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The cosmological evolution of the void regions differs drastically from the evolution of the universe as a whole: there is a long stage when the curvature term dominates, which prevents the formation of galaxy clusters and massive galaxies. Hence, although even the emptiest regions of voids contain more than ~15% of the average matter density ...
A map of the Boötes Void. The Boötes Void (/ b oʊ ˈ oʊ t iː z / boh-OH-teez) (colloquially referred to as the Great Nothing) [1] is an approximately spherical region of space found in the vicinity of the constellation Boötes, containing only 60 galaxies instead of the 2,000 that should be expected from an area this large, hence its name.
In a universe with zero curvature, the local geometry is flat. The most familiar such global structure is that of Euclidean space, which is infinite in extent. Flat universes that are finite in extent include the torus and Klein bottle. Moreover, in three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 ...
Outer space, especially the relatively empty regions of the universe outside the atmospheres of celestial bodies; Vacuum, a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure; Free space, a perfect vacuum as expressed in the classical physics model
The term outward space existed in a poem from 1842 by the English poet Lady Emmeline Stuart-Wortley called "The Maiden of Moscow", [13] but in astronomy the term outer space found its application for the first time in 1845 by Alexander von Humboldt. [14] The term was eventually popularized through the writings of H. G. Wells after 1901. [15]
This is an accepted version of this page This is the latest accepted revision, reviewed on 24 December 2024. Problem of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy between ...
In 1973, he proposed that the universe is a large-scale quantum fluctuation in vacuum energy. This is called vacuum genesis or the zero-energy universe hypothesis. He has been quoted as saying, "the universe is simply one of those things that happens from time to time." [14] In 1967, he began working at Columbia University as a research assistant.
The Universe is assumed homogeneous (space has the same metric properties (measures) in all points) and isotropic (space has the same measures in all directions). Friedmann's solutions allow two possible geometries for space: closed model with a ball-like, outwards-bowed space ( positive curvature ) and open model with a saddle-like, inwards ...