Just to make sure: If the sun suddenly magically stopped existing (along with its whole mass), the earth would still be subjected to the exact same gravitational field until the moment when it stops receiving photons from the sun, right? This is what I meant when I talked about gravity “travelling” at the speed of light…
I might be wrong and I probably didn’t give enough thought to this but… It appears to me that anything else would cause all sorts of problems with GR…

The thing about the black hole never forming is maybe just a question of semantics? The singularity “exists” in the sense that things that fall into it do it in finite time from their own point of view… But for any outside observer, the singularity and event horizon would never be “observed” to form in finite time.
Does that make sense? For an event horizon to be “observable” from outside in the sense that there is this “visible” radius from which no light escapes, there has to be a singularity beyond it, right? Let’s say the event horizon starts with no radius and grows as more matter falls into it, but for an outside observer, nothing ever falls into it!
So there is no “obsevable” radius that we can call the event horizon of a black hole, just some very dense matter that’s going slower and slower and denser and denser… Never reaching the infinite density required for us to “observe” a black hole because that would take infinite time! Or is that wrong?

I guess the question I’d like to have answered is: what would the formation of a regular black hole look like for an outisde observer looking at the star collapsing? Because according to my own mental differential equation solver it would look like just what I described above (no visible event horizon, ever)

I hope I’m not just confusing myself even more….

Gravity doesn’t need to “travel” faster than the speed of light. Gravity doesn’t escape from a black hole. In GR gravity is a function of local conditions. I fall toward Earth because of the differential properties of space right here where I am, not way over there where Earth is. The field equations represent a continuously differentiable curve from the singularity all the way to infinity. There’s no hiccup at the event horizon. The field just above or below the horizon knows nothing of the horizon itself; it only knows how it’s being tugged upon by the field just infinitesimally off to one side.

If you still want your classical black holes with an event horizon and a singularity to exist in our universe as something else than a limit as time goes to infinity… Then you must believe that gravity can travel faster than light, because you are talking about receiving gravitational information from a singularity which has formed later than when the light you receive was emitted. I have some trouble accepting that this can be true…

I hope someone can explain this to me …

Spacetime at the event horizon is moving toward the singularity at the speed of light relative to any observer who is maintaining hight above it. Spacetime inside that horizon doesn’t exist in the normal sense for anyone who’s accelerating to maintain altitude.

Mike’s example about building a structure above the horizon from which to hang a rope should mention that the total gravitational acceleration of any object hanging from such a structure down to the horizon places an infinate strain on the rope. You can’t maintain hight at the horizon by any means.
The strains on any such structure would also be immense anywhere near the horizon.

Now, an observer that freefalls toward the singularity sees things a little differently, and (other than the extremely distorted viewpoint from all the light bending) it’s all normal enough in terms of how you’d expect to fall and what the outside universe would look like as you fell. Regardless, any attempt to stop falling requires them transferring into the inertial frame of those things stationary at an infinate distance, which requires infinate acceleration at the event horizon, and pretty extreme amounts further out too, depending on the local spacetime curvature.

The appearance of stopping at the horizon is simply that below there none of your light emissions escape, the last light seen above was from just before you crossed, which takes a very long time to escape to any significant distance.

Theories about the potential for non-collapse of the original matter are quite complex, and involve pressures being generated slightly beyond where the horizon would form due to complete mass to energy conversion through various relativistic electromagnetic effects, keeping the total density below the critical point.

hi mark, thanks for trying to help.
if you say that light do slow down because of time issues, then you would have the situation that for the lights frame of reference, the light would still be able to get out. Just like phil says that stuff do fall into the black hole in his video. So I don’t think this can be the cause of a black hole forming. Or what?
I don’t think you can explain lights failure to escape with escape velocity and that was why i pointed out phils mistake.

Major Tom will approach c as he approaches the horizon if he starts from a radius of infinity and zero velocity. Let’s say the black hole has built about it a rigid cage with finite radius greater than the event horizon. Major Tom could jump off that cage and would only acquire velocity less than c as he reached the horizon.

I think Poor Ol’ Major Tom would still acquire velocity=c relative to the horizon even if he jumps from rest at radius r_0 > r_horizon. For a stationary observer at radius r (r_horizon <= r r_horizon, v->1 (i.e., c). Of course, this is an asymptotic result, since no stationary observer can be located at the horizon. Then again, the same is true if the object falls from rest at infinity.