B What are the biggest misconceptions about black holes?

[Intresting]

I think the biggest misconception is 'How can black holes not let light escape when photons have no mass?'

Kinda surprised nobody refuted this. Though the mass of a photon is zero, it nevertheless carries energy and momentum. Enough for a BH to trap.
I have a niggling feeling I may have misread your statement. It's like a double entendre without the innuendo or a double negative. Grammar isn't my strong point. If I have misread you're statement, I apologise.

 

[Intresting]

No, and I can't imagine why you conflate the two.

I am not sure if I should dignify this with a response. Yet I have. Let's say Earth (A) has a influence on time due to its mass (which it has) That's why satellites (B) have to adjust its time in orbit due to Earths gravity, even though it is a fraction not mentioning but yet it still affects satnav or GPS relating to Earths gravity, but there is still time dilation. Now magnify that with a super massive black hole. It is not an illusion. I conflated the two too signify time and space time to try and convey a thought.

 

[Flyx]

Kinda surprised nobody refuted this. Though the mass of a photon is zero, it nevertheless carries energy and momentum. Enough for a BH to trap.
I have a niggling feeling I may have misread your statement. It's like a double entendre without the innuendo or a double negative. Grammar isn't my strong point. If I have misread you're statement, I apologise.

I was saying how many people say that, and it is a misconception.

 

[write4u]

IMO, the term Black Hole itself is a misnomer.

In all of the previous posts I have not seen one mention that a BH is not a *hole* at all. It is a massive singularity surrounded by a gravitational sphere. So instead of a hole a BH is really a *black sphere*, which has actually separated itself from external spacetime and is not visible to us. Hence the appearance of a *hole*.

But the inside the Black Spere may be very bright in the 3D spherical space between the gravitational event horizon and the central singularity. It's just that this brightness curves into itself and becomes *invisible*, giving the appearance of a hole.

A separate universe within a galaxy?

The gravitational sphere of the sun (an average, if not small singularity), may be as large as

The Sun's gravitational field is estimated to dominate the gravitational forces of surrounding objects out to about two light years (125,000 AU).

Now visualize a BH singularity some few million times more massive than our sun, we may get a scope and gravitational influence of a BH singularity.

This image shows the disk galaxy NGC 1277, as seen by the Hubble Space Telescope. The small, flattened galaxy has one of the biggest central super-massive black holes ever found in its center, the equivalent of 17 billion suns. Credit: NASA / ESA / Andrew C. Fabian / Remco C. E. van den Bosch (MPIA)

- See more at: http://www.space.com/18668-biggest-black-hole-discovery.html#sthash.DKGcTRKP.dpuf

Obviously we can see the surrounding galaxy, but in the center of this galaxy resides a Black Sphere which is invisible to us because it cannot emit radiation from inside its event horizon.

 

[Cecil Tomlinson]

It is not the massiveness of a black hole that makes it a black hole; it is its density. In theory, there are black holes at the centers of galaxies, billions of times the mass of our sun. Yet, our sun could become a black hole if it were sufficiently compressed. Every mass, regardless of size, has a Schwarzschild radius (correct me if I'm wrong about that). In fact, there is no amount of matter so small that it cannot become a black hole if it is sufficiently dense. That being said, and considering the huge amount of energy within every perceptible piece of matter, isn't it possible that all sub-atomic particles are black holes? I think the greatest misconception about black holes is that they are all extremely massive objects that exist mainly at the centers of galaxies.

 

[phinds]

It is not the massiveness of a black hole that makes it a black hole; it is its density. In theory, there are black holes at the centers of galaxies, billions of times the mass of our sun. Yet, our sun could become a black hole if it were sufficiently compressed. Every mass, regardless of size, has a Schwarzschild radius (correct me if I'm wrong about that). In fact, there is no amount of matter so small that it cannot become a black hole if it is sufficiently dense.

That's correct, although I do believe that there is a lower limit, in that an atom, for example, cannot become a black hole and certainly an electron cannot.

That being said, and considering the huge amount of energy within every perceptible piece of matter, isn't it possible that all sub-atomic particles are black holes?

Now you're off in la-la land and you want to watch yourself on stuff like this. Personal theories are not permitted here.

I think the greatest misconception about black holes is that they are all extremely massive objects that exist mainly at the centers of galaxies.

Not sure if this is a misconception or not, but there may be some laymen who think they are only at the center of galaxies because they mis-interpreted a pop-science article or TV show.

 

[phinds]

... so from point A, point B should not evaporate overtime

This is not correct. Just because A sees what he knows is an illusion, that doesn't mean the evaporation doesn't happen.

So a super massive black hole distorting space time to breaking point is also an illusion?

No, and I can't imagine why you conflate the two.

I am not sure if I should dignify this with a response. Yet I have. Let's say Earth (A) has a influence on time due to its mass (which it has) That's why satellites (B) have to adjust its time in orbit due to Earths gravity, even though it is a fraction not mentioning but yet it still affects satnav or GPS relating to Earths gravity, but there is still time dilation. Now magnify that with a super massive black hole. It is not an illusion. I conflated the two too signify time and space time to try and convey a thought.

Yes, but you conflated two very different things. The fact that point A does not see point B evaporate does NOT follow from the correct facts in your subsequent post. What you are missing is that over time the black hole DOES evaporate and if point A is around long enough it WILL see point B evaporate. SO ... it's good that you did "dignify" it with a response since perhaps now you have learned something that you didn't realize.

 

[guhan]

Another misconception: An in-falling person will not experience anything abnormal at the exact moment she is crossing the event horizon. Truth: It is a popular hypothesis, but not a fact (and continues to be challenged as in firewall etc).

In fact, any statement on what happens at or within the horizon is only a hypothesis (as of now?).

 

[votingmachine]

That being said, and considering the huge amount of energy within every perceptible piece of matter, isn't it possible that all sub-atomic particles are black holes?

Now you're off in la-la land and you want to watch yourself on stuff like this. Personal theories are not permitted here.

I think everyone sufficiently imaginative has entertained that idea at some point. It just doesn't work though. Consider neutron decay. A neutron that was a black hole would have nothing ever come out of it. One black hole would never split into two black holes. Yet a free neutron will split into electron, proton, and neutrino. A neutron that was a "mini-black-hole" seems like it would quickly hoover up the nearest neutron to it in a nucleus. Somewhere a photon would hit an electron and not escape ... that would just be annoying, as the photon could be any size, so electrons could be arbitrary mass after a while.

I'm not a physicist, so these objections are also just imagination at work ... I'm sure there are more substantive reasons. There is currently a thread as to why this gets out of hand quickly:
https://www.physicsforums.com/threads/why-wont-you-look-at-my-new-theory-comments.866043/

 

[votingmachine]

I assume (since I find it confusing) that most people don't have a clear conception of why a black hole does not defy the universal requirement for increasing entropy. That is not a misconception, just a thing that is difficult.

Evaporation would have to be another thing that is often not a clear concept in general understanding.

I'm stretching the definition of misconception ... but if you (OP) want to consider beyond the general idea that a black hole is just the big thing with all the gravity that light cannot escape ... in that simple thing, entropy and evaporation don't fit.

 

[PAllen]

Another misconception: An in-falling person will not experience anything abnormal at the exact moment she is crossing the event horizon. Truth: It is a popular hypothesis, but not a fact (and continues to be challenged as in firewall etc).

In fact, any statement on what happens at or within the horizon is only a hypothesis (as of now?).

It removes confusion to talk in terms of what model of BH you are using. That nothing unusual happens at horizon crossing is mathematical fact of the classical GR black holes. Firewalls are a feature of a semi-classical treatment of quantum gravity, under commonly held assumptions (there treatments in this realm, with less accepted assumptions that don't involve firewalls; such eminent physicists as Juan Maldacena think the firewall hypothesis will ultimately be rejected). There is no full, consistent treatment in quantum gravity because there is no complete theory. Apart from all this, you are clearly correct that we don't, and may never, have a way to verify this feature of real world BH. The best we can do is choose to believe the predictions of a complete QG theory that is verified elsewhere (whenever that is achieved).

 

[write4u]

If I may be permitted a set of analogies.
In context of a *multiverse*, perhaps BHs are the *eggs* of new *baby galaxies*, or *tunnels* to new *baby universes*, invisible to us?

 

[pinball1970]

Sorry I joined the party late - a comment about colour and black holes

wavelengths in the vis spectrum are colour not beyond, you would not refer to microwaves as colour

 

[rootone]

If I may be permitted a set of analogies.
In context of a *multiverse*, perhaps BHs are the *eggs* of new *baby galaxies*, or *tunnels* to new *baby universes*, invisible to us?

What is the evidence for this?, as far as I know there is none.
On that basis, one might equally well argue that black holes are portals to the holy kingdom of the flying spaghetti monster.

 

[guhan]

It removes confusion to talk in terms of what model of BH you are using. That nothing unusual happens at horizon crossing is mathematical fact of the classical GR black holes.

I don't think one can apply a theory beyond its domains of validity and call it factual. It would have been ok before the limitations of classical theory came up, by virtue of it being an 'unknown unknown' problem, but not anymore since it is a 'known unknown'.

On firewalls etc, sure they are hotly debated, with eminent names on either side, and I don't have the expertise to pick a side on this. Mentioned it merely to exemplify my case.

 

[PAllen]

I don't think one can apply a theory beyond its domains of validity and call it factual. It would have been ok before the limitations of classical theory came up, by virtue of it being an 'unknown unknown' problem, but not anymore since it is a 'known unknown'.

On firewalls etc, sure they are hotly debated, with eminent names on either side, and I don't have the expertise to pick a side on this. Mentioned it merely to exemplify my case.

Please note: I said mathematical fact. There is no ambiguity or need for qualification in this statement. At present, no one knows what the bounds of validity of classical GR are. In particular, whether it is fully applicable to high precision at the horizon of a large BH is itself subject to dispute. However, what the math of classical GR predicts is not disputed at all.

 

[guhan]

Please note: I said mathematical fact. There is no ambiguity or need for qualification in this statement. At present, no one knows what the bounds of validity of classical GR are. In particular, whether it is fully applicable to high precision at the horizon of a large BH is itself subject to dispute. However, what the math of classical GR predicts is not disputed at all.

I am sure neither of us is keen on prolonging this over pedantics! :) I believe the definition of 'mathematics of a theory' also includes those statements on no-go domains, where we know** that the physics is unknown or not established. It is absolutely ok if you believe otherwise.

**as you said, the region at (and within) the horizon is known to be an unsolved domain

 

[PAllen]

I am sure neither of us is keen on prolonging this over pedantics! :) I believe the definition of 'mathematics of a theory' also includes those statements on no-go domains, where we know** that the physics is unknown or not established. It is absolutely ok if you believe otherwise.

**as you said, the region at (and within) the horizon is known to be an unsolved domain

It is only unknown per theories other than GR. For example, Newtonian mechanics domain of applicability is not determined by Newtonian mechanics, it is determined by SR/GR. One regularly speaks of predictions of Newtonian mechanics that are wrong in that they reach into where SR//GR is required. However, they are still predictions of Newtonian mechanics, and are mathematical facts of Newtonian mechanics taken as a theory. For example, I've never heard anyone dispute the statement that "Newtonian mechanics states that the momentum of a ball of mass m, moving at twice the speed of light, is 2mc".
With what GR says about the horizon, the situation is not even quite like this. We know that the above statement is outside the domain of validity of Newtonian mechanics (based on our knowledge of other well established theories). Statements GR (as a self contained theory) makes about the horizon are NOT known to be outside its domain of applicability. Instead, it is an open question, which is very different status from known to be superseded by a different theory in this domain.

 

[votingmachine]

Since there is a debate here about the event horizon, I have a question. Is the event horizon an important boundary, or just the distance beyond which nothing from the surface can be seen?

That is vague and I will walk thru the question. The black hole cannot emit light that can escape. There is an event horizon, where if you parked our spaceship just outside it, you would not see the thing in the center, no matter how bright a flashlight you shone at it. But what about a thing not far inside that event horizon. Say you shot a bottle rocket at the black hole and it goes 100 feet and blows up ... do you see that?

I hope that is not too vague a question about what the event horizon is. And if it is answered in another thread ... just point that direction.

 

[PAllen]

No, you would not see the bottle rocket blow up. However, if you shine a flashlight at it, the bottle rocket would be hit by the light (inside the horizon), and would reflect it, but this reflected light would not progress toward the horizon. Instead, it would simply 'fall' much slower than the bottle rocket.

Per other debate: this is all per classical GR. If the firewall hypothesis is true, the description would be completely different.

 

[write4u]

What is the evidence for this?, as far as I know there is none.
On that basis, one might equally well argue that black holes are portals to the holy kingdom of the flying spaghetti monster.

I don't know how you came to that conclusion.
In a multiverse each universe would be invisible to the other, but each universe, for it to contiue as a universe (Hawking), it would have to have mathematical properties and chemical reactions, similar to our universe. Nothing divine or *ridiculous* in my statement.

I do admit, it was a purely speculative statement, but then the concept of a multiverse is speculative to begin with, yet it is discussed by serious cosmologists. I was speaking in that context. I am an atheist, I like spaghetti on my plate with lots of sauce.

If we live in a multiverse, when and how do they form ?

 

[phinds]

I don't know how you came to that conclusion.

I think he came to that conclusion because your speculation does not comport with physics as we know it. The "black hole as an egg for a new universe" just doesn't work. His point was, and I agree with it, that your speculation was nonsensical.

 

[write4u]

I think he came to that conclusion because your speculation does not comport with physics as we know it. The "black hole as an egg for a new universe" just doesn't work. His point was, and I agree with it, that your speculation was nonsensical.

I used the egg as a metaphor. In context the singularity from which this universe originated can be metaphorically described as an *universal egg*.

And as far as I know the center of a BH is a singularity (a metaphorical egg) and maybe...could be the singularity from which a new universe expands. We would not know about this because we cannot observe what goes on inside the separated spacetime of a BH.

We know what goes in and we what occasionally *leaks*out, but do we know much more than that?

 

[phinds]

I used the egg as a metaphor. In context the singularity from which this universe originated can be metaphorically described as an *universal egg*.

And as far as I know the center of a BH is a singularity (a metaphorical egg) and maybe...could be the singularity from which a new universe expands. We would not know about this because we cannot observe what goes on inside the spacetime of a BH.

But the universal egg cannot be, as you stated it to be, a black hole, so I still think what you said makes no sense.

 

[write4u]

But the universal egg cannot be, as you stated it to be, a black hole, so I still think what you said makes no sense.

Where did I state that?

Assuming a multiverse, should all that have happened all at once with the inflation of *our* universe? Or are new universe being created constantly? If so, where would the energy come from? Hyper massive BH contain a lot of potential energy, no?.

 

[phinds]

Where did I state that?

You said it here. Do you not even understand what you said?

If I may be permitted a set of analogies.
In context of a *multiverse*, perhaps BHs are the *eggs* of new *baby galaxies*, or *tunnels* to new *baby universes*, invisible to us?

In what way does this not specifically say that "perhaps BH's are eggs" ?

Assuming a multiverse, should all that have happened all at once with the inflation of *our* universe? Or are new universe being created constantly? If so, where would the energy come from? Hyper massive BH contain a lot of potential energy.

Individual BH's are utterly trivial compared to the universe.

 

[write4u]

You said it here. Do you not even understand what you said?
In what way does this not specifically say that "perhaps BH's are eggs" ?

You don't seem to understand the implication of a metaphorical egg, which expands, first inside the shell, then breaking out of the shell and creating a whole new *system*, which has no resemblance to an egg anymore. Let's also not forget the phenomenon of metamorphosis

Individual BH's are utterly trivial compared to the universe.

Of course it would seem that way to us., We can only see the *entrance* of a BH. Beyond that what do we know what goes on inside ? I can visualize an type of universal hour-glass configuration with mass/energy constantly trickling (tunneling) from our universe through the "relatively" small BH into the singularity (the metaphorical egg), but eventually expanding into a new separate universe, invisible to us.

Question: in a multiverse are all universes the same size as our universe?

Instead of calling it nonsense, why don't you explain why this could NOT be so according to what we know from our science of BH. To me that would be useful.

If you recall, I qualified my probing metaphor as pure speculation. What happens when a BH singularity reaches a physical and gravitational limit? Do they blow up, do they evaporate? Into what? Back ito our own universe? What are the limits of BH and what happens when those limits are reached.. Does anyone know and wish to share?

I am merely posing hypothetical questions, but as yet have not seen a coherent answer.

 

[Droidriven]

[HIDE]You don't seem to understand the implication of a metaphorical egg, which expands, first inside the shell, then breaking out of the shell and creating a whole new *system*, which has no resemblance to an egg anymore. Let's also not forget the phenomenon of metamorphosis Of course it would seem that way to us., We can only see the *entrance* of a BH. Beyond that what do we know what goes on inside ? I can visualize an type of universal hour-glass configuration with mass/energy constantly trickling (tunneling) from our universe through the "relatively" small BH into the singularity (the metaphorical egg), but eventually expanding into a new separate universe, invisible to us.

Question: in a multiverse are all universes the same size as our universe?

Instead of calling it nonsense, why don't you explain why this could NOT be so according to what we know from our science of BH. To me that would be useful.

If you recall, I qualified my probing metaphor as pure speculation. What happens when a BH singularity reaches a physical and gravitational limit? Do they blow up, do they evaporate? Into what? Back ito our own universe? What are the limits of BH and what happens when those limits are reached.. Does anyone know and wish to share?

I am merely posing hypothetical questions, but as yet have not seen a coherent answer.[/HIDE]

Even after several warnings about posting things in the direction of your personal theories, you are still posting on the same subject. I think you are pushing your limits, my friend.

 

[PAllen]

You said it here. Do you not even understand what you said?

In what way does this not specifically say that "perhaps BH's are eggs" ?

Individual BH's are utterly trivial compared to the universe.

Note that Lee Smolin pushed a model of black holes seeding new universes, extracting testable predictions from this model. If I recall correctly, this model is close to being ruled out by observation.

 

[write4u]

Even after several warnings about posting things in the direction of your personal theories, you are still posting on the same subject. I think you are pushing your limits, my friend.

In context of the OP question, you could have also said. "W4U, this is one of the *Misconceptions* about Black Holes" , instead of a veiled threat implied in your of "pushing my limits". Moreover, those previous warnings were about my posting of "disallowed links" to lectures of qualified physicists, to wit, Renate Loll's proposition of CDT (causal dynamical triangulation) and not about my "personal theories".

Causal dynamical triangulation (abbreviated as CDT) invented by Renate Loll, Jan Ambjørn and https://en.wikipedia.org/w/index.php?title=Jerzy_Jurkiewicz&action=edit&redlink=1 , and popularized by Fotini Markopoulou and Lee Smolin, is an approach to quantum gravity that like loop quantum gravity is background independent.

https://en.wikipedia.org/wiki/Causal_dynamical_triangulation

If you are a theoretical scientist, you seem possesses a very narrow and limited viewpoint. Give me a break will you. I am here because I am interested in science, but if you keep threatening me because I use *informal* language (English is my second language), I'll just leave and won't waste any more of your valuable time having to give me warnings. In fact, I won't waste my valuable time anymore on this forum. You have just managed to lose a member. Be well all. Bye, bye...

Physics Forums - The Fusion of Science and Community ?

Oh, and please stop inviting me back. After leaving once before, I am not going to subject myself to try once more and then being "warned" on semantics.. At 76, I don't need that anymore in my life.

Note that Lee Smolin pushed a model of black holes seeding new universes, extracting testable predictions from this model. If I recall correctly, this model is close to being ruled out by observation.

Thank you Sir, for that reply. Now I have something to research. Seems my thought processes (right or wrong) are along the lines of Lee Smolin.

p.s. I wonder how many warnings he would get if posting his hypotheses on this forum without revealing his name and qualifications.