[Nic321 (OP)]

Hello everone,

I had a question regarding the possibiliy of a black hole existing inside another black hole.

Theoretically, an objet that goes through the horizon of a black hole sees nothing special ( except for the firewall theory but let's keep things simple for now ).

That should also be true for a black hole in particular. Lets take the example of a small black hole, let's say of stellar mass, falling in a very large black hole like a galactic black hole. At the horazon of the galactic black hole the gravitational field is not very strong and space is flat at its horizon.

When the small BH enters the large one, its gravitationnal field adds to that of the large one, so obviously the large one has a stronger gravitionnal field and its horizon expands accordingly. The 2 black hole can be said to "merge". However the small black hole remains intact inside the large one.

In other words a photon trapped inside the small black hole continues to be trapped inside that small region of space-time after the small black hole has fallen into the large one.

As for what happens to the small black hole once inside the large one, I don't know but I guess several possibilities could be imagined, such as:
- when the small BH gets close to the center the gravitationnal field becomes so strong that the small BH is torn apart and destroyed.
- the small BH evaporates before it gets to the center
- the small black hole swallows all the matter located in the center and grows until all the content of the large BH in the center has been swallowed and thus it becomes the large BH.

I guess that scientists have already thought about that kind of things, so I was wondering if you knew what they thought was happening.

Thank you,
Regards,
Nic321.

[ScientificSorcerer]

I was talking about such things in another thread above yours, called "Big bang and first law of thermodynamics"  you might find my theory on the subject enlightening. As for your question about black holes, yes the small black hole remains intact as it merges with a bigger black hole. This is because of the "state of matter" that black holes are in.  you see black holes are in a 5th state of matter called the bose-einstine condensate (bec) In which the empty space of atoms is turned into 0% this is because of the way gravity pushes the nuclei of atoms together so much that the force of gravity overcomes the electromagnetic repulsion force of the electron cloud. when black-holes merge the state of matter that they are in doesn't change, the small black hole just adds it's clump of atoms in the BEC state to the larger black hole's atoms in the BEC state.
the light trapped in the BEC still can't escape because the "state of matter" hasn't changed.

[Ethos_]

the small black hole just adds it's clump of atoms in the BEC state to the larger black hole's atoms in the BEC state.
the light trapped in the BEC still can't escape because the "state of matter" hasn't changed.

Agreed, but one could presume that this doesn't happen until the smaller black hole reaches the singularity of the larger. Interesting thought nevertheless! Wouldn't it be an incredible sight to watch this process unfold as the two singularities merge together? Sadly, this spectacle will remain beyond our visual scrutiny unless we learn how to view this process without the aid of electromagnetic radiation.

[Nic321 (OP)]

Hi ScientificSorcerer

I was talking about such things in another thread above yours, called "Big bang and first law of thermodynamics"  you might find my theory on the subject enlightening. As for your question about black holes, yes the small black hole remains intact as it merges with a bigger black hole. This is because of the "state of matter" that black holes are in.  you see black holes are in a 5th state of matter called the bose-einstine condensate (bec) In which the empty space of atoms is turned into 0% this is because of the way gravity pushes the nuclei of atoms together so much that the force of gravity overcomes the electromagnetic repulsion force of the electron cloud. when black-holes merge the state of matter that they are in doesn't change, the small black hole just adds it's clump of atoms in the BEC state to the larger black hole's atoms in the BEC state.
the light trapped in the BEC still can't escape because the "state of matter" hasn't changed.

There is probably something at the center of the blackhole, maybe a quark-gluon fluid or whatever. However, light stays inside the BH because of its gravitationnal field. The source of the gravitationnal field could be anything.

Also, at the horizon of a large BH, like a galactic BH, the gravitationnal field is in fact low and space is flat at the horizon. Anything that falls in the large BH would see nothing special happening, it wouldn't even know it's inside a BH.

I don't know what would happen at the center but things may change however because the gravitationnal field would be huge there, which would possibly desintegrate the small BH.

We can speculate on what happens at the center but it's really speculative because we don't have a good theory of quantum gravity.

[jeffreyH]

The surface of the horizon of the smaller black hole that is nearer to the singularity would be distorted. This distortion should alter the energy-density relationship internally and reduce the escape velocity at the horizon. This should have an expanding effect that would remove the matter from the smaller object so that it combines with the matter of the larger BH at the centre. Also Ve at the larger BH's horizon will start to exceed c so that an expansion of its own horizon will occur to compensate.

[Bill S]

  Also Ve at the larger BH's horizon will start to exceed c so that an expansion of its own horizon will occur to compensate.

Does Ve actually exceed c?   If so, how does expansion of the EH compensate?

[Kryptid]

Of possible relevance: https://en.wikipedia.org/wiki/Holeum#Black_holeums

[Bill S]

"Holeum"  Sounds like something from Dr Seuss!

Interesting link - shame about the maths. 

[jeffreyH]

If state changes in the Holeum cause gravitational radiation and they do actually constitute dark matter there should be perturbations in galactic halos. I am not sure how this could be detected.