A question I ought to know......

Discussion in 'Astronomy, Exobiology, & Cosmology' started by John Connellan, Aug 9, 2004.

  1. John Connellan Valued Senior Member

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    .........but have forgotten the answer I think!

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    Q: Although we know space is expanding, is the absolute amount of energy/matter increasing in the universe increasing as well (on the same scale)?

    I am almost sure the answer is no and that the energy/matter density of the universe is diluting. Is that correct?
     
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  3. MewSkitty Sciforums.com sucks! Registered Senior Member

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    The Universe is curently expanding and no new matter/energy is being added so you are correct.
     
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  5. eburacum45 Valued Senior Member

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    Actually that may not be the case; as the universe is not only expanding, but that expansion is accelerating, the amount of supposed dark energy seems to be increasing; the energy per unit volume stays the same, despite the increase in volume.

    the Universe seems to be the ultimate free lunch, going against all notions of thermodynamics.

    Perhaps it balances out when you see the whole picture, including other branes/dimensions etcetera; but it certainly does not balance out at this moment in time in this universe.
     
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  7. John Connellan Valued Senior Member

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    Are u serious?!

    Any references?
     
  8. eburacum45 Valued Senior Member

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    From here
    http://physicsweb.org/article/world/13/11/8

    In other words, the vacuum energy density remained constant as the universe expanded, but the total vacuum energy increased as the volume of space increased. This extra energy came from the gravitational potential energy of the universe

    which says the increase in vacuum energy is balanced by the decrease in the energy of the gravitational system, as galaxies are moved apart. So I suppose in a strange way it does balance out,but the expansion of the universe will continue unstoppably, all things remaining as they are.

    If you read the whole article it gives several interesting scenarios which imply the expansion might be only temporary, or perhaps simply localised.

    ----
    SF worldbuilding at
    www.orionsarm.com
     
  9. bigal Registered Senior Member

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    So, the universe is expanding. It is getting faster, energy diluting or not, maybe the increasing dark energy will actually decrease the expansion of the universe to the point of total reversal. The universe expansion to slow down, stop, retreat until centre point is reached. Big bang 2?
    How much can you care?
     
  10. John Connellan Valued Senior Member

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    Why can't the collapsing universe be slowed down too rather than accelerating. Imagine a universe where energy and matter can dissappear entirely!

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  11. Lemming3k Insanity Gone Mad Registered Senior Member

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    To my knowledge the ammount of matter in the universe stays the same regardless if its expanding or collapsing, since matter cannot be created or destroyed. I believe what you said about diluting is correct.
     
  12. RawThinkTank Banned Banned

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    so what if I create a huge spaceship , pack all the stars in the universe in it just like shown in MIB, and time travel in the past and just sprinkel all the stars all over ... bla bla ...

    will that increase the total mass and energy ?
     

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