I Could a Star Avoid a Supernova and Form a Black Hole?

[Boca]

TL;DR Summary

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]

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.

 

[MikeeMiracle]

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 occurring 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.

 

[Boca]

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]

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.

 

[geoelectronics]

I describe a Black Hole as anybody 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]

I describe a Black Hole as anybody 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.

 

[HankDorsett]

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?

 

[weirdoguy]

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 completely 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]

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 completely 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.

 

[weirdoguy]

We have many theories on black holes Beyond Einstein

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?

What have we actually observed from a black hole?

I think it's pretty easy to find out using google. E.g. this:
https://arxiv.org/pdf/1312.6698.pdf

 

[HankDorsett]

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?

 

[weirdoguy]

I edited my post when you posted yours, so again:

https://arxiv.org/pdf/1312.6698.pdf

 

[HankDorsett]

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:
https://arxiv.org/pdf/1312.6698.pdf

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]

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]

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.

 

[mfb]

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]

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.

Also, here is an image of one:

 

[OCR]

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. . . .

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. . . .

.

 

[trevor white]

"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]

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.

 

[trevor white]

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]

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).

 

[trevor white]

It was though not an error what I question was that idea.

 

[jbriggs444]

It was though not an error what I question was that idea.

The event horizon is not a place where the curvature becomes undefined.

 

[trevor white]

that information can not escape a black hole sic why would that be the default position?

 

[DaveC426913]

I'm having trouble discerning whether your questions are inter-related.
Are you still asking about why the curvature is well-defined at the EH? Or is this a new question? I'll assume it's a new question.

that information can not escape a black hole sic why would that be the default position?

What do you mean by 'default position'? Do you mean why do scientists assume it to be so?

Well, it's not an assumption. Einstein's GR predicts BHs. With sufficient mass in a compact enough volume, space-time becomes so curved that even light cannot escape - the escape velocity exceeds c. Having GR predict such a possibility, we went looking for it, and found it.

If light cannot escape the gravity well of a massive object, then neither can information.

 

[Mary Conrads Sanburn]

From the National Science Foundation:

Black holes are extremely dense pockets of matter, objects of such incredible mass and miniscule volume that they drastically warp the fabric of space-time. Anything that passes too close, from a wandering star to a photon of light, gets captured. Most black holes are the condensed remnants of a massive star, the collapsed core that remains following an explosive supernova. However, the black hole family tree has several branches, from tiny structures on par with a human cell to enormous giants billions of times more massive than our sun.
[ . . .]

HOW ARE BLACK HOLES STUDIED?
Black holes have long inspired the imagination yet challenged discovery. However, from a combination of theory and observation, scientists now know much about these objects and how they form, and can even see how they impact their surroundings.
[ . . . ]
So, how does one study a region of space that is defined by being invisible?
Theorists can calculate properties of black holes based on their understanding of the universe, and such discoveries have come from a range of great thinkers, from Albert Einstein to Stephen Hawking to Kip Thorne. However, despite being so powerful, it's hard to see something that does not emit photons, let alone traps any light that passes by.

Now, nearly a century after scientists suggested black holes might exist, the world now has tools to see them in action. Using powerful observatories on Earth, astronomers can see the jets of plasma that black holes spew into space, detect the ripples in space-time from black holes colliding, and may soon even peer at the disc of disrupted mass and energy that surrounds the black hole's event horizon, the edge beyond which nothing can escape.
# # #
https://www.nsf.gov/news/special_reports/blackholes/

 

[weirdoguy]

Black holes are extremely dense pockets of matter, objects of such incredible mass and miniscule volume that they drastically warp the fabric of space-time.

Ironically:
-black holes are vacuum
-there is no meaningfull way to assign a volume to them
-there is no meaningfull way to assign a density to them
-there is no fabric of space-time
-they don't warp space-time, they are speciffically warped space-time


Long live pop-science!

 

[davenn]

Ironically:
-black holes are vacuum
-there is no meaningfull way to assign a volume to them
-there is no meaningfull way to assign a density to them
-there is no fabric of space-time
-they don't warp space-time, they are speciffically warped space-timeLong live pop-science!

haha yup, agree with you...
and there's more

astronomers can see the jets of plasma that black holes spew into space,

The jets, that have actually been observed for many years, at radio wavelengths, don't come from
within the black hole as such but from an area OUTSIDE the black hole

 

[Mary Conrads Sanburn]

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..." NSF is vital because we support basic research and people to create knowledge that transforms the future. This type of support:

• Is a primary driver of the U.S. economy
• Enhances the nation's security
• Advances knowledge to sustain global leadership

With an annual budget of $8.1 billion (FY 2019), we are the funding source for approximately 27 percent of the total federal budget for basic research conducted at U.S. colleges and universities. In many fields such as mathematics, computer science and the social sciences, NSF is the major source of federal backing.
We fulfill our mission chiefly by issuing limited-term grants -- currently about 12,000 new awards per year, with an average duration of three years -- to fund specific research proposals that have been judged the most promising by a rigorous and objective merit-review system. Most of these awards go to individuals or small groups of investigators. Others provide funding for research centers, instruments and facilities that allow scientists, engineers and students to work at the outermost frontiers of knowledge.

[. . .]

###
https://www.nsf.gov/about/glance.jsp

 

[jbriggs444]

The National Science Foundation (NSF) is

A source of pop-science malarky in this case.

 

[weirdoguy]

Doesn't matter, they contradict what textbooks on general relativity say.

 

[Mary Conrads Sanburn]

jbriggs444 , perhaps you didn't look at the Staff Directory
https://www.nsf.gov/staff/staff_list.jsp?orgId=496&subDiv=y&org=NSF&from_org=

 

[jbriggs444]

jbriggs444 , perhaps you didn't look at the Staff Directory

It does not matter who says a thing. Wrong is wrong.

 

[weirdoguy]

perhaps you didn't look at the Staff Directory

Perhaps you didn't look at the PF rules concerning acceptable sources.

 

[mfb]

jbriggs444 , perhaps you didn't look at the Staff Directory
https://www.nsf.gov/staff/staff_list.jsp?orgId=496&subDiv=y&org=NSF&from_org=

What is your point?
Popular science descriptions are always simplified, can often be misleading and they are never a good source for actual science, no matter who writes them.

 

[FactChecker]

On the lighter side:
The first "photo" of a black hole was recently (April, 2019) taken. Here is an interesting TEDx talk by Katie Bouman on the problems with taking a photo. And here is a cute (IMHO) photo of her reaction to first seeing the "photo".

 

[PAllen]

Funny that just today I was wondering about how to address the intuition that a BH has a density when it really doesn't (at least per GR) - it is mostly vacuum, and suffered a topology change making volume not meaningful, and you can basically get almost any volume you want depending on how you slice it. I came up with the following:

For a collapsed body, the state you currently see from the outside is of the body epsilon before the surface passed into the horizon. This will always be true, with ever shrinking epsilon (and a very generous definition of 'see'). This past state you currently see does have a meaningful volume and density (it is coordinate dependent, but there are defensible 'reasonable coordinates'). However it is not simply using the Schwarzschild radius in a Euclidean geometry sphere formula - the interior geometry is not at all flat, and is given by some complex Ricci curvature along with Weyl curvature. However, to rough order of magnitude, the simple approach would work ok, giving you a sense of how low the density of a supermassive BH would have been in the past, if it formed all at once. Of course, supermassive BH do not form all at once, so a low density state just before horizon crossing has never existed for them.

In this limited past (or hypothetical past for the supermassive case) sense you can give some meaning to density intuitions. You are answering: if this event horizon I detect evidence of, were the result of a monolithic collapse leading to that horizon state (assuming truth of no hair theorem), then the density just before horizon crossing would be such and such.

 

[mfb]

Do we need to make it so complicated? Make a very large box around the black hole. Consider how much volume it would have without the black hole, consider how much accessible volume it has with the black hole. Subtract. It gives a volume of the order of the Schwarzschild radius cubed. Not sure how to define the accessible volume for rotating black holes, but it gives at most a numerical prefactor.

 

[PAllen]

Do we need to make it so complicated? Make a very large box around the black hole. Consider how much volume it would have without the black hole, consider how much accessible volume it has with the black hole. Subtract. It gives a volume of the order of the Schwarzschild radius cubed. Not sure how to define the accessible volume for rotating black holes, but it gives at most a numerical prefactor.

The problem I have with this is that the volume of box with the BH, treated with spacelike slices, can be infinite for perfectly reasonable slices. So you are really doing infinite - infinite equals some finite value.

Maybe my argument seems complicated, but it sidesteps this problem by going to the past, before the interior topology change.

 

[Dragrath]

The problem I have with this is that the volume of box with the BH, treated with spacelike slices, can be infinite for perfectly reasonable slices. So you are really doing infinite - infinite equals some finite value.

Maybe my argument seems complicated, but it sidesteps this problem by going to the past, before the interior topology change.

Honestly I think sidesteping the sigularity is missing the point as the emergence of the singularity within the event horizon is considered one of the reasons we "know" GR can't be the final say as it is generally accepted that the emergence of infinities are evidence of the break down of a theory. Perhaps more importantly because no observations can emerge from within a black hole's event horizon any interpretation of what, if anything, exists inside a black hole is inheretly outside the scope of science as it can not be falsified. With the observations of M87*'s photon sphere, the distance at which light orbits the black hole and thus the closest we could ever hope to see light to a black hole, and gravitational waves produced by two black holes merging we can say that fudamentally unless indicated by some new theory of everything these observations rule out anything not observationally indistinguishable from a black hole. The question of if a Black hole is actually a hole is so far outside the fields of science.

 

[Drakkith]

The question of if a Black hole is actually a hole is so far outside the fields of science.

Science may not be able to answer every detail of what a black hole is, but we can certainly put many constraints on it, and I believe that we can confidently say that a black hole is not a 'hole' in the normal sense of the word.

 

[Dragrath]

Science may not be able to answer every detail of what a black hole is, but we can certainly put many constraints on it, and I believe that we can confidently say that a black hole is not a 'hole' in the normal sense of the word.

True in the familiar 3D sense at the very minimum so I guess I can agree with that but the main point I had wanted to convey was the limitations of science as much of the conversation seemed focused on the interior of a black hole. We have lots of untested hypothesizes out there and I am leery about supporting any of them acknowledging the lack of observational tests. As there is a long history of wild theorizing disconnected from observations.