Definition of dark matter Dark matter
We found 4 definitions of dark matter from 4 different sources.
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What does dark matter mean?
WordNet
Noun |
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| dark matter - (cosmology) a hypothetical form of matter that is believed to make up 90 percent of the universe; it is invisible (does not absorb or emit light) and does not collide with atomic particles but exerts gravitational force | ||
| matter that which has mass and occupies space; "physicists study both the nature of matter and the forces which govern it" | ||
| cosmogeny, cosmogony, cosmology the branch of astrophysics that studies the origin and evolution and structure of the universe | ||
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Wiktionary 
- dark matter (Noun)
Particles of matter that cannot be detected by their radiation but whose presence is inferred from gravitational effects.
OmegaWiki DictionaryOmegaWiki Dictionary Ω
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dark matter
Matter that cannot be detected by their radiation but whose presence is inferred from gravitational effects.
Wikipedia 
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We can use physics and mathematics to understand how strongly gravity affects something if we know enough about that thing, mainly how much mass it has. This way, we can understand how objects act on Earth. However, astrophysicists have learned that the way things in deep space behave is different.
Many scientists have tried to understand why the rules are different in deep space. One idea is that we do not really understand gravity as well as we think we do. Another idea, which many think is more likely, is that there is something called dark matter. If you do calculations on the things in deep space with "extra" mass, the then the rules work there too. So the idea is that there is more matter in the universe than we thought. This is called dark matter because we know nothing about it, and because so far we cannot find it.
Because dark matter does not seem to give off light, x-rays, or any other radiation, the instruments which can find normal matter are unable to find dark matter. It seems that dark matter is not made of the same thing as the matter we see everyday on Earth.
Recently, a group of scientists claimed they had found a way to observe dark matter. Since dark matter is supposedly very different from normal matter, it is expected to act differently. They observed two galaxies placed in such a position that normal matter would be stuck behind while dark matter would not, and by measuring gravity they were able to detect what they say is two clouds of two different k
