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Black holes as the source of dark energy

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Re: Black holes as the source of dark energy

#21

Post by garbagecoder »

There are lots of plausible explanations for why some of our observations don't match GR predictions. It's been a long time since I studied this stuff so I'm pretty sure I'm way out of date, but dark energy still seems like epicycles to me and I'm not sure it's the Occam's razor explanation either. No, we don't want to abandon GR, but we know it's not the complete theory, and a lot of this stuff might make perfect sense if we have a theory of quantum gravity.

I'm fine with wild speculations like there are new universes inside blackholes that look like white holes to the people inside (or "Big Bangs") and I love to think about all of it, and higher dimensions, and all of that, but I'm just a nerd. I'm not putting it in a journal or a press release or trying to justify funding on the basis of it.

Re: Black holes as the source of dark energy

#22

Post by pdonis »

pmontra wrote: post #20
pdonis wrote: post #6

Earlier quoted context omitted.

> I always thought we could put a black box around a black hole, and it would be indistinguishable from any other mass - that is, any other mass that can be treated as a point mass. Yes, that's what the standard theory of black holes says. > this result implies that the black box with the black hole will gain mass over time, even without adding any mass into the black box? Sort of. First, it's important to note that…

If I understood the paper [1] correctly, the idea is that all black holes don't contain a singularity. They have vacuum energy instead and that leads to the increase of mass and dark energy. [1] https://iopscience.iop.org/article/10.3847/2041-8213/acb704/...

> the idea is that all black holes don't contain a singularity

More precisely, theoretically, we can construct models of compact objects that look like standard black holes, but don't have a singularity (and also don't have an event horizon, they only have apparent horizons). Any such compact object must contain "vacuum energy" or something equivalent, i.e., something that looks similar to a cosmological constant in the Einstein Field Equation--that is the only way to evade the conclusions of the various singularity theorems that apply to standard black holes. That type of compact object is what is being hypothesized in the paper under discussion.

Re: Black holes as the source of dark energy

#23

Post by andrewflnr »

fsakura wrote: post #9
2bitencryption wrote: post #4

In my imagination, I always thought we could put a black box around a black hole, and it would be indistinguishable from any other mass - that is, any other mass that can be treated as a point mass. I.e. put a black hole with solar mass 1 in a black box. Put a star with solar mass 1 in another black box. From a gravitational point of view, you couldn't tell the difference, yes? But this result implies that the black…

Why do you think the black box with the black hole will gain mass over time? AFAIK: On the contrary it will lose mass over time due to Hawking Radiation and evaporate eventually (though that might take literally forever). Also spacetime curvature will be slightly different for point mass vs distributed mass.

Because of the ideas in the article?

Re: Black holes as the source of dark energy

#24

Post by AmericanOP »

2bitencryption wrote: post #4

In my imagination, I always thought we could put a black box around a black hole, and it would be indistinguishable from any other mass - that is, any other mass that can be treated as a point mass. I.e. put a black hole with solar mass 1 in a black box. Put a star with solar mass 1 in another black box. From a gravitational point of view, you couldn't tell the difference, yes? But this result implies that the black…

The expansion of space-time is an observed property of space. It has always been expanding, but at different rates.

My interpretation of this theory is that spacetime beyond the event horizon is also expanding. This expansion increases vacuum space, which contains vacuum energy.

This either correlates or is coupled with vacuum energy in our observable universe.

Re: Black holes as the source of dark energy

#25

Post by ketralnis »

2bitencryption wrote: post #3

For those with an interest in this topic, but a disdain for "science news", I recommend checking out Sabine Hossenfelder's youtube channel: https://www.youtube.com/@SabineHossenfelder She's a theoretical physicist, and covers topics such as this from the point of view of a real expert, and doesn't "talk down" to the audience at all. (Though I must say, she does engage in clickbait-style video titles and thumbnails, b…

She's generally good but in addition to the clickbait she also has a habit of "it's so easy, it's just [controversial pet theory] and the rest of science disagrees because they are wrong".

I find that most physicists in educational roles shy away from interjecting with opinions and even mild speculation more than they should but she tends to overcorrect in the other direction. This tends to attract a particular type of fan as well, the kind that likes to feel like they're in on the secret knowledge and loudly have opinions about things they don't truly understand

Re: Black holes as the source of dark energy

#26

Post by smath »

ianred wrote: post #10
smath wrote: post #7

Earlier quoted context omitted.

You mention point mass. Yes, the volume also matters. If your second black box contains the same mass but over a bigger volume, then the spacetime curvature it will cause will be less extreme than the black hole in the first box. The book I most like on this topic is Kip Thorne's Black Holes and Time Warps. IMO Thorne is a better explainer than Hawking.

Are we talking about the volume of the event horizon? If I understood it correctly, the total of the mass of a black hole is in its singularity. The volume of the event horizon will depend on the total mass of the black hole.

Oh I just mean when comparing (A) block hole in a black box, vs (B) a non-black-hole start of the same mass, B will likely be over a large volume, and hence will produce different spacetime curvature.

Re: Black holes as the source of dark energy

#27

Post by btilly »

DiogenesKynikos wrote: post #16
2bitencryption wrote: post #4

In my imagination, I always thought we could put a black box around a black hole, and it would be indistinguishable from any other mass - that is, any other mass that can be treated as a point mass. I.e. put a black hole with solar mass 1 in a black box. Put a star with solar mass 1 in another black box. From a gravitational point of view, you couldn't tell the difference, yes? But this result implies that the black…

The "no-hair theorem" says that black holes only have three properties: mass, angular momentum and electric charge. If a black hole is perturbed (for example, by merging with another black hole or swallowing a star), it will temporarily be more complicated, but then it quickly goes back to having only above three properties. The extra properties (such as the gravitational quadrupole moment) asymptomatically decay, ov…

The "no hair theorem" is a theorem of classical general relativity.

Attempts to try to model it with some quantum mechanics thrown in show a tremendous amount of additional state that scales with the surface area of the black hole.

This work suggests even more complications to that picture. That it looks very different from the classical theory.

All of this should come with disclaimers and fudge factors because of our lack of a real theory reconciling GR with QM.

Re: Black holes as the source of dark energy

#28

Post by [deleted] »

2bitencryption wrote: post #4

In my imagination, I always thought we could put a black box around a black hole, and it would be indistinguishable from any other mass - that is, any other mass that can be treated as a point mass. I.e. put a black hole with solar mass 1 in a black box. Put a star with solar mass 1 in another black box. From a gravitational point of view, you couldn't tell the difference, yes? But this result implies that the black…

[deleted]

Re: Black holes as the source of dark energy

#29

Post by AmericanOP »

2bitencryption wrote: post #3

For those with an interest in this topic, but a disdain for "science news", I recommend checking out Sabine Hossenfelder's youtube channel: https://www.youtube.com/@SabineHossenfelder She's a theoretical physicist, and covers topics such as this from the point of view of a real expert, and doesn't "talk down" to the audience at all. (Though I must say, she does engage in clickbait-style video titles and thumbnails, b…

Similarly I recommend the ‘History of the Universe’ channel for an understanding of cosmology:

https://youtube.com/@HistoryoftheUniverse

Re: Black holes as the source of dark energy

#30

Post by ericbarrett »

thricegr8 wrote: post #12

Cross-posting /r/bestof ( https://www.reddit.com/r/worldnews/comments/113casc/scientis... ) because it really does a nice job with history and breaking down the highlights (to me at least:) -------- Reading the paper, this is the best summary I can make. Note that I'm an engineer, not an astrophysicist. The basic thought is that in 1963, a guy named Kerr seems to have come up with the best approximation of black hole…

What a fantastic summary, thanks for reposting it.

This could be Nobel Prize research if it holds up in the coming years.

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