Do black holes really exist in the real world or are they just virtual objects

It is quite difficult fighting on so many fronts when people are arguing different points at varying levels of education, maturity and intellectual curiosity.

The fact is that we cannot draw a reasonable line of simultaneity between us and the interior of a black hole in General Relativity. This is a fact. If you want to dispute this fact then please do so with logic and preferably math. BruceP, you said you've already done this, could you please link to what you were referring to?

 

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Correct! And with wording like that, clearly it means you agree that this phenomena exists!

 

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:bugeye:

I'm about to check out of this conversation.

 

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You may have made to much sense for this crew who believes you can transform away an object by just making a coordinate change. We can't know it exists even after we spent all that time learning how GR works. There's really nothing clever about the prediction, they're hanging there thinking caps on, it's the prediction the Schwarzschild remote bookkeeper makes because there's a coordinate singularity in the Schwarzschild metric solution at r=2M. People like to pretend this remote observation precludes external observers from knowing the black hole exists. I don't know if you saw the link, I posted in the beginning of this thread, depicting the HST capture of a dying pulse train at Cygnus X-1. That's very interesting [LOL] since it's exactly what the remote bookkeeper predicts for the 'piece' of accretion disk observed falling towards and into the black hole. Just like you said 'scientists agree'. Just how the scientific method is supposed to work. Physiscists get to transform from metric to metric and between remote and local coordinates since they went to school and learned how. LOL. Can't transform away a spacetime event [the existence of the black hole] based on frame dependent coordinates. That's against the rules.

 

Maybe you should. To paraphrase, you are saying over and over "black holes exist but they do not exist.". You describe what we call a black hole, agree that it exists, then say again that black holes do not exist.

You agree that whatever is happening or will happen at the center of Cygnus X-1 will never be observable. Well, that's what it means to BE a black hole!

Lets try a little thought experiment:

Say you have a clock made of unobtanium that could transmit time signals to you from inside a star, not at the center. You receive these time signals and see that they come at regular intervals.

Then the star begins to collapse.

Now I'm not certain of the exact mechanism of the collapse, but I would think it happens from the inside-out and propagates outward, carrying an event horizon with it. As this happens, the collapse wave and event horizon pass the clock and cut it off from the outside. What happens to it afterwards, we can never know, but what we see is that the time signals suddenly start dilating, hyperbolically lengthening the intervals between the time signals you receive, toward infinity.

Agree?

 

Where are you getting this "infinite future" from? It's well known that a free-falling trajectory into a black hole will both cross the event horizon and reach the gravitational singularity in finite proper time.

Yes, including parts of the singularity itself.

Short answer: yes.

The longer, more technical answer: two events being spacelike separated in spacetime means that you can identify a spacelike path (i.e. a path whose tangent vector is spacelike at every point) that connects them. A spacelike path is an invariant concept (a path is either spacelike or it isn't, regardless of the coordinates you use to describe it), and the 'length' of the curve (the integrated spacetime interval along it) is likewise invariant. In general there will be multiple spacelike paths you could trace between two spacelike separated events, and the length will be path dependent, but you can get a unique answer to the "distance" in the obvious way just by taking the shortest one. (Compare: the distance between Paris and Amsterdam along any path connecting them depends on the path you're considering, but when we ask for the "distance" between Paris and Amsterdam, we normally mean the shortest distance, minimised over all the possible paths connecting them.)

So, pick an event within the event horizon of a black hole and an event along the worldline of an external observer that are spacelike separated, and you can define a unique and invariant distance between them as the length of the shortest spacelike path connecting them.

 

I bolded your time-prejudiced terms. When does the collapse propagate outward? When does it pass the clock? When do the time signals dilate? How do you determine that these things are occurring at the same time? Because they happen at the same time in your imagination? I need specifics. Defining simultaneity in a rigorous manner is crucial to this discussion.

Also, earlier I had suspected that you were confused about something and now I'm certain of it. The clock would start to dilate before being over taken by the event horizon, freezing to a complete stop just as it is taken over by it. You don't need unobtainium to measure this, you just need paddoboy's infinite infra-red telescope. In this scenario we would see the clock red-shifting more and more as it falls toward the center of the never-quite-forming event horizon "point" at the center of the collapsed star's mass.

 

No, I was simply pointing out your erroneous claim that makes quite clear that you are arguing absent the proper knowledge. You claimed that it "changes the meaning of the time", I pointed out that it doesn't. This is what happens when you collect your knowledge from pop sci.

 

Yep, sure, but that is common knowledge for anyone that knows anything about BHs.
The point is for the umpteenth time, the EH [or region where "c" or the escape velocity of light is reached] and the observed effects on matter/energy and the space/time surrounding it, is the evidence we need to theorise BHs do exist now.

 

Time descriptive isn't prejudiced and those are not meaningful questions because those are event descriptions not timeline description. But I'll try:

This is a thought experiment: it starts at an arbitrary beginning. If you're asking in who'se frame; every frame witnesses it starting.

At the time the clock was reading when it passed. Again, that's just an event.

Technically speaking, this is a massive object, so they are always dilating, but the dilation suddenly increases as the event horizon approaches.

We don't. we don't care when they happened, we only care that they happened.

Yes - or at least asymptotically approaching a complete stop. And the time that is asymptotically being approached on the display is the time the event horizon passed.

I know you agree with all of this even as you are being argumentative about it. The fact that the event horizon cuts us off from seeing inside and what was happening just outside gets frozen to our view is not controversial.

 

Are you sure about that? How would you handle measuring the proper distance between two events separated by the event horizon?

 

No. We definitely care when they happened, particularly if the theory that you people think you're defending predicts that they haven't happened yet. :shrug:

EDIT: Expanding on this...the clock counts as an outside observer too, correct? At least initially? Would you agree that, from its perspective in your gedanken experiment, the event horizon rushes up and overtakes it? This is contradicted by GR because it would require mass which was closer to the center of the star to cross over the event horizon from the clock's perspective! This is something that never happens. If the clock was given an infinite infra-red telescope it could, in principle, continue to "watch" those atoms nearer the center of the mass fall toward the new borne event horizon point for eternity, and the event horizon would never grow, nor would it "engulf" the clock.

 

Er, "that they happened" means happened in the past. Whose past? Our past. The theory predicts all of this and if we are watching that clock, we would observe it. You must agree: the fact that the event horizon cuts us off from ever seeing the clock tick again is your main complaint!

 

Huh? Do you mean calculate, or do you literally mean experimentally measure? (Because you said nothing about actual measurement before, and if two events in spacetime are spacelike separated, that's true regardless of how easy or difficult it is to measure the distance between them.)

 

Yes.

No. You flying into the black hole and the event horizon expanding to consume you are equivalent. Objects closer to the event horizon are flying in formation with you and if you see yourself cross the event horizon, you must see them cross first. That is indeed a prediction of the theory.

The two situations are the same - in both the falling in case and the expanding event horizon case, the clocks freeze from our perspective as they approach/cross the event horizon. What I find useful to note is the last time seen on the clock as it freezes.

[edit] Also, the exact way the event horizon forms is not critical here. It may propagate outward or it may form, static, in place. I'm not really certain. The point is that it forms and cuts us off from viewing new readings on the clock, making it "freeze". I think we're in agreement that this happens, right?

The reason I'm exploring a clock that starts inside the radius of the event horizon before the event horizon forms is that I think it is instructive. You are seeming to argue that the fact that an in-falling clock is never seen to cross the event horizon implies that the event horizon isn't there. That's a contradiction of course (it is the event horizon that causes us to perceive it freezing), but it is one that is easier to get past when considering a clock already behind where the event horizon will be when it forms.

 

What makes you think that your question is such a clever one? The answer is quite trivial: \(ds=\frac{dr}{\sqrt{1-r_s/r}}\) where \(r\) is the current location of the observer.

 

Does the singularity of a black hole exist at absolute zero or does pressure make the singularity hot?

If it was at absolute zero, it would be a superconductor with zero resistance. This scenario would forever keep it at absolute zero, since zero resistance to energy can't it heat up, no matter what falls into the hole. You may get flashing at the event horizon.

On the other hand, if it is very hot due to accumulating mass/pressure, than superconductivity is out of the question, and low conduction and high resistance would result in it getting hotter and hotter possibly changing phases many times; classifications.

The question one might ask is, how can the core ever become absolute zero if there is so much pressure=work. One explanation involves entropy. For entropy to increase it needs to absorb heat. Therefore, there would need to be a phase change into extreme entropy for a rapid absorption of energy; quick chill. One way is tangible matter phase changing into pure quarks, with the extreme entropy of the quarks resulting in an entropic rapid chill into super conductor stability.

 

You don't know enough about Einsteins theory and how it works. So you don't really know what's important to solving problems. You can evaluate the local path of the freefalling observer using the metric. You can't test your predictions for inside the black hole for obvious reasons. The rain metric, I showed you, evaluates the path using the freefalling observers clock, dt_rain, and dr_schwarzschild = dr_rain.

So you can evaluate the entire path, outside and inside r=2M, using this metric. Not the only one. The entire path being the entire spacetime event 'observer falling into the black hole'. In this case you could compare ticks from your remote coordinates to the predicted tick rate of the freefalling observers clock. Over this path it's not spacelike, it's timelike. There is no coordinate singularity. This is what you asked for.
The distance component of the Schwarzschild metric

dr_shell = dr/(1-2M/r)^1/2

Integrate dr_shell and this is the result

dr_shell=[r^1/2(r-2M)^1/2 + 2M ln{r^1/2 + (r-2M)^1/2}] This eliminates the coordinate singularity at r=2M and is good for determining the distance for 'any r' from far away [boundary] to r<<0.

 

A quark/gluon state has been theorised to exist deep within the bowels of a Neutron Star......a state of matter between Neutron star and BH.

Whatever state of matter existing at the Singularity will be Interesting indeed.

 

There's lots of evidence that black holes exist. GR predicts they exist, the standard model tells us there are no stable condensed stars > 1.4 solar mass, my favorite is the 'dying pulse train' predicted by GR. Because they exist is a good reason to want to understand what's happening at r=0.