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TwentyninthDigitOfPi t1_izb2jsz wrote

Would it be possible to harness dark energy to leave a black hole?

My understanding is that dark energy is the current "fill-in" to explain why the universe is expanding. Farthest away from us, that expansion is faster even than the speed of light, due to the cumulative effect. So, if we stipulate (a) that dark energy is indeed the cause for this expansion, and (b) that we can manipulate it to expand pockets of the universe at will, then would we be able to use that to essentially expand our way out of a black hole? I'm imagining a craft that could expand space behind it (closer to the singularity) and essentially ride that expansion to get out of the event horizon, without ever having to travel faster than light in its local patch of space.

I realize that "could we do this thing predicated on unknown physics" is a bit of an impossible answer; so I guess what I'm really interested in is whether the math of current theories would allow for such a thing, assuming the two stipulations above.

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davidjara t1_izbidwk wrote

Long story short, no. Dark energy is the energy of space itself. We cannot move it/compress it/manipulate it in anyway whatsoever. If I understood your idea correctly you want to put a lot of dark energy in a tiny space and see what happens. This is like asking if you can put a big chunk of space in a little space.

I want to stress that even though dark energy is code term for "weird energy of empty space we don't understand anything about" by its very nature, it cannot be manipulated and hence dark energy BH are simply not possible.

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TwentyninthDigitOfPi t1_izbk5jp wrote

How certain are we of that? Just from reading wikipedia, it looks like some models of dark energy are compatible with what you said (e.g. a cosmological constant), but other models seem to be more "normal" kinds of energy (like quintessence).

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davidjara t1_izbrmp2 wrote

Certain beyond reasonable doubt. Let me first say that the cosmological constant is not a model of dark energy. The cosmological constant is a low energy, effective description of whatever dark energy really is.

Dark energy is the term coined to describe the accelerated expansion of the universe, most people (myself included) believe that this is due to vacuum energy. The quintessence story is a way of explaining the expansion, not as vacuum energy, but as interactions with a field. This field violates basically every single reasonable expectation (that's why not many people like it) and (to my knowledge) it barely works even in the simplest situations. If the expansion of the universe is due to a field like in the quintessence story, then it's possible you could something with it. However, you will struggle to find a single researcher that believes the expansion of the universe is due to something different that vacuum energy.

So just to put a bit of salt on it. My answer was regarding the energy of empty space. I believe that beyond any reasonable doubt dark energy is the energy of empty space. If this is true, there is no way to make dale energy BH. On the other hand, if it turns out that the universe expansion is due to some matter fields then you could in principle build stuff with it (like BH).

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