Some black hole questions, I think I brain is broken.

[Hoki]

First and foremost, I am NOT a scientist or math person. I just watch science stuff on TV.

The reason I even have these questions is because I was day dreaming and ended up on a logic path that singularities orbit each other at the speed of light or faster and thus travel back through time. DERP

 

1) I have the understanding that a black hole has a singularity at the center which is a massive object of infinite density. Does this mean that the singularity has no measurable size? I just assumed that it has no size I didn't see that on TV or anything.

 

2) IF a singularity has no size, then when we talk about a black hole being supermassive or large, we're only talking about it's event horizon correct? This assumes a singularity has no size. :\

 

3) IF 1 and 2 are true, then when we talk about black holes merging/combining, are we talking about two singularities merging or are we talking about 2 or more singularities orbiting each other but sharing the same event horizon bubble thing. And by that I mean the singularities aren't merged but their combined gravity make it so that light cannot escape the same spherical area.

 

4) I have the understanding that as two objects orbit each other more closely, the faster the orbit becomes, and the slower the two object approach each other. Is this correct?

 

5) Assuming 5 is correct and 1 is correct, wouldn't two sizeless objects just continue to orbit each other forever?

 

6) Assuming 6 is correct, is it possible for two singularities to orbit each other at the speed of light?

 

7) And then finally, assuming all of the above is correct, is it possible for two singularities to orbit each other faster than the speed of light?

 

6 and 7 seem to break the laws of physics and since singularities do exist in this universe, I must be getting something very wrong somewhere.

 

Edited May 10, 2013 by Hoki

[ajb]

1) I have the understanding that a black hole has a singularity at the center which is a massive object of infinite density. Does this mean that the singularity has no measurable size? I just assumed that it has no size I didn't see that on TV or anything.

Classically the singularity at the center of a non-rotating black hole is a point, for a rotating one we have ring singularities of zero thicnkness.

 

Anyway, one would expect quantum effects to smear out these singularities and as such no-one beleives singularities are actually realised in nature. However, without a proper quantum theory of gravity, it is impossible to say exactly what happens.

2) IF a singularity has no size, then when we talk about a black hole being supermassive or large, we're only talking about it's event horizon correct? This assumes a singularity has no size. :\

Yes, by size we usually mean the size of the event horizon.

3) IF 1 and 2 are true, then when we talk about black holes merging/combining, are we talking about two singularities merging or are we talking about 2 or more singularities orbiting each other but sharing the same event horizon bubble thing. And by that I mean the singularities aren't merged but their combined gravity make it so that light cannot escape the same spherical area.

This is a sensible question to ask. I think that the two sigularites will spirall in and merge.

 

However what happens near a black hole is not nessisarily what a distant observer sees.

 

As far as a distant observer is conserned, he never sees an object actually pass the event horizon.

4) I have the understanding that as two objects orbit each other more closely, the faster the orbit becomes, and the slower the two object approach each other. Is this correct?

To conserve angular momentum they speed up.

5) Assuming 5 is correct and 1 is correct, wouldn't two sizeless objects just continue to orbit each other forever?

They could have stable orbits, but that is not nessisarily the case.

6) Assuming 6 is correct, is it possible for two singularities to orbit each other at the speed of light?

 

7) And then finally, assuming all of the above is correct, is it possible for two singularities to orbit each other faster than the speed of light?

You can have angular effects that give apparant local faster than speed of light motion. But I am sure that the singularities would not actually travel faster than light. Asking me to prove it is another question!

 

There are lots of papers about the evolution of orbiting black holes, I don't know if you can find proper answers in some of them. Numerical stuidies of black holes is outside my area of expertese.

[Hoki]

Classically the singularity at the center of a non-rotating black hole is a point, for a rotating one we have ring singularities of zero thicnkness.

 

Anyway, one would expect quantum effects to smear out these singularities and as such no-one beleives singularities are actually realised in nature. However, without a proper quantum theory of gravity, it is impossible to say exactly what happens.Yes, by size we usually mean the size of the event horizon.This is a sensible question to ask. I think that the two sigularites will spirall in and merge.

 

However what happens near a black hole is not nessisarily what a distant observer sees.

 

As far as a distant observer is conserned, he never sees an object actually pass the event horizon.To conserve angular momentum they speed up.They could have stable orbits, but that is not nessisarily the case.You can have angular effects that give apparant local faster than speed of light motion. But I am sure that the singularities would not actually travel faster than light. Asking me to prove it is another question!

 

There are lots of papers about the evolution of orbiting black holes, I don't know if you can find proper answers in some of them. Numerical stuidies of black holes is outside my area of expertese.

Thanks ajb!

 

Again I must pretense that I am no scientist, I'm either quoting or misquoting stuff I've read online or watched on science programs.

 

Never heard of a ring singularity, more stuff for me to read into.

 

I keep forgetting about the regulating effect of approaching the speed of light! Its like limits in math. You can approach the speed of light, even if you accelerate infinitely, time will just keep dilating.

 

What is the alternative to the center of a black hole if not a singularity? Are there other states of matter that can have enough gravity that it would prevent light from escaping? Like a dense, fused ball of particles?

 

As for the merging part, assuming they are two singularities merging, both with infinite density.

Is it possible to draw matter/energy out of a singularity after its already gone inside? Thats part of what I cant wrap my head around. A singularity is believed to only be able to eat so much matter/energy at a time, and another infinitely dense singularity is probably more than another singularity could hope to swallow at once.

 

Now I'm making the assumption that a black hole has to gobble up another black hole and cannot simply absorb into each other. Quasars have this overfeeding problem I believe. They can't eat everything that's being served to them all at once, so they spit out huge jets.

 

Getting lost upside down in thought again.. just gonna write questions as they come to me.

 

1) Is a singularity an infinitely dense particle or can it be infinitely dense and made up of pure energy?

 

2) When matter is consumed by a singularity I've heard that it is theorized to enter at the speed of light or near the speed of light. Would this mean that everything that is consumed is first pulled in as pure energy?

 

3) Can matter/energy ever be pulled or extracted from a singularity after being consumed, even by another singularity that is much more massive? I don't know the math involved in black holes, but if something is infinitely dense, I would just assume you would need infinite pull in order to pull energy or matter out of it.

 

4) Could two or more orbiting singularities in an unstable orbit slingshot a blackhole out of a galaxy like stars can?

 

5) IF one of the merging singularities must be pulled apart in order for the other more massive singularity to eat it, would the less massive one blow up, or would it slowly leech away matter like binary stars do?

[ajb]

What is the alternative to the center of a black hole if not a singularity? Are there other states of matter that can have enough gravity that it would prevent light from escaping? Like a dense, fused ball of particles?

 

We just don't understand the quantum effects of gravity to really describe what we think lies in the centre of a black hole. The object would not really have a definite size, it would be fuzzy with a typical scale at around the Planck length. When viewed at larger scales it would look like a point, as it must do according to general relativity.

 

As for the merging part, assuming they are two singularities merging, both with infinite density.

Is it possible to draw matter/energy out of a singularity after its already gone inside? Thats part of what I cant wrap my head around. A singularity is believed to only be able to eat so much matter/energy at a time, and another infinitely dense singularity is probably more than another singularity could hope to swallow at once.

 

You should examine the Penrose process. The trouble as I see it generally, is that one can only extract energy from black holes when that energy is stored outside the event horizon. Extracting energy from the sigularity itself, if there were come method, could not be used to extract energy from the black hole.

 

Now I'm making the assumption that a black hole has to gobble up another black hole and cannot simply absorb into each other. Quasars have this overfeeding problem I believe. They can't eat everything that's being served to them all at once, so they spit out huge jets.

 

Quasar emissions are powered by the accretion disk. Material gets heated as it falls into the black

hole.

 

1) Is a singularity an infinitely dense particle or can it be infinitely dense and made up of pure energy?

 

The singularity at the centre of a black hole (not a coordinate singularity, which is something else) is according to general relativity a point.

 

 

2) When matter is consumed by a singularity I've heard that it is theorized to enter at the speed of light or near the speed of light. Would this mean that everything that is consumed is first pulled in as pure energy?

 

We just don't really understand what happens right at the singularity.

 

For objects of small, but finite size, we have the effects of strong tital forces that would rip the object to peices.

 

3) Can matter/energy ever be pulled or extracted from a singularity after being consumed, even by another singularity that is much more massive? I don't know the math involved in black holes, but if something is infinitely dense, I would just assume you would need infinite pull in order to pull energy or matter out of it.

 

I have already pointed to the penrose process. The other thing you should be aware of is Hawking radiation. Black holes should be loosing energy all the time, however for stella mass and larger black holes this energy loss is tiny.

 

 

4) Could two or more orbiting singularities in an unstable orbit slingshot a blackhole out of a galaxy like stars can?

 

Black holes can be thrown out of a galaxy in exactly the same way as stars. Gravitationally, stars and black holes "look the same".

 

5) IF one of the merging singularities must be pulled apart in order for the other more massive singularity to eat it, would the less massive one blow up, or would it slowly leech away matter like binary stars do?

 

I don't know what pulling apart a singularity means.

[Airbrush]

"4) Could two or more orbiting singularities in an unstable orbit slingshot a blackhole out of a galaxy like stars can?"

 

I think, as with stars, it would take 3 supermassive black holes to slingshot one of them out. Or it can be done with a supermassive black hole, and 2 stellar-mass black holes.

 

There are hypervelocity neutron stars, so maybe there are also hypervelocity stellar black holes.

Edited May 14, 2013 by Airbrush

[Hoki]

Thanks guys, that clears up a few things.

 

I also don't know what pulling apart a singularity means.

 

I thought a black hole eats matter by pulling it apart in bite sized chunks, but thats probably not required.

[ajb]

Thanks guys, that clears up a few things.

 

I also don't know what pulling apart a singularity means.

 

I thought a black hole eats matter by pulling it apart in bite sized chunks, but thats probably not required.

 

Due to the large tidal effects you get what is called spaghettification, of if you are from the orient, the noodle effect. Finite sized objects get strectched and compressed in the presence of strong tital forces. As classically a singularity is a point, there is no spaghettification, but then in light of quantum gravity the singularity is a fuzzy object of some "average size" maybe there would be some spaghettification. Without a proper theory of quantum gravity I could not really say what happens.