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Universe AgeSize with respect to DM?

  1. Apr 25, 2005 #1
    What are the prospects of Aging the Universe with respect to the Dark Matter Content of our percieved Universe?..and can we gauge the size of the Universe with respect to the percentage of Dark Matter?..ie..DM amounts to about 95%,,does this have a baring on the Universe age and size?
  2. jcsd
  3. Apr 25, 2005 #2


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    The total mass in dark matter should not change with time, but its density relative to the critical density will. In other words, its relative contribution to the flatness of the universe changes with time. Before the "lambda transition" where the dark energy became the dominant contribution to the flatness, dark matter's contribution had been increasing with time. Now, we think that its contribution is decreasing.

    I'm not sure where your "95%" number came from. The current percentage of the critical density that's dark matter is about 23%.

    Oh, and yes, the relative contributions of dark matter and dark energy do make a difference for the size and expansion rate of the universe. The relative contributions of baryonic and dark matter to the total matter budget don't impact the expansion rate or size, however.
  4. Apr 25, 2005 #3
    I see, can you point me to a source that explains the Big-Bang evolved from a Proton Sized entity..and is this Proton sized 'object', Dark Matter free?

    A simpler question is:Was the Dark Matter 'percentage' always the same ratio( 75% *) at the Big-Bang?..and would there be a small 'fraction' still evident within ..say a Proton today?

    Thanks for the correction, I was incorrect in my original ratio.
  5. Apr 26, 2005 #4


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    I don't think we have a strong enough grasp of physics to confidently extrapolate that far back (if it even goes that far), but whatever the dark matter is, it would be in an entirely different form at that point.

    The ratio of non-baryonic matter to baryonic matter has been the same for most of the history of the universe. Whether it has always been the same is an issue for particle physicists to address (i.e. whether baryon number is always conserved). Dark matter, however, can include some baryonic matter (like planets). Thus, the ratio of dark matter to luminous matter will change with time.

    I'm not sure what you mean by that.
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