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Steven Weinberg | 624 pages | 28 Apr 2008 | Oxford University Press | 9780198526827 | English | Oxford, Cosmology - Wikipedia

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These cycles have and will last forever, driven by desires. considers the , or universe, as an uncreated entity, existing since , the shape of the universe as similar to a man standing with legs apart and arm resting on his waist. This Universe, according to , is broad at the top, narrow at the middle and once again becomes broad at the bottom. Babylonian cosmology. Babylonian c. The Earth and the form a unit within infinite "waters of chaos"; the earth is flat and circular, and a solid dome the "" keeps out the outer "chaos"-ocean. The Universe is unchanging, uniform, perfect, necessary, timeless, and neither generated nor perishable. is impossible. Plurality and change are products of epistemic ignorance derived from sense experience. Temporal and spatial limits are arbitrary and relative to the Parmenidean whole. Genesis creation . The Earth and the Heavens form a unit within infinite "waters of chaos"; the " firmament " keeps out the outer "chaos"-ocean. The universe contains only two things: an infinite number of tiny seeds and the void of infinite extent. All atoms are made of the same substance, but differ in size and shape. Objects are formed from aggregations and decay back into atoms. Incorporates ' of : "nothing happens at random; everything happens out of reason and necessity". The universe was not ruled by . Pythagorean universe. At the center of the Universe is a central fire, around which the Earth, , and revolve uniformly. The Sun revolves around the central fire once a year, the stars are immobile. The earth in its motion maintains the same hidden face towards the central fire, hence it is never seen. First known non- of the Universe. Pseudo- d. The Universe then is a system made up of and earth and the elements which are contained in them. There are "five elements, situated in spheres in five regions, the less being in each case surrounded by the greater — namely, earth surrounded by water, water by air, air by fire, and fire by ether — make up the whole Universe. The is finite and surrounded by an infinite void. It is in a state of flux, and pulsates in size and undergoes periodic upheavals and conflagrations. Geocentric , static, steady state, finite extent, infinite time. Spherical earth is surrounded by concentric . Universe exists unchanged throughout . Contains a fifth element, called aether , that was added to the four classical elements. Earth rotates daily on its axis and revolves annually about the sun in a circular orbit. Sphere of fixed stars is centered about the sun. Universe orbits around a stationary Earth. Planets move in circular epicycles , each having a center that moved in a larger circular orbit called an eccentric or a deferent around a center-point near Earth. The use of added another level of complexity and allowed astronomers to predict the positions of the planets. The most successful universe model of all time, using the criterion of longevity. the Great System. The Earth rotates and the planets move in elliptical orbits around either the Earth or Sun; uncertain whether the model is geocentric or heliocentric due to planetary orbits given with respect to both the Earth and Sun. Medieval philosophers — A universe that is finite in time and has a beginning is proposed by the Christian philosopher , who argues against the notion of an infinite past. Logical arguments supporting a finite universe are developed by the early Muslim philosopher Alkindus , the Jewish philosopher Saadia Gaon , and the Muslim theologian Algazel. Multiversal cosmology. Fakhr al-Din al-Razi — There exists an infinite beyond the known world, and has the power to fill the vacuum with an infinite number of universes. Maragha school — Various modifications to Ptolemaic model and Aristotelian universe, including rejection of and eccentrics at , and introduction of Tusi-couple by Al-Tusi. — A universe in which the planets orbit the Sun, which orbits the Earth; similar to the later Tychonic system. Copernican universe. — First described in De revolutionibus orbium coelestium. A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the earlier Nilakanthan model. Rejects the idea of a hierarchical universe. Earth and Sun have no special in comparison with the other heavenly bodies. The void between the stars is filled with aether , and matter is composed of the same four elements water, earth, fire, and air , and is atomistic, animistic and intelligent. Kepler's discoveries, marrying mathematics and , provided the foundation for our present conception of the Solar system, but distant stars were still seen as objects in a thin, fixed . Static evolving , steady state, infinite. Every in the universe attracts every other particle. Matter on the large scale is uniformly distributed. Gravitationally balanced but unstable. Cartesian Vortex universe. System of huge swirling whirlpools of aethereal or fine matter produces what we would call gravitational effects. But his vacuum was not empty; all space was filled with matter. , Johann Lambert , 18th century. Einstein Universe with a . Contains uniformly distributed matter. Uniformly curved spherical space; based on Riemann's hypersphere. Expanding flat space. Steady state. Based on Einstein's . Space expands with constant acceleration. increases exponentially constant inflation. William Duncan MacMillan s. New matter is created from radiation ; starlight perpetually recycled into new matter . Friedmann universe , spherical space. Positive curvature. Friedmann universe , hyperbolic space. Hyperbolic expanding space. Negative curvature. The Sun is a star around which Earth and the other planets revolve, and by extension every visible star in the sky is a sun in its own right. Some stars are intrinsically brighter than the Sun; others, fainter. Much less is received from the stars than from the Sun because the stars are all much farther away. Indeed, they appear densely packed in the only because there are so many of them. The actual separations of the stars are enormous, so large that it is conventional to measure their distances in units of how far light can travel in a given amount of time. Thus in terrestrial terms the Sun, which lies light-seconds from the Earth, is very far away; however, even the next closest star, Proxima Centauri , at a distance of 4. The stars that lie on the opposite side of the Milky Way from the Sun have distances that are on the order of , light-years, which is the typical diameter of a large . If the kingdom of the stars seems vast, the realm of the is larger still. The nearest galaxies to the Milky Way system are the Large and Small Magellanic Clouds , two irregular satellites of the Galaxy visible to the naked eye in the Southern Hemisphere. The Magellanic Clouds are relatively small containing roughly 10 9 stars compared to the Galaxy with some 10 11 stars , and they lie at a distance of about , light-years. The nearest large galaxy comparable to the Galaxy is the also called M31 because it was the 31st entry in a catalog of astronomical objects compiled by the French astronomer Charles Messier in , and it lies at a distance of about 2,, light-years. The Magellanic Clouds, the Andromeda Galaxy, and the Milky Way system all are part of an aggregation of two dozen or so neighbouring galaxies known as the . The Galaxy and M31 are the largest members of this group. The Galaxy and M31 are both spiral galaxies, and they are among the brighter and more massive of all spiral galaxies. The most luminous and brightest galaxies, however, are not spirals but rather supergiant ellipticals also called cD galaxies by astronomers for historical reasons that are not particularly illuminating. Elliptical galaxies have roundish shapes rather than the flattened distributions that characterize spiral galaxies, and they tend to occur in rich clusters those containing thousands of members rather than in the loose groups favoured by spirals. The brightest member galaxies of rich clusters have been detected at distances exceeding several thousand million light-years from the Earth. Cosmology Article Media Additional Info. Article Contents. Home Science Astronomy. Print print Print. Table Of Contents. Facebook Twitter. Cosmology | Science News

Example sentences from the Web for cosmology Whether those facts match the cosmology of an Iron Age text is not their problem. Really, Dr. The Enchiridion Epictetus. The Folk-Tales of the Magyars Various. Outspoken Essays William Ralph Inge. Tracks of a Rolling Stone Henry J. The scientific study of the origin, evolution, and structure of the universe. A specific theory or model of the origin and evolution of the universe. All rights reserved. Every day? One reason why fans watch Star Trek is for the various depicted in the show, including different conceptions of space, time, and the . Examples of cosmology in a Sentence Recent Examples on the Web His diagrams are now the lingua franca of cosmology. Now They Have a Nobel Prize. Send us feedback. See more words from the same year Dictionary Entries near cosmology cosmologic cosmological constant cosmology cosmonaut cosmonautics cosmoplastic. Accessed 21 Oct. Keep scrolling for more More Definitions for cosmology cosmology. Please tell us where you read or heard it including the quote, if possible. Test Your Knowledge - and learn some interesting things along the way. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free! Whereas 'coronary' is no so much Put It in the 'Frunk' You can never have too much storage. What Does 'Eighty-Six' Mean? We're intent on clearing it up 'Nip it in the butt' or 'Nip it in the bud'? After a few hundred thousand years, the temperature must have dropped sufficiently for electrons to remain attached to nuclei to constitute atoms. Galaxies are thought to have begun forming after a few million years, but this stage is very poorly understood. Star formation probably started much later, after at least a , and the process continues today. Observational support for this general model comes from several independent directions. The expansion has been documented by the observed in the spectra of galaxies. Furthermore, the radiation left over from the original fireball would have cooled with the expansion. The shape of the observed spectrum is an excellent fit with the theoretical blackbody spectrum. The present best value for this temperature is 2. The spectrum of this cosmic radio noise peaks at approximately a one-millimetre wavelength, which is in the far infrared, a difficult region to observe from Earth; however, the spectrum has been well mapped by the Cosmic Background Explorer COBE , Wilkinson Microwave Anisotropy Probe , and Planck satellites. Additional support for the big bang theory comes from the observed cosmic abundances of deuterium and . Normal stellar nucleosynthesis cannot produce their measured quantities, which fit well with calculations of production during the early stages of the big bang. Early surveys of the cosmic background radiation indicated that it is extremely uniform in all directions isotropic. Calculations have shown that it is difficult to achieve this degree of unless there was a very early and rapid inflationary period before the expansion settled into its present mode. Nevertheless, the isotropy posed problems for models of galaxy formation. Galaxies originate from turbulent conditions that produce local fluctuations of density, toward which more matter would then be gravitationally attracted. Such density variations were difficult to reconcile with the isotropy required by observations of the 3 K radiation. This problem was solved when the COBE satellite was able to detect the minute fluctuations in the cosmic background from which the galaxies formed. Astronomy - Cosmology | Britannica

Understanding Ghost Particle Interactions Sep. This model building is part of a larger project to understand the role of have now done just Each star is shrouded by a gaseous disk which includes molecules of sodium chloride, commonly known as table salt, and Gravity Causes of the Universe Sep. Summaries Headlines. This precision measurement to one of the most magnetic objects in the Universe could help Its discovery has shaken solar system origin The also reveals that current models can't explain This Universe, according to Jainism , is broad at the top, narrow at the middle and once again becomes broad at the bottom. Babylonian cosmology. Babylonian literature c. The Earth and the Heavens form a unit within infinite "waters of chaos"; the earth is flat and circular, and a solid dome the "firmament" keeps out the outer "chaos"-ocean. The Universe is unchanging, uniform, perfect, necessary, timeless, and neither generated nor perishable. Void is impossible. Plurality and change are products of epistemic ignorance derived from sense experience. Temporal and spatial limits are arbitrary and relative to the Parmenidean whole. Genesis creation narrative. The Earth and the Heavens form a unit within infinite "waters of chaos"; the " firmament " keeps out the outer "chaos"-ocean. The universe contains only two things: an infinite number of tiny seeds atoms and the void of infinite extent. All atoms are made of the same substance, but differ in size and shape. Objects are formed from atom aggregations and decay back into atoms. Incorporates Leucippus ' principle of causality : "nothing happens at random; everything happens out of reason and necessity". The universe was not ruled by gods. Pythagorean universe. At the center of the Universe is a central fire, around which the Earth, Sun, Moon and planets revolve uniformly. The Sun revolves around the central fire once a year, the stars are immobile. The earth in its motion maintains the same hidden face towards the central fire, hence it is never seen. First known non-geocentric model of the Universe. Pseudo-Aristotle d. The Universe then is a system made up of heaven and earth and the elements which are contained in them. There are "five elements, situated in spheres in five regions, the less being in each case surrounded by the greater — namely, earth surrounded by water, water by air, air by fire, and fire by ether — make up the whole Universe. The cosmos is finite and surrounded by an infinite void. It is in a state of flux, and pulsates in size and undergoes periodic upheavals and conflagrations. Geocentric , static, steady state, finite extent, infinite time. Spherical earth is surrounded by concentric celestial spheres. Universe exists unchanged throughout eternity. Contains a fifth element, called aether , that was added to the four classical elements. Earth rotates daily on its axis and revolves annually about the sun in a circular orbit. Sphere of fixed stars is centered about the sun. Universe orbits around a stationary Earth. Planets move in circular epicycles , each having a center that moved in a larger circular orbit called an eccentric or a deferent around a center-point near Earth. The use of equants added another level of complexity and allowed astronomers to predict the positions of the planets. The most successful universe model of all time, using the criterion of longevity. Almagest the Great System. The Earth rotates and the planets move in elliptical orbits around either the Earth or Sun; uncertain whether the model is geocentric or heliocentric due to planetary orbits given with respect to both the Earth and Sun. Medieval philosophers — A universe that is finite in time and has a beginning is proposed by the Christian philosopher John Philoponus , who argues against the ancient Greek notion of an infinite past. Logical arguments supporting a finite universe are developed by the early Muslim philosopher Alkindus , the Jewish philosopher Saadia Gaon , and the Muslim theologian Algazel. Multiversal cosmology. Fakhr al-Din al-Razi — There exists an infinite outer space beyond the known world, and God has the power to fill the vacuum with an infinite number of universes. Maragha school — Various modifications to Ptolemaic model and Aristotelian universe, including rejection of equant and eccentrics at Maragheh observatory , and introduction of Tusi-couple by Al-Tusi. Nilakantha Somayaji — A universe in which the planets orbit the Sun, which orbits the Earth; similar to the later Tychonic system. Copernican universe. Nicolaus Copernicus — First described in De revolutionibus orbium coelestium. A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the earlier Nilakanthan model. Rejects the idea of a hierarchical universe. Earth and Sun have no special properties in comparison with the other heavenly bodies. The void between the stars is filled with aether , and matter is composed of the same four elements water, earth, fire, and air , and is atomistic, animistic and intelligent. Kepler's discoveries, marrying mathematics and physics, provided the foundation for our present conception of the Solar system, but distant stars were still seen as objects in a thin, fixed celestial sphere. Static evolving , steady state, infinite. Every particle in the universe attracts every other particle. Matter on the large scale is uniformly distributed. Gravitationally balanced but unstable. Cartesian Vortex universe. System of huge swirling whirlpools of aethereal or fine matter produces what we would call gravitational effects. But his vacuum was not empty; all space was filled with matter. Immanuel Kant , Johann Lambert , 18th century. Einstein Universe with a cosmological constant. Contains uniformly distributed matter. Uniformly curved spherical space; based on Riemann's hypersphere. Expanding flat space. Steady state. Based on Einstein's general relativity. Space expands with constant acceleration. Scale factor increases exponentially constant inflation. William Duncan MacMillan s. New matter is created from radiation ; starlight perpetually recycled into new matter particles. Friedmann universe , spherical space. Positive curvature. Friedmann universe , hyperbolic space. Hyperbolic expanding space. Negative curvature. Said to be infinite but ambiguous. Expands forever. Dirac hypothesis. Demands a large variation in G , which decreases with time. Gravity weakens as universe evolves. Named after but not considered by Friedmann. Universe has initial high-density state "primeval atom". Followed by a two-stage expansion. Oscillating universe Friedmann-Einstein. Time is endless and beginningless; thus avoids the beginning-of-time paradox. Perpetual cycles of Big Bang followed by . Save Word. Definition of cosmology. Keep scrolling for more. Cosmology and Star Trek Most and include some kind of cosmology to explain the nature of the universe. First Known Use of cosmology circa , in the meaning defined at sense 1a. Learn More about cosmology. Time Traveler for cosmology The first known use of cosmology was circa See more words from the same year. Dictionary Entries near cosmology cosmologic cosmological constant cosmological principle cosmology cosmonaut cosmonautics cosmoplastic See More Nearby Entries. More Definitions for cosmology. English Language Learners Definition of cosmology. Comments on cosmology What made you want to look up cosmology? Get Word of the Day daily email! Test Your Vocabulary.

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Since philosophy and physics intertwine at the far reaches of cosmology , this makes him a much more satisfying guide than most. It is even permissible to say that he took physics or cosmology too lightly. As to the cosmology of the story-tellers, all we can say is, that they appear to uphold the Zetetic school. We have just shown that, thus understood, totemism also has it cosmology. A supramundane physics or cosmology was evolved at the same time. The specialist sees only through his microscope, and knows about as much of cosmology as does his microbe. A system of beliefs that seeks to describe or explain the origin and structure of the universe. A cosmology attempts to establish an ordered, harmonious framework that integrates time, space, the planets , stars , and other celestial phenomena. In so-called primitive societies, cosmologies help explain the relationship of beings to the rest of the universe and are therefore closely tied to religious beliefs and practices. In modern industrial societies, cosmologies seek to explain the universe through astronomy and mathematics. These are all pressing problems for those who hold that the principle of indifference is essential to making cosmological predictions. Furthermore, one way of implementing this approach leads to absurd consequences. The Doomsday Argument, for example, claims to reach a striking conclusion about the future of the human species without any empirical input see, e. We should then expect that there are nearly as many before and after us in overall birth rank. The challenge to advocates of indifference applied to observers is to articulate that avoid such consequences, while still solving alleged problems such as that of freak observers. In sum, one approach to anthropic reasoning aims to clarify the rules of reasoning applicable to predictions made by observers in a large or infinite universe. This line of work is motivated by the idea that without such principles we face a severe skeptical predicament, as observations would not have any bearing on the theory. Yet there is still not general agreement on the new principles required to handle these cases, which are of course not scientifically testable principles: they are philosophically based proposals. According to an alternative approach, selection effects can and should be treated within the context of a Bayesian approach to inductive inference see Neal ; Trotta There is much further work to be done in clarifying and assessing these and other approaches to anthropic reasoning. Fine-tuning arguments start from a conflict between two different perspectives on certain features of cosmology or other physical theories. On the first perspective, the existence of creatures like us seems to be sensitive to a wide variety of aspects of cosmology and physics. To be more specific, the prospects for life depend sensitively on the values of the various fundamental constants that appear in these theories. The SM includes about 10 constants, and the standard model includes about 20 more. Yet it does seem plausible that requires an organism with complex structural features, living in a sufficiently stable environment. At a bare minimum, the existence of life seems to require the existence of complex structures at a variety of scales, ranging from galaxies to planetary systems to macro-molecules. Such complexity is extremely sensitive to the values of the fundamental constants of nature. From this perspective, the existence of life in the universe is fragile in the sense that it depends sensitively on these aspects of the underlying theory. This view contrasts sharply with the status of the constants from the perspective of fundamental physics. Particle typically regard their theories as effective field theories, which suffice for describing interactions at some specified energy scale. These theories include various constants, characterizing the relative strength of the interactions they describe, that cannot be further explained by the effective field theory. The constants can be fixed by experimental results, but are not derivable from fundamental physical principles. If the effective field theory can be derived from a more fundamental theory, the value of the constants can in principle be determined by integrating out higher-energy degrees of freedom. But this merely pushes the question back one step: the constants appearing in the more fundamental theory are determined experimentally. Similarly, the constants appearing in the SM are treated as contingent features of the universe. There is no underlying physical principle that sets, for example, the cosmological densities of different kinds of matter, or the value of the Hubble constant. So features of our theories that appear entirely contingent, from the point of view of physics, are necessary to account for the complexity of the observed universe and the very possibility of life. The unease develops into serious discomfort if the specific values of the constants are taken to be extremely unlikely: how could the values of all these constants be just right , by sheer coincidence? In many familiar cases, our past experience is a good guide to when an apparent coincidence calls for further explanation. As Hume emphasized, however, intuitive assessments from everyday life of whether a given event is likely, or requires a further explanation, do not extend to cosmology. Recent formulations of fine-tuning arguments often introduce probabilistic considerations. Introducing a well-defined probability over the constants would provide a response to Hume: rather than extrapolating our intuitions, we would be drawing on the formal machinery of our physical theories to identify fine-tuning. Promising though this line of argument may be, there is not an obvious way to define physical probabilities over the values of different constants, or over other features of the laws. There is nothing like the structure used to justify physical probabilities in other contexts, such as equilibrium statistical mechanics. The response replaces a single, apparently finely-tuned universe within an ensemble of universes, combined with an appeal to anthropic selection. Suppose that all possible values of the fundamental constants are realized in individual elements of the ensemble. Many of these universes will be inhospitable to life. In calculating the probabilities that we observe specific values of the fundamental constants, we need only consider the subset of universe compatible with the existence of complexity or some more specific feature associated with life. If we have some way of assigning probabilities over the ensemble, we could then calculate the probability associated with our measured values. These calculations will resolve the fine-tuning puzzles if they show that we observe typical values for a complex or life-permitting universe. Many cosmologists have argued in favor of a specific version of the multiverse called EI. On this line of thought, the multiverse should be accepted for the same reason we accept many claims about what we cannot directly observe— namely, as an inevitable consequence of an established physical theory. It is not clear, however, that EI is inevitable, as not all inflationary models, arguably including those favored by CMB observations, have the kind of potential that leads to EI. There have been two distinct approaches to recovering some empirical content in this situation. Detection of a distinctive signature that cannot be explained by other means would provide evidence for the multiverse. However, there is no expectation that a multiverse theory would generically predict such traces; for example, if the collision occurs too early the imprint is erased by subsequent inflationary expansion. The process of forming the pocket universes is assumed to yield variation in the local, low-energy physics in each pocket. The aim is to obtain probabilistic predictions for what a typical observer should see in the EI multiverse. Yet there are several challenges to overcome, alongside those mentioned above related to anthropics. The assumption that the formation of pocket universes leads to variation in constants is just an assumption, which is not yet justified by a plausible, well-tested dynamical theory. It is difficult to define a measure because the EI multiverse is usually taken to be an infinite ensemble, lacking in the kinds of structure used in constructing a measure. On our view, these unmet challenges undercut the hope that the EI multiverse yields probabilistic predictions. And without such an account, the multiverse proposal does not have any testable consequences. If everything happens somewhere in the ensemble, then any potential observation is compatible with the theory. Supposing that we grant a successful resolution of all these challenges, the merits of a multiverse solution of fine-tuning problems could then be evaluated by comparison with competing ideas. Claims that we occupy one of infinitely many possible pocket universes, filled with an infinity of other observers, rest on an enormous and speculative extrapolation. Such claims fail to take seriously the concept of infinity, which is not merely a large number. Hilbert [] emphasized that while infinity is required to complete mathematics, it does not occur anywhere in the accessible physical universe. One response is to require that in cosmology should have a restricted use. It may be useful to introduce infinity as part of an explanatory account of some aspect of cosmology, as is common practice in mathematical models that introduce various idealizations. Yet this infinity should be eliminable, such that the explanation of the phenomena remains valid when the idealization is removed. In sum, interest in the multiverse stems primarily from speculations about the consequences of inflation for the global structure of the universe. As mentioned at the start, the uniqueness of the universe raises specific problems as regards cosmology as a science. First we consider issues to do with verification of cosmological models, and then make a comment as regards interpreting the human implications of cosmology. The basic challenge in cosmology regards how to test and evaluate cosmological models, given our limited access to the unique universe. As discussed above, current cosmological models rely in part on extrapolations of well-tested local physics along with novel proposals, such as the inflaton field. Distinctions that are routinely employed in other areas of physics, such as that between laws and initial conditions, or chance and necessity, are not directly applicable, due to the uniqueness of the universe. Recent debates regarding the legitimacy of different lines of research in cosmology reflect different responses to this challenge. One response is to retreat to hypothetico-deductivism HD : a hypothesis receives an incremental boost in confidence when one of its consequences is verified and a decrease if it is falsified. A second response is that the challenge requires a more sophisticated . This may take the form of acknowledging explicitly the criteria that scientists use to assess desirability of scientific theories Ellis , which include considerations of explanatory power, consistency with other theories, and other factors, in addition to compatibility with the evidence. These come into conflict in unexpected ways in cosmology, and these different factors should be clearly articulated and weighed against one another. Alternatively, one might try to show that some of these desirable features, such as the ability to unify diverse phenomena, should be taken as part of what constitutes empirical success. Finally, a key issue is what scope do we expect our theories to have. Ellis makes a distinction between Cosmology , which is the physically based subject dealt with in the textbooks listed in this article, dealing with the expansion of the universe, galaxies, number counts, background radiation, and so on, and Cosmologia , where one takes all that as given but adds in consideration about the meaning this all has for life. Clearly the anthropic discussions mentioned above are a middle ground. We will make just one remark about this here. If one is going to consider Cosmologia seriously, it is incumbent on one to take seriously the full range of data appropriate to that enterprise. That is, the data needed for the attempted scope of such a theory must include data to do with the meaning of life as well as data derived from telescopes, laboratory experiments, and particle colliders. It must thus include data about good and evil, life and death, fear and hope, love and pain, writings from the great philosophers and writers and artists who have lived in human history and pondered the meaning of life on the basis of their life experiences. This is all of great meaning to those who live on Earth and hence in the Universe. To produce books saying that science proves there is no purpose in the universe is pure myopia. It just means that one has shut ones eyes to all the data that relates to purpose and meaning; and that one supposes that the only science is physics for psychology and biology are full of purpose. Work on this entry was supported by a grant from the John Templeton Foundation. The statements made here are those of the authors and are not necessarily endorsed by the Foundation. Philosophy of Cosmology First published Tue Sep 26, The second is Cosmology deals with the physical situation that is the context in the large for human existence: the universe has such a nature that our life is possible. Global Interplay in Cosmology 2. Underdetermination 2. Origins of the Universe 3. Anthropic Reasoning and Multiverse 4. Testing models 5. There are several distinctive epochs in the history of the universe, according to the SM, including the following: Quantum gravity : Classical general relativity is expected to fail at early times, when quantum effects will be crucial in describing the gravitational degrees of freedom. There is considerable uncertainty regarding physics at this scale. The predicted light-element abundances depend on physical features of the universe at this time, such as the total density of baryonic matter and the baryon to photon ratio. Agreement between theory and observation for a specific baryon to photon ratio Steigman is a great success of the SM. Dark Ages : After , baryonic matter consists almost entirely of neutral hydrogen and helium. Once the first generation of stars form, the dark ages come to an end with light from the stars, which re-ionizes the universe. Structure Formation : Cold dominates the early stages of the formation of structure. Dark matter halos provide the scaffolding for hierarchical structure formation. The first generation of stars aggregate into galaxies, and galaxies into clusters. Massive stars end their lives in explosions and spread through space heavy elements that have been created in their interiors, enabling formation of second generation stars surrounded by planets. Domination : Dark energy or a non-zero cosmological constant eventually comes to dominate the expansion of the universe, leading to accelerated expansion. Global Interplay in Cosmology Although cosmology is generally seen as fitting into the general physics of everything being determined in a bottom up manner, as in the discussion above, there is another tradition that sees the effect of the global on the local in cosmology. This has to be due to special initial conditions at the start of the universe Ellis It is because of this effect that studies of structure such as the BAO and CMB anisotropies give us strong limits on the parameters of the background model Ade et al. Underdetermination Many philosophers hold that evidence is not sufficient to determine which scientific theory we should choose. This question arises in several concrete cases: Existence of low CMB anisotropy power at high and angular scales relative to that predicted by the SM Schwarz et al. Origins of the Universe Cosmology confronts a distinctive challenge in accounting for the origin of the universe. Projecting observed features of the universe backwards leads to an initial state with three puzzling features: [ 35 ] Uniformity : The FLRW models have a finite particle horizon distance, much smaller than the scales at which we observe the CMB. It is challenging to explain both properties dynamically. In the standard FLRW models, the perturbations have to be coherent on scales much larger than the Hubble radius at early times. One form of this response challenges appeals to probability, undermining the claim that there are unexplained coincidences. Alternatively, fine-tuning is taken to reveal that the laws alone are not sufficient to account for some features of nature; these features are properly explained by the laws in conjunction with various contingent facts. Designer : Newton famously argued, for example, that the stability of the solar system provides evidence of providential design. For the hypothesized Designer to be supported by fine-tuning evidence, we require some way of specifying what kind of universe the Designer is likely to create; only such a specific Design hypothesis, based in some theory of the nature of the Designer, can offer an explanation of fine-tuning. New Physics : The fine-tuning can be eliminated by modifying physical theory in a variety of ways: altering the dynamical laws, introducing new constraints on the space of physical possibilities or possible values of the constants of nature , etc. Multiverse : Fine-tuning is explained as a result of selection, from among a large space of possible universes or multiverse. Testing models As mentioned at the start, the uniqueness of the universe raises specific problems as regards cosmology as a science. First we consider issues to do with verification of cosmological models, and then make a comment as regards interpreting the human implications of cosmology 5. Bibliography Ade, P. Aghanim, M. Arnaud, F. Arroja, M. Ashdown, J. Aumont, C. Baccigalupi, M. Ballardini, A. Banday, R. Barreiro, et al. Barbour, Julian B. Barnes, L. Barrow, John D. Batterman, Robert W. Hawking and W. Beringer, J. Arguin, R. Barnett, K. Copic, O. Dahl, D. Groom, C. Lin, J. Lys, H. Murayama, C. Wohl, et al. Physics Reports , 5—6 : — Brout, R. Englert, and E. This model represents the target to beat as cosmologists push their descriptions of the universe deeper into the past and into the future. As successful as -CDM has been, it still has plenty of kinks that need working out. Cosmologists get conflicting results when they try to study the universe's current expansion, depending on whether they measure it directly in nearby galaxies or infer it from the CMB. This model doesn't say anything about the makeup of dark matter or energy, either. Then there's that troublesome first second of existence, when the universe presumably went from infinitesimal speck to relativistically well-behaved bubble. No one knows how inflation worked in detail, however, or why it stopped where it presumably did. Steinhardt said that inflation should have continued in many regions of space, implying that our universe is just one slice of a "multiverse" containing every possible physical — an untestable idea that many experimentalists find disquieting. To make on questions like these, cosmologists look to precision measurements from space-based telescopes like the Hubble Space Telescope and the upcoming James Webb Space Telescope, as well as experiments in the emerging field of gravitational wave astronomy, such as the National Science Foundation's Laser Interferometer Gravitational-Wave Observatory. Cosmologists also join particle physicists and astrophysicists in an interdisciplinary race to detect particles of dark matter. Just as cosmology couldn't begin until other had matured, it won't be able to finish revealing the history of the universe until other areas are more complete. Farrar said she doesn't know if that will happen but marvels that people have grasped the complexities of the universe as much as they have. Live Science. Please deactivate your ad blocker in order to see our subscription offer. The universe is full of stars, gas clouds, galaxies, black holes and a whole lot more. Cosmologists ask, "Why? https://files8.webydo.com/9590958/UploadedFiles/EBE36EE4-1521-F779-11F7-A5834BD67239.pdf https://static.s123-cdn-static.com/uploads/4639367/normal_601f3a3ac3d50.pdf https://files8.webydo.com/9588607/UploadedFiles/154FBA80-A8B0-D69A-D64B-658F03D8487F.pdf https://static.s123-cdn-static.com/uploads/4641159/normal_601ee3facf954.pdf