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I would like to start be saying I'm no Physicist.

I was wondering if known and mostly unknown black holes could be the reason for the "expanding" of the universe.

Qmechanic
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calc8
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    Since you are not asking anything specific, a simple no should answer your question. – Yukterez Jul 20 '22 at 19:21
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    You can remove the inverted commas because it is expanding. See the FLRW metric for a starting point to understand this. – StephenG - Help Ukraine Jul 20 '22 at 19:32
  • I think the question's based on the everyday form of "spatial expansion", as in the increase of space inside a house by the removal of a superfluous piece of furniture (whose ashes, in a municipal incinerator, would eventually occupy less space than the piece of furniture had occupied, at least if faint expansions of nearby junk by residual heat would not be taken into account.). Because the spacetime which the event horizon of a black hole surrounds isn't part of our universe (regardless of whether it's "local" or literally "universal"), my layman's opinion is that the question is an OK one. – Edouard Jul 22 '22 at 20:28
  • I should clarify that any BH remaining indirectly observable (typically by the circular orbit followed by the former binary partner of BHs which have resulted from stellar collapse) is not part of the outer space in our universe for the reasons described by Benrg in his previous answer, which he has cited in his comment: The possibility that a BH's "apparent horizon" might be real exists, but the evidence for its reality remains (so far) only indirect, at least in General Relativity. – Edouard Jul 22 '22 at 20:54
  • Possibly, in models where the scale differs between the interior of a "local universe" in a multiverse & its externality, the nature of the differences in scale might vary between the spatial scale and the temporal scale, with the passage of time, in the permanently and totally separated local universe, possibly being different in one sense (resulting in time intervals that would be very long), even while the spatial intervals in the newer universe might be so short as to lack discretization even at the highest magnification energies that might conceivably be accessible for our use. – Edouard Jul 24 '22 at 02:55

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Welcome to the stack exchange. The quick answer to your question is no, black holes can not contribute to the expansion of the universe. Black holes are very localized and their gravity is no greater than the sum of the stars that they have collapsed from. Do a google search and you will find lots on this. However, there is a new theory that the opposite is true, that expansion of the universe might cause black holes to grow. The main reason is that because everything in the universe is moving, black holes are more likely to bump into other stars or black holes, and thus grow. Take a look at this easy to read paper: Universe Expansion Directly Impacts Black Hole Growth

foolishmuse
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  • Note: your link goes to a news article, not to a technical paper. – rob Jul 20 '22 at 21:18
  • @rob Yes it does. There's an old saying "know your audience". I don't think this paper would be appropriate for the OP https://iopscience.iop.org/article/10.3847/2041-8213/ac2fad – foolishmuse Jul 20 '22 at 21:20
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    The paper is wrong—or rather, the theoretical foundation of their model is wrong. It's the same mistake I described in this answer (and the paper I mentioned there has a coauthor in common with one of the papers these authors cite in support of their model). The problem is that assuming a black hole in a FLRW background is equivalent to assuming a black hole surrounded by uniform matter at the critical density. The black hole expands because it absorbs that matter. In real life, that matter isn't there (it's elsewhere; see the other answer). – benrg Jul 21 '22 at 03:32