# Thread: Is the inside of a Black Hole not black?

1. Member
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May 2007
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## Is the inside of a Black Hole not black?

I was listening to the audio book of "Death by Black Hole" by Neil deGrasse Tyson on my way into work yesterday and I came up with this question: Is the inside of a Black Hole not black? Here is my thought process behind the question and I would be interested in hearing if this was possible.

At the event horizon of a black hole, the gravitational forces exceed that of the speed of light so that light can not escape. However, I read that a black hole is an example of a Singularity with all of its mass located at one point in space. According to Newton's gravity equation, the gravitational forces created by a sphere can be calculated “as if” all of the sphere's mass is located at the center of the sphere. The Shell Theory states that if each layer of a sphere has a consistent distribution of mass, then as one travels in side the sphere the layers (Shells) further away from the center point from your distance can be ignored in calculating the gravitational forces created by the sphere at that point.

Example: If you assume a uniform density of mass for the Earth for discussion purposes, at ½ the radius of the Earth the gravitational forces are ½ that of at the surface of the Earth. This is because the distance has been cut in half, but the volume for a sphere at ½ the radius is 1/8 the total.

So, it is possible for a region in space to have enough matter to create a black hole effect with matter distributed throughout the region. But if the gravity were so high, wouldn't all the matter collapse into a singularity? One item to I would like to ask is wouldn’t the fact that time is also warped in a gravitational field that should be taken in consideration? It is my understanding that inside a gravitational field that is strong enough to prevent light from escaping would also warp time to slow down until it stops. If time nearly stops inside this large gravitational field, the movement of matter to the center point would also nearly stop or it would exceed the speed of light.

In this scenario, would it be possible for the gravitational forces inside a black hole region to be less inside the region than at the event horizon to the point that it is not greater than the speed of light? In this case, we could never see into the region, but light/space/time could exist.

Just a thought – I would be interested in reading any comments. Thanks!

2. Assuming that general relativity holds inside a black hole, the singularity theorems of Hawkings and Penrose show that once you have an event horizon a singularity inevitably follows in any physically plausible case.

However, the apperance of a singularity tends to indicate that the theory doesn't hold, so what really happens inside a black hole is, if not anyone's guess, at least an open question.

3. Established Member
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Dec 2002
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You know how the Buddhists say, "If a tree falls in the woods when no one is around to hear it, would it make a sound?" ?

Well, the same holds true for conditions inside a black hole.

Ain't no way anybody's gonna survive being there long enough to notice anything.

4. Ain't no way anybody would survive a diving head first into the sun to look at the core, yet we try to work out something. As for the inside of the black, I think it wouldn't be black, because of all the photons it has sucked in. But that is my guess.

5. If a black hole is sufficiently big, you should be able to survive for some considerable span of time after crossing the event horizon, certainly more than enough to notice a few things.

6. Order of Kilopi
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Apr 2004
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I think you'll find the answer to the original question at John Baez' Usenet Physics FAQ and Ten Bunn's Black Hole FAQ.

No, the inside of a black hole is not black. It's pretty much like being in ordinary space. You would see the stars shining outside. Until you hit the singularity, at least.

7. Established Member
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Objects that are outside the black hole viewed from inside might be affected by the alleged Lens-Thirring effect associated with "spining" black holes as well as any variations in isotropy.

8. you might also see two, three, infinity copies of stars from all the gravitational distortion as well. You will also see a looming black mass in the field of view, continually expanding and pushing the starlight into smaller and smaller space. And that singularity is in your future--if you try to accelerate away from it, in that strange bent-up space you are actually shortening the time it takes to get there--the slowest descent is free fall. This is from "Black Holes and Time Warps: Einstein's Outrageous Legacy" by Kip Thorne, which I recommend.

9. Since no light can escape, I'm sure it all builds up inside. So just within the Event horizon would be pretty bright, with all that "hoarded" unescaped light. Not that anyone will ever see it.

10. What's it like inside a white dwarf? It is unimaginably dense with matter. How about a neutron star? Unimaginable6! I would guess that light isn't going to travel very far before hitting something and being re-emitted. A natural* black hole has to be the next step in the progression. It's got to be unimaginably dense to the ? power, and I kinda doubt this question really has any meaning.

* Yes, I've read about very large black holes with the density of water where crossing the event horizon would just require some scuba gear. But are these just possible mathematical solutions? I can't imagine such a configuration would be at all stable. Black holes are matter crushed beyond our comprehension - indeed, beyond all known physics.

11. Interesting question -- couldn't answer it myself, but I'd like to offer this thought: I think part of the answer lies in "what part of the spectrum do you view"? Radiation escapes black holes (or at least the edges), but it may not be visible radiation.

12. Tell your worst enemy to go find out.

13. My impression was that the whole history of the universe would pretty much elapse before you hit the event horizon. Not sure how you would see stars shining outside the blackhole from inside it then (or even what effect an infinite blueshift and intensifying of all the incoming energy would have on you).

14. i would think that after you crossed the event horizon, if you looked out, everything would be the most intense shade of white, and if you looked directly in towards the middle, it would be blacker than the blackest black, times infinity..

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