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I'm also not a physicist but I think I can guess a plausible answer to these? 1. Because if you don't have a black hole yet then there is no event horizon to p

I'm also not a physicist but I think I can guess a plausible answer to these? 1. Because if you don't have a black hole yet then there is no event horizon to prevent you from falling in and creating one. I think the event horizon wouldn't form at exactly the same point whose crossing would finally increase density enough to create it, so this shouldn't be a problem. (Although, again, since the event horizon doesn't exist yet, I think it might still not be a problem even in that case?) I would also expect that quantum fluctuations can also inject matter into a black hole, just as they can remove matter from it. 2. Again, they wouldn't take forever to form -- see above. I'm pretty sure black holes have been observed indirectly, so the idea that they actually don't exist would require a pretty rock solid alternative explanation!

pdonis 8y ago
> I'm pretty sure black holes have been observed indirectly What we have observed indirectly are compact objects that emit no light, but contain a large enough mass in a small enough volume that they can't be anything else but a black hole, if we only take classical GR into account. As I responded in another post just now, it is possible that black holes, in the sense of objects with actual event horizons (boundaries of regions from which light will never escape, even in the infinite future), cannot exist when quantum gravity effects are taken into account. If that is the case (and it is not clear whether it is--as I said, this is an open area of research), then the objects we call black holes based on our current observations won't have actual event horizons--eventually, in the very far future, light will escape from those compact regions. But they will still have apparent horizons, i.e., surfaces from which outgoing light is not escaping now (or for a very long time in the future). And that, in itself, is sufficient to show that the issues raised by darkmighty are not valid.

pdonis 8y ago

> I'm pretty sure black holes have been observed indirectly What we have observed indirectly are compact objects that emit no light, but contain a large enough mass in a small enough volume that they can't be anything else but a black hole, if we only take classical GR into account. As I responded in another post just now, it is possible that black holes, in the sense of objects with actual event horizons (boundaries of regions from which light will never escape, even in the infinite future), cannot exist when quantum gravity effects are taken into account. If that is the case (and it is not clear whether it is--as I said, this is an open area of research), then the objects we call black holes based on our current observations won't have actual event horizons--eventually, in the very far future, light will escape from those compact regions. But they will still have apparent horizons, i.e., surfaces from which outgoing light is not escaping now (or for a very long time in the future). And that, in itself, is sufficient to show that the issues raised by darkmighty are not valid.