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B Questions about the origin and evolution of dark energy.

  1. Dec 27, 2016 #1
    Dark Energy; origin and evolution

    I have read the threads but I still have some unanswered questions about the origin and evolution of dark energy.

    Has dark energy existed since the big bang? If so, why did it remain dormant for billions of years. Or did it spontaneously jump into existence later on?

    If it was dormant then why did it suddenly become active?

    Gravity pulls objects of mass towards each other. Dark energy pushes objects of mass away from each other. Is dark energy a reverse function of gravity? A type of anti- gravity?

    Our 4 dimensional universe is continuing to pick up speed in an "outward" direction. Is dark energy getting more powerful or is the total amount of dark energy increasing over time? How is that possible?

    I've read that the acceleration of our universe might be on an exponential curve. Does that mean someday all objects of mass will be flying outward from our point of origin and from each other at 99% of the speed of light someday?

    Is that too many questions? Am I asking the wrong questions? My Dad encouraged my innate sense of curiosity by telling me there are no stupid questions. That got me into trouble in Sunday school. I hope it doesn't get me into trouble here.

  2. jcsd
  3. Dec 27, 2016 #2


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    As far as we know, yes
    This is a common misconception. It was not at all dormant. It was simply much weaker than gravity when the average matter density throughout the universe was high. About 6 billion years ago, it became roughly equal in effect and since then it has become dominant over gravity.

    In effect yes, but do NOT think of it as "anti-gravity" that's a sci-fic concept.

    The unit density of dark energy remains constant so the total amount increases with time.
    Good question.

    No, it means that even objects within our Observable universe are ALREADY receding from us at about 3c. This is recession, not proper movement. I recommend the link in my signature.
    No, it's not too many questions, but it really is better to focus on one at a time and move on to the next after you have absorbed the first one since it may answer some of the subsequent ones, as I believe you will see in this thread.
  4. Jan 4, 2017 #3
    If dark energy is produced by star activity similar to neutrinos, it is possible that dark energy did not exist immediately after the big bang.
  5. Jan 4, 2017 #4


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    No, it isn't . Gravity due to matter and radiation is attractive. This includes also neutrinos. In contrast to any source of gravity which is attractive dark energy exerts negative pressure.
  6. Jan 4, 2017 #5


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    In this context "pick up speed" means accelerated expansion. What drives the expansion is not the "total amount of dark energy" but its density. And that is constant over time according to observational date we have till now. What happens is that while the dark energy density is constant the matter density is decreasing due to expansion. That means that the former becomes more and more dominant and will cause the universe to expand exponentially in the far future.
  7. Jan 4, 2017 #6
    Do you have any argument that star activity does not produce dark energy?
  8. Jan 4, 2017 #7


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    You have that backwards. You are making an unsubstantiated claim that star activity produces dark energy. You need to substantiate that claim or retract it.
  9. Jan 4, 2017 #8
    Sure. We understand how stars work: nuclear fusion. We can replicate this process in the lab and understand it and measure it exactly. If dark energy was leaking out of these reactions, the energy equations would not balance, and they do. It's happened before that way, when physicists first started to calculate the energies of fission exactly, they did notice a minute amount of energy missing. We've since discovered that it was because a neutrino popped out. But that's it, once the neutrino was added, the equations balanced.

    Stars are really not that exotic, astronomically speaking, they're pretty mundane. Just nuclear physics, not even any interesting degenerate matter yet.
  10. Jan 4, 2017 #9


    Staff: Mentor

    Please bear in mind the PF rules regarding personal theories.
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