On the nature of the infinite fall toward the EH

[PeterDonis]

So when material is said to fall into the singularity, it's not a movement through space but though time?

Correct. Whether or not the object moves through "space" as well depends on what coordinates you adopt; most common coordinate charts have the infalling object moving through space as well as it falls. The key point is that the reason the singularity is unavoidable once

But is it possible to reach this singularity without also reaching an r=0 position? I suspect the answer is yes.

You suspect incorrectly. The answer is "mu": the question itself is not well-defined, because r = 0 is not a "position"; it's an instant of time. It's true that there are many possible spatial positions that you could be in when you reach this instant of time, just as there are many possible spatial positions you could be in when you reach next Tuesday at precisely noon GMT. But *all* of the spatial positions you could be in when you reach the singularity are labeled with r = 0, just as all of the spatial positions you could be in when you reach next Tuesday at precisely noon GMT are labeled as "noon GMT". The label "r = 0" labels an instant of time, not a place in space.

 

[PeterDonis]

If Alice is pointing her flashlight outward, Bob can catch up to some of this light after he falls through the event horizon.

Correct. But when he catches up to it, he (and it) will be at a *smaller* value of $r$ then Alice was when she emitted the light. So the light does fall inward towards the singularity; it just falls slower than Alice does, so Bob can catch up to it.

 

[.Scott]

Correct. Whether or not the object moves through "space" as well depends on what coordinates you adopt; most common coordinate charts have the infalling object moving through space as well as it falls. The key point is that the reason the singularity is unavoidable once

If the object is traveling through time to reach the singularity, should it take a shorter or longer period of time to reach it depending on when the object starts it journey?

You suspect incorrectly. The answer is "mu": the question itself is not well-defined, because r = 0 is not a "position"; it's an instant of time. It's true that there are many possible spatial positions that you could be in when you reach this instant of time, just as there are many possible spatial positions you could be in when you reach next Tuesday at precisely noon GMT. But *all* of the spatial positions you could be in when you reach the singularity are labeled with r = 0, just as all of the spatial positions you could be in when you reach next Tuesday at precisely noon GMT are labeled as "noon GMT". The label "r = 0" labels an instant of time, not a place in space.

Excellent. Then why is extreme spaghettification presumed?

 

[PeterDonis]

If the object is traveling through time to reach the singularity

It's only traveling through time in the same sense that everything "travels through time"; the infaller's "travel through time" to the singularity is no different from your "travel through time" to tomorrow.

should it take a shorter or longer period of time to reach it depending on when the object starts it journey?

Not depending on when it starts, no. The time to fall depends on how far above the hole's horizon the object starts.

Then why is extreme spaghettification presumed?

It's not presumed, it's derived by solving the Einstein Field Equation. The solution that applies to a black hole shows that tidal gravity increases without bound as the singularity is approached.

 

[PAllen]

This just in: Stephen Hawking has completely remodeled black holes, eliminating the event horizon and spaghettification and replacing it with a "wall of fire".

He just replaced a true horizon with an apparent horizon, which makes virtually no difference to discussions on this thread. His paper rejects the firewall hypothesis. It would help to actually read the paper.

 

[.Scott]

He just replaced a true horizon with an apparent horizon, which makes virtually no difference to discussions on this thread. His paper rejects the firewall hypothesis. It would help to actually read the paper.

When I first posted, I couldn't find a link to the original paper. But now, here it is:
http://arxiv.org/pdf/1401.5761v1.pdf
I'm not sure whether it makes a difference or not. He's saying that below this apparent horizon is a chaotic layer with the ability to so scramble energy that, in effect, information is lost. That doesn't sound like a healthy place to be.

 

[PAllen]

When I first posted, I couldn't find a link to the original paper. But now, here it is:
http://arxiv.org/pdf/1401.5761v1.pdf
I'm not sure whether it makes a difference or not. He's saying that below this apparent horizon is a chaotic layer with the ability to so scramble energy that, in effect, information is lost. That doesn't sound like a healthy place to be.

It may not be healthy, but it is just a result of noting that the classical no hair theorems say nothing about interior of apparent horizon (they describe exterior observations), and real collapses can't have perfect symmetries, so the interior will chaotically contain information about the details. Note, he claims information is not lost, only effectively inaccessible in the same sense as a chaotic classical system. My point is that macroscopically, his new picture is indistinguishable from a classical BH externally. Fall through the horizon is macroscopically the same as well. The difference is that the idea of an extended smooth interior fall until close to the singularity for an old, isolated, supermassive BH is no longer expected.