| Physical cosmology | | | | Related topics | | | | edit Cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ...
Image File history File links Download high resolution version (2198x1274, 1278 KB)WMAP map of CMB anisotropy, from NASA.gov File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
The age of the Universe is defined as the largest possible value of proper time integrated along a timelike curve from the Earth at the present epoch back to the Big Bang. ...
According to the Big Bang theory, the universe originated in an extremely dense and hot state (bottom). ...
The comoving distance or conformal distance of two objects in the universe is the distance divided by a time-varying scale factor representing the expansion of the universe. ...
In cosmology, the cosmic microwave background radiation (CMB) is a form of electromagnetic radiation discovered in 1964 that radiates throughout the universe in the microwave range. ...
In cosmology, dark energy is a hypothetical form of energy which permeates all of space and has strong negative pressure. ...
In cosmology, dark matter refers to hypothetical matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. ...
The Friedmann-Lemaître-Robertson-Walker (FLRW) metric describes a homogeneous, isotropic expanding/contracting universe. ...
The Friedman equations relate various cosmological parameters within the context of general relativity. ...
In astrophysics, the questions of galaxy formation and evolution are: How, from a homogeneous universe, did we obtain the very inhomogeneous one we live in? How did galaxies form? How do galaxies change over time? The formation of galaxies is still one of the most active research areas in astrophysics...
Hubbles law is the statement in physical cosmology that the redshift in light coming from distant galaxies is proportional to their distance. ...
Astronomy and cosmology examine the universe to understand the large-scale structure of the cosmos. ...
ΛCDM or Lambda-CDM is an abbreviation for Lambda-Cold Dark Matter. ...
In cosmology, Big Bang nucleosynthesis (alternately: Primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. ...
Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to that of the Sun (left). ...
The shape of the universe is a subject of investigation within cosmology. ...
This timeline of the Big Bang describes the events that have occurred and will occur according to the scientific theory of the Big Bang. ...
The timeline of cosmology lists the sequence of cosmological theories and discoveries in chronological order. ...
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Spiral Galaxy ESO 269-57 Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature and chemical composition) of astronomical objects such as stars, galaxies, and the interstellar medium, as well as their interactions. ...
General relativity (GR) is the geometrical theory of gravitation published by Albert Einstein in 1915. ...
Particles erupt from the collision point of two relativistic (100GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ...
// Headline text Quantum gravity is the field of theoretical physics attempting to unify the theory of quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. ...
| The Friedmann-Lemaître-Robertson-Walker (FLRW) metric describes a homogeneous, isotropic expanding/contracting universe. Depending on geographical/historical preferences, this may be referred to under the names of a preferred subset of the four scientists Alexander Friedmann, Georges Lemaître, Howard Percy Robertson and Arthur Geoffrey Walker, e.g. Friedmann-Robertson-Walker (FRW) or Robertson-Walker (RW). In mathematics, in Riemannian geometry, the metric tensor is a tensor of rank 2 that is used to measure distance and angle in a space. ...
Homogeneity in physics In physics, homogeneity is the quality of having all properties independent of the position. ...
Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ...
The deepest visible-light image of the cosmos. ...
Alexander Alexandrovich Friedman (June 16, 1888 – September 16, Russian cosmologist and mathematician. ...
Georges-Henri Lemaître (July 17, 1894 – June 20, 1966) was a Belgian Roman Catholic priest and astronomer. ...
Howard Percy Robertson (January 27, 1903 - August 26, 1961) was a scientist known for contributions related to cosmology and the uncertainty principle. ...
Arthur Geoffrey Walker (17 July 1909 - 31 March 2001) was a leading mathematician and cosmologist. ...
The FLRW metric is used as a first approximation for the standard big bang cosmological model of the universe. Because the FLRW assumes homogeneity, some popular accounts mistakenly assert that the big bang model cannot account for the observed lumpiness of the universe. In actuality, the FLRW is used as a first approximation for the evolution of the universe because it is simple to calculate, and models which calculate the lumpiness in the universe are added onto FLRW as extensions. As of 2003, the theoretical implications of the various extensions to FLRW appear to be well understood, and the goal is to make these consistent with observations from COBE and WMAP. According to the Big Bang theory, the universe originated in an extremely dense and hot state (bottom). ...
2003 is a common year starting on Wednesday of the Gregorian calendar, and also: The International Year of Freshwater The European Disability Year Events January events January 1 Luíz Inácio Lula Da Silva becomes the 37th President of Brazil. ...
The Cosmic Background Explorer (COBE), also referred to as Explorer 66, was the first satellite built dedicated to cosmology. ...
Alternate meaning: WMAP (AM) Artist depiction of the WMAP satellite at the L2 point The Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA satellite whose mission is to survey the sky to measure the temperature of the radiant heat left over from the Big Bang. ...
The metric can be written as
![ds^2 = c^2 dt^2-a(t)^2[dr^2+bar{r}^2 dOmega^2]](http://en.wikipedia.org/math/4/a/f/4af6b51fd315eb8e9f276de6fb1e7ffa.png) - where:
- a(t) = the scale factor of the universe at time t
 - where RC = the absolute value of the radius of curvature
- dΩ2 = dθ2 + sin2θdφ2
- In this formulation of the metric,
- r gives the comoving distance from the observer
 gives the proper motion distance. The solution to the FLRW metric for a fluid with constant density and pressure is given by the Friedmann equations. Most cosmologists agree that the observable universe is well approximated by an almost FLRW model, that is, a model which follows the FLRW metric apart from primordial density fluctuations. In a strictly FLRW model, there are no clusters of galaxies, stars or people, since these are objects much denser than a typical part of the universe. The scale factor, parameter of Friedmann-Lemaître-Robertson-Walker model, is a function of time which represents the relative expansion of the universe. ...
In mathematics, the absolute value (or modulus1) of a real number is its numerical value without regard to its sign. ...
The comoving distance or conformal distance of two objects in the universe is the distance divided by a time-varying scale factor representing the expansion of the universe. ...
In physics, proper length is the length of an object or a contour as measured in the reference frame of the object itself in the context of special relativity. ...
The Friedman equations relate various cosmological parameters within the context of general relativity. ...
The observable Universe is a scientific term used in cosmology to describe a spherical region of the Universe surrounding the Earth. ...
Primordial fluctuations are density variations in the early universe which are considered the seeds of all structure in the universe. ...
However, for brevity, the almost FLRW model is often referred to simply as the FLRW model (or the FRW model).
External links
- Ellis, George F. R., van Elst, Henk. Cosmological models (Cargèse lectures 1998). arXiv.org eprint archive. URL accessed on July 30, 2005.
July 30 is the 211th day (212th in leap years) of the year in the Gregorian Calendar, with 154 days remaining. ...
2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ...
References - d'Inverno, Ray (1992). Introducing Einstein's Relativity, Oxford: Oxford University Press. ISBN 0-19-859686-3.. See chapter 23 for a particularly clear and concise introduction to the FRW models.
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