Dark Matter

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Dark Matter
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• space matter that can not be seen is called dark matter – it does not give off light – unlike stars and galaxies.
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• much more dark matter in the Universe than bright. (some scientists think 97% of matter is dark.)
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• astronomers know about dark matter because its gravity pulls on stars and galaxies, changing their orbits and the way they rotate.
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• visible stars in the Milky-Way galaxy are only thin part – embedded in a big ball of dark matter.
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• dark matter is of two kinds; the matter in galaxies (galactic) and the matter between them (intergalactic).
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• Galactic dark matter – similar to ordinary matter – however, it burnt out early in the life of the Universe.

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BSL Version

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WIMPs
(Weakly Interacting Massive Particles)

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• some WIMPs are called “cold”
  – because they are travelling slowly.
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• other WIMPs are called “hot”
  – because they are travelling very quickly.
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Future of the Universe

• depends on how much dark matter there is – if there is too much, its gravity will eventually stop Universe’s expansion, and make it shrink again. (See The Big Bang)

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BSL Version