NationMaster - Encyclopedia: Scale factor (Universe)

The scale factor, parameter of Friedmann-Lemaître-Robertson-Walker model, is a function of time which represents the relative expansion of the universe. It relates physical coordinates (also called proper coordinates) to comoving coordinates. The Friedmann-LemaÃ®tre-Robertson-Walker (FLRW) metric describes a homogeneous, isotropic expanding/contracting universe. ... The deepest visible-light image of the cosmos. ... 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. ...

$L = lambda ; a(t)$

where $L$ is the physical distance, $λ$ is the distance in comoving units, and $a (t)$ is the scale factor. Proximity (2001) is also a movie with Rob Lowe, Fred Ward and James Coburn. ...

The scale factor could, in principle, have units of length or be dimensionless. Most commonly in modern usage, it is chosen to be dimensionless, with the current value equal to one: $a (t 0) = 1$ , where t is counted from the birth of the universe and $t 0$ is the present age of the universe: 13.7+/-0.2 Gyr. 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. ...

The evolution of the scale factor is a dynamical question, determined by the equations of general relativity, which are presented in the case of a locally isotropic, locally homogeneous universe by the Friedmann equations. General relativity (GR) is the geometrical theory of gravitation published by Albert Einstein in 1915. ... The Friedmann equations relate various cosmological parameters within the context of general relativity. ...

The Hubble parameter is defined: Hubbles law is the statement in astronomy that the redshift in light coming from distant galaxies is proportional to their distance. ...

$H = {dot{a}(t) over a(t)}$

where the dot represents a time derivative.

Category: Cosmology

Results from FactBites:

Hubble law and the expanding universe (840 words)
	Discussions about the expansion of the universe often refer to a density parameter Ω which is the density divided by the critical density, such that Ω = 1 represents the critical density condition.
	Hubble's law is a statement of a direct correlation between the distance to a galaxy and its recessional velocity as determined by the red shift.
	The Hubble parameter is the ratio of the rate of change of the scale factor to the current value of the scale factor R: The scale factor R for a given observed object in the expanding universe relative to R

Scale factor (Universe) - Wikipedia, the free encyclopedia (180 words)
	The scale factor, parameter of Friedmann-Lemaître-Robertson-Walker model, is a function of time which represents the relative expansion of the universe.
	The scale factor could, in principle, have units of length or be dimensionless.
	The evolution of the scale factor is a dynamical question, determined by the equations of general relativity, which are presented in the case of a locally isotropic, locally homogeneous universe by the Friedmann equations.

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