I Are black holes actually holes?

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Are black holes actually holes?
I have been curious if there is anything that would prevent a star that has the mass to supernova from going supernova at the end of its life. If that were possible could it then also be possible that black holes are not actually holes but something so massive that light and anything that comes close enough will be drawn to it and since no light is able to escape it looks as though it fell into a hole.
 

Drakkith

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You hit the nail on the head. Black holes are not holes. They are left over remnants from a collapsed star where the gravity is so strong that nothing can escape. Falling into a black hole doesn't put you 'somewhere else' in the universe (like a hole might), you're just behind the event horizon.
 
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Indeed, we don't know what occurs after you cross that event horizon, we can only guess based on our current understanding of physics. Unfortunately General Relativity breaks down at this point so cannot provide a clear picture, the equations cease to make sense as I understand it. We believe that everything ends up in a singularity.

There are many theories / ideas of what might happen but these are all speculation at this time. This is one of those questions that we may likely never solve. A new theory of gravity may emerge in the future that does a better job of explaining what might be occuring inside, unfortunately I do not see a way of us ever being able to test any theory's that emerge due to the fact no information can escape the black hole for us to measure.
 
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Thank you for your replies. I also imagine if one were somehow unaffected by the forces the view from inside the event horizon would be very bright.
 

jbriggs444

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Indeed, we don't know what occurs after you cross that event horizon, we can only guess based on our current understanding of physics. Unfortunately General Relativity breaks down at this point so cannot provide a clear picture, the equations cease to make sense as I understand it. We believe that everything ends up in a singularity.
General relativity does not break down at the event horizon. It models space-time at and beyond the horizon. Its predictions for the neighborhood of the singularity, however, involve curvatures which exceed all finite bounds. It is expected that those predictions become incorrect at some point.
 
I describe a Black Hole as any body that has an escape velocity that equals or exceeds the speed of light in a vacuum. Forces such as gravity and magnetism are unaffected. Do you agree?

Thanks
George Dowell
 

jbriggs444

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I describe a Black Hole as any body that has an escape velocity that equals or exceeds the speed of light in a vacuum. Forces such as gravity and magnetism are unaffected. Do you agree?
A black hole is a portion of the geometry of space time. It is not a body at all. The model of general relativity predicts that black holes contain [almost] nothing but vacuum everywhere. No material object can exist in the interior of a black hole for longer than it takes to fall to the singularity. In general relativity, gravity is not a force. Magnetism is affected by space-time geometry. Purely magnetic effects cannot cross the horizon outbound any more than electromagnetic effects (light waves) can.

But yes, the escape velocity of a black hole at its event horizon is equal to the speed of light.
 
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HankDorsett

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Curious why there are so many matter-of-fact post regarding black holes? We have no scientific proof of anything regarding black holes, so why do we have so many people posting information as if it scientifically proven?
 
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We have no scientific proof of anything regarding black holes
But we have a theory - general relativity - that works so good and gives such an accurate predictions regarding so many observable phenomena that there is no reason to think that what it says about this single topic is completly wrong. Besides, what you say is wrong, we observe black holes in many places in the Universe and we can check some facts about them.
 

HankDorsett

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But we have a theory - general relativity - that works so good and gives such an accurate predictions regarding so many observable phenomena that there is no reason to think that what it says about this single topic is completly wrong. Besides, what you say is wrong, we observe black holes in many places in the Universe and we can check some facts about them.
We have many theories on black holes Beyond Einstein, I'm curious if any of the information given in this post was from something other than relativity. What have we actually observed from a black hole? We only have an image as well as posable locations of a few. We can only theorize how they are made, what's going on inside and what they can do.
 
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HankDorsett

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I'll try to remember some of the various theories I've heard lately and post them soon. As I do, can you list all of the scientific observations we have with black holes?
 

HankDorsett

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Can you name few of them and tell us what is their empirical status? How they cope with eplaining thousands of observations, that GR explains well to great accuracy?



I think it's pretty easy to find out using google. E.g. this:
I'm wondering if I'm using the wrong term here regarding observation. rewording my question, what has been scientifically proven with black holes? I started reading the document you posted and I'm wondering if it's mainly theoretical, were they able to collect data to prove what they are saying?
 

Vanadium 50

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Curious why there are so many matter-of-fact post regarding black holes? We have no scientific proof of anything regarding black holes, so why do we have so many people posting information as if it scientifically proven?
Wow. That's really gunning for bear, isn't it? That's not so much a question as a very, very bold claim.

what has been scientifically proven with black holes?
That's not really a reasonable question. "Please write down everything we know about transistors" or "fluid dynamics" or any of a number of things is equally problematic.

Perhaps a better starting point is for you to do your own research and ask us specific questions.
 

russ_watters

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We have no scientific proof of anything regarding black holes, so why do we have so many people posting information as if it scientifically proven?
We have many theories on black holes....

What have we actually observed from a black hole? We only have an image as well as posable locations of a few. We can only theorize how they are made, what's going on inside and what they can do.
This is a mixture of misunderstandings about the scientific method and black holes. A "theory" is an idea that is already well supported by evidence. And there is a lot more observational evidence about black holes than you apparently realize, when you apply what is known from the rest of General Relativity and other theories related to black holes, which we should.

Just by knowing the mass and approximate size of a black hole, you know based on our understanding of the structure of matter what it can NOT contain. That's what speculations such as the OP are about - it's not about GR or even directly about black holes. E.G., we know a black hole isn't just a big neutron star mostly because of what we know about neutrons/neutron stars: a neutron star isn't/can't be that dense.
 
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We know there are objects that are extremely compact and don't emit light. We call them black holes. While there are no proofs in physics in general their existence has been shown beyond reasonable doubt. We know they cause time dilation as predicted by general relativity, we know their innermost stable orbits are at the place general relativity predicts, we know that no type of matter can resist a collapse at the size of these black holes. We know they merge with the gravitational wave signals we expect from general relativity. And many more things. Outside they behave like general relativity predicts in every way we could test so far. We can't study what happens inside, that's the point of a black hole, but it also doesn't matter for the outside. People are posting this as fact because it is one.
Forces such as gravity and magnetism are unaffected.
They are affected by the modified spacetime geometry just like everything else. In fact - gravity is this modified spacetime geometry. With the same result: What happens inside can't influence what happens outside.
 

DaveC426913

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We have directly observed an object at the centre of our galaxy
- whose huge mass we can determine, based on the period of the stars orbiting it, and
- whose physical radius we can set an upper limit on, based on the near apsis (closest approach) of stars orbiting it.

Such a small object with such a huge mass cannot be explained by anything in our physics except for what we call a black hole.

Black-hole-workable.gif



Also, here is an image of one:
1565493349016.png
 

OCR

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Unfortunately General Relativity breaks down at this point so cannot provide a clear picture, the equations cease to make sense as I understand it.

. . .unfortunately I do not see a way of us ever being able to test any theory's that emerge due to the fact no information can escape the black hole for us to measure.

Thank you. . . . :ok:

Curious why there are so many matter-of-fact post regarding black holes? We have no scientific proof of anything regarding black holes, so why do we have so many people posting information as if it scientifically proven?

Thank you. . . . :ok:

.
 
"Unfortunately General Relativity breaks down at this point so cannot provide a clear picture"

I have considered this position with interest over many years including the conclusion that the equations leads to a point source. Within maths, infinity whether infinitely small or large, is a defined limit which does not indicate either a point source or an infinitely large expanse. Rather a point at which it is not possible to mathematically define any further mathematical reality.
It seems that the event horizon represents only a information limit at which point the curvature becomes undefined. How far that curvature continues from this point though obviously towards the centre, does not need to imply a point source. Although arguably even as energy this will be passingly small, there may or will be a point where the collapse encounters a barrier imposed by the properties of that energy and the curvature may then be considered to be flat.
 

jbriggs444

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It seems that the event horizon represents only a information limit at which point the curvature becomes undefined.
The curvature is perfectly well defined at the event horizon. And beyond. It is defined for every point in the space-time. It is not defined at the singularity. But the singularity is not part of the space-time.
 
The curvature is perfectly well defined at the event horizon. And beyond. It is defined for every point in the space-time. It is not defined at the singularity. But the singularity is not part of the space-time.
This appears to be a statement of what I had indicated rather than an answer to the questions also contained in my comment?
 

DaveC426913

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This appears to be a statement of what I had indicated rather than an answer to the questions also contained in my comment?
Yes. He was simply correcting an error in one part of what you said (the part he quoted).
 
It was though not an error what I question was that idea.
 

jbriggs444

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