in Particle Physics, may reflect an equilibrium between the dynamics of the ultimate constituents of matter and the deep structure of space and time. -
The Ups and Downs of Baryon Oscillations
The Ups and Downs of Baryon Oscillations Eric V. Linder Physics Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720 ABSTRACT Baryon acoustic oscillations, measured through the patterned distribution of galaxies or other baryon tracing objects on very large (∼> 100 Mpc) scales, offer a possible geometric probe of cosmological distances. Pluses and minuses in this approach’s leverage for understanding dark energy are discussed, as are systematic uncertainties requiring further investigation. Conclusions are that 1) BAO offer promise of a new avenue to distance measurements and further study is warranted, 2) the measurements will need to attain ∼ 1% accuracy (requiring a 10000 square degree spectroscopic survey) for their dark energy leverage to match that from supernovae, but do give complementary information at 2% accuracy. Because of the ties to the matter dominated era, BAO is not a replacement probe of dark energy, but a valuable complement. 1. Introduction This paper provides a pedagogical introduction to baryon acoustic oscillations (BAO), accessible to readers not necessarily familiar with details of large scale structure in the universe. In addition, it summarizes some of the current issues – plus and minus – with the use of BAO as a cosmological probe of the nature of dark energy. For more quantitative, arXiv:astro-ph/0507308v2 17 Jan 2006 technical discussions of these issues, see White (2005). The same year as the detection of the cosmic microwave background, the photon bath remnant from the hot, early universe, Sakharov (1965) predicted the presence of acoustic oscillations in a coupled baryonic matter distribution. In his case, baryons were coupled to cold electrons rather than hot photons; Peebles & Yu (1970) and Sunyaev & Zel’dovich (1970) pioneered the correct, hot case. -
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Ai miei genitori. ii Indice Introduzione ................................................................................................... 1 1. Cent’anni di Cosmologia ............................................................................ 2 2. Il Modello Cosmologico Standard ΛCDM .................................................. 6 3. Questioni aperte e modelli alternativi (cenni) .......................................... 12 4. Conclusioni .............................................................................................. 14 Bibliografia .................................................................................................. 16 Ringraziamenti ............................................................................................. 18 iii iv “La più sublime, la più nobile tra le Fisiche scienze ella è senza dubbio l’Astronomia. L’uomo s’innalza per mezzo di essa come al di sopra di se medesimo, e giunge a conoscere la causa dei fenomeni più straordinari.” (Giacomo Leopardi 1) Introduzione Il presente lavoro intende offrire un riassunto dello “stato dell’arte” della Cosmologia: dopo averne ripercorso per sommi capi la storia degli ultimi cent’anni (cap.1), verrà illustrato il Modello Cosmologico Standard “ ΛCDM” (cap.2), che è quello generalmente accettato dalla comunità scientifica allo stato attuale delle conoscenze; infine, si farà un breve “excursus” sulle questioni “aperte” e sui modelli cosmologici alternativi (cap.3). La Cosmologia si può definire in maniera sintetica come lo studio dell’Universo -
Rayappa a Kasi Rusch to Riches.Pdf
RUSH TO RICHES The War on Creation Paul Wiegelmann Lectures on Environmental Studies: 2 RUSH TO RICHES The War on Creation Rayappa A. Kasi Dharmaram Publications Bangalore 560 029, India 2011 Rush to Riches: The War on Creation By Rayappa A. Kasi A. Kattupadi Post Vellore 632011, India Website: www.planetschaser.com Email: [email protected]; Phone: 09443537885 Paul Wiegelmann Lectures on Environmental Studies: 2 © Faculty of Philosophy Dharmaram Vidya Kshetram Bangalore 560 029, India Email: [email protected] First Edition, 2011 Published by Dharmaram Publications ISBN: 978-81-89958-45-9 Printed at: National Printing Press, Bangalore Price: INì 395; US$ 40 Dharmaram Publications Dharmaram College, Bangalore 560 029, India Tel. 080/4111 6227; 4111 6137; 4111 6111 E-mail: [email protected] Web: www.dharmarampublications.com In memory of all the species of animals and plants perished in the war on creation Other Publications from the Author 1. Earth: The Lost Paradise of Happiness (2009) 2. Global Warming: Everything You Want to Know! (2009) 3. Biosphere: The Fragility of Our Natural Heritage (2010) 4. Lithosphere: A Destructive Creator (2010) 5. Hydrosphere: The Giver of Life (2010) 6. Atmosphere: A Thin Line between Life and Death (2010) 7. Earth: Designed for Biodiversity (2010) 8. Youth: An Avatar of New Earth (2011) 9. Apes to Angels: Man Reaches his Omega Point (2011) Cover Illustration This picture, the oil-soaked bird from Gulf of Mexico, represents the agony and pain that the Creation is undergoing as a result of human conflict with Nature. It is a loud cry of Creation for help. -
AST4220: Cosmology I
AST4220: Cosmology I Øystein Elgarøy 2 Contents 1 Cosmological models 1 1.1 Special relativity: space and time as a unity . 1 1.2 Curvedspacetime......................... 3 1.3 Curved spaces: the surface of a sphere . 4 1.4 The Robertson-Walker line element . 6 1.5 Redshifts and cosmological distances . 9 1.5.1 Thecosmicredshift . 9 1.5.2 Properdistance. 11 1.5.3 The luminosity distance . 13 1.5.4 The angular diameter distance . 14 1.5.5 The comoving coordinate r ............... 15 1.6 TheFriedmannequations . 15 1.6.1 Timetomemorize! . 20 1.7 Equationsofstate ........................ 21 1.7.1 Dust: non-relativistic matter . 21 1.7.2 Radiation: relativistic matter . 22 1.8 The evolution of the energy density . 22 1.9 The cosmological constant . 24 1.10 Some classic cosmological models . 26 1.10.1 Spatially flat, dust- or radiation-only models . 27 1.10.2 Spatially flat, empty universe with a cosmological con- stant............................ 29 1.10.3 Open and closed dust models with no cosmological constant.......................... 31 1.10.4 Models with more than one component . 34 1.10.5 Models with matter and radiation . 35 1.10.6 TheflatΛCDMmodel. 37 1.10.7 Models with matter, curvature and a cosmological con- stant............................ 40 1.11Horizons.............................. 42 1.11.1 Theeventhorizon . 44 1.11.2 Theparticlehorizon . 45 1.11.3 Examples ......................... 46 I II CONTENTS 1.12 The Steady State model . 48 1.13 Some observable quantities and how to calculate them . 50 1.14 Closingcomments . 52 1.15Exercises ............................. 53 2 The early, hot universe 61 2.1 Radiation temperature in the early universe . -
Hubble's Diagram and Cosmic Expansion
Hubble’s diagram and cosmic expansion Robert P. Kirshner* Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 Contributed by Robert P. Kirshner, October 21, 2003 Edwin Hubble’s classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929) Proc. Natl. Acad. Sci. USA 15, 168–173]. The chief result, that a galaxy’s distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble’s Law, and the Hubble time, that the article itself is rarely referenced. Even though Hubble’s distances have a large systematic error, Hubble’s velocities come chiefly from Vesto Melvin Slipher, and the interpretation in terms of the de Sitter effect is out of the mainstream of modern cosmology, this article opened the way to investigation of the expanding, evolving, and accelerating universe that engages today’s burgeoning field of cosmology. he publication of Edwin Hub- ble’s 1929 article ‘‘A relation between distance and radial T velocity among extra-galactic nebulae’’ marked a turning point in un- derstanding the universe. In this brief report, Hubble laid out the evidence for one of the great discoveries in 20th cen- tury science: the expanding universe. Hubble showed that galaxies recede from us in all directions and more dis- tant ones recede more rapidly in pro- portion to their distance. His graph of velocity against distance (Fig. 1) is the original Hubble diagram; the equation that describes the linear fit, velocity ϭ ϫ Ho distance, is Hubble’s Law; the slope of that line is the Hubble con- ͞ stant, Ho; and 1 Ho is the Hubble time. -
Observational Cosmology - 30H Course 218.163.109.230 Et Al
Observational cosmology - 30h course 218.163.109.230 et al. (2004–2014) PDF generated using the open source mwlib toolkit. See http://code.pediapress.com/ for more information. PDF generated at: Thu, 31 Oct 2013 03:42:03 UTC Contents Articles Observational cosmology 1 Observations: expansion, nucleosynthesis, CMB 5 Redshift 5 Hubble's law 19 Metric expansion of space 29 Big Bang nucleosynthesis 41 Cosmic microwave background 47 Hot big bang model 58 Friedmann equations 58 Friedmann–Lemaître–Robertson–Walker metric 62 Distance measures (cosmology) 68 Observations: up to 10 Gpc/h 71 Observable universe 71 Structure formation 82 Galaxy formation and evolution 88 Quasar 93 Active galactic nucleus 99 Galaxy filament 106 Phenomenological model: LambdaCDM + MOND 111 Lambda-CDM model 111 Inflation (cosmology) 116 Modified Newtonian dynamics 129 Towards a physical model 137 Shape of the universe 137 Inhomogeneous cosmology 143 Back-reaction 144 References Article Sources and Contributors 145 Image Sources, Licenses and Contributors 148 Article Licenses License 150 Observational cosmology 1 Observational cosmology Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors. Early observations The science of physical cosmology as it is practiced today had its subject material defined in the years following the Shapley-Curtis debate when it was determined that the universe had a larger scale than the Milky Way galaxy. This was precipitated by observations that established the size and the dynamics of the cosmos that could be explained by Einstein's General Theory of Relativity. -
Time in Cosmology
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Philsci-Archive Time in Cosmology Craig Callender∗ C. D. McCoyy 21 August 2017 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 under- stood 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. Different claims about time have long been at the heart of cosmology. Ancient creation myths disagree over whether time is finite or infinite, linear or circular. This speculation led to Kant complaining in his famous antinomies that metaphysical reasoning about the nature of time leads to a “euthanasia of reason”. But neither Kant’s worry nor cosmology becoming a modern science succeeded in ending the speculation. Einstein’s first model of the universe portrays a temporally infinite universe, where space is edgeless and its material contents unchanging. -
Introducing Astrogen: the Astronomy Genealogy Project
Journal of Astronomical History and Heritage, 19(3), 298–304 (2016). INTRODUCING ASTROGEN: THE ASTRONOMY GENEALOGY PROJECT Joseph S. Tenn Sonoma State University, Rohnert Park, CA 94928, USA. Email: [email protected] Abstract: The Astronomy Genealogy Project (―AstroGen‖), a project of the Historical Astronomy Division of the American Astronomical Society (AAS), will soon appear on the AAS website. Ultimately, it will list the world‘s astronomers with their highest degrees, theses for those who wrote them, academic advisors (supervisors), universities, and links to the astronomers or their obituaries, their theses when on-line, and more. At present the AstroGen team is working on those who earned doctorates with astronomy-related theses. We show what can be learned already, with just ten countries essentially completed. Keywords: Academic genealogy, astronomers, Ph.D. theses, dissertations 1 INTRODUCTION ries we have studied (listed in Section 3) went to Arthur Williams Wright (Figure 1), who became AstroGen is coming. The Astronomy Genealogy the first person outside Europe to earn a Ph.D. Project will soon appear on the website of the in science and one of the first three Ph.D.s in American Astronomical Society (AstroGen: any subject in the United States. His thesis, https://astrogen.aas.org/). Under construction Having Given the Velocity and Direction of since early 2013, the project will list the world‘s Motion of a Meteor on Entering the Atmosphere doctoral theses (dissertations) on astronomy- of the Earth, to Determine its Orbit about the related topics, along with information about the Sun, Taking into Account the Attraction of Both theses and their authors.