The Paradoxical Nature of Black Holes

[imatfaal]

The event of falling toward the EH is outside the EH and is in principle observable by anyone outside the EH.

Yes - and from outside the EH we observe Alice falling towards the EH- what we do not observe is crossing. The 'event' in question is crossing not falling towards.

 

And you also accept that BHs evaporate, yes? So if you never see Alice cross the EH and the BH evaporates then on which side of the EH was/is Alice?

From where are you observing the black hole evaporate? and how?

 

It's not a fact. It's a conjecture that has never been evidenced except by math that is known to be incomplete.

This is grasping at straws. The same theory that states that an outside observer in an accelerated reference frame will not see Alice cross the EH says that Alice's space time sends her through the EH without her noticing any local change.

 

 

I suggest you read Leonard Susskind's "The Black Hole War" because he disagrees with you. In fact the only way he can reconcile it is by invoking "black hole complementarity" in the same vein as particle-wave complementarity.

Well in Susskind's lectures at Stanford he quite clearly states that Alice goes straight through the EH. This is repeated in the black hole war - I will dig out a a page number. The information that Alice entails and how to deal with it is highly debatable and contested - but not crucial here.

 

Actually this is still hotly debated.

Not in the sense that you are debating it. This is covered in undergrad level text books (look at Hartle An Intro to E's GR ) . I notice you haven't bothered to comment on my notes on proper time v coordinate time and your incorrect choice of coordinates.

[Slinkey]

From where are you observing the black hole evaporate? and how?

 

Hawking radiation.

 

Well in Susskind's lectures at Stanford he quite clearly states that Alice goes straight through the EH. This is repeated in the black hole war - I will dig out a a page number. The information that Alice entails and how to deal with it is highly debatable and contested - but not crucial here.

 

He says it quite early on. I have the audio book so don't have a page number.

[imatfaal]

Hawking radiation.

the question was from where are you observing it - and how are you observing it.

 

 

He says it quite early on. I have the audio book so don't have a page number.

 

I have the book and have read the opening of it (been delayed) - he is quite clear that Alice goes through the EH.

 

 

 

[Slinkey]

the question was from where are you observing it - and how are you observing it.

 

You accept Hawking radiation, yes?

You have already stated that you will never see Alice cross the EH due to the infinite time dilation.

BHs evaporate due to HR.

As you will never see Alice cross the EH, when the BH has evaporated, where is Alice?

 

I have the book and have read the opening of it (been delayed) - he is quite clear that Alice goes through the EH.

 

I'll have to re-listen to the audio book and find the part.

[imatfaal]

the question was from where are you observing it - and how are you observing it.

[csmyth3025]

Chris,

 

I'm inclined to think they don't exist at all.

I understand that this is, indeed, your inclination. At the same time, I wonder how you reconcile it with observational evidence that seems to point rather strongly to the existence of black holes. Perhaps the most notable observations have been carried out over the past 15 years in regard to Sagittarius A*:

 

Astronomers are confident that these observations of Sagittarius A* provide good empirical evidence that our own Milky Way galaxy has a supermassive black hole at its center, 26,000 light-years from the Solar System^[5] because:

 

• The star S2 follows an elliptical orbit with a period of 15.2 years and a pericenter (closest distance) of 17 light hours (1.8×1013
  m) from the center of the central object.^[14]
• From the motion of star S2, the object's mass can be estimated as 4.1 million solar masses.^[2]
• The radius of the central object must be significantly less than 17 light hours, because otherwise, S2 would either collide with it or be ripped apart by tidal forces. In fact, recent observations^[15] indicate that the radius is no more than 6.25 light-hours, about the diameter of Uranus' orbit.
• The only known type of object which can contain 4.1 million solar masses in a volume that small is a black hole.

While, strictly speaking, there are other mass configurations that would explain the measured mass and size, such an arrangement would collapse into a single supermassive black hole on a timescale much shorter than the life of the Milky Way

(ref. http://en.wikipedia....tral_black_hole )

 

Chris

[Slinkey]

I understand that this is, indeed, your inclination. At the same time, I wonder how you reconcile it with observational evidence that seems to point rather strongly to the existence of black holes. Perhaps the most notable observations have been carried out over the past 15 years in regard to Sagittarius A*:

 

If you are asking do I have an alternative theory, then no I don't, but I do have a question about the article. It states

 

"In fact, recent observations[15] indicate that the radius is no more than 6.25 light-hours, about the diameter of Uranus' orbit."

 

I worked out the Schwarzchild radius for 4.1 million solar masses and it came out 12,109,072,691.52m, or 40.39 light seconds (feel free to check that), so if the mass is not confined within that radius it isn't a BH. Agreed?

 

6.25 light hours is substantially larger than 40.39 light seconds.

 

So, you tell me. Are you sure there's a BH there?

 

the question was from where are you observing it - and how are you observing it.

 

Anywhere outside the EH. I thought that would be obvious. Edit: Didn't answering the "how" bit. I'm looking through a McDonalds straw because it's fun.

 

Feel free to answer my question from post 129.

Edited May 18, 2011 by Slinkey

[MigL]

You keep picking and choosing statements from people's replies without reading their whole post.

I have previously stated that Hawking radiation is due to a black hole's absorption of one half of a virtual particle pair, wether you choose to assign negative energy or positive energy to it.

If you accept that Hawking radiation occurrs, you cannot maintain that black holes cannot injest mass because they will evaporate before that mass can cross the event horizon.

EVAPORATION IS DUE TO MASS CROSSING THE EVENT HORIZON!!!

[alan2here]

Crossing it an infinite time after falling into the black hole with respect to an outside observer?

[Slinkey]

You keep picking and choosing statements from people's replies without reading their whole post.

 

I always read the entire reply and choose what I see as the relevant statements.

 

I have previously stated that Hawking radiation is due to a black hole's absorption of one half of a virtual particle pair, wether you choose to assign negative energy or positive energy to it.

 

No, that's incorrect. According to Hawking the mass loss of the BH is due to negative energy crossing the EH. If positive energy crosses then it gains weight.

 

If you accept that Hawking radiation occurrs, you cannot maintain that black holes cannot injest mass because they will evaporate before that mass can cross the event horizon.

 

In fact I can think of a way round this. The EH does not have a precise location. If it did it would defy Heisenberg Uncertainty. If a virtual particle-antiparticle pair is created within that region then one could appear beneath the horizon and the other above it. If the positive particle is above the horizon then the BH loses mass due to the negative particle forming below it. Thus it can still evaporate.

 

Point of fact is physicists say that you will never see anything cross the EH due to the infinite time dilation, yet they also accept HR. So, their scenario is the one that says the BH will evaporate before anything crosses the EH. So in a way you have pointed out the flaw in their logic as well.

 

In fact the more I think about it, it doesn't matter if photons (or massless particles) do cross the EH. Anything falling towards it cannot cross the EH as it takes an infinite amount of time to do so for any observer above the EH, and the BH exists for a finite time. All this would do is make me change my argument slightly and the main point still remains.

 

EVAPORATION IS DUE TO MASS CROSSING THE EVENT HORIZON!!!

 

Negative energy/mass.

[imatfaal]

OK Here's a quote from the book you said supports your case

 

 

"Bob never sees her fall through the horizon; to him it takes an infinite time for Alice to reach the point of no return. But in Alice's frame of reference, she falls right past the horizon and begins to feel funny only when she approaches the singularity.

 

The horizon of the Schwarzschild Black hole is at the Schwarzschild Radius. Alice may be doomed when she crosses the horizon, but just like the pollywogs, she still has some time before being destroyed at the singularity"

 

 

Leonard Susskind -"The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics" Back Bay Books/NYC 2008 - Paperback edition 2009. page 45

 

Which bit of that makes you think that Alice doesn't cross the event horizon?

 

Your flippant answer to my serious question of from where and how Charlie is watching the black hole evaporate makes it quite clear that you have no understanding of different reference frames and seem to think there is a privileged reference frame from which everything is uniquely objective. If you did understand this you would realise that you can say nothing about observations of blackholes without specifying the frame of reference .

 

If you are asking do I have an alternative theory, then no I don't, but I do have a question about the article. It states

 

"In fact, recent observations[15] indicate that the radius is no more than 6.25 light-hours, about the diameter of Uranus' orbit."

 

I worked out the Schwarzchild radius for 4.1 million solar masses and it came out 12,109,072,691.52m, or 40.39 light seconds (feel free to check that), so if the mass is not confined within that radius it isn't a BH. Agreed?

 

6.25 light hours is substantially larger than 40.39 light seconds.

So, you tell me. Are you sure there's a BH there?

 

That's selective quoting - a few lines down the same article explains.

The only known type of object which can contain 4.1 million solar masses in a volume that small is a black hole.

While, strictly speaking, there are other mass configurations that would explain the measured mass and size, such an arrangement would collapse into a single supermassive black hole on a timescale much shorter than the life of the Milky Way.

The article also makes it quite clear that the 6.25 light hours is an upper bound based on orbital data - not an estimate on the actual size.

 

I have quoted below a section from the article upon which the wikipedia figure of 6.25 light hours is taken - to make it clear that the weight of scientific opinion agrees with the existence of the supermassive BH

 

 

 

Together, the stellar motions reveal a central dark mass of 3.7(±0.2) × 10^ 6 (R_o/8kpc)³M⊙ and confine it to within a radius of a mere 45 AU or equivalently 600 Rsh, dramatically strengthening the case for a supermassive black hole, the location of which is now determined to within ± 1.3 mas (10 AU). Consequently, the dark mass at the center of the Milky Way has become the most ironclad case of a supermassive black hole at the center of any normal type galaxy

A M Ghez et al "Stellar Orbits Around the Galactic Center Black Hole" Astrophys.J.620:744-757,2005. page 22 available at http://arxiv.org/PS_...6/0306130v2.pdf

[MigL]

The only reason you can call it negative energy is because it has to be paid back to the universe, according to conservation laws, at the end of e period of time dictated by the Heisenberg Uncertainty principle. You are using concepts you don't understand and drawing the wrong conclusions. Energy, wether negative or positive, has a mass ( remember E=MC^2 ??? ). Maybe you would like to give your definition of negative energy and how it differs from positive energy ???

 

Forget Susskind and re-read ( if you ever did ) Hawking on Hawking radiation. Maybe read it several times to be sure you understand it. Then come back and argue.

 

Incidentally, if you are questioning the very existence of black holes, maybe you can tell us what magical device will keep a 4 solar mass stellar core from collapsing no farther than neutron star density. I know it can't be neutron degeneracy, so pray tell, what exactly stops the collapse ???

[Slinkey]

Your flippant answer to my serious question of from where and how Charlie is watching the black hole evaporate makes it quite clear that you have no understanding of different reference frames and seem to think there is a privileged reference frame from which everything is uniquely objective. If you did understand this you would realise that you can say nothing about observations of blackholes without specifying the frame of reference .

 

Err, no. It's precisely because of the different reference frames that this argument comes about and even the part you quoted states it. In the reference frame outside the EH an infinite amount of time must pass before we see anyone cross the EH. The other reference frame - falling in - crosses the EH and is obliterated.

 

As the BH evaporates in less than infinite time then the person outside will never see anyone cross the EH.

 

You can argue all you like about the person claimed to be falling in but it can never be observed from outside the EH as Susskind clearly states.

 

Now we have two different histories.

1) we never see anyone cross the EH and the BH evaporates before they can for any observer outside the EH and they survive.

2) someone falls in and is obliterated.

 

Your assumed flippancy of my reply is simply irrelevant. You just don't want to address what is staring you in the face. There's two histories and they cannot be mixed in any way. You can't both fall in and be crushed to death and someone never observe you fall in before the BH evaporates and survive.

 

It seems that you want to ignore reference frames rather than me not understand them. It's the very fact that there are differing reference frames that this paradox is there.

 

That's selective quoting - a few lines down the same article explains.

 

There is no known.... is our knowledge complete? No, it isn't. Thus this is an assumption. It's not selective quoting because you, being of a scientific mind, should know that the case is not proven.

 

The article also makes it quite clear that the 6.25 light hours is an upper bound based on orbital data - not an estimate on the actual size.

 

No, really? /sarcasm. The point I'm making, which you have skillfully evaded, is that a BH of that mass is far smaller than that radius. ie. it could conceivably still be an object that is not a BH because it can conceivably be larger than the required Schwarzchild radius. A BH is not a BH until it reaches that radius. As we have no direct evidence that the object is a Schwarzchild radius then this is an assumption.

 

I have quoted below a section from the article upon which the wikipedia figure of 6.25 light hours is taken - to make it clear that the weight of scientific opinion agrees with the existence of the supermassive BH

 

So what? Concensus does not make fact.

 

The only reason you can call it negative energy is because it has to be paid back to the universe, according to conservation laws, at the end of e period of time dictated by the Heisenberg Uncertainty principle. You are using concepts you don't understand and drawing the wrong conclusions. Energy, wether negative or positive, has a mass ( remember E=MC^2 ??? ). Maybe you would like to give your definition of negative energy and how it differs from positive energy ???

 

Ok, I agree that my description of this is poor. It should be more correctly described as a particle-antiparticle pair being created at the EH with one escaping to infinity and the other not escaping. The energy that was used to create the pair would need to come from the BH in order for it to evaporate in this way.

 

Forget Susskind and re-read ( if you ever did ) Hawking on Hawking radiation. Maybe read it several times to be sure you understand it. Then come back and argue.

 

"If you ever did". Nice ad hominem. I've read it. Deal with it.

 

Incidentally, if you are questioning the very existence of black holes, maybe you can tell us what magical device will keep a 4 solar mass stellar core from collapsing no farther than neutron star density. I know it can't be neutron degeneracy, so pray tell, what exactly stops the collapse ???

 

I have no idea. Does that mean I am wrong? No.

[Slinkey]

Well, looking back on this thread I'm sad to see it fell into bickering. Apologies for my part in that bickering. I got a little frustrated at not getting my point across, and felt I was not being understood.

 

I'd like to reignite this thread in a more congenial manner. We have fundamental disagreement on the existence of black holes, and looking above I could've used a different way of explaining myself to make my point clearer.

 

First though I would like to hear thoughts on this article which made me come back to this thread.

 

http://www.natureworldnews.com/articles/9187/20140925/are-black-holes-mathematically-impossible.htm

Edited June 2, 2015 by Slinkey

[Strange]

There has been some discussion of that before:

http://www.scienceforums.net/topic/85716-blacks-holes-yesno/

[Slinkey]

There has been some discussion of that before:

http://www.scienceforums.net/topic/85716-blacks-holes-yesno/

Thanks for the link.

 

Interesting to read the remarks.

[imatfaal]

!

Moderator Note

 

50 odd posts have been split off to a thread in Speculations. Whilst not all the posts were promoting novel ideas the general trend was towards discussion of a new and personal hypothesis.

 

The new thread is here

 

http://www.scienceforums.net/topic/89790-speculation-arising-from-the-paradoxical-nature-of-black-holes/

 

Please PM me if I have moved a post in error or I missed one