This refers to the cosmological use of the term. For other uses, see Dark matter (disambiguation)

In cosmology, dark matter refers to matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation (light) to be detected directly, but whose presence may be inferred from gravitational effects on visible matter such as stars and galaxies. Dark matter explains several anomalous astronomical observations, such as anomalies in the rotational speed of galaxies (the galaxy rotation problem). Estimates of the amount of matter present in galaxies, based on gravitational effects, consistently suggest that there is far more matter than is directly observable. The existence of dark matter also resolves a number of seeming inconsistencies in the Big Bang theory, and is crucial for structure formation.

The dark matter component has vastly more mass than the "visible" component of the universe At present, the density of ordinary baryons and radiation in the universe is estimated to be equivalent to about one hydrogen atom per cubic meter of space. Only about 4% of the total energy density in the universe (as inferred from gravitational effects) can be seen directly. About 22% is thought to be composed of dark matter. The remaining 74% is thought to consist of dark energy, an even stranger component, distributed diffusely in space. baryonic dark matter) makes a contribution to dark matter, but constitutes only a small portion ^*" target="_blank" >[http://arxiv.org/abs/astro-ph/0002058. Determining the nature of this missing mass is one of the most important problems in modern cosmology and particle physics. Its urgency is underlined by David B. Cline in a 2003 article in Scientific American, in which he writes: "The terms . . . 'dark matter' and 'dark energy,' serve mainly as expressions of our ignorance", much as the marking of early maps with 'Terra Incognita'.

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dark matter...//...http://bit.ly/18hbPz
Dolphilyrik (Dolphilia ) Wed, 04 Nov 2009 13:07:05 -0000
dark matter...//...http://bit.ly/18hbPz
Is Dark Matter Behind the Hazy Radiation at the Milky Way's Center? http://bit.ly/44wGq0
thealienproject (Andre Heath) Wed, 04 Nov 2009 13:04:04 -0000
Is Dark Matter Behind the Hazy Radiation at the Milky Way's Center? http://bit.ly/44wGq0
Completed Dark Matter Excavation #epicpetwars http://www.epicpetwars.com
Shatter_Force (KYZER DAVIS) Wed, 04 Nov 2009 12:55:08 -0000
Completed Dark Matter Excavation #epicpetwars http://www.epicpetwars.com
Completed Dark Matter Excavation #epicpetwars http://www.epicpetwars.com
dentagsegnegott (leonard) Wed, 04 Nov 2009 12:52:45 -0000
Completed Dark Matter Excavation #epicpetwars http://www.epicpetwars.com
@RzBg yes, but its like dark matter, you can't see it and if you try to create it, it goes back in time to destroy itself.
sillypunk (sillypunk) Wed, 04 Nov 2009 12:50:04 -0000
@RzBg yes, but its like dark matter, you can't see it and if you try to create it, it goes back in time to destroy itself.
Subject: Royal Society On-line 60min Lecture: Dark (Matter & Energy) - by: anthonyjtracey: Really interesting t.. http://bit.ly/1LlPiH
IrishAstronomy (Irish Astronomy) Wed, 04 Nov 2009 12:47:55 -0000
Subject: Royal Society On-line 60min Lecture: Dark (Matter & Energy) - by: anthonyjtracey: Really interesting t.. http://bit.ly/1LlPiH

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