Why do most cosmologists believe that the first large-scale structures to appear did so as clumps in the dark matter that comprises most of the universe?

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    Dark matter forms clumps more easily than normal matter because it interacts very strongly with other dark matter. Normal matter does not interact so strongly with other normal matter.
     When we look at dark matter today, we find that it is very lumpy.
     The background radiation in the early universe was so intense that it prevented normal matter from forming clumps, just as the radiation pressure in stars prevents them from collapsing. Dark matter is relatively unaffected by radiation.
     There is so much more dark matter than normal matter that it overwhelms the interactions of normal matter
     Normal matter did not exist until later in the formation of the universe.
asked Sep 20, 2012 in Astronomy by anonymous
    

1 Answer

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The background radiation in the early universe was so intense that it prevented normal matter from forming clumps, just as the radiation pressure in stars prevents them from collapsing. Dark matter is relatively unaffected by radiation.
answered Sep 22, 2012 by SkyStar ~Expert~ (2,855 points)



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