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I heard dark energy is the intrinsic property of space and it cannot be particle because particle's density dilute when volume increase, I do not know how nothingness can have property and Einstein came up with a cosmological constant to fix his static universe model therefore mathematically he proved that space by itself can expand. Imagine a universe where empty space is devoided of energy and matter, can it expand?

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    $\begingroup$ Dark energy isn't exactly the cause of expansion. Dark energy causes the expansion to accelerate. A cosmological constant causes a constant rate of expansion (or contraction). $\endgroup$ – PM 2Ring Jan 22 '19 at 4:00
  • $\begingroup$ see en.wikipedia.org/wiki/Dark_energy $\endgroup$ – anna v Jan 22 '19 at 4:58
  • $\begingroup$ A cosmological constant does not cause a constant rate of expansion, which would be $a\propto t$; it causes exponential expansion, $a\propto e^{Ht}$. I think you meant to say that a cosmological constant causes a constant Hubble parameter, which is $\dot{a}/a$, not $\dot{a}$. $\endgroup$ – G. Smith Jan 22 '19 at 5:09
  • $\begingroup$ The model I'm referring to is called Einstein blunder as the author of the science journal said, i also know there are many other models such as phantom field and one which requires us to know the true energy of higgs field instead of lowest potential and many more. Hope it clear up the confusion, thanks. $\endgroup$ – user6760 Jan 22 '19 at 5:15
  • $\begingroup$ see hyperphysics.phy-astr.gsu.edu/hbase/Astro/dareng.html $\endgroup$ – anna v Jan 22 '19 at 5:22
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The universe can expand without matter or radiation, but it cannot expand without energy. You can have “dark energy” without either matter or radiation.

In fact, right now dark energy is driving the accelerating expansion of our unverse, and the matter and radiation in it are playing a diminishing role. In the current standard cosmologcal model, the effect of matter and radiation will become negligible and the dark energy will cause exponential expansion.

You should not think of spacetime as nothingness. It has nontrivial geometric structure and the metric field that determines its geometry can carry energy, momentum, and angular momentum from place to place just like the electromagnetic field does.

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  • $\begingroup$ Do you have any links? the reason we know about dark energy is because of its effects on matter and radiation that we observe and quantify. A hypothetical universe without matter and radiation cannot be recorded, even if the mathematics exists for such a model, imo. $\endgroup$ – anna v Jan 22 '19 at 6:25
  • $\begingroup$ The philosophical issue you raise is not one that physics can settle. Everyone agrees on the math, and it seems obvious to me, based on our current understanding, that the universe will keep expanding due to dark energy even as the matter and radiation in it dilute to insignificance. I don’t think it’s going to care that no one may be around to record it. I am not in the camp that thinks consciousness creates the universe or keeps it going. $\endgroup$ – G. Smith Jan 22 '19 at 6:30
  • $\begingroup$ That is another story, of how the present model evolves, and different from starting with nonexistence of matter and energy. It is not philosophic, it is how models fit data and if data exist. In the present universe model the standard model is postulated. in an empty of radiation and matter universe this standard model cannot be assumed., because there would have been in the beginning matter and radiation and remnants all the way to infinity $\endgroup$ – anna v Jan 22 '19 at 6:35
  • $\begingroup$ Obviously there is no data for a universe without matter and radiation. There is only a mathematical model for such a thing. $\endgroup$ – G. Smith Jan 22 '19 at 6:37
  • $\begingroup$ that is why I asked for a link. $\endgroup$ – anna v Jan 22 '19 at 6:42

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