Question: How is a gravitational singularity possible?

[RadarArtillery]

If this question has already been answered, please direct me to the thread. I tried to do a search, but came up empty.

 

The way I understand it, a black hole is a point in space where matter has infinite density. The question I have is: Doesn't this conflict with the idea that matter occupies space, and that no two bits of matter can occupy the same space? Wouldn't there be a point where it is impossible for something to become any more dense, because there just isn't any more space between particles?

 

If the density of the object in question was infinite, wouldn't the gravity it produced also be infinite?

 

If the density of the object in question was infinite, wouldn't it be compressed into an area that takes up no space at all, and therefore not exist?

[Moontanman]

If this question has already been answered, please direct me to the thread. I tried to do a search, but came up empty.

 

The way I understand it, a black hole is a point in space where matter has infinite density. The question I have is: Doesn't this conflict with the idea that matter occupies space, and that no two bits of matter can occupy the same space? Wouldn't there be a point where it is impossible for something to become any more dense, because there just isn't any more space between particles?

 

If the density of the object in question was infinite, wouldn't the gravity it produced also be infinite?

 

If the density of the object in question was infinite, wouldn't it be compressed into an area that takes up no space at all, and therefore not exist?

 

 

Your understanding of black holes is a bit simplistic.

 

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

[RadarArtillery]

 

 

Your understanding of black holes is a bit simplistic.

 

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

Well, that is what I'm asking questions for. If I understood them very well, I obviously wouldn't be asking questions about them.

*Click*

[Moontanman]

Well, that is what I'm asking questions for. If I understood them very well, I obviously wouldn't be asking questions about them.

*Click*

 

 

Well then, I guess you are glad i provided a link to that info...

[RadarArtillery]

 

 

Well then, I guess you are glad i provided a link to that info...

After reading this, yes, it answered one of my questions. My first two still stand, but should be taken to apply to the singularity itself. the last seems like it would be better asked somewhere else.

 

Understand that my motivation behind asking this is so that I don't go around saying things that aren't correct, and because I'm curious.

[ajb]

Doesn't this conflict with the idea that matter occupies space, and that no two bits of matter can occupy the same space?

It is not that simple when you take into account quantum mechanics, but okay it seems rather strange I agree. Now I direct you to my comments on your next question.

 

Wouldn't there be a point where it is impossible for something to become any more dense, because there just isn't any more space between particles?

Maybe so.

 

Physicists don't really think that the classical singularity found at the centre of a black hole us actually physically realised. It is expected that quantum mechanical effects of space-time itself will regulate this and so we will in effect have some maximum density allowed by nature. This should be quite high as we expect in some limit to recover the classical theory of black holes.

 

If the density of the object in question was infinite, wouldn't the gravity it produced also be infinite?

Yes and this is the seen as the curvature singularities in general relativity.

[RadarArtillery]

It is not that simple when you take into account quantum mechanics, but okay it seems rather strange I agree. Now I direct you to my comments on your next question.

 

 

Maybe so.

 

Physicists don't really think that the classical singularity found at the centre of a black hole us actually physically realised. It is expected that quantum mechanical effects of space-time itself will regulate this and so we will in effect have some maximum density allowed by nature. This should be quite high as we expect in some limit to recover the classical theory of black holes.

 

 

Yes and this is the seen as the curvature singularities in general relativity.

Thanks a bunch for your answers, ajb!

[hoola]

I can certainly see that there is no "infinite" gravity in the black hole, only a very high amount, and that there are no infinite anythings in the universe, as they seem to lead to break-downs in logic. I conclude there are no infinities even in math, and the physical universe is expressed in those limited mathematical terms, not simply measured by them..

I am a little curious as to the gravity of black holes....do they all have the same amount of gravity when measured at the event horizon? And if black holes are essentially "hitting the ceiling" on allowable gravity force in the natural universe, how is that force comparable to the gravity force of the original singularity that started everything? ..I have often heard of it referred to as having "infinite density and infinite gravity"....that seems an increasingly suspect idea if black holes along with other parameters of this universe are held to some finite limit...although is easy to think in a superficial manner that the singularity, while not being infinite, was of a greater density and gravity than the black holes that developed out of it later.....if the singularity did have a greater gravity/density force than is possible post inflation, could this be a reason for the one time only superluminality of the inflationary period?

one last question as to black holes...I have heard about possible mini-black holes naturally occurring in the upper atmosphere or at cern. I presume that these holes have an event horizon, albeit briefly before they evaporate. Does theory predict that a gravity force measured at the event horizon of the mini holes equal the force of the larger and more stable hole event horizons, at the center of galaxies? In other words, would black holes of various sizes have symmetrical structure values, and only vary in externally measured horizon size? How massive must a black hole be before it becomes stable and escapes rapid evaporation? And, indeed, does the hole's gravity peak at the horizon, or closer to the center of mass? And what about the center of the singularity? Is it is a true point with a minimum of dimensions, that being one, or dimensionless, as I have heard it described? If it is on a specific point on a one dimensional line, then cannot it be considered to be located on a minimum finite fraction of a single dimension, since it cannot extend into the theoretical length on any of the lines that might describe it's allowable physical position?...

Edited February 12, 2014 by hoola

[Strange]

If the density of the object in question was infinite, wouldn't the gravity it produced also be infinite?

 

But note that any given distance, the gravity will be exactly the same as that due to a normal object of the same mass at that distance. So, for example, if the Sun became a black hole, it would make no difference to the Earth's orbit.

[Endy0816]

Better to just call the density at the center undefined rather than infinite.

 

Density = Mass / Volume

 

likely we either don't understand the physics well enough(a minimum volume exists) or our density equation isn't developed enough for the situation.

 

Most of the effects of the 'whatever' are back behind the event horizon(escape velocity = speed of light). A lot of the answers to your questions on the interior are in the "unknown and possibly unknowable" category as a result.

 

There isn't a magic size, so much as needing the correct conditions to grow or not evaporate. Smallest we suspect is about 5-10 solar masses.

[ajb]

...do they all have the same amount of gravity when measured at the event horizon?

You need a way of quantifying this. One method is to look at the surface gravity which (loosely) is the acceleration needed to keep an object at the horizon. For the Schwarzschildblack hole this is

 

[math]\kappa = \frac{1}{4M}[/math],

 

in some suitable units.

 

It is more complicated for a Kerr black hole and for truly dynamic black holes I am not sure what can be said. However, astrophysical black holes will probably be very close to Kerr black holes over short periods of time.

[Endercreeper01]

Even though the density is infinite, the mass is not. Black holes have a finite mass, since they are enclosed in an infinitely small volume.

[hoola]

when you say infinite as regards to density, doesn't that mean that the density is as high as can be allowed in this universe, and not defacto an incalculable number associated with it's value? And I have to think the volume is not "infinitely" small, only a small volume, perhaps a single point, but of some theoretical plank-sized minimum volume state...

when infinities come through the door, logic goes out the window...