Dark Matter
  • kensamaykensamay
    Just read & watched the link too the bbc report on the hunt for dark matter.They know its there but they can't see it or explain it...Great stuff :)

    The bit on working down in a mine trying too locate it & how they can now make a map of it in the Universe amazing:)

    The less we know the more we want to know..Great :)

    Thanks for all the info i'v found on this site,i'v learn't so much in a very short time:)

    So just so i am clear if we didn't have Dark Matter the galaxy stars would just spin off in all directions instead off clustering together ?
  • EyestotheskiesEyestotheskies
    Kensamay it is definitely weird for sure ! Isn't dark matter about 70% of the mass in the universe, stuff that cannot be seen? Nobody knows what it is, and I have heard that the visible galaxies rotate and act as though they should really be far bigger :-/

    To think that we only know what 30% of the universe is. Only in astronomy would you get such unfathomable mysteries !
  • John_BradyJohn_Brady
    Most of the stuff in the universe is unknown...what a thought. Dark matter accounts for around 25% of the mass in the cosmos that;s invisible.

    Dark matter doesn't react with, emit, or reflect any light. It doesn't do anything at with light, but it can be found by its gravity.

    Yes Kensamay the stars at the outside edges of galaxies are rotating about the central core so fast, they should fly outwards into intergalactic space. Something is holding them there.

    Check this out, "The Jelly Bean Universe" http://chandra.harvard.edu/resources/flash/univ_pie.html

    Dark energy sounds similar but is totally different, it is the unkown force/energy that's making the universe expand faster and faster.
  • Lemmy
    As you say, dark energy is thought to be the reason the expansion of the universe is accelerating, but is only thought to have been the case for about 4.5 billion years (co-incidentally about the life of the solar system) i.e. before that the expansion was slowing down.
  • John_BradyJohn_Brady
    Yes the expansion accelaration rate changes over time. From what I read it started speeding up by a lot around 7.5 billion years ago. Some even think it could be an illusion, due to us living in a fairly empty region of the Universe.

    This Nasa page has a good image showing the expansion rate due to dark energy. http://science1.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/
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