Black holes from my knowledge are created from the collapse of a star’s own gravity crushing itself, Now my question is well two questions, is it really infinitely dense to where space-time can be distorted to the point where it just stops? if so, this would mean objects caught in the event horizon would freeze and time would be stopped how is the black hole itself not effected by it’s own mass wouldn’t it just cease to exist in the first place?
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$\begingroup$ Also, 'to the point where it just stops' is a vast oversimplification. Space and time definitely exist there, but they get mangled in ways that are quite hard to describe. A lot of fundamental concepts (like 'distance' and 'period of time') common to our unintuitive understanding completely change their meaning. Just how black holes can exist is a subject for a lengthy book, long story short the spacetime is mangled in such a way that they can exist in it. $\endgroup$– SF.Commented Mar 27, 2018 at 6:38
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$\begingroup$ Your understanding of space-time physics that "objects caught in the event horizon would freeze and time would be stopped" is inaccurate (i.e. wrong). $\endgroup$– JensCommented Mar 27, 2018 at 11:59
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$\begingroup$ Experts disagree on what happens inside an event horizon, and since the only way to observe it is on a one-way suicide mission, that will likely always be true. But the effects of the event horizon are seen on its surroundings, so in that sense, we can say they do exist. $\endgroup$– Ken GCommented Mar 27, 2018 at 13:50
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2$\begingroup$ There is also a key difference between the black hole as a macroscopic object or system - the density of the whole thing if we use the event horizon as a size can be pretty low - and the density of the central singularity, which is undefined (since it is not even meaningfully zero size, being spacelike). $\endgroup$– Anders SandbergCommented Mar 27, 2018 at 15:13
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3$\begingroup$ I'm voting to close this question as off-topic because this is discussed and reported ad nauseum $\endgroup$– Carl WitthoftCommented Mar 27, 2018 at 15:22
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2 Answers
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The literal answer to your question is "yes". We can see clear astronomical evidence of black holes of a variety of sizes in this and other galaxies. It is possible of course that all that evidence is actually the result of some unknown physical process(es) and not black holes, but it would be a remarkable coincidence that it looks so much like we would expect black holes to look.
So I'll take your question as asking for a way to understand what black holes are. The best answer to that question is basically just equations -- solutions to the governing equations of general relativity that have event horizons, but I'm going to assume that is not what you want here.
So we are left looking for a better intuitive explanation or understanding, bearing in mind that this is at best inexact, and at worst misleading. If you have a lot of matter in a small region of space, and you look at it from the outside you see that the light coming from the surface of the region is red-shifted and (which is basically the same thing) that clocks on the surface seem to run more slowly. As you pack the matter in more tightly this effect becomes more pronounced. But because the clocks are running more slowly, whatever process is packing the matter in also runs more slowly. Eventually, as seen from the outside the clocks on the surface approach a complete standstill, and you will receive a final few extremely red-shifted photons from the surface and then nothing. What you have is now a black hole. From your point of view it is "frozen" and all you can see of it from the outside is the gravitational field surrounding it (and maybe an electric field as well). No information can ever leave it (I'm ignoring Hawking radiation and quantum mechanics in this answer, which is reasonable for big black holes).
Relativity being relativity, things can look quite different from another point of view. If you are falling freely into the black hole (and it is big enough that tides don't rip you apart) everything seems fine, as in this simulation Light from the rest of the universe is blue-shifted and increasingly distorted by gravity, but locally everything is OK. However, no matter what you do, within a finite time (a few days for the largest black holes we know about) you will reach a singularity -- a place where the equations of general relativity break down, and some other physics must presumably apply. We don't know what happens there, but we do know that no information about it can come back out of the black hole, so we can't send in any kind of probe to tell us about it.
answered Mar 27, 2018 at 15:13
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The honest answer is: Nobody knows for certain.
They exist only in theories. Physicists regularly construct elaborate mathematical equations, and the Black Hole is something they essentially created to fill the gaps in certain theories, or to artificially 'complete' them.
In other words, for many of their theories to be correct, Black Holes MUST exist.
In reality, though, we have no idea. Something that's infinitely dense and small destroys all logic, physics and observable reality.
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7$\begingroup$ The first sentence is technically true, though in kind of a vacuous way. The rest is nonsense. Nobody had to just add black holes to anything. They arise naturally out of the theory of general relativity. The theory predicts they should exist, though non-existence would not disprove GR. The black hole solutions need not be physical ones, and unknown quantum effects at the extreme conditions they should come into existence at may prevent them (though some crazy stuff would have to happen to stop supermassive black holes from actually being black holes). $\endgroup$ Commented Mar 28, 2018 at 13:50
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2$\begingroup$ One of the many problems with this answer is that we have experimental evidence of black holes, not just theory. The LIGO detector measured the merger of blackholes, and we now have a picture of a black hole (though that didn't exist when you wrote this answer, so we can give you a pass on that one). How would you explain that data if black holes didn't exist in reality? $\endgroup$– KevinCommented May 23, 2019 at 17:20