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It's only necessarily infinitely dense from an outside reference frame. Inside you could have anything you'd want according to GR. One certainty is that the sp

by waps 13y ago

It's only necessarily infinitely dense from an outside reference frame. Inside you could have anything you'd want according to GR. One certainty is that the space inside a black hole is bigger than the size of the black hole observed from outside of it. So it's entirely possible that you could have a solar system or even an entire universe on the inside. According to GR the space inside a black hole should pretty much behave like the rest of the universe, as long as the black hole is growing. As for "not getting out", well it's impossible to approach the edge of the universe too, despite that border having a physical location. But it's expanding at light speed, so ... no way to get there. So density of a black hole is an entirely different concept from the outside and the inside. Seen from the outside it is infinite. Seen from the inside it is probably not infinite.

fennecfoxen 13y ago
> One certainty is that the space inside a black hole is bigger than the size of the black hole observed from outside of it. So it's entirely possible that you could have a solar system or even an entire universe on the inside. That is not a certainty at all. The entire premise of Hawking's paper is that the object we call a 'black hole' is just a really degenerate dense lump that slowly turns incoming matter/energy into background radiation with as much entropy as possible. And that's it. No fancy Time Lord bigger-on-the-inside science proposed here.
pdonis 13y ago
it's impossible to approach the edge of the universe too, despite that border having a physical location. No, it doesn't. There is no edge to the universe. Our best current model is that the universe is spatially finite, but even if it turns out to be spatially finite, it is unbounded--the spatially finite model is a 3-sphere; like the surface of the Earth but with one more dimension. The surface of the Earth is finite, but it has no edge; a spatially finite universe would be the same way but with one more dimension. Seen from the outside it is infinite. No, it isn't. Seen from the outside, the hole has a finite mass in a finite volume, so its density is finite. (The finite volume an outside observer would assign, based on the surface area of the hole's horizon, is not the "actual" volume of the hole; but it works well enough as an "effective volume", the volume that the hole occupies from the standpoint of the rest of the universe.) The singularity can be viewed as infinitely dense, but the singularity does not occupy the entire black hole; it only occupies the center at r = 0.

by waps 13y ago

fennecfoxen 13y ago

> One certainty is that the space inside a black hole is bigger than the size of the black hole observed from outside of it. So it's entirely possible that you could have a solar system or even an entire universe on the inside. That is not a certainty at all. The entire premise of Hawking's paper is that the object we call a 'black hole' is just a really degenerate dense lump that slowly turns incoming matter/energy into background radiation with as much entropy as possible. And that's it. No fancy Time Lord bigger-on-the-inside science proposed here.

pdonis 13y ago

it's impossible to approach the edge of the universe too, despite that border having a physical location. No, it doesn't. There is no edge to the universe. Our best current model is that the universe is spatially finite, but even if it turns out to be spatially finite, it is unbounded--the spatially finite model is a 3-sphere; like the surface of the Earth but with one more dimension. The surface of the Earth is finite, but it has no edge; a spatially finite universe would be the same way but with one more dimension. Seen from the outside it is infinite. No, it isn't. Seen from the outside, the hole has a finite mass in a finite volume, so its density is finite. (The finite volume an outside observer would assign, based on the surface area of the hole's horizon, is not the "actual" volume of the hole; but it works well enough as an "effective volume", the volume that the hole occupies from the standpoint of the rest of the universe.) The singularity can be viewed as infinitely dense, but the singularity does not occupy the entire black hole; it only occupies the center at r = 0.