cosmology Cosmology () 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'', with the meaning of "a speaking of the wo ...

, flatness is a property of a space without

curvature In mathematics, curvature is any of several strongly related concepts in geometry that intuitively measure the amount by which a curve deviates from being a straight line or by which a surface deviates from being a plane. If a curve or su ...

. Such a space is called a "flat space" or

Euclidean space Euclidean space is the fundamental space of geometry, intended to represent physical space. Originally, in Euclid's ''Elements'', it was the three-dimensional space of Euclidean geometry, but in modern mathematics there are ''Euclidean spaces ...

. Whether the

universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...

is “flat″ could determine its ultimate fate; whether it will expand forever, or ultimately collapse back into itself. The

geometry Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...

of spacetime has been measured by the

Wilkinson Microwave Anisotropy Probe The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP and Explorer 80), was a NASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic mic ...

(WMAP) to be nearly flat. According to the WMAP 5-year results and analysis, “WMAP determined that the universe is flat, from which it follows that the mean

energy density In physics, energy density is the quotient between the amount of energy stored in a given system or contained in a given region of space and the volume of the system or region considered. Often only the ''useful'' or extractable energy is measure ...

in the universe is equal to the critical density (within a 1% margin of error). This is equivalent to a mass density of 9.9 × 10⁻³⁰ g/cm³, which is equivalent to only 5.9 protons per cubic meter.”NASA:Wilkinson Microwave Anisotropy Probe:Cosmology, The Study of the Universe
/ref> The WMAP data are consistent with a flat geometry, with Ω = 1.02 +/- 0.02.

References

External links

* http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/FlatnessProblem.html {{Webarchive, url=https://web.archive.org/web/20090530084230/http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/FlatnessProblem.html , date=2009-05-30 Physical cosmology

See also

References

External links