Cosmologie Pdf

[Breanna Mangels]

Cosmologyfrom Ancient Greek κόσμος (cosmos) 'the universe, the world', and λογία (logia) 'study of') is a branch of physics and metaphysics dealing with the nature of the universe, the cosmos. The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia,[2] and in 1731 taken up in Latin by German philosopher Christian Wolff in Cosmologia Generalis.[3] Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology. In the science of astronomy, cosmology is concerned with the study of the chronology of the universe.

Physical cosmology is the study of the observable universe's origin, its large-scale structures and dynamics, and the ultimate fate of the universe, including the laws of science that govern these areas.[4] It is investigated by scientists, including astronomers and physicists, as well as philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Because of this shared scope with philosophy, theories in physical cosmology may include both scientific and non-scientific propositions and may depend upon assumptions that cannot be tested. Physical cosmology is a sub-branch of astronomy that is concerned with the universe as a whole. Modern physical cosmology is dominated by the Big Bang Theory which attempts to bring together observational astronomy and particle physics;[5][6] more specifically, a standard parameterization of the Big Bang with dark matter and dark energy, known as the Lambda-CDM model.

Theoretical astrophysicist David N. Spergel has described cosmology as a "historical science" because "when we look out in space, we look back in time" due to the finite nature of the speed of light.[7]

Physics and astrophysics have played central roles in shaping our understanding of the universe through scientific observation and experiment. Physical cosmology was shaped through both mathematics and observation in an analysis of the whole universe. The universe is generally understood to have begun with the Big Bang, followed almost instantaneously by cosmic inflation, an expansion of space from which the universe is thought to have emerged 13.799 0.021 billion years ago.[8] Cosmogony studies the origin of the universe, and cosmography maps the features of the universe.

In Diderot's Encyclopdie, cosmology is broken down into uranology (the science of the heavens), aerology (the science of the air), geology (the science of the continents), and hydrology (the science of waters).[9]

Metaphysical cosmology has also been described as the placing of humans in the universe in relationship to all other entities. This is exemplified by Marcus Aurelius's observation that a man's place in that relationship: "He who does not know what the world is does not know where he is, and he who does not know for what purpose the world exists, does not know who he is, nor what the world is."[10]

Physical cosmology is the branch of physics and astrophysics that deals with the study of the physical origins and evolution of the universe. It also includes the study of the nature of the universe on a large scale. In its earliest form, it was what is now known as "celestial mechanics," the study of the heavens. Greek philosophers Aristarchus of Samos, Aristotle, and Ptolemy proposed different cosmological theories. The geocentric Ptolemaic system was the prevailing theory until the 16th century when Nicolaus Copernicus, and subsequently Johannes Kepler and Galileo Galilei, proposed a heliocentric system. This is one of the most famous examples of epistemological rupture in physical cosmology.

Modern scientific cosmology is widely considered to have begun in 1917 with Albert Einstein's publication of his final modification of general relativity in the paper "Cosmological Considerations of the General Theory of Relativity"[11] (although this paper was not widely available outside of Germany until the end of World War I). General relativity prompted cosmogonists such as Willem de Sitter, Karl Schwarzschild, and Arthur Eddington to explore its astronomical ramifications, which enhanced the ability of astronomers to study very distant objects. Physicists began changing the assumption that the universe was static and unchanging. In 1922, Alexander Friedmann introduced the idea of an expanding universe that contained moving matter.

Subsequent modelling of the universe explored the possibility that the cosmological constant, introduced by Einstein in his 1917 paper, may result in an expanding universe, depending on its value. Thus the Big Bang model was proposed by the Belgian priest Georges Lematre in 1927[15] which was subsequently corroborated by Edwin Hubble's discovery of the redshift in 1929[16] and later by the discovery of the cosmic microwave background radiation by Arno Penzias and Robert Woodrow Wilson in 1964.[17] These findings were a first step to rule out some of many alternative cosmologies.

Since around 1990, several dramatic advances in observational cosmology have transformed cosmology from a largely speculative science into a predictive science with precise agreement between theory and observation. These advances include observations of the microwave background from the COBE,[18] WMAP[19] and Planck satellites,[20] large new galaxy redshift surveys including 2dfGRS[21] and SDSS,[22] and observations of distant supernovae and gravitational lensing. These observations matched the predictions of the cosmic inflation theory, a modified Big Bang theory, and the specific version known as the Lambda-CDM model. This has led many to refer to modern times as the "golden age of cosmology".[23]

In 2014, the BICEP2 collaboration claimed that they had detected the imprint of gravitational waves in the cosmic microwave background. However, this result was later found to be spurious: the supposed evidence of gravitational waves was in fact due to interstellar dust.[24][25]

Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation and eschatology. Creation myths are found in most religions, and are typically split into five different classifications, based on a system created by Mircea Eliade and his colleague Charles Long.

Cosmology deals with the world as the totality of space, time and all phenomena. Historically, it has had quite a broad scope, and in many cases was found in religion.[28] Some questions about the Universe are beyond the scope of scientific inquiry, but may still be interrogated through appeals to other philosophical approaches like dialectics. Some questions that are included in extra-scientific endeavors may include:[29][30]

La cosmologie est une branche de la physique qui regroupe les tudes scientifiques portant sur les proprits de l'univers dans son ensemble, sa structure. La cosmologie permet d'tudier l'origine et l'volution de l'univers. Les thories et les hypothses permettent d'tablir des modles, qui sont tests avec des observations. La thorie dominante sur l'origine et l'volution de notre Univers est la thorie du Big Bang.

La Terre est une plante de taille relativement modeste (environ 6 370 km de rayon), en orbite autour d'une toile de la Squence principale, le Soleil. Par dfinition, la distance Terre-Soleil est utilise pour dfinir l'unit astronomique, soit environ 150 millions de kilomtres. D'autres plantes orbitent autour du Soleil. La plante la plus loigne du Soleil (en ne comptant pas les plantes naines) est Neptune, distante d'environ 4 milliards et demi de kilomtres du Soleil, soit trente fois la distance Terre-Soleil.

Le systme solaire est lui-mme li une structure, la Galaxie (dans le cas de notre galaxie : la Voie lacte), comprenant plusieurs centaines de milliards d'toiles. L'toile la plus proche du Soleil, Proxima du Centaure, est situe un peu plus de 4 annes-lumire, soit 38 000 milliards de kilomtres de celui-ci, soit 260 000 fois plus que la distance Terre-Soleil (UA soit l'unit astronomique). La plupart des toiles visibles l'œil nu dans le ciel nocturne sont des distances de plusieurs dizaines, voire centaines d'annes-lumire. Le Soleil est situ la priphrie de la Galaxie. Il en est environ 25 000 annes lumire ; la Galaxie a un rayon environ 2 fois plus grand que cette distance, pour un diamtre d'environ 100 000 annes-lumire. Ces dimensions en font une galaxie typique de l'univers.

La masse volumique de la Terre est d'environ 5 tonnes par mtre cube. tant donn sa taille, sa masse est d'environ 61024 kg. Le Soleil, qui est une toile typique, est environ 300 000 fois plus massif, soit 21030 kg. Pour les objets plus gros (galaxies, amas de galaxies), il est de coutume d'utiliser la masse solaire comme unit de masse, le kilogramme devenant une unit trop petite au vu des nombres en jeu.

Les observations indiquent que les galaxies sont significativement plus massives que les toiles qui les composent. On est peu prs certain aujourd'hui qu'en plus de la matire ordinaire dont nous sommes fait, il existe une autre forme de matire, actuellement inconnue en laboratoire, appele matire noire. Contrairement la matire ordinaire, cette matire noire n'interagit pas avec la lumire et se trouve donc invisible. De plus, elle ne forme pas de structures compactes comme des toiles, des plantes ou des astrodes, mais a une rpartition nettement plus diffuse au sein des galaxies. La masse de la matire noire au sein des galaxies (et dans l'univers tout entier) est environ six fois plus leve que celle de la matire ordinaire. La masse de notre galaxie est donc d'un peu plus de mille milliards de masses solaires.

La masse estime des superamas est d'environ quelque 1015 masses solaires. Rapports leur taille, les superamas sont des objets extrmement peu denses : quelques dizaines d'atomes par mtre cube seulement. La masse de l'univers observable est estime 1,41024 masses solaires[N 2].

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