Black Holes

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skeptic

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ramparts":1i08utnb said:
A black hole certainly has a position in space and time which can be labeled using four dimensions.
Interesting thought, ramparts. Inasmuch as space is contracted to zero in the radial direction at the horizon and time dilated to zero as well, one wonders what those coordinates would be. Inside the horizon, some say the three space dimensions become three time dimensions and the one time dimension becomes a single space dimension. Others say that although the mathematics implies the dimensions become imaginary inside the horizon, that doesn't mean that space and time exchange roles. In any event, one wonders how one would specify the coordinates for location of the singularity.
 
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passingcloud

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Your opinions on this would be greatly appreciated.A black hole have infinite mass and density ,and infinitely small :cool: :D :D would surely fall via gravity through space.There is no reason that space shouldn't have an up and down.The assumed existance of wormholes and other dimensions rubbing together like soap bubbles in water implies a breakable barrier.An object of infinite m and g and infinitelty small would slip through any field less dense.while creating a massive gravitational pull it would create an ever widening suction vortex perhaps then causing the new formation of downward galaxes which when it had fallen forever would become self perpetuating and thus light appearing to be sucked into a black hole is just curving down the edge of newly formed galaxies.I hear that now scientists tracing black holes have noted they seem to be in a line outwards to deep space .This would also infer that they were falling downwards in the same direction.I could write considerably more but im sure you will get my drift and would love your feelings on this and hope this will give you something to think about .I live where Issac Newton used to ,his always giving me food for thought.
 
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origin

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passingcloud":11gsi0fx said:
Your opinions on this would be greatly appreciated.A black hole have infinite mass and density ,and infinitely small :cool: :D :D would surely fall via gravity through space.There is no reason that space shouldn't have an up and down.The assumed existance of wormholes and other dimensions rubbing together like soap bubbles in water implies a breakable barrier.An object of infinite m and g and infinitelty small would slip through any field less dense.while creating a massive gravitational pull it would create an ever widening suction vortex perhaps then causing the new formation of downward galaxes which when it had fallen forever would become self perpetuating and thus light appearing to be sucked into a black hole is just curving down the edge of newly formed galaxies.I hear that now scientists tracing black holes have noted they seem to be in a line outwards to deep space .This would also infer that they were falling downwards in the same direction.I could write considerably more but im sure you will get my drift and would love your feelings on this and hope this will give you something to think about .I live where Issac Newton used to ,his always giving me food for thought.
Welcome to spacedotcom.

Unfortunately I think that you ideas don't make much sense.

first you say
Your opinions on this would be greatly appreciated.A black hole have infinite mass and density ,and infinitely small :cool:
That is wrong, black holes do not have infinite mass.

You then say:
would surely fall via gravity through space.There is no reason that space shouldn't have an up and down.
This doesn't make any sense, things do not fall through space. Masses attract each other, there is no up or down which things fall.

It doesn't get any better from here.

You also said:
I hear that now scientists tracing black holes have noted they seem to be in a line outwards to deep space .This would also infer that they were falling downwards in the same direction.
Do you have any evidence of this - like a link?
 
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FlatEarth

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bdewoody":20ko4u4v said:
What I'm curious about is whether it's possible that there are enough black holes spread across the universe to make up most of the so called missing mass. Since they can only be detected by the activity of visible matter in their vicinity or the distortion of light from objects behind them it seems at least possible that they are responsible for some of that missing matter.
I've asked the same question because I was sure that was a better answer to the missing matter question than non-baryonic dark matter. It seems this is ruled out because there is a limit to the amount of baryonic matter in the universe based on how much deuterium is detected. The following is from an earlier post I made about dark matter.

During the first few minutes after the Big Bang, helium began to be synthesized, and that happened only when the energy levels in the universe were low enough for deuterium to survive. Most of deuterium, the isotope of hydrogen that has one neutron and one proton, got locked up in helium nuclei, but a small amount of it remained free. That amount is predicted to be a certain percentage of the universe made up of baryons (neutrons and protons).*

It was discovered that there is too much deuterium in the universe relative to the amount of baryonic matter that was detected. That also puts a limit on how much dark baryonic matter there can be in the universe, or in other words, a limit on brown dwarfs, planets, dust, and black holes formed from normal matter. More baryonic matter results in less deuterium. That means the remaining matter is something else: Non-baryonic dark matter.

* Source: The Extravagant Universe by Robert P. Kirshner
 
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csmyth3025

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In view of the fact that the singularity contained within the event horizon of a black hole is believed to be a point of immense mass and density (I'm reluctant to characterize it as infinite density) and, I would suppose, also immense temperature - I wonder if the phisics community considers the singularity to be similar to the initial state of affairs at the very beginning of the Big Bang. I welcome comments from anyone who has knowledge in this area. If the two are considered dissimilar in certain respects, please let me know what those differences may be.

Chris
 
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origin

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csmyth3025":rn24rh0c said:
In view of the fact that the singularity contained within the event horizon of a black hole is believed to be a point of immense mass and density (I'm reluctant to characterize it as infinite density) and, I would suppose, also immense temperature - I wonder if the phisics community considers the singularity to be similar to the initial state of affairs at the very beginning of the Big Bang. I welcome comments from anyone who has knowledge in this area. If the two are considered dissimilar in certain respects, please let me know what those differences may be.

Chris
A singularity by definition has infinite density. So it sounds like you do not think there is a singularity but instead an area of very high density. I would also imagine that the temperature is very high but of course it isn't measureable because no EM radiation can escape across the event horizon! I would say a black hole is similar to the pre big bang state of the universe - ah probably :? .
 
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csmyth3025

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If a singularity is, indeed, infinitely dense but is not, as you pointed out in your earlier post, infinitely massive then it must have zero spatial dimensions. I read another post (by skeptic, Jan 29) which related that possibly the three spatial dimensions become time-like and the single time dimension becomes a spatial dimension within the event horizon. Is this proposal an outcome of Einstein's field equations or is it just speculation?

I can vaguely conceive of a one dimensional object (a "line" of zero width if viewed from the "side" and a "point" of zero radius if viewed "head-on"). In this regard I can only imagine "zero" as being some immeasurably small unit of length such as the Plank length - equal to 1.616252(81)×10−35 meters. I can also vaguely imagine how such an object might possess seemingly infinite density but finite mass. I'm at a total loss when it comes to imagining three dimensions of time, however.

Are there people who can actually picture these sorts of things in their heads?

Chris
 
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Saiph

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@passingcloud...I'm afraid you're really misinformed. I suggest reading a couple of books about black holes, look for some by an author "Kip Thorne".

@Origin, the singularity does not necessarily have infinite density. A spinning BH for example, would have a disk or ring shaped singularity, giving it a real volume... yes, this breaks the mathematical definition, but only a non-charged, non-spinning BH that collapsed completely uniformly have a true mathematical singularity.

After the initial descriptions of a BH the models have matured a bit, but the term 'singularity' was now tacked to the BH's incomprehensibly dense and small core...not just to the mathematical description.
 
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observer7

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Just finished reading "The Black Hole War" by Leonard Susskind. He describes the "battle" between himself and Stven Hawking concerning black holes and information loss. This is a very good read, easy to understand and I highly recommend it.

One of the points in the book concerns quantum mechanical (QM) treatments of black holes and how they can be described as elementary particles with very high masses. Using string theory they describe particles as strings wrapped up in varios ways in the 10 dimensions of string theory. The "windings" in the small dimensions of the string has effects on the mass, have enough winding and the mass becomes that required to make a black hole.

This approach led to an understanding of how black holes evaporate (Hawking radiation) and also how they can preserve information instead of destroying it. Information is like energy, you can't destroy it, only change its form.

The book does a much better job of explaining these concepts, but if you want to understand black holes and some of the latest advances in merging GR and QM this book is a required read.

O7
 
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