Do black holes really exist?

[Vane]

I always thought they did but i've been hearing and reading that people/scientists believe that they are just myths, What do you think?

[rkman]

i've been hearing and reading that scientists believe that they are just myths

Sources please?

[NovaSilisko]

Myths is a very wrong word. There are a number of theories for alternate objects that produce the same effects as black holes, but I don't think anyone short of flat-out conspiracy theorists who think the sky is a fixed crystal sphere thinks they flat-out don't exist.

They are generally accepted to be gravitational singularities resulting from the collapse of massive stars, though. But there will always be alternate theories (and sometimes those turn out to be right, so who knows what we may learn) http://en.wikipedia.org/wiki/Black_hole#Alternatives

[FanaticalFighter]

Are you talking about the whole "Stephen Hawking says Black Holes don't exist thing"? Because I read the paper where he's supposed to have said so, and he never said such a thing. I can try to explain, but seriously, his paper would do a helluva lot better job of it than me: http://arxiv.org/abs/1401.5761

[stupid_chris]

As Nova said, basically there will always be people who don't eblieve what you'll tell them.

Black holes have never been directly observed. We have tons and tons of indirect observations, and a lot of them point to some very massive, dark bodies. The evidence of the existence of black holes is rock solid, even more solid than the big bang theory, and that last one is probably the theory in cosmology that has the most solid concrete-built evidences. But since we're stuck here on Earth, it's really hard to be able to affirm without a doubt that they do exist. They are wonderful theoric objects, and if they turned out not to exist, it would be quite a shame. There are indeed alternatives, but it's widely agreed on that Black Holes is the most likely one by far. Another thing that popped up lately annd that made the media put words into Hawking's mouth, is that the even horizon of black holes might not actually be a thing. Basically Hawking published a paper end of last year IIRC, where he explained his reasoning, and you can watch

if you want to know more, but he made no calculations. Thing is he said "there is no black holes" by meaning that there is no event horizon, not that the object doesn't exist. Edited April 1, 2014 by stupid_chris

[Nuke]

this is just the media failing science class and being sensational about things they dont understand.

[Albert VDS]

Basically what Hawking said was that Black Holes don't have an event horizon, he used this to fix the firewall paradox.

So the media thought "No event horizons = no black holes". But this fix has been disproven, mainly because there is no firewall paradox because Hawking radiation comes in pairs.

One particle enters the Black Hole and the other escapes.

[problemecium]

I can't remember whether I made this up or heard it somewhere, but there's a certain hypothesis I know regarding black holes and the reasons for our universe's laws of physics.

Nobody knows for sure what is inside a black hole, so it's not impossible that it contains what is for all practical purposes its own universe (at least from the perspective of anything inside). The universe may have the same laws of physics as ours - or slightly different ones, which might vary depending on the conditions in which the black hole formed. If so, every time a black hole forms it makes a new universe based on information inherited from the one where it formed. This is fundamentally the same as biological reproduction, and hence is subject to the Law of Natural Selection. Following this train of thought, one could conclude that our universe exists the way it does because it is the result of many successive generations of universes evolving to produce as many individual black holes as possible, which would explain why ours has SO DARN MANY.

Far-out? Yes. But it holds a surprising amount of water for such an odd idea, which is why I like it.

[Sillychris]

parameciumkid, I have never heard of the natural selection idea you just introduced. I like it.

[stupid_chris]

I can't remember whether I made this up or heard it somewhere, but there's a certain hypothesis I know regarding black holes and the reasons for our universe's laws of physics.

Nobody knows for sure what is inside a black hole, so it's not impossible that it contains what is for all practical purposes its own universe (at least from the perspective of anything inside). The universe may have the same laws of physics as ours - or slightly different ones, which might vary depending on the conditions in which the black hole formed. If so, every time a black hole forms it makes a new universe based on information inherited from the one where it formed. This is fundamentally the same as biological reproduction, and hence is subject to the Law of Natural Selection. Following this train of thought, one could conclude that our universe exists the way it does because it is the result of many successive generations of universes evolving to produce as many individual black holes as possible, which would explain why ours has SO DARN MANY.

Far-out? Yes. But it holds a surprising amount of water for such an odd idea, which is why I like it.

parameciumkid, I have never heard of the natural selection idea you just introduced. I like it.

Did we just shift from "do black holes exist" to multiverses being produced by gravitational singularities?

[78stonewobble]

Do black holes exist?

I believe so... I thought it was more or less proven that there exists systems of stars whose movement can only be accurately describe via a massive object so dense, that according to our known theories it will gravitationally collapse, to the point where even light cannot escape and create an event horizon and thus a black hole.

While I believe in objects that have can have the gravity necessary for an event horizon I don't believe in "singularities". Which is more a question of the theories breaking down, but something like fuzzballs? Sure...

[*Aqua*]

I would like to know in what kind of state matter exist inside a black hole.

As far as I know atoms can't exist there, the gravitation will rip it apart. So do the core consists of electrons, protons and neutrons? Or can't they exist under such conditions, too? If they can't, is the core made of quantum particles? Wouldn't it be better in this case to refer to them as quantum stars?

[Idobox]

I would like to know in what kind of state matter exist inside a black hole.

As far as I know atoms can't exist there, the gravitation will rip it apart. So do the core consists of electrons, protons and neutrons? Or can't they exist under such conditions, too? If they can't, is the core made of quantum particles? Wouldn't it be better in this case to refer to them as quantum stars?

Just below the event horizon, the conditions are not that different. Actually, form the point of view of somebody falling in a black hole, they never cross the event horizon. Of course, the tidal forces get stronger and stronger, but nothing especially exotic here.

The problems arise when you get to the singularity. Physics hate singularities and infinite quantities, which are usually considered a sign that your theory does not work in these conditions. Because we don't have an accepted theory that allows to remove this infinity, it doesn't make much sense to discuss what happens there. It would be like trying to treat black holes with Newtonian mechanics: you know the theory doesn't work, and whatever result you get will just be wrong.

[*Aqua*]

So nobody knows* how matter looks like near or in the center of the core?

* I mean a theory. Nobody knows for sure, what's going on there.

[NeoMorph]

We can't see the black holes but we CAN see their accretion discs.

Here is a REAL image of what may be a black hole accretion disc.

Have a read here... http://www.spacetelescope.org/science/black_holes/

What I want to know about are white holes. WAYYY more interesting.

Edited April 1, 2014 by NeoMorph

[stupid_chris]

Just below the event horizon, the conditions are not that different. Actually, form the point of view of somebody falling in a black hole, they never cross the event horizon. Of course, the tidal forces get stronger and stronger, but nothing especially exotic here.

The problems arise when you get to the singularity. Physics hate singularities and infinite quantities, which are usually considered a sign that your theory does not work in these conditions. Because we don't have an accepted theory that allows to remove this infinity, it doesn't make much sense to discuss what happens there. It would be like trying to treat black holes with Newtonian mechanics: you know the theory doesn't work, and whatever result you get will just be wrong.

Event horizons are pretty mysterious. The debate on firewalls which emerged last years is probably the best example of it. The singularity has a theoretical volume of zero, and just that leads to a lot of infinities we have to deal with.

We can't see the black holes but we CAN see their accretion discs.

Here is a REAL image of what may be a black hole accretion disc.

http://upload.wikimedia.org/wikipedia/commons/thumb/4/4f/NGC_4261_Black_hole.jpg/220px-NGC_4261_Black_hole.jpg

Have a read here... http://www.spacetelescope.org/science/black_holes/

What I want to know about are white holes. WAYYY more interesting.

Accreation disks aren't only typical to black holes unfortunately, we can't conclude that the thing creating it is a black hole. Being massive, emmiting strong jets of gamma rays and having an accreation disk doesn't mean you are a black hole. They're defined essentially by event horizons, which is what is not easy to identify.

[GreatWyrmGold]

Did we just shift from "do black holes exist" to multiverses being produced by gravitational singularities?

It's awesome, isn't it?

Both the multiverse thing* and the fact that it came up.

*Which is an idea that occurred to me at one point. I couldn't figure out what the black hole absorbing more energy or releasing Hawking radiation would be on the universal scale.

So nobody knows* how matter looks like near or in the center of the core?

* I mean a theory. Nobody knows for sure, what's going on there.

Well, since the "core" is presumably inside the event horizon, and past the event horizon gravity is strong enough to draw even light to the black hole rather than letting it escape...five bucks says it doesn't look like anything.