Black holes as the source of dark energy
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Black holes as the source of dark energy
1–10 of 81 posts
Re: Black holes as the source of dark energy
#2I don't remember this quote exactly, or whom to attribute it to but it goes something along the lines of "throwing two unsolved problems at each other doesn't create a solution".
Re: Black holes as the source of dark energy
#3For 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, but the video content is much better than that implies)
I guarantee she will have something to say about this topic in her next video :)
Re: Black holes as the source of dark energy
#4In 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 box with the black hole will gain mass over time, even without adding any mass into the black box? So you could distinguish it from another mass?
Or do I have that wrong? My understanding is as someone who is interested but has no real education on these topics.
Re: Black holes as the source of dark energy
#5In 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…
It is my understanding that, from a gravity-only standpoint, you are right. But I actually thought that black holes slowly evaporate, i.e., lose mass, from emitting Hawking radiation. It isn't clear from the article whether the vacuum energy black holes still have that property.
The article confuses me on something else. It mentions a link between black hole mass and the expansion of the universe, but then it seems to imply that the expansion causes the black holes to gain mass which in turn causes the expansion to accelerate. It doesn't seem to address why the universe is expanding in the first place. But I guess dark energy was proposed as the thing that was doing the expansion acceleration, and not the expansion cause.
Re: Black holes as the source of dark energy
#6In 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…
> 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 the paper is talking about a special type of "black hole", an object that has "vacuum energy" inside it (which means something that acts like a cosmological constant in the Einstein Field Equation)--which isn't a standard black hole (those have zero stress-energy inside). The claim is basically that the total vacuum energy inside such an object can increase as the universe expands.
However, this does not mean that the ordinary "mass" of the black hole would increase. Vacuum energy doesn't work like ordinary mass. The effect that this model is claimed to account for is the accelerated expansion of the universe due to dark energy; basically this model is supposed to provide a mechanism for how dark energy could come into existence as a result of black hole formation (but, again, it's a special kind of "black hole", not the ordinary kind).
Re: Black holes as the source of dark energy
#7In 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…
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.
Re: Black holes as the source of dark energy
#8In 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…
It is my understanding that, from a gravity-only standpoint, you are right. But I actually thought that black holes slowly evaporate, i.e., lose mass, from emitting Hawking radiation. It isn't clear from the article whether the vacuum energy black holes still have that property. The article confuses me on something else. It mentions a link between black hole mass and the expansion of the universe, but then it seems t…
> I actually thought that black holes slowly evaporate
This is believed to be true, but the time scale is something like 60 or more orders of magnitude longer than the age of the universe, so (a) no evidence for this effect exists or is likely to be found any time soon, and (b) it's irrelevant for the dynamics of our current universe anyway.
Re: Black holes as the source of dark energy
#9In 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.
Re: Black holes as the source of dark energy
#10In 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…
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.