Formation of black holes, impossible?

[Digix]

Recently I found article which claims that black holes cannot exist and it appears to be quite correct.

If black hole can destroy all information (according to current thinking), including charge parity, all matter which falls inside is turned into photons.
If black hole is small (it cant become big instantly) everything will evaporate immediately.

So instead of forming black hole there will be gamma burst and all matter will disappear. I think that could even provide some energy for exploding star to reignite it.

How do current theories deal with this problem?

[Hornblower]

Recently I found article which claims that black holes cannot exist and it appears to be quite correct.

If black hole can destroy all information (according to current thinking), including charge parity, all matter which falls inside is turned into photons.
If black hole is small (it cant become big instantly) everything will evaporate immediately.

So instead of forming black hole there will be gamma burst and all matter will disappear. I think that could even provide some energy for exploding star to reignite it.

How do current theories deal with this problem?

Can you show us, in appropriate mathematical/technical detail, why you think any of these assertions have any merit?

[swampyankee]

Recently I found article which claims that black holes cannot exist and it appears to be quite correct.

If black hole can destroy all information (according to current thinking), including charge parity, all matter which falls inside is turned into photons.
If black hole is small (it cant become big instantly) everything will evaporate immediately.

So instead of forming black hole there will be gamma burst and all matter will disappear. I think that could even provide some energy for exploding star to reignite it.

How do current theories deal with this problem?

Not sure, especially since there is considerable evidence that black holes exist. Could you cite the paper?

[violentquaker]

If black hole is small (it cant become big instantly) everything will evaporate immediately.

Not immediately, just very quickly. If the rate of mass gain is faster than the mass loss, it will not evaporate. If the rate of mass gain is slower than the mass loss, it will evaporate but will contain so little mass that the energy released will be negligible, allowing the star to continue to collapse and reform the black hole (I imagine it like a car starting with a stutter).

[nauthiz]

There was an article about this a couple years back. . . I'm having trouble finding it right now, but I do remember it got a writeup on Bad Astronomy.

The basic story, if I remember it right, is that some folks modeled the collapse of a spherically symmetric, non-rotating object. They predicted that due to a combination of different effects, the object's physical radius would never quite catch up with its Schwarzschild radius. It'd always radiate away just a little bit faster than it could collapse. Therefore, neither an event horizon nor a singularity ever actually forms, so there's no actual black hole.

However, the paper did point out that the object's physical radius could be only infinitesimally larger than its Schwarzschild radius, and that a distant observer should not be able to tell the difference between an object like this and a black hole that is actively feeding. The implication is that the objects that astronomers have observed might be black holes in every practical sense (i.e., you do not want to fall into one), but just don't have event horizons. The idea at least seems plausible to me to the extent that I don't believe anyone's shown any evidence of an event horizon, just evidence of the kinds of phenomena you'd expect to see from an extremely dense object.

[Strange]

There was another thread about black holes here recently that you might find useful. That was more about the relativistic "paradox".

http://www.bautforum.com/space-astro...hole-form.html

But one of the points made was that when a black hole forms, most of the mass is already inside (what will become) the event horizon. So the black hole doesn't have to grow from very small, it is large "instantly". So I don't think that argument holds much water.

As for everything "turning into photons", well we don't know much about what goes on inside black holes and even less about what is really happening at the singularity. Although I have never heard a suggestion like that before - highly compressed degenrate matter seems to be the usual assumption. But even if everything turned into photons, they still couldn't escape (it is a black hole, after all).

[TrAI]

Recently I found article which claims that black holes cannot exist and it appears to be quite correct.

If black hole can destroy all information (according to current thinking), including charge parity, all matter which falls inside is turned into photons.
If black hole is small (it cant become big instantly) everything will evaporate immediately.

So instead of forming black hole there will be gamma burst and all matter will disappear. I think that could even provide some energy for exploding star to reignite it.

How do current theories deal with this problem?

This may be a foolish question, but if an object approaches black hole density, will it not have such a massive gravitational time dillation that if it was becomming a burst of photons in a very short time in a local frame of reference, to an external observer this would take a very, very long time? So that to an outside observer there may be no practical difference between a black hole and an object like this?

[Digix]

Hornblower & swampyankee
Unfortunately That article did not had any mathematical proof and also I have some trouble to find it now.

thats seems to be same article as nauthiz mentioned here

Not immediately, just very quickly. If the rate of mass gain is faster than the mass loss, it will not evaporate. If the rate of mass gain is slower than the mass loss, it will evaporate but will contain so little mass that the energy released will be negligible, allowing the star to continue to collapse and reform the black hole (I imagine it like a car starting with a stutter).

It is opposite, is blachole mass is small evaporation is extremely fast.
but if lets say 1gram of mass will me 10e-30m in diameter, it will radiate intense gamma rays of relatively same wavelength however such tiny spot cannot easily suck anything.
and if we assume that black hole starts from something even smaller it will have big trouble to grow.

This may be a foolish question, but if an object approaches black hole density, will it not have such a massive gravitational time dillation that if it was becomming a burst of photons in a very short time in a local frame of reference, to an external observer this would take a very, very long time? So that to an outside observer there may be no practical difference between a black hole and an object like this?

This can be explanation what astronomers see. Of course it can be that some heavy object will behave like black hole for outside observer, but inside it is still not black hole, because there is no singularity.
also time dilation may be significant but it will never be infinite. so it does not prevent photons from reaching surface.

[Strange]

t is opposite, is blachole mass is small evaporation is extremely fast.
but if lets say 1gram of mass will me 10e-30m in diameter, it will radiate intense gamma rays of relatively same wavelength however such tiny spot cannot easily suck anything.

Indeed. And that is why no one is really worried about the LHC swallowing the Earth.

and if we assume that black hole starts from something even smaller it will have big trouble to grow.

But a stellar mass BH doesn't start small. It starts with stellar mass.

photons formed inside can go out without any trouble if their wavelength is comparable to diameter of black hole.

Is that true?

[tommac]

Wouldnt a small black hole that would immediately evaporate be microscopic?

There is a rate of evaporation:
http://en.wikipedia.org/wiki/Hawking...le_evaporation

tev = 5120 pi G^2 M^3/ hc^4

For a black hole of one solar mass ( = 1.98892 × 1030 kg), we get an evaporation time of 2.098 × 1067 years—much longer than the current age of the universe at 13.73 ± 0.12 x 109 years.

Now ...from what I understand black holes dont grow up from small black holes ... they form from collapsing stars ... so it already has the mass so that it doesnt instantly evaporate.

Or at least that is my take on the mainstream viewpoint. I am sure some corrections will follow.

Recently I found article which claims that black holes cannot exist and it appears to be quite correct.

If black hole can destroy all information (according to current thinking), including charge parity, all matter which falls inside is turned into photons.
If black hole is small (it cant become big instantly) everything will evaporate immediately.

So instead of forming black hole there will be gamma burst and all matter will disappear. I think that could even provide some energy for exploding star to reignite it.

How do current theories deal with this problem?

[tommac]

Also found this:
http://xaonon.dyndns.org/hawking/

[korjik]

Indeed. And that is why no one is really worried about the LHC swallowing the Earth.



But a stellar mass doesn't start small. It starts with stellar mass.

Which, just in case anyone misses it, is the very definition of not small

Is that true?

Quantum tunneling(ish). With the wavelength close to the size of the 'hole, some of the photon is 'outside' the 'hole, so it can pop out.

[TrAI]

...

This can be explanation what astronomers see. Of course it can be that some heavy object will behave like black hole for outside observer, but inside it is still not black hole, because there is no singularity.

I would say that the concept of black holes is seperate from what theories we have about what goes on inside it. It doesn't matter much to an outside observer whether the singularity is a point or a larger object, or if the time dillation prevents the object from actually collapsing to a singulaity at all before it evaporates as Hawking radiation.

Or put another way, anything that looks and acts like a black hole is a black hole, figuring what goes on inside them is just a refinement, perhaps there even might be different types of internal structure to these things, we would have no way to know(at least with current or forseeable knowledge and technologies).

also time dilation may be significant but it will never be infinite. so it does not prevent photons from reaching surface.

I wouldn't think it needed to be infinite, only large enough for the time to be on the scale of the Hawking evaporation time of a current model black hole ...

Hmmm... That is an interesting thought, would we even be able to tell the difference between those photons and Hawking radiation? Isn't there some theory about evaporating black holes emitting bursts of gamma rays when they are in a terminal stage? Perhaps the type of object we are discussing would look pretty similar when it was in a terminal stage...

[ShinAce]

I can't help but think of Zeno's arrow paradox. This just seems like a failure of logic, not a failure of physics. Other views can be taken to bypass the event horizon as a singularity.

Zeno:
Imagine an arrow in flight. Watch it for a second, and you can find out pretty well where it will land.
Watch it for 1/10th of a second. You can still find where it will land, just not with the same precision.
Watch it for an instant, it does not move. You cannot determine if it's moving forward or backward.

Even though the idea and the logic deserve attention, it doesn't mean an arrow stops flying when time is removed.

I just feel like the same kind of logic is being applied here. Every second, we cut the distance between ourselves and the rabbit in half. Since we can divide forever, we'll never catch the rabbit.

[Digix]

Wouldnt a small black hole that would immediately evaporate be microscopic?
There is a rate of evaporation:
http://en.wikipedia.org/wiki/Hawking...le_evaporation

tev = 5120 pi G^2 M^3/ hc^4

Now ...from what I understand black holes dont grow up from small black holes ... they form from collapsing stars ... so it already has the mass so that it doesnt instantly evaporate.

Or at least that is my take on the mainstream viewpoint. I am sure some corrections will follow.

If you claim that black hole forms during star collapse, it must grow from small to big. before collapsing star is not a black hole but if it explodes by ejecting outer layers center is gradually compressed, so small black hole can form there like in LHC. But since it is very tiny at the beginning it will evaporate and resist further compression, or if surrounding matter is transparent this microblackhole will annihilate all incoming matter until nothing is left.

If that is wrong there should be some other detailed explanation how does instantly big black hole forms during star collapse.
and there is still big question if explosion can provide enough pressure.

[Strange]

If you claim that black hole forms during star collapse, it must grow from small to big.

Someone else already said it better than I can:

The event horizon forms when the density inside the event horizon exceeds a threshold. Since the density of the core is roughly isotropic at the time of collapse, the whole thing exceeds the density at once. This gives you an event horizon that forms at the point where the distant observer cannot get information from the collapsing core.

Or, even more succinctly:

You seem to be assuming that the collapse is a shell. It is a filled sphere, so the mass inside the event horizon is already inside the event horizon.

[Digix]

I would say that the concept of black holes is seperate from what theories we have about what goes on inside it. It doesn't matter much to an outside observer whether the singularity is a point or a larger object, or if the time dillation prevents the object from actually collapsing to a singulaity at all before it evaporates as Hawking radiation.

Or put another way, anything that looks and acts like a black hole is a black hole, figuring what goes on inside them is just a refinement, perhaps there even might be different types of internal structure to these things, we would have no way to know(at least with current or forseeable knowledge and technologies).

If black hole is not singularity it may behave in little different way, such blackhole will be not so unescapeable. Light will go out freely, but just severely redshifted so it may look as hawking radiation.
but in the end all that mass will cool and stop all emissions.
so it should behave in opposite way than hawking radiation theory.

I wouldn't think it needed to be infinite, only large enough for the time to be on the scale of the Hawking evaporation time of a current model black hole ...

Time dilation does not apply to light speed. Photons still escape at speed of light, they just redshift in process.
so theoretically time dilation does nothing, same energy as you gain by falling down you loose when going up.
Of course time will be quite slow down there, but do not forget that temperature is equally high to offset that.

Hmmm... That is an interesting thought, would we even be able to tell the difference between those photons and Hawking radiation? Isn't there some theory about evaporating black holes emitting bursts of gamma rays when they are in a terminal stage? Perhaps the type of object we are discussing would look pretty similar when it was in a terminal stage...

If we think that way there will be no such thing as blackhole because there is no sharp transition from neutron star to backhole.

[Frog march]

I had a similar idea Digix, which I started a thread in ATM about.

http://www.bautforum.com/against-mai...ate-stars.html

I think that although the small black holes are powerful, they don't have much energy, on there own...so I'm not sure what would happen...even if there were trillions of mini-black holes in the center of a dying star....At some point they would be overwhelmed if the mass were large enough.

[cjl]

If you claim that black hole forms during star collapse, it must grow from small to big

Not necessarily. The Schwarzschild radius of a black hole is proportional to its mass (R_s = 2GM/c²). However, the volume enclosed is proportional to the radius cubed. With some rearrangement, you can see that the density required (assuming a uniform, isotropic sphere) to collapse into a black hole is proportional to 1/M², so the more mass a sphere contains, the less density is required for it to become a black hole.

Because of this, a uniform collapsing sphere will reach the density at which it will become a black hole before any regions within the sphere will reach their critical densities. Basically, at the point at which the entire core can become a black hole, a small portion of the center is quite far from being dense enough to be a black hole on its own. So, rather than starting as a small black hole in the middle of the core and growing, the black hole will in essence form all at once, with the entire mass of the core contained (and will therefore not evaporate immediately).

[tommac]

If you claim that black hole forms during star collapse, it must grow from small to big.

Why? Why cant the hole just form big? With all of the mass that is inside of the eventual EH turning into a BH simultaneously?

[tommac]

If you claim that black hole forms during star collapse, it must grow from small to big. before collapsing star is not a black hole but if it explodes by ejecting outer layers center is gradually compressed, so small black hole can form there like in LHC. But since it is very tiny at the beginning it will evaporate and resist further compression, or if surrounding matter is transparent this microblackhole will annihilate all incoming matter until nothing is left.

If that is wrong there should be some other detailed explanation how does instantly big black hole forms during star collapse.
and there is still big question if explosion can provide enough pressure.

Doesnt the SR exists regardless of if a BH exists or not? Once the collapse happens where the mass density is great enough so that a BH would exist, everything inside of the SR is now inside of the BH ....

[Digix]

Not necessarily. The Schwarzschild radius of a black hole is proportional to its mass (R_s = 2GM/c²). However, the volume enclosed is proportional to the radius cubed. With some rearrangement, you can see that the density required (assuming a uniform, isotropic sphere) to collapse into a black hole is proportional to 1/M², so the more mass a sphere contains, the less density is required for it to become a black hole.

Because of this, a uniform collapsing sphere will reach the density at which it will become a black hole before any regions within the sphere will reach their critical densities. Basically, at the point at which the entire core can become a black hole, a small portion of the center is quite far from being dense enough to be a black hole on its own. So, rather than starting as a small black hole in the middle of the core and growing, the black hole will in essence form all at once, with the entire mass of the core contained (and will therefore not evaporate immediately).

In that case everything is solved with evaporation.

But, if formation is not instant, if that core is capable to withstand gravitational pressure before becoming black hole it should be capable to hold itself at later point, because nothing changes much

We have mass M enclosed in some volume and after we add 1g it becomes black hole.
Such small change of mass should not result instant collapse of everything into mathematical dot.

[Frog march]

Why? Why cant the hole just form big? With all of the mass that is inside of the eventual EH turning into a BH simultaneously?

but all the mass of the star is seen as outside of the event horizon, and falling in;;;would that set up just pop into existence where before there had just been a collapsing body?

[Digix]

Doesnt the SR exists regardless of if a BH exists or not? Once the collapse happens where the mass density is great enough so that a BH would exist, everything inside of the SR is now inside of the BH ....

SR concept of inescapable black holes is based on assumption that black hole is mathematical dot.

if we could imagine black hole not as singularity but as large object it is not unescapeable anymore, you can just stand on its surface and climb out using lader.

or alternatively we can imagine black hole as star which lost all mass beyond Schwarzschild radius, but it inside it is not singularity.

[cjl]

In that case everything is solved with evaporation.

But, if formation is not instant, if that core is capable to withstand gravitational pressure before becoming black hole it should be capable to hold itself at later point, because nothing changes much

We have mass M enclosed in some volume and after we add 1g it becomes black hole.
Such small change of mass should not result instant collapse of everything into mathematical dot.

The core isn't capable of withstanding the pressure before it becomes a black hole. That's why it's collapsing. The collapse isn't instantaneous though - it takes some finite time, during which the density is increasing. Light is still able to escape until the star falls within its own schwarzschild radius though.

[tommac]

but all the mass of the star is seen as outside of the event horizon, and falling in;;;would that set up just pop into existence where before there had just been a collapsing body?

The event horizon does not exist until the critical mass density reaches a certain threshold, At that point you have a massive BH. The SR radius already contains, lets say a solar mass of mass when it forms.

[tommac]

SR concept of inescapable black holes is based on assumption that black hole is mathematical dot.

if we could imagine black hole not as singularity but as large object it is not unescapeable anymore, you can just stand on its surface and climb out using lader.

or alternatively we can imagine black hole as star which lost all mass beyond Schwarzschild radius, but it inside it is not singularity.

What do you think a EH is? What is inside doesnt really matter, as we can not observe it. Also the EH itself is a singualrity I believe.

[tommac]

SR concept of inescapable black holes is based on assumption that black hole is mathematical dot.

if we could imagine black hole not as singularity but as large object it is not unescapeable anymore, you can just stand on its surface and climb out using lader.

This is not true. the ladder would collapse, space curves in on itself in such a way that light travelling in the direction away from the singularity can not escape because of the space-time curvature.

Anything that you try to do to escape would fail because space time is blocked off from the outside universe.

[Strange]

SR concept of inescapable black holes is based on assumption that black hole is mathematical dot.

No. The black hole is a sphere (spheroid) with Schwarzschild radius.

if we could imagine black hole not as singularity but as large object it is not unescapeable anymore, you can just stand on its surface and climb out using lader.

Maybe you should suggest that to NASA as a replacement for the shuttle.

[Digix]

This is not true. the ladder would collapse, space curves in on itself in such a way that light traveling in the direction away from the singularity can not escape because of the space-time curvature.
Anything that you try to do to escape would fail because space time is blocked off from the outside universe.

this depends on strength of lader.
and you dont have any reason to believe that gravity is more powerful than Pauli exclusion which gives things volume. In any case force is not infinite and not much different than pressure in the center of star so theoretically it may be possible to withstand it.
if core managed to withstand that pressure before collapse why it should not hold it after colapse?

I do not claim any ATM theory here, but GR does not take into account lots of things assuming that they are insignificant.

Impossibility of escape is based on fact that You have rocket you cant have more fuel than yous mass. And below horizon you need more fuel than your mass to escape assuming 100% mass to energy conversion.
But if we use ladder this is no longer valid.