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Hudimir t1_jango8k wrote

Reply to comment by nivlark in Why do cosmologists say that gravity should "slow down" the expansion of the universe? by crazunggoy47

What you said about dark energy acting as a repulsive source, I am now confused how so.e scientist recently came to the conlusion that black could be sources of dark energy. Especially because afaik black holes are incredibly dense objects made form "normal" matter that collapsed due to their gravity. Here dark energy being a repulsive force doesnt make sense to me if all we can observe is the incredibly powerful gravitational waves of black holes.

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summitrow t1_jao6p2q wrote

Dark energy and black holes are separate. Black holes are objects that are black because their gravity well is so strong that light cannot escape them. Dark energy is a force that pervades all of spacetime. We measure how much dark energy there is by the red shift of galaxies outside of our local group, and other standard candles like class 1a supernova and Cepheid variable stars. Is there a dark energy particle? Is it a fundamental force like the strong force in an atom? We don't know. So far we can just measure its impact on the expansion of the universe.

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Hudimir t1_jao97us wrote

Correct me if i misunderstood. So in that article where they say black holes might be the source of dark energy they say so, because they measured/observed more dark energy impact around those black holes? Also fyi i am currently studying undergrad physics so the very basics(e.g. black holes are black because light cannot escape them) I think, I understand, so you can complicate more if you have the knowledge.

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VegaGraviton t1_jaok1al wrote

I had a brief reread of the articles discussing the theory. Bear in mind that my personal background is in Cosmic Inflation and so I'm not intimately familiar with this theory. From what I gleamed Einsteins Equations can predict an object that is essentially a concentrated bundle of Vacuum Energy, which is a commonly theorised candidate for Dark Energy. This object would look and act like a Black Hole to outside observers. Therefore, any Black Hole that we observe could in fact be a source of Dark Energy, and we wouldn't be able to tell with our current understanding of the model.

Essentially its a mathematical model that has been proposed, rather than any new observations.

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summitrow t1_japc8y4 wrote

Yes light cannot escape them, which is because of the incredibly strong gravity well of a black hole.

The very recent articles on black holes and dark energy are very speculative.

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