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

The singularity isn't the most important, much less the only feature of a black hole. Your objection is like looking at my car and saying that since you don't know what is in its trunk, my car doesn't exist!

 

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It isn't just the singularity; no point within the event horizon exists in the past light cone of any external observers. In a sense the black hole only exists "in the future" for everyone and therefore cannot be said to exist today.

 

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It doesn't matter if you don't know anything about what is going on inside my car. That doesn't change the issue at all.

In addition, I think you are conflagurating the fact with the theory. Since we can't see what is going on inside the black hole, we theorize it. But the fact of its existence does not depend on the theory of what is going on inside or even if the theory is right.

 

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So, you have learned a few buzzwords about event horizon and light cones. The existence of black holes is decided experimentally, not theoretically. There are quite a few experiments going on right now intended for the detection of black holes.

 

The inside of your car is located a finite distance away from me; it's fair to speculate that "something" exists there. New Year's Eve 2013 exists in the future; speculating that it exists today makes no sense.

 

Let's try by defining "black how":

A black hole is a region of space containing an object so massive/dense that its escape velocity exceeds C and thus does not reflect or emit light as normal objects (stars, planets) do.

Those objects have been observed to exist.

 

New Year's Eve 2013 is an event, black holes aren't events. This is one difference. The other fact, that you seem unaware of, is that the existence of black holes is determined experimentally. Theory (GR in this case) predicts, experiment verifies.

 

We don't need to speculate about what or if is inside my car. The existence or non-existence of what is inside is not a required part of the observed fact that the car exists.

Let's say you speculate that my car has an engine. Oops, wrong: I removed the engine. This error in your theory about what is inside does not change the fact that you observed that my car exists.

 

Or we can try another way: what is Cygnus X-1?

 

Cygnus X-1 is a location where you may find a black hole if you traveled there; I'm not saying that inside these regions you would find cream cheese. What I AM saying, though, is that black holes do not exist today by any reasonable definition of the phrase "existing today". Any positive features that we can measure or confirm experimentally are those which have a source in our past light cones and therefore are not from the black hole itself, but rather from conditions leading up to its creation (which has not occurred yet!)

 

This is patently false, demonstrating that you do not know the experimental basis of BH detection. Hint: the methods have nothing to do with any light cones, past present or future.

This is utterly false as well, you don't have to travel to Cygnus in order to detect the presence of a BH there.

 

May? Either it is or it isn't. You are contradicting yourself by suggesting that if we go there, we might discover a black hole (in addition to the absurdity of suggesting we need to go there, as pointed out).

But you do agree that it is SOMETHING, right? What else could it be? Is it a star? A planet? A really big car?

 

If you're asking me what is there RIGHT NOW, the answer is a highly compressed celestial body on the brink of gravitational collapse. It isn't a contradiction to say that we may find something different if we traveled there because that necessitates movement through space as well as movement through time into the future (one can say the infinite future from our frame). We already agree that New Year's Eve 2013 does not exist in the present, but only in the future (as of Nov 4th, 2013), correct? If we agree that something only exists in the future then it does not exist in the present...yes?

 

So that object exists, right? For the sake of linguistic utility, would it not be useful to give such an object a name?
(Minor caveat: if it is highly compressed, it has probably already collapsed.)

I thought your argument was that a black hole's existence is ALWAYS in the future for any external observer?

 

We can call the mathematical, theoretical object a Black Hole but I believe the physical region should be referred to by something else. What about a Dark Star?

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It is. It's always in the future, and a theoretical future at that! If some process or mechanism (e.g. Hawking radiation) were to prevent the Black Hole from forming in finite time from our frame of reference then the mathematical Black Hole would never exist at all.

 

Why? Don't they share the same external properties? The name "dark star" implies it has more in common with a star than a black hole.

Or the other way: when viewed externally, what is the observable difference between a black hole and a "dark star"?

OK, so again, if it is always in the future for any external observer, then you CAN'T (by your logic) ever travel there and discover a black hole.

 

AH!! This is exactly the problem and exactly my point. It has not already collapsed, for if it had then it would exist in our (or SOME universe-observer's) past light cone.

 

For the most part, yes; they're both dark areas of dense matter and gravity. They are not identical though.

I don't know, depends on how you look at it. The math suggests that black holes provide a mechanism for travelling into the infinite future from an outsider's perspective. If I told you that (say) "heaven" exists, but only in the infinite future, how would you respond?

 

No: the event horizon of Cygnus X-1 is about 50 km in diameter. If it used to be a star, as your name for it implies, it would have been a million km in diameter

 

Please state at least one external difference.

An event that is infinitely far away in either time or distance can never be arrived at.