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Comment by ars | Hacker News Reader

I reached the same conclusion years ago, and the answer is very simple (and controversial): Black holes do not exist.

If they existed they could exist, but it's impossible for them to form.

I've asked many many physicists this very same question, and none could answer me (or I've gotten hand-wavy non answers). It's like no one wants to be the first to declare this well accepted thing as non-existing.

The black holes observed by astronomers are not actually black holes, but rather super massive neutron starts. It's not possible to distinguish between these two objects, astronomers assume a black holes based on size, not based on observed phenomena.

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I've wondered the same, found this:

http://physics.stackexchange.com/questions/21319/how-can-any...

"The objects that can be very similar to black holes are called collapsars. They are virtually indistinguishable from actual black holes after a very short time of the formation. They consist only of matter outside the radius of the event horizon of a BH with the same mass. This matter is virtually frozen on the surface like with actual BH, due to high gravity level.

Such collapsars possibly can become BHs for a short time due to quantum fluctuations and thus emit hawking radiation.

Astrophysicists do not separate such collapsars from actual black holes and call all them BHs due to practical reasons because of their actual indistinguishability."

In your model you get a skin forming around the event horizon. However, stuff would still be attracted to that object. This increased mass would increases the size of the event horizon. So, your hypothetical border would need to expand as matter accumulates. One of the odd things about black holes is there density decreases as their size increases. At really large scales even the 'vacuum' between galaxies is dense enough to form a black hole in a static universe.

PS: In reality black holes are molded by the full general relativity equation which most physicists don't actually understand. Much like how most programmers don't understand how GPU drivers work in detail.

Not true: http://motls.blogspot.co.at/2008/11/why-can-anything-ever-fa...

That explained nothing whatsoever.

I'll even quote:

"At some moment, the radius of the star drops below the Schwarzschild radius - that's where the yellow and orange lines intersect. At this moment, the star is pretty much doomed. Right now I am not sure whether one can generally prove that the event horizon becomes inevitable at this point but I am sure that it is going to be there in a moment according to the picture above which is surely realistic."

He simply skips right past the impossible point: "the radius of the star drops below the Schwarzschild radius". It will take that Sun an infinite amount of time to do that. Any conclusions you draw after that point are unscientific.

He draws all sort of conclusions from the diagram, without ever showing that his diagram is actually true.

There was some talk of how to be a stationary observer near the black hole you must keep accelerating, but a: I fail to see how that explains the infinite time, and b: who said I have to be near the black hole to look at it?

> It will take that Sun an infinite amount of time to do that (drops below the Schwarzschild radius). Any conclusions you draw after that point are unscientific.

Not true. You incorrectly assume that when the star collapses there is already an event horizon, somewhere. But it isn't. The event horizon will only form at some particular proper time, and at that time most (but not all) of the stellar mass will be trapped by the horizon and will form a singularity (interestingly all the trapped matter will reach the singularity at the same proper time).

This is all very clearly explained here: http://www.aei.mpg.de/~rezzolla/lnotes/mondragone/collapse.p...

Related physics stack-exchange answer: http://physics.stackexchange.com/a/28837

I don't want to sound rude, but you really need to understand GR. The seminal work on the subject is "The Mathematical Theory of Black Holes" by Subrahmanyan Chandrasekhar, you need to know GR very well to be able to understand it, but the pdf I linked is comparatively much simpler on the GR and the mathematics required.

> You incorrectly assume that when the star collapses there is already an event horizon

I made no such assumption. You don't need an event horizon to dilate time, just a massive gravitational field, and something resisting it.

When the sun collapses either the outer layers experience a repulsive force of some kind from below (a bounce perhaps, which is already theorized for supernovas, or maybe neutron degeneracy), or the outer layers accelerate to nearly the speed of light, either way they dilate time, and from the POV of an outside observer take an infinite amount of time to collapse.

Because of this dilation the rate of light output (as seen from outside) will drop and the sun will "turn off" - i.e. it will look [almost] identical to a black hole, except without the physics breaking singularity or event horizon.

One visible effect will be extreme red-shift of the light, which will look (to us) like a very distant object hubble-red-shifted by distance/time.

> just a massive gravitational field

There is no massive gravitational field inside a star.

In the exact center, no. But there certainly is everywhere else in the star.

After all, if there was no massive gravitational field, what's causing it to collapse? You can't have it both ways.

Thank you both for this interesting discussion, helped me grasp a few things.

Astrophysicists aren't insisting that black holes have singularities on the insides (just speculating that there are objects that are well described as a gravity well with an event horizon).

Astrophysicists do not see an event horizon. All they see is massive gravity.

Yeah, that's why I said "speculating", and they will also say that they are speculating, if you ask them to be careful.

(edited for clarity)

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