AFAIK, scientists do not believe in the singularity, one way out of the singularity is quantum gravity, but as we have no testable theory of quantum gravity what do scientists think a black hole is?
Currently, the best answer is a region of spacetime from which light, locally, cannot escape. The more technical term would be a "trapped region". Such a region is bounded by a trapped surface, which is also called an apparent horizon. The open question is whether these apparent horizons are associated with actual event horizons (regions from which light can never escape, not just regions from which it can't escape at present). The technical definition of a black hole requires there to be an actual event horizon; but that just means that, if we end up discovering that there are no actual event horizons, only apparent ones, we'll probably redefine the term "black hole" to cover that case.what do scientists think a black hole is?
In the highly speculative models where a black hole gives birth to a "baby universe" instead of having a singularity at the center, there would be a new baby universe for each BH, and all of them would be disconnected from each other.It has been said that the black hole leads to a worm hole to another universe, would that be a universe for each BH or the same for all BHs
The definition of "black hole" is precisely the point at issue, so you can't just help yourself to this statement as it stands. You have to actually describe what there is plenty of evidence for the existence of, without using the term "black hole". I tried to do that in post #8; a quick summary would be that there is plenty of evidence for apparent horizons into which matter can or has collapsed.There is plenty of evidence that black holes exist.
At the center of all (or almost) all galaxies there is an invisible object, the size of which is in the millions or billions of solar masses. Black holes are the only description that fits according to current theory.The definition of "black hole" is precisely the point at issue, so you can't just help yourself to this statement as it stands. You have to actually describe what there is plenty of evidence for the existence of, without using the term "black hole". I tried to do that in post #8; a quick summary would be that there is plenty of evidence for apparent horizons into which matter can or has collapsed.
Once again, the point at issue is the definition of "black hole". If you are defining "black hole" to mean "event horizon and the region inside it", then your claim is not justified; an apparent horizon is a description that also fits according to current theory. The only way to distinguish an apparent horizon from an actual event horizon, according to current theory, is to know the entire future of the spacetime, and we don't know that.Black holes are the only description that fits according to current theory.
Cannot escape just right now, or cannot escape forever? That's the difference between an apparent horizon and an event horizon.The simple and obvious definition of a black hole is a bounded region of space wherein photons cannot escape.
That would come as a great surprise to all the participants in what Susskind calls the Black Hole War, in which the question of whether there are any actual event horizons, or only apparent ones, is critical.Any further details are irrelevant.
What does "virtual" mean here? If you mean we don't know if it's an event horizon or an apparent horizon, that's true, but that doesn't mean the event horizon is "virtual". The definition of an event horizon is perfectly precise: it's the boundary of the causal past of future null infinity. If there is no such boundary in a spacetime, i.e., if the entire spacetime is in the causal past of future null infinity--which will be the case if all horizons are only apparent horizons--then it's not correct that there is a "virtual event horizon". There is no event horizon, period.While typically robust, all event horizon are strictly virtual.
This is one way of describing the model in which there is an event horizon, but the region inside it only exists until the black hole evaporates away completely (instead of existing infinitely into the future as in classical GR). I'm not up to date on the latest in the Black Hole War, but AFAIK Susskind a few years ago was claiming that his side had won, which if true would mean the model just described is not viable (Susskind's side was the side that said the presence of any event horizon at all, no matter how small the region inside it, would violate unitarity and thus be inconsistent with QM).it can be argued a black hole is only a black hole so long as the walls of its EH remain standing
Love the humor!If you're interested in wormholes, see the Wikipedia article: https://en.wikipedia.org/wiki/Wormhole
Although the concept of wormholes has been investigated mathematically in various ways, I think that all potentially interesting ideas (such as being able to fall into a black hole and survive a journey to somewhere else) rely on non-standard theories or a large pinch of unobtainium.
But this isn't necessarily true. In Hawking's original model of an evaporating black hole, it isn't; there is a genuine event horizon and an interior region behind it that cannot send any light signals to infinity. That interior region has a future boundary because the hole ends up evaporating, but it's still there, and information still gets trapped inside it.Since black holes are generally believed to evaporate, it is destined to return [albeit with little urgency] its disconnected volume of space back to the causal universe at large.
Could it be that nuclear particles show a similar property like crushed atoms? In the "crushed" state still unknown subquark particles may play a major role. The principle even could be recursive in a way that subquarks of increasing order enter the game in more and more exotic conditions.We have no idea what happens when even neutron degeneracy cannot hold up against further infalling matter.
Do you have a reference for this? If not, please bear in mind the PF rules on personal theories.In the "crushed" state still unknown subquark particles may play a major role. The principle even could be recursive in a way that subquarks of increasing order enter the game in more and more exotic conditions.