Debate: Do black holes exist?

No, Ben, we're both mature enough to recognize your ignorance.

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Hah, ok man settle down, I'm kidding. But your attitude pisses me off. Please notice that in none of my posts do I say "This is the way it is!". If you read my OP I'm posting my logic and thought process, with a pleading for someone to explain why it is wrong. D H has basically said it's not technically wrong but rather a matter of semantics, which I can live with. You, on the other hand, seem threatened any time you hear an idea that differs from what your famous friends tell you. Forget them, try growing as a critical thinker and actively debate my points. And simply announcing that I "failed. miserably" is not an active debate.

D H: I've given an off-the-cuff description to what happens to B trying to cross the event horizon: CBR turns destructive as B is infinitely accelerated relative to it and the rocket ship is destroyed. Plausible? No idea, just the first thought that popped into this layman's head.

 

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I see, so you would give BenTheMan and AlphaNumeric that same suggestion regarding String Theory?

 

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Hmm. I'm not so sure. In the flat space limit, one should recover the SR equations, and I can always take the Schwarzchild radius big enough to recover the flat space limit. Corrections to the SR equation should become less important as you take R_s -> infinity. The GR corrections to the SR equations should become more important for R_s -> 0.

Of course, then I've only proved that v \neq c for very large black holes, but very large black holes are a subset of all black holes and I win.

And even if you don't buy that argument, you still have to acknowledge that his calculation of v = c is invalid on the same grounds.

This is correct if you ignore the fact that the Schwarzchild radius increases as the mass of the black hole (which is accreting observers in this example, and gas/dust in Nature). I have had more than a few conversations on this subject with people whom I consider experts in black hole physics.

Only if you ignore back-reaction.

 

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Yes and no.

The yes answer first: http://www.sciforums.com/showpost.php?p=2599287&postcount=6

The "not yet" in my yes answer is the key to my no answer. String theory is at least conceptually falsifiable (all they need is a collider the size of the Moon), and the goal of at least some string theorists is to make it practically falsifiable: To turn string theory into a true scientific theory. On the other hand, those who venture into string theory purely for the math (to heck with reality) and/or the eschatological nature of things: They aren't scientists.

 

D H: Fair enough! Did you read this post of mine:

 

RJ Beery: The GR equations do not show t = Infinity 3 kilometers from the Event Horizon.

You apparently did not understand the calculations & conditions described in my post #34

 

You're right, I don't understand. I thought you were saying that the event horizon of the entire system would grow after the event horizons of each individual body came in contact. Re-reading below it appears you think that this will happen before that point.

This is just confusing. You believe there would be a 6 km (roughly) spherical EH? Because I do not. Would you say the same thing if none of the bodies had reached critical mass? Don't make it so complex, just stick with 2 BH and let them approach each other...again, you are trying to convince me that event horizons exist by presuming they exist and then imagining their behavior.

Dinosaur my logic is simple: IF...
1) From A's frame, B does not cross the hypothetical event horizon in finite time AND...

2) The black hole dissipates due to ("pre"-)Hawking radiation in finite time THEN...

3) B does not cross the EH and the EH does not expand. FURTHERMORE...

4) The same MUST be said about the material that supposedly preceded B's journey, including all mass that would theoretically make up the BH. It is all stuck in time, waiting to be evaporated as radiation, never quite reaching that critical mass threshold which would create an event horizon.

FORGET B's experience, for now. Deal with this logic flow and let me know what you think is wrong with it.

 

What's wrong is that you haven't supported your point with any sort of calculations. You first have to SHOW that this is the case mathematically.

It is, after all, how theoretical physics works.

 

Ben: I'm biting my tongue here...I gave you calculations in post 28 and you dismissed them with a few words. Dinosaur says

...which post in fact contains no calculations, just a description, yet I still try to understand what he is saying and respond. With respect, it is clear to me that even if I did persuade you on some point you would never, ever admit it. You are not discussing Physics, you are defending something else (ego? your text book? famous cronies? maybe just the concept that a PHD makes you infallible?). I don't know but to this point your feedback is not valuable to me and it is clear that my thoughts are not valuable to you so let's just avoid each other.

 

Bite your tongue all you want---I'm telling you that your calculations are wrong. You've done nothing to address my refutation of them at all, and refusing to do so doesn't make you right.

I've already addressed DH's point that SR shouldn't apply to the near horizon kinematics. This is wrong because I can always take the horizon to be sufficiently large, making space-time near the horizon sufficiently flat. As you know, the flat space limit of GR is SR, so there should be no problem.

If you want to consider small horizons, then he is correct and you'd have to go back to Einstein's equations in full.

And either way, your simple calculation doesn't amount to a full relativistic treatment, which is what is necessary when you are dealing with large velocities.

Additionally, as Dinosaur points out, and as I have pointed out to DH, you ignore back-reaction. The process of an infalling observer has the consequence of increasing the mass of the black hole, and thus the Schwarzchild radius. Given this, it should be clear that there exist many frames outside the Schwarzchild radius for which observer A can see B falling into the black hole. Even if you don't agree with this (it's right, but that's not stopped you before), you haven't addressed DH's point that an observer hovering at distance D from the event horizon ( R < D < 1.5 R ) will see the in-falling observer cross the horizon, even int he absence of back-reaction. Thus, there exist an infinite number of frames in which static observers can watch the in-falling observer cross the horizon. If it is your contention that this is not true, you have to show why this statement is not correct.

So you can summarily dismiss my objections if you want, I won't lose any sleep over it.

 

In order to "take the horizon to be sufficiently large" you must first create it. I question whether this creation is possible. That's the equivalent of saying "breeding unicorns is simple, you just start with a stallion unicorn and a broodmare unicorn..."

If what I'm suggesting is true then no amount of mass can ever "infall" beyond its own Schwarzschild radius so back-reaction would not exist. Nevertheless, GIVEN that the hypothetical EH existed, I neither understand why back-reaction might change things nor why being within the photon sphere might change things. Are you contending that A *would* observe B fall into and beyond the EH if A were hovering above the BH within the photon sphere? Please be gracious enough to show me the calculation for this, as I did for you, because I believe you are all mistaken.

 

I don't understand your method of argument. You must first show a contradiction between the existence of black holes, and the tennets of the commonly accepted theory. If you cannot show such a contradiction, then you are wrong, and your discussion belongs in pseudoscience.

Having realized you can't refute my point, you're changing your argument. In post 28, you had no problem making a calculation that you felt proved your point, which was that the presence of an event horizon predicts that an infalling observer would have infinite velocity, which leads to a contradiction. Now that you realize that this claim was wrong, or that you couldn't actually DO the appropriate calculation, you shift your claim to ``it's useless to calculate it because no horizon forms in the first place''.

Surely you realize the ex post facto nature of this argument. You cannot assume that something doesn't exist, then look for things that break when you make this assumption, and then use those things as evidence of a contradiction.

I don't think a calculation is necessary, nor do I think you'd understand it if I dug out the references and posted it. The point is that an in-falling observer has mass, and you do not argue that in his own frame, the observer crosses the event horizon. The fact that the mass of the black hole increases, and that the radius (which is proportional to the mass) also increases, is also not up for debate. Then it is not difficult to see that photons hovering slightly above the event horizon get swallowed when the black hole expands. The photons slightly above those guys (who were on their way out anyway) escape, and the observer sees B disappear.

You still haven't given me any criteria to assess whether your claim is true or not. You have only refused to show any evidence of how you synthesized your claim in the first place. Should I link you to something by Bacon, so we can brush up on our scientific method?

 

I believe you have this backwards which is why I mentioned breeding unicorns. I said you cannot get a BH with size such that it is essentially flat space-time near the EH without first passing the BH size range in which is it heavily (infinitely?) curved.

I do not accept that in B's frame he would cross the EH; I claim he would be destroyed before he got there. I also said to ignore B's experience (for now). Your demand to see my calculations, hand-waving to say they are wrong, and then claiming that it would be a waste to show me the correct ones smacks of hypocrisy and BULLSHIT. I challenge you to do it. I'm calling you out, Ben, it's your chance to impress and teach me something at the same time. I'm claiming that there does not exist a frame above the EH that would observe B crossing the EH. "No longer seeing B" does not count, as my OP claims the same thing: B would appear to slow in movement and intensity from A's perspective until he had disappeared completely, essentially frozen in time.

This would be true whether A was within the photon sphere or at an infinite resting distance. Please explain what you and DH meant by implying that something special happens within the photon sphere. Also, please provide the correct accelerative forces formula when in the vicinity of a hypothetical EH. The one I used was \(a = \frac{GM}{R^2 \sqrt{1 - \frac{R_s}{R}}}\).

Thanks for your help!

 

BenTheMan: The following has become applicable to this thread.

I am giving up on this thread. Perhaps you should also.

 

Wow Dinosaur that's the closest thing to a concession I've read on this forum. Thanks, I guess.

 

...and presuming that this thread has not actually ended I have one more question: what is the difference in calculating EH cross-over times from the infinite observer's frame whether the local region flat or not? I believe the calculation is infinite, regardless, which is all I need to make my case.

 

Yeah, I think I'm with you.

I got nothing to prove.

 

Section 1.2.

Please don't equate you plucking expressions and claims from nowhere with actual rigorously derived results.

No, you gave an equation, not calculations. Speaking from experience the proper analysis of space-time close to, on and in an event horizon is extremely non-trivial and you can't just slap in an SR or Newtonian expression and hope it has some relevance.

This was the problem you had when you first joined here. You seem to be suffering from it again.

At least he has a PhD, famous cronies and has read books. Ben isn't infallible, none of us are. But that applies to you too and if I had to pick which one of you I'd back to be most correct without having read a thread I'd pick Ben every time.

After all, at least he has a working understanding of SR and GR and QFT. Do you? I'd imagine not. Plus you're obviously not familiar with black hole mechanics as you haven't heard of 'black hole surface gravity', which plays an important role in the first and second law of black hole thermodynamics (after being defined in the zeroth law). Your acceleration formula is infinite at R=2M, \(\kappa\) is not. I'd wonder what your formula even physically means, as defining acceleration in curved space-time for various observers is a dubious issue. If you look at the lecture notes my first link is derived from you'll see there's very little which resembles anything seen in Newtonian mechanics or even SR.

 

Despite more ad hominem attacks, this was finally a reply with some meat. I'll keep it simple:

There's your first problem. I am questioning the existence of the BH while you are PRESUMING it and forcing the math to fit. When the equations break down at the EH you do not question the BH, rather you question the math and just switch metrics in that area. This is sleight of hand. Go ahead and use these metrics or any others of your choosing and determine "when" B crosses the EH as calculated from A in the OP. You are going to get an indeterminate result no matter what you do. Telling me that metric ABC is ill-defined at the EH while metric XYZ is ill-defined at the infinite observer is not a defense -- the math problem remains. Admit it or don't. :shrug:

 

BenTheMan: Interesting comment by RJ

He did not get it. I think you did.