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Could Dark Energy be a form of Dark Matter

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  1. Sep 19, 2013 #1
    Dark Energy is said to be present in order to drive the observed acceleration of the expansion of the universe and Dark Matter is hypothesised to be present to drive observed gravitational effects.

    Would a large mass of dark matter distributed around the outer parts of the universe have the same effect as the mooted Dark Energy, as its attraction would tend to draw all the other material towards it, thus accelerating the outward movement.
     
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  3. Sep 19, 2013 #2

    Drakkith

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    No, dark energy and dark matter are distinctly different things. Furthermore, there are no "outer parts" of the universe. The universe is not believed to have any edges.
     
  4. Sep 19, 2013 #3

    Chronos

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    The only connection between dark matter and dark energy is linguistic - dark, meaning we don't know what it is. If they are connected, that would be a remarkable coincidence.
     
  5. Sep 20, 2013 #4

    mathman

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    Dark matter is stuff - we just don't know what. It is "observed" by its gravitational effect.

    Dark energy, which may not even be energy, is something responsible for the acceleration of the universe expansion.
     
    Last edited: Sep 20, 2013
  6. Sep 20, 2013 #5

    Chronos

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    The 'we don't know what it is' meaning of the term dark was applied to this weird 'energy' hypothesized to exist as a result of supernova studies [re: Perlmutter, et al]. But 'we don't know what it is' could have been applied to the coelacanth and the recently discovered algae prototheca cutis. If biologists had the same laid back attitude as cosmologists, they could have just as easily allowed them to be called 'dark fish' and 'dark algae'. Similarly, the recently discovered meteoritic mineral, panguite, could just as easily been called 'dark mineral' by indifferent geologists. It would not have taken much to grow legs for conspiracy theories linking the three, and then with dark matter and dark energy. Imagine the pandemonium that would ensue should physicists discover a weird new elementary particle and, unable to decide who gets the credit, chose to allow the media to call it the 'dark particle'.
     
  7. Sep 21, 2013 #6

    mathman

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    Your point?
     
  8. Sep 21, 2013 #7
    could be...if by 'outer parts' you mean beyond the observable universe.....but there is no mainstream theory to provide such a configuration...nor a reasonable rationale. In fact the mainstream FLRW cosmological model posits something quite different.....that space looks everywhere the same on large scales....The FLRW metric starts with the assumption of homogeneity and isotropy of space.


    also, why posit 'large dark matter', just posit lots of regular mass, way out there.
     
    Last edited: Sep 21, 2013
  9. Sep 21, 2013 #8

    Drakkith

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    I don't think it would be the same. The expansion causes recession velocities to increase linearly, while gravity should cause it to increase exponentially, right?

    Also, wouldn't this kind of setup be similar to a hollow sphere where the net force inside is zero?
     
  10. Sep 22, 2013 #9
    I can't think of anything that would really be the 'same' as a uniform cosmological constant or an equivalent uniform distribution throughout all of space.....That's likely a better answer.
     
  11. Sep 22, 2013 #10

    Astronuc

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    This may help somewhat with the distinction between DE and DM.
    http://home.web.cern.ch/about/physics/dark-matter

    My embolding for emphasis.

    See also - http://hubblesite.org/hubble_discoveries/dark_energy/de-what_is_dark_energy.php
     
    Last edited: Sep 28, 2013
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