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[Starver]

Our (internal) senses cannot propagate faster than light (in fact, significantly slower) so increasing the separation of two sensory elements that might create non-instantaneous reaction to anything gravitational, but long before that your head will be wondering if your feet have started walking yet and your feet will be wondering how long it will be before you are not still stubbing your toes on that rock.

edited for awful editing

[wierd]

Hmm.. Strange thought borne from this discussion.

(this is just insane pontification and mental masturbation, but feedback is welcome.)


One could envision a non-spinning black hole as being analogous to a standing gravity wave with an infinite amplitude, because the amplitude is being reinforced by the matter it has pulled inside.

With that analogy in mind, a more understandable gravity wave (such as from a neutron star merger)  could be seen as an expanding spherical shockfront. If the amplitude of that shockfront is sufficient, that it too can scoop up even tiny amounts of matter as it expands, and overpower all other forms of repulsion such that singularity formation at the crest of the wave is inevitable, an interesting kind of singularity should occur, right?  One that is spherical, and keeps expanding outwards, but is hollow inside?

If it failed to keep eating, it would shatter into a shower of high speed black holes,  but if rate of ingestion was sufficient to match its rate of expansion, this would occur, right?

Some part of my brain says this cannot happen because massed objects, (including singularities) cannot travel at light speed, and thus cannot be sustained in the critical section of the wave as it propagates...  but still...  hmmm...

[Hanslanda]

This conversation is way over my head but that last thing vaguely sounds like a black hole bomb.

[Max™]

Feynman already made it more understandable: http://www.feynmanlectures.caltech.edu/II_42.html#mjx-eqn-EqII423

Set out an arbitrarily accurate grid across the entire planet, get the area, get the circumference, calculate what the radius should be, then dig yourself one hell of a hole to measure directly and learn it's 1.5 mm deeper than it was supposed to be, our star is half a kilometer deeper than you calculated, and a black hole from the outside seems to be infinitely deeper than it should be. Lots of possible ways shit inside an event horizon might look, but mathematically one would expect all worldlines to terminate at the singularity in finite time, or put another way, you could point and say "the future is over there" because the future is literally over there for everything inside an event horizon... we think.

All that goes out the window if some of the weirder models turn out to be true.

[wierd]

A point singularity is indeed the simplest (and most likely to appear naturally), yes.

But there are other kinds of mathematical singularities.  Some functions can collapse into an infinite line type singularity.  Other modifications of that outcome can close the line into a circle for the function that produces it.

A hollow sphere with zero thickness would be the 3space decomposition of the closed circle solution.

The idea was that the g-wave makes space "deeper" than it should be, in the same way that a gravity well does to a massed object. The G-wave could have sufficient amplitude that when matter interacts with it, it forces the matter to exceed the schwarzchild radius limit, and thus collapse.  (this would be one hell of a g-wave but still..)  When matter collapses like that, it itself produces a small g-wave from the collapse. That wave could be used to reinforce this doom-and-gloom expanding sphere of oblivion, preventing it from losing amplitude as it expands, as long as it keeps interacting with matter.

Again, I know this cannot happen, because the resulting cloud of point singularities would not stay embedded in the wave. (they are massed, and the wave is massless. The wave will always drop them.)

[Kagus]

Have we actually observed a black hole collapsing/dying, or evidence to indicate that one has done so in the past?

The idea of spacetime and its implications for time progression in extreme gravity just brings up some troubling questions... At least for me, but I'm an idiot.

[wierd]

time dilation has been experimentally proven, as has frame dragging.

https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment
https://en.wikipedia.org/wiki/Gravity_Probe_B

[Kagus]

I'm aware that at least some measure of time dilation has been proven (and it's even necessary to account for it with GPS calculations, due to one satellite second being slightly different from one earth second), I'm just trying to imagine what that means in the extremes of a black hole's gravity... I've heard of singularities described as being "ruptures" or otherwise "breaking" space and gravity, which would imply that the -time component of spacetime would similarly end up "broken".

So if the center of a singularity is so incredibly dense as to create an unimaginably powerful gravity impression, then the flow of time at that center must also be modified to a similar degree... Implying that, for the intents and purposes of the rest of the non-singularity universe, the core of a black hole has effectively stopped moving through time.

Which could also mean that for an "outside observer", matter moving towards the center of the singularity would first accelerate as it nears the middle and comes under the influence of the stronger gravitic pull... And then slow down again as time dilation caps its relative movement. Eventually you reach a point where matter is moving at near-light speed towards the center, but that relative near-light speed is effectively static compared to outside the gravity well due to time dilation.

So what's happening at the center? Does time actually stop as gravity reaches its maximum strength, resulting in an "immortal" black hole that will remain in perpetuity because the reactions that would lead to the singularity's eventual collapse simply don't "have the time" to proceed?

Or is this rather just a misguided train of thought rising from an incorrect assumption of how time functions as a dimension and its actual relationship with 3D space?

[Madman198237]

We call that thing at the center of the black hole the "singularity" of the black hole. This is a fancy term that is scientist-speak for "I dunno".

Most of our equations break down when we attempt to apply them across an event horizon or to the inside of a black hole, we just don't know what could possibly be in there or how it works.


Yes, time does do almost exactly the really strange things you described as you approach a black hole, by the way.

[Trekkin]

We call that thing at the center of the black hole the "singularity" of the black hole. This is a fancy term that is scientist-speak for "I dunno".

Most of our equations break down when we attempt to apply them across an event horizon or to the inside of a black hole, we just don't know what could possibly be in there or how it works.

Well, no. A gravitational singularity is simply a point where gravity is calculated to be infinite regardless of coordinate system, which is aphysical. It's a mathematical artifact, not a physical object, and functionally describes a region where quantum effects dominate over gravitational effects. You could as well argue that quarks are "scientist-speak for 'I dunno.'"

[Starver]

I'm aware that at least some measure of time dilation has been proven (and it's even necessary to account for it with GPS calculations, due to one satellite second being slightly different from one earth second),

Doubly so.

Special Relativity (frame-movement requiring time adjustments in one direction) and General Relativity (being less in the gravity well than us, it has to be adjusted in the other direction). They don't cancel out, but when the satellites were sent up they were given software switches able to make them not account for each effect, just in case they didn't happen as predicted. (Spoiler: they did, so two decades of GPS use has been confirming there's exactly what we think there is in those (relatively mundane, but still effective) realms of weirdness.)

[Madman198237]

-snip-

Well, no. A gravitational singularity is simply a point where gravity is calculated to be infinite regardless of coordinate system, which is aphysical. It's a mathematical artifact, not a physical object, and functionally describes a region where quantum effects dominate over gravitational effects. You could as well argue that quarks are "scientist-speak for 'I dunno.'"

Yes, it's a mathematical artifact, probably. But we still don't actually know what is there and what it does, hence why the term singularity can be equally-well-used to apply to a point in space that we don't understand because the math breaks down. Besides, I'm paraphrasing (IIRC, maybe it was somebody else) Phil Plait when I use the words "singularity is a word for 'we don't know'", so, you know, if he thinks that's a valid way to summarize/simplify the concept of the center of a black hole I'm perfectly willing to just re-use his terminology, since I know far less about the subject than he does.

[Trekkin]

-snip-

Yes, it's a mathematical artifact, probably. But we still don't actually know what is there and what it does, hence why the term singularity can be equally-well-used to apply to a point in space that we don't understand because the math breaks down. Besides, I'm paraphrasing (IIRC, maybe it was somebody else) Phil Plait when I use the words "singularity is a word for 'we don't know'", so, you know, if he thinks that's a valid way to summarize/simplify the concept of the center of a black hole I'm perfectly willing to just re-use his terminology, since I know far less about the subject than he does.

"An astronomer or maybe somebody else probably said something like this somewhere I'm not going to cite so don't blame me if I parroted something inaccurate" is certainly an interesting argument, but hardly a strong one.

That having been said, it's fundamentally incorrect to think of uncertainty in such binary terms, although you're hardly unique in doing so. A gravitational singularity is not "a point we don't understand", full stop; we know, by dint of it being a gravitational singularity, that it's a point where gravity doesn't work like it does elsewhere in the universe, and it's possible to glean considerable insight from that fact. We also know, and can confirm by observation, that whatever laws govern the behavior of the singularity do not apply outside it to the exclusion of normal gravitational phenomena, because things orbiting (putative) black holes work as though they're orbiting any other large mass. The existence of the event horizon further informs our understanding of the area around and within the Schwarzschild volume, thanks in part to no-hair and other bounds we can put on what crosses it in what direction.

Nor is it correct to say the math "breaks down"; the result is entirely correct, just aphysical, which should tell you that our assumptions about the matter inside that region don't actually apply -- and, in fact, no one ever thought they would. That doesn't mean they're total enigmas, just that they play by different rules.

A gravitational singularity is a specific mathematical artifact arising from the inapplicability of our normal field equations to specific phenomena. It is not a general purpose "gosh, I dunno" and it's absurd to suggest we can equate the two.

[Gentlefish]

LANDING SOON!

[Madman198237]

Um, it was definitely an astronomer, just possibly not Dr. Plait.

Anyway, the terminology is not necessarily binary though you're welcome to strawman it into binary terms if you wish. We don't understand it simply means that we cannot draw precise conclusions about it, not that we can't draw ANY conclusions about it.

Clearly you define "the math breaks down" differently than I do. When I say "the math breaks down" I mean "it spits out zeroes or infinities in places there cannot physically be zeroes or infinities". It's not like some Lovecraftian horror devours parts of the equations and literally breaks the math, but rather that the equations at this particular point cease to properly describe reality.

I mean, it's pretty much equivalent though. If you have such a singularity at a point in space in your equations, you cannot describe that point in space. You do not know what happens there. You can guess and estimate and provide bounds on what can be happening there, but you do not (presently) KNOW, because your theory cannot properly describe it.