Spinning Singularities?

[Riogho]

Okay, I know there is observational evidence for spinning black holes, so therefore I must be confused about something, and I want you to tell me what.

 

 

If you have a star that is spinning, therefore it has orbital angular momentum (mass revolving around a point), then as it is collapsing in a black hole, it shoots out particles that probably take some of that with it, but not all, and because angular momentum is conserved the black hole will spin.

 

However, it is my understanding that the actually 'massy' part of the black hole is a simple point structure with a large mass and density with (almost?) infinite curvature. But if it is a point, there is no mass to revolve around this point therefore no more orbital angular momentum.

 

I've probably screwed up already, but my idea is that like an electron (which is a point particle that has angular momentum) instead of having orbital angular momentum it is transformed into spin angular momentum, (where it acts as if it is 'spinning' though it does not) this would seem to explain it away.

 

Correct? No?

 

Thanks for the help.

[Dark matter]

I'm not totally sure, so don't hurt me if I'm wrong but the particles inside the center of a black hole are converted into height the size of an atom, infinite volume, and as you said, infinite curvature. However particles at the center of a black hole are under such tremendous force at such a small area (Hence P=F/A), they only stay in that infinite stage for fractions of a millisecond, and are converted into energy.

[Riogho]

I've never heard that one. I know it is much smaller then an atom however, and it is supposed to be only a point.

[antimatter]

I've actually heard that it's approximatly

the size of a baseball.

[Riogho]

Then it definitely wouldn't be a singularity.

 

Which is what it is.

[Klaynos]

I've actually heard that it's approximatly

the size of a baseball.

 

GR tells us that blackholes are singularities... This can't really be true because QM has issues with it, and physicists don't like 0's they're not pleasant and they never turn out to be real.

 

So they're probably not singularities, but what's going on with blackholes we don't really know... our physics breaks down around them. So discussion on this and whether they are spinning or not spinning (tbh I think for conservation of angular momentum they should be) will be quite hard, although there's probably a bit of observable evidence out there...

[antimatter]

I don't think that they are singularities,

the amount of gravitational force pulls the space fabric into an inverted cone,

at least that's what I have read.

[Riogho]

Really, because I read singularity.

 

SOMEONE SMART!!! HELP!!!

[Martin]

Okay, I know there is observational evidence for spinning black holes, so therefore I must be confused about something, and I want you to tell me what.

...

 

Riogho you asked for somebody smart to address your confusion. I don't claim to be especially smart but I will try to help.

 

I don't know any reputable scientist who claims that singularities exist in nature. Do you? that is the sort of thing they say to journalists and which the write popularization books to sell to the public.

 

But by definition a singularity is a flaw in a manmade theory. A place where the formula fails to compute, where the model blows up and gives infinities or some nonsense answer. A singularity is not necessarily a POINT. It can be a point, a line, a circle. For a scientist a singularity represents the boundary of applicability of a model. Up to the boundary, it works, but then the model breaks down.

 

the black hole singularity is a breakdown or glitch in General Relativity, not in nature. Other manmade theories have had singularities and they have been fixed by improving the theory.

 

So it might be a good idea simply not to worry about spinning black hole singularities, because Nature does not have singularites and what actually happens has not been discovered yet.

 

However if you don't care about Nature, and are a real General Relativity buff, then you would want to find out about the theory of Kerr spinning black holes and what THEIR singularities look like. And how they have spin!

http://en.wikipedia.org/wiki/Kerr_metric

 

Remember that a singularity does not have to be a point (that is just the impression that popular mass market books and magazines give). So it might be quite interesting to delve into spinning BH singularities. they might not be points or even spherically symmetric. The event horizon might be oblate etc. etc. All sorts of good stuff.

 

But above all remember that what you are finding out about is a model, and indeed the specific locus where a model breaks down, and not Nature.

[Riogho]

Sometimes I wish there was popular science out there that wasn't dumbed down, just math free.

 

*sighs*

 

I'm just sitting patiently with my thumb up my butt waiting for my math education to catch up with my science.

[antimatter]

I know how you feel.

I've been reading a lot of science books that are above where my science education is, but unfortunatly I haven't really learned anything in math yet that can help me with science.

[Riogho]

I mean, don't get me wrong I know my math well enough, I taught myself enough calculus to get through the Feynman lectures on mechanics, but there is no way I can do the group theory stuff, etc, without a course or something on it. and that's where the good stuff is.

[antimatter]

Right, well you're probably in a much higher grade than I am...

[Riogho]

*shrugs*

 

I'm a junior.

[Martin]

Sometimes I wish there was popular science out there that wasn't dumbed down, just math free.

...

 

I mean, don't get me wrong I know my math well enough, I taught myself enough calculus to get through the Feynman lectures on mechanics,..

 

I'm impressed. You are doing all right. It was also quite respectable that you figured out on your own that something was wrong with the schwarzschild black hole picture----or limited: it couldn't handle spin, I mean angular momentum. Seems like you have some math sense or some physical intuition.

 

How does a classical point spin? (you may have been thinking)

 

that's good. It might not be right, but it means you thought. You might try to get one of the others to teach you something.

Atheist is a physics PhD student. I think ajb is too. there is swansont and severian who are pros. Someone with a fourdigit name like "5614" is an advanced undergrad physics major, I think. some of the phd students here may have moved on to postdoc, I don't keep track.

 

Bug these guys, if you think you are smart and can learn something from them.

 

So you did Volume 1 of the threevolume Feynman Physics Lectures? With selftaught calculus? You are in highschool? Or have I misunderstood and gotten you confused with someone else.

[NeonBlack]

Great post Martin (#9).

I was going to post something to a similar effect, but I think you said it better than I could have.

I die a little bit each time someone says something like "The big bang was a singularity" because I suspect that most people who talk about things like that have no idea what the word means.

 

I have been thinking that it would be good to be more careful with our language. Instead of saying "a black hole is a singularity," we should say something like "GR is singular in a black hole." I think this would retard the misconception that singularities are something that exist in nature.

 

And don't forget about Klaynos. He'll never stop nagging you.

[ajb]

I just want to say that you have to be careful to make the distinction between coordinate singularities (bad choice of coordinates), the event horizon(s) (if it exist; cosmic censorship etc.) and true singularities where the curvature genuinely blows up. (All stated in the context of general relativity.)

[kaneda]

A singularity being one dimensional cannot spin yet we detect that all black holes spin so they must have size. I think "infinitely dense" is a wrong guess since I don't think even gravity could escape such an object.

 

Neutron stars can have an escape velocity of 2/3 light speed. Still neutrons! So maybe for such an increase in mass/gravitational forces, black holes have a compact spinning ball of electrons, quarks and such at their centre?

[antimatter]

Exactly, I'm a freshman next year...

[Riogho]

I'm impressed. You are doing all right. It was also quite respectable that you figured out on your own that something was wrong with the schwarzschild black hole picture----or limited: it couldn't handle spin, I mean angular momentum. Seems like you have some math sense or some physical intuition.

 

How does a classical point spin? (you may have been thinking)

 

Yea, I knew how an object with volume would spin, (mass revolving around a point, like a top or the such), and I know that there is an intrinsic property of elementary particles (which are treated as point-like) that since they have angular momentum and yet no volume, they don't actually spin, but just have the properties of something that spin, and my original question was since the black hole started out as a spinning star (obviously orbital angular momentum) if that angular momentum was actually transformed into spin angular momentum.

 

But now that you say it isn't a singular point at all it kind of breaks down my idea. But then again I guess it breaks down everyone's theory there, eh?

 

 

that's good. It might not be right, but it means you thought. You might try to get one of the others to teach you something.

Atheist is a physics PhD student. I think ajb is too. there is swansont and severian who are pros. Someone with a fourdigit name like "5614" is an advanced undergrad physics major, I think. some of the phd students here may have moved on to postdoc, I don't keep track.

 

Bug these guys, if you think you are smart and can learn something from them.

 

I'd rather not upset my coworkers of the future

 

So you did Volume 1 of the threevolume Feynman Physics Lectures? With selftaught calculus? You are in highschool? Or have I misunderstood and gotten you confused with someone else.

 

 

Yes, I've worked my way through the first half of my Christmas present (Volumes I and II of the feynman lectures), which means I've completed volume one, with just a minimal bit of help from my precalc teacher.

 

Yes, I am in high school.

 

And people have gotten me confused with Keanu Reeves before. Just checkin.

[Klaynos]

I think I speak for most people with knowledge when I say they don't mind being bugged, it's good to pass on information and knowledge to those who aspire to gain it... Physicists in my experience are always very very willing to answer questions and to teach people knew things.

 

My first summer placement a few years ago in my physics school, I said to the post doc that was showing me how to use a silver evaporator, that he must find it annoying having to show summer students this kind of thing when he could be getting on with proper research, his response was completely the opposite of this and he said that it's great to show others how to do things so they can do it in the future. Physics is very collaborative, we're a very talkative bunch about our research or in fact anything that we know about if questioned....

 

Spread the knowledge, someone else will think of something you haven't!

[Martin]

Riogho, Klaynos,

we seem to be the only ones around Physics (Astro in particular) at the moment. I am used to Swansont being around.

 

If either of you sees a thread that is overly speculative, where you suspect the author could be just spouting words without an underlying quantitative understanding, please write me a PM about it.

 

You don't have to be sure it's wacky, if you suspect that it might be, don't hesitate to let me know. I'll make my own determination what to do. It is not like reporting a post for being spam, or something. You would be helping me out. I don't have time to check everything.

 

I only have partial moderator options, I can just perform limited housekeeping, I can't lock threads that are out of control (as a real moderator could).

The moderators names are in blue. Mine is in green. Swansont is a moderator but doesnt seem to be here just now.

 

Anyway, since we seem to be short-staffed just now. Please let me know about any threads that might need attending to, in the physics section.

If we do our best to keep the quality up, I'm optimistic that things will eventually improve.