# What events occur inside a black hole?

1. Nov 23, 2012

### F1225

As we know, the gravitational pull of the black hole is too strong, not even light can escape from it...

Let me assume 2 person: A and B
A is sucked into a black hole while B is outside the event horizon...
At first, B will notice that A has disappeared due to the lights(image) of A is sucked by the black hole...
On the other hand, A will still see the image of B because the lights(image) of B is being sucked into the black hole.

What this all mean? Do this event relates to relativity which both of them are in different inertial frame causing things which they observed to differs?

Thanks for spending your time reading the entire post...*(it's quite long)...haha :tongue:

Last edited: Nov 23, 2012
2. Nov 23, 2012

### phinds

Person B will NOT see A sucked into the black hole, he will see A move more and more slowly as A approaches the event horizon of the BH. That isn't what actually happen to A of course, but it is what B will see. A will just continue on through the EH as though it were not there.

You are correct that A will continue to see B, even after A passes the event horizon

3. Nov 23, 2012

### Staff: Mentor

4. Nov 23, 2012

### phinds

Well, that's not what you said in your original post, thus my answer.

The sphagettification may occur either inside or outside the BH, depending on its size.

5. Nov 24, 2012

### Staff: Mentor

I'm confused who are you talking about, I only posted once. ???

6. Nov 24, 2012

### phinds

DOH ! Sorry about that. I clearly wasn't paying attention and though you were the OP again.

7. Nov 24, 2012

### Staff: Mentor

NP, I thought one of us had fallen into that black hole and I wasnt sure which one.

8. Nov 24, 2012

### ahhaha

No events occur inside a black hole because black holes don't have an interior.

9. Nov 24, 2012

### phinds

You are right (according to most theories) but the term "inside a black hole" normally just means "inside the event horizon".

10. Nov 24, 2012

### ahhaha

"inside the event horizon" can't be made rigorous, if only because the notion of event horizon( assuming it can be made rigorous) is no more rigorous than the notion of BH interior since an event horizon is an asymptotic limit of future null infinity. In the usual OpSnyVolk representation of Schwarz that's where the radial coordinate magically turns into the temporal coordinate. At that point you don't know where you are! Next to nonsense, or in it?

11. Nov 24, 2012

### Staff: Mentor

This is incorrect. Inside the event horizon can easily be made rigorous. E.g. The region without a timelike killing vector.

Also, there are several coordinate charts that are well behaved at the EH, so the failure of one is clearly a problem with those coordinates, not the EH itself.

12. Nov 24, 2012

### ahhaha

Your "region" can't be well defined since its domain is rest of universe. A singularity or BH can only make sense when it's approached from asymptotic spatial infinity and an effective approach may not be complete in the assumed metric. So I would ask you where in the approach is the path without timelike vector?

13. Nov 24, 2012

### Staff: Mentor

Yes, an effective approach may not be possible in some metrics, but the Schwarzchild metric solution to the Einstein field equations isn't one of these. You just have to transform from the Schwarzchild coordinates to some other coordinates that are better-behaved at the event horizon.

Dalespam didn't say "without a timelike vector", he said "without a timelike Killing vector". There's no shortage of timelike vectors at and inside the event horizon. The lack of a timelike Killing vector just means that there exists no coordinate system in which the metric components can be independent of time - not too surprising because all timelike geodesics converge on the central singularity.

Last edited: Nov 25, 2012
14. Nov 25, 2012

### Staff: Mentor

This is a complete non-sequitor. What do the size of a domain or required approaches have to do with being well-defined? Well defined means only that it has a definition which is unambiguous, not any of the unrelated concepts you are trying to bring in. The term "inside the EH" is well defined.

I don't know what you are trying to say here.