[tegeek]

What is more poetic than a mathematical model of a black hole? Look at this

A "finished" black hole (The end state of the gravitational collapse) doesn't have a volume or any density.

This is the mathematical solution first obtained by Schwarzschild in 1916. So standard mathematical solutions of the black holes are vacuum solutions.

There is "nothingness" inside the event horizon.

The outside observer would see a collapsing sphere of dust, but over time, as the radius of the sphere approaches the (yet to form) event horizon, gravitational time dilation makes everything appear increasingly in slow motion. The actual moment of horizon formation is never seen, it remains forever in the future for the outside observer.

For the in falling observer, the situation is different. The moment once the horizon is crossed, there is no escape. The observer will find himself inside an ever shrinking “universe” of dust everywhere. The singularity is an unavoidable future moment in time, when the density of this “universe” becomes divergent and time itself comes to an end.

So there you've a vacuum. A "universe" of vacuum everywhere where there is no time exists.

[simiones]

You shouldn't forget that, since the mathematical equations have a singularity at the center of a black hole, we can be reasonably sure that they are in fact incomplete and can't accurately describe the internal structure of a black hole.

So, take any such description with a grain of salt. It's much more correct to say that our current models can't accurately predict what is happening past the event horizon of a black hole.

[tegeek]

First there is nothing called center of a blackhole. What mathematics tells us is exactly what is a black hole. After crossing the event horizon, there is no time so there is no "information" exists. Its the end of "everything" which I wrote "nothingness". Thats what is in the black hole. Thats the structure.

[gizmo686]

There is very much time after crossing the event. It happens to not correspond to the "t" coordinate that a distant observer would call time, but it still exists.

The mathematics describes 2 singularities with black holes. 1 singularity occurs when describing the black hole using the coordinate system of an observer at constant distance. This is a coordinate singularity and goes away under an appropriate change of coordinates.

Another singularity occurs at what the constant distance observer would describe as the "center" of the black hole. This is not a coordinate singularity. The curvature there goes infinite regardless of your coordinate system.

Whether or not you want to call this singularity the "center" is a matter of opinion. An observer within the event horizon would describe the singularity as a time, not a location, so "center" certainly has some connotations that you may want to avoid. On the other hand. In the coordinate system that I normally see used to describe the interior of black holes, the singularity occurs at the surface r=0; which sounds kind of center-ish.

[TeMPOraL]

> For the in falling observer, the situation is different. The moment once the horizon is crossed, there is no escape. The observer will find himself inside an ever shrinking “universe” of dust everywhere.

Makes me wonder. We used to believe that it's possible for our universe to eventually collapse, reversing the Big Bang in a Big Crunch. From what I recall, current evidence points against it, but if we were to live in such a universe doomed to a collapse - wouldn't that mean we'd be living in a universe-sized black hole?

(A black metahole if you like.)