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Black hole singularity is a surface not a point

arxiv.org

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Re: Black hole singularity is a surface not a point

#151

Post by inigyou »

IsTom wrote: post #119
rf15 wrote: post #57

Earlier quoted context omitted.

As someone with basically only popsci knowledge of black holes: people claiming it would be a literal point never made much sense - fundamentally, common sense (as much as it can apply here) dictates that you cannot compress particles to an absolute point.

Yeah, wouldn't this cause trouble with Pauli exclusion principle?

Only if they all had the same energy level.

And if they didn't form a superconductor. I'm not sure why they would but if they did they would violate it. That's actually what makes superconductors superconducting - the really weird state where electron pairs act like bosons.

Re: Black hole singularity is a surface not a point

#152

Post by inigyou »

somat wrote: post #98
rf15 wrote: post #57

Earlier quoted context omitted.

As someone with basically only popsci knowledge of black holes: people claiming it would be a literal point never made much sense - fundamentally, common sense (as much as it can apply here) dictates that you cannot compress particles to an absolute point.

My rather pop-sci understanding is that when you start playing around with relativity math, trying various masses and densities you hit something rather worrisome. As you approach some great, but still possible, value the plot goes infinite, the singularity. This is bad for the theory because going asymptotic like that usually indicates a fundamental problem in the math. But relativity does so well everywhere else...…

AFAIK from the outside point of view it takes infinite time. We see the falling object redshift to infinity (blackshift, really) and merge into the black sphere we observe.

But in the object's own time coordinates the math says it does hit the singularity. If you fell in you wouldn't die of old age before you hit it.

Re: Black hole singularity is a surface not a point

#153

Post by catlifeonmars »

inigyou wrote: post #149
sigmoid10 wrote: post #90

Earlier quoted context omitted.

>The fact that both have the same name They don't just have the same name, they are the same thing. A Schwarzschild black hole has both: a removable singularity at the event horizon that is just an artefact of a particular choice of coordinates and a true non-removable mathematical singularity at r=0 where curvature really does go to infinity. It also wouldn't be much of an issue in classical physics, because this si…

We don't actually know if a black hole has an inside. Some theories/hypotheses say spacetime just stops at the event horizon.

This is like saying the Riemann zeta function is only defined for real numbers. You can always extend the singularity mathematically by incorporating new axioms.

My point is, it’s not super meaningful to argue whether a black hole has an inside.

Re: Black hole singularity is a surface not a point

#154

Post by inigyou »

rramon wrote: post #142
somat wrote: post #115

Earlier quoted context omitted.

My rather limited understanding is that. first there is a lot going on and due to the forces and gravitational gradients involved, matter itself probably would not survive the journey that close to the horizon. But ignoring that, When in compressed time, from the point of view of someone freefalling, timewise everything is normal, the rest of the universe has accelerated and in the case of a black hole has just aged…

I can only guess as well, infinite time compression might result in a big bang when it applies to everything. All black holes could lead to the same moment causing the bang.

There are a lot of curious coincidences between properties of black holes and properties of the whole universe that lead some physicists to the idea that they could be connected. There's also that Penrose diagram showing another universe beyond a black hole. (Seems like a copout to me though. Penrose diagrams are drawn in 1D space, so the black hole cuts the universe in half. If you had 2D or better space couldn't you just travel around behind the black hole to the other side of it?)

Re: Black hole singularity is a surface not a point

#155

Post by inigyou »

XorNot wrote: post #78
rf15 wrote: post #57

Earlier quoted context omitted.

As someone with basically only popsci knowledge of black holes: people claiming it would be a literal point never made much sense - fundamentally, common sense (as much as it can apply here) dictates that you cannot compress particles to an absolute point.

Common sense - the experience gained from your common everyday experience of reality - does not apply in black holes. Common sense would tell you they can't exist at all because you can't compress atoms - you have lived your entire life with atoms being entirely incompressible for the practical purpose of anything you do. Leaning on common sense to discuss fundamental physics has been wrong since round about the star…

Common sense actually says that atoms don't exist and if you squish cheese really hard you just get really hard and slightly smaller cheese, or maybe you invent a new type of dairy product.

Re: Black hole singularity is a surface not a point

#156

Post by inigyou »

TheOtherHobbes wrote: post #107
goatlover wrote: post #68

Earlier quoted context omitted.

Aren't fundamental particles like electrons and quarks treated as points?

Points are a realist view - there's a real object there. Although some physicists disagree, QM slants very anti-realist. There are no objects anywhere, no particles, no waves, only probabilistic interactions, some of which can be snapshotted into localised partially definite results. So there are only interactions between probability distributions in space and time, and "particle-like events." No pointy objects, and…

Wouldn't it be both? Electrons occupy probability clouds, but the overall probabilities of things happening are summed over the whole cloud as if, at each point, the electron was a point particle at that point?

Re: Black hole singularity is a surface not a point

#157

Post by inigyou »

XorNot wrote: post #88
aqfamnzc wrote: post #66

Earlier quoted context omitted.

Sounds like that would be true if you were inside any closed surface.

Not quite: inside a closed surface you can't escape, but things can repeat. You can avoid a coordinate, for example by choosing not to go there, or revisit another one repeatedly. A black hole on the other hand doesn't have that: you cannot revisit old locations - attempting to do so moves you closer to the singularity.

Unless it's a spinning black hole, which contains closed timelike curves that can be reached from and can escape back to the outside universe?

Re: Black hole singularity is a surface not a point

#158

Post by inigyou »

sfink wrote: post #46

Off-topic, but it makes me think of "reasoning black holes": you get enough like-minded people together that they start reinforcing each other's logic and beliefs until not only those people get completely detached from reality, but anyone who interacts with them gets sucked in as well unless their own logic ("velocity") is adequate to skirt the edge and escape, forever altered by the experience. Similar questions ar…

I believe that's called an echo chamber, and exemplified by a board meeting.

Re: Black hole singularity is a surface not a point

#159

Post by inigyou »

0x20cowboy wrote: post #33
ben_w wrote: post #24

Earlier quoted context omitted.

Normally people think of gravity as pulling on objects. You can instead think of it as pulling on the space those objects are in. A black hole happens when there is enough gravity that space gets pulled inwards somewhere, at at least the speed of light. Gravity falls off with distance, and the distance where space is being pulled inwards at exactly the speed of light is called the "event horizon". It has this name be…

> Normally people think of gravity as pulling on objects. You can instead think of it as pulling on the space those objects are in. (Very uneducated person here) I’ve always wondered if large objects caused gravity, or if maybe large objects form in the places where there is a lot of gravity. This is probably elementary, but I’ve never looked in to it. Maybe today is the day!

Scientists have directly measured the gravity coming from big balls of lead. The gravity didn't make the scientist put the lead there, and the gravity wasn't there before the lead. The lead must have made the gravity.

Re: Black hole singularity is a surface not a point

#160

Post by inigyou »

dekdrop wrote: post #13

How does one descr blackhole to a non-physicist without losing much accuracy? I just it of a very-dense-object.

Why not just say it's something with such strong gravity you can't escape even if you go at the speed of light? Maybe that loses too much accuracy for you?
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