Starship Asterisk*

Qev wrote:An event horizon forms when the density increases to the point where the surface escape velocity reaches the speed of light. It's a pretty straightforward calculation for a single body, v(esc) = sqrt( 2GM / r ).

Hm, something occurred to me...

What does "velocity" mean in the presence of enough concentrated mass to affect the time continuum in a significant way?

I'm not saying black holes don't or can't exist, but I'm wondering whether equations as simple as v(esc) = sqrt( 2GM / r ) can even apply directly in a significantly relativistic environment.

I'm no mathematician, and I'm certainly not an astrophysicist, but my experience with people in this world in general is that they tend to oversimplify things so that they fit within their own frames of reference.

Just food for thought.

-Noel

Hello All

The Chicken and the egg.


A black hole cannot form unless it has mass(matter) added.

Progressive formation of a black hole after a supernova is dependent on the amount of matter(mass) available.

This will detemine whether a neutrons star, a quark star or what ever composite.

The mass is part of the formulae to create a zone where subatomic particals such as quarks and preon paricals can remain stable. The forces required to keep this stable are so great that the escape velocity of light cannot escape. The vector forces point into the ultra dense matter (black Hole). In so doing all EMR cannot escape and thefore our communication line is broken.

People talk about time stopping and all that fantasy stuff. Its just a communication problem.

Roy Orbison said communication breakdown.

kovil wrote:I interpret this statement to show that mini-black holes do not exist, meaning that high density is not the factor to cause an event horizon, it is more a function of a critical mass. Without the sufficient mass, an event horizon will not form, regardless of virtual density.

I wouldn't say that, exactly. It's more an inverse relationship between mass and density. For very small masses (ie. mini-black holes), the required density in order for an event horizon to form would be much higher than that needed for the formation of a stellar-mass black hole. Apparently, a supermassive black hole of one billion solar masses has an average density of only 20 kg/m^3, which is much less than that of water.

NoelC wrote:What does "velocity" mean in the presence of enough concentrated mass to affect the time continuum in a significant way?

I'm not saying black holes don't or can't exist, but I'm wondering whether equations as simple as v(esc) = sqrt( 2GM / r ) can even apply directly in a significantly relativistic environment.

That equation is definitely a simplification of things, I have no doubt; it's based primarily on the Schwartzchild model of black holes, which is a simple, non-rotating solution from Einstein's relativity. I don't think 'velocity' changes its meaning in warped spacetime, at least outside of an event horizon, but I could be wrong.

Hello All

Qev said

I wouldn't say that, exactly. It's more an inverse relationship between mass and density. For very small masses (ie. mini-black holes), the required density in order for an event horizon to form would be much higher than that needed for the formation of a stellar-mass black hole. Apparently, a supermassive black hole of one billion solar masses has an average density of only 20 kg/m^3, which is much less than that of water.

20 Kg/m^3 is not correct: Which paper quoted this?

The pregresive density and size compared to our sun

Sun's core 10^5 I question this.

Neutron star 10^15 to 10^18 10kms Dia

Quark Star 10^18 to 10^22 4 M Dia

Preon Star 10 ^ 22 to 10^35 400mm Dia

Black Holes over 10^35 very small


In order to create zones for degerated matter to occur. You need extreme heat and matter.

A large star will go through billions of years. Its central inner core near the end before the suprnova loses its mass and from this its control to hold onto the solar envelope and its ability to control heat release from the inner core. High energy photons are released in the solar envelope hitting the accumulated iron causing a very fast fission reaction breaking the iron down very quickly in a chain of events that huge amounts of energy from the fission and fusion reaction is realeased causing the supernova.

The zone is set for extreme heat and lots of matter in the form of neutrons formed from the Iron and other elements breaking down to neutrons.

These neutron all collect in the inner core creating a Neutron Star.

The progressive compaction is determined by the amount of matter(MASS).

At what density the black hole is formed. That I do not know.

But! there are stars out there 1000's of times that of our sun and do not form a black hole just by there size and mass.

harry wrote:Hello All

Qev said

I wouldn't say that, exactly. It's more an inverse relationship between mass and density. For very small masses (ie. mini-black holes), the required density in order for an event horizon to form would be much higher than that needed for the formation of a stellar-mass black hole. Apparently, a supermassive black hole of one billion solar masses has an average density of only 20 kg/m^3, which is much less than that of water.

20 Kg/m^3 is not correct: Which paper quoted this?

No paper, it's a straightforward calculation.

Given a black hole massing one billion solar masses (2.0e39kg), it ends up having a Schwartzchild radius of 2.96e12m, enclosing a volume of 1.09e39m^3. Mass over volume = density, and this works out to be 18.32kg/m^3, which is roughly 50 times less dense than water.

Since a black hole forms when you compress a given amount of matter inside it's own event horizon, as counterintuitive as this seems, it works out.

At what density the black hole is formed. That I do not know.

It depends on the amount of mass.

But! there are stars out there 1000's of times that of our sun and do not form a black hole just by there size and mass.

That's certainly true! Well, a hundred times, anyway. Other forces come into play, most important of which is probably radiation pressure due to the fusion reactions that power stars. This prevents further collapse and blows away otherwise-accretting matter, and is why we have stars instead of black holes everywhere.

The calculations I'm doing here are assuming that the matter involved is inert, ie. incapable of fusion. Realistically, you're not going to see a billion solar masses of inert matter all accumulating in one place to a density like 20kg/m^3... but if it DID happen, you'd wind up with a black hole.

Hello Qev

A neutron star has a density 10^14 g/cc and 10 Km Dia compared to the sun.
How can a black hole have a density much much less and prevent light from escaping.

harry wrote:Hello Qev

A neutron star has a density 10^14 g/cc and 10 Km Dia compared to the sun.
How can a black hole have a density much much less and prevent light from escaping.

Because really, the density has little to do with anything once a black hole forms. All that matters is the strength of the gravitational field. The average density of a supermassive black hole (across the entire volume enclosed by the event horizon) may be small, but the total mass is not, nor is the gravitational field strength.

Hello Qev

I must be slow.

You said

Because really, the density has little to do with anything once a black hole forms. All that matters is the strength of the gravitational field. The average density of a supermassive black hole (across the entire volume enclosed by the event horizon) may be small, but the total mass is not, nor is the gravitational field strength.

A blck hole forms because of the intense density. The forces that hold the density as a neucleon are aslo responsible for preventing light from escaping. The gravitational fied is created by the density= mass/volumn.

I hope you do not think a black hole is a well.

But! I do understand your logic with the event horizon been part of the Volumn. I do not consider this when calculating the density of the compact core.

Hello Qev

You may find this interesting reading

http://articles.adsabs.harvard.edu//ful ... 1.000.html

Regarding this density discussion... Are we perhaps talking about two different things? The density inside the entire event horizon, and the density within the body made of compressed matter that is creating the event horizon?

Harry, your posts may be intended to make folks think, but you do tend to come across in a matter-of-fact, almost dismissive tone, as though you know it all and we readers of your posts know nothing. Please try to keep in mind that you may have strong opinions but that to state them as simple fact comes across as rather arrogant. It would help to say "this may be happening" instead of "this is happening".

-Noel

NoelC wrote:Regarding this density discussion... Are we perhaps talking about two different things? The density inside the entire event horizon, and the density within the body made of compressed matter that is creating the event horizon?

That's the point of confusion. As a body collapses into a black hole, the event horizon does not form at the solid surface (or singularity as the case may be), but rather approximately at the radius where the escape velocity equals the speed of light. As I understand, these generally are not equal due to collapse.

NoelC wrote:Regarding this density discussion... Are we perhaps talking about two different things? The density inside the entire event horizon, and the density within the body made of compressed matter that is creating the event horizon?

Oh, well, for my part I'm referring to the averaged density of the entire volume enclosed by the event horizon. One can't really speak of the density of the singularity (or whatever is in there), because we really don't have a decent model of what the heck is going on in there yet.

iamlucky13 wrote:That's the point of confusion. As a body collapses into a black hole, the event horizon does not form at the solid surface (or singularity as the case may be), but rather approximately at the radius where the escape velocity equals the speed of light. As I understand, these generally are not equal due to collapse.

This is certainly correct in the real world. I would imagine that a black hole forming from collapsing matter would sort of have it's event horizon 'balloon outward' from within, as the regions of highest density would cross that critical threshold before the entirety of the thing could collapse. If that made any sense at all. oO

harry wrote:A black hole forms because of the intense density. The forces that hold the density as a neucleon are aslo responsible for preventing light from escaping. The gravitational fied is created by the density= mass/volumn.

A black hole forms because of intense gravity. Density plays a role in this, as the matter must be dense enough that it all falls within its own Schwartzchild radius, but that's all.

Let me put it another way: If I have a gigantic amount of matter (let's use that 1 billion solar masses of inert stuff from before), and pack all of it into a spherical region that's ~3 billion kilometers in radius (which just happens to be the Schwartzchild radius for that amount of mass), which corresponds to a density of roughly 20kg/m^3, what is the surface escape velocity going to be?

v(esc) = sqrt( 2GM/r )

v(esc) ~ 3.0e8 m/s

The surface escape velocity for this ball of matter, which has a density of around 20kg/m^3, equals the speed of light (I'm not using very precise numbers, so the result is off by a slight margin, but good enough for government work, they say ). It must collapse into a black hole.

Hello Qev

Just mass by itself will not form an event horizon.

It requires the intense compaction of the subatomic particals creating a zone where the forces within hold back light and other EMR.

and what causes compaction of subatomic particles ? some heavy guy sitting on one ? That statement seems to flow out of keyboards as easy as I can say beer.

A black hole forms because of intense gravity

That's one way to look at it. I happen think that gravity is just a side effect of the relativistic effects of mass density on the passage of time. So I tend to agree more with the wording of Harry's statement that says:

A bl[a]ck hole forms because of the intense density.

-Noel

I am sure you are mixing up Newtonian Physics with Quantum Mechanics when discussing density as the common denominator. There is a huge difference between gravitational forces and mutual attraction.

NoelC wrote:

A black hole forms because of intense gravity

That's one way to look at it. I happen think that gravity is just a side effect of the relativistic effects of mass density on the passage of time. So I tend to agree more with the wording of Harry's statement that says:

A bl[a]ck hole forms because of the intense density.

-Noel

The required density is a function of the total mass, however. There is no one fixed density limit for the formation of an event horizon. The greater the total mass, the lower the required density. I imagine we're just saying the same thing from different directions, really. Mass and density both play a role, I'm just trying to point out that the density doesn't need to be particularly high, when dealing with large amounts of mass.

Qev; I am beginning to see where this is going.

With a superduper high density, mini black holes would form (assuming this is possible, i myself doubt it),

Then with a dozen solar masses a black hole would form (whatever is beyond a neutron star) and have a density (average inside the event horizon) less than a neutron star. (not a fair comparison as the escape velocity is less than light speed for the neutron star)

With a million solar mass (sm) black hole (bh) the event horizon (eh) would be further out than the dozen sm bh, and the average density inside the eh would be less than the dozen sm bh.

A billion sm bh would have a bigger diameter eh than a million sm bh and so the average density inside the eh would be lower than for the million sm bh.

Let's jump ahead a little bit to where we are at the size of an octillion sm bh and its eh is very large indeed, and so the average density of the space inside the eh is much lower than the bh's of smaller total mass index previously.

To go to the end of this exercise, if we define our visible universe, or our awareable universe (what we can be aware of, as anything further is not sending us any light-speed information) ; Our Universe in other words, our awareable universe is a black hole, as the escape velocity at the perimeter is above light speed, as no information can reach us ! And it is such a large solar mass number, 10^100 solar masses (maybe, I'm totally guessing) the solar masses number is so great, the average density can be so low, it matches the vacuum of space that we see !!!!!!!!!!!!!!!!!!!!!!!!

We are living inside an event horizon !

Thanks, Qev, I'd not seen it this way before.


Sorry I took so long to get to the point.

To go another step further, I think someone has calculated the average density we see locally in the galaxy and for a few billion light years or so. Using that average density number, can you calculate what the total solar masses would be and then what the event horizon diameter would be for that number of masses, and what the average density would be, and does that match the average density of the universe we see? By working it back and forth a little to get things to match up, can this tell us where the border of our awareable universe should be? Does it work out to 15 billion light years?

Or to go the other way, how much mass would be needed to make an event horizon of 30 billion light years in diameter and what would the average density be within that volume? Does this correspond to what we experience???

If not, can any numbers we do experience be plugged into this formula and will it calculate what the size of our universe should be, and then will the new super-large telescopes be able to look that far or farther. Will observational astronomy be able to see 'the wall' ! , beyond which we cannot see beyond.

Hello All

Hi! Kovil

Our universe cannot be a BH and cannot have an event horizon regarless of the mass.

Some of the super dooper super galaxy clusters of clusters of galaxies do not have an event horizon.


One day we will see beyond where no man has dreamt of seeing. Need to wait a few more years,,,,,,,,,,,,,,,,,,,giant telescope.

Many years ago I discussed this issue with NASA.

They said to me that once we see past 5 billion light years we shall start to see the birth of the universe in its early stages, than they said 6, than 7 and so on upto 13.2 Gyrs. They said we should have seen the birth, but we see a mixture of animals old and young, somethiing that we did not expect.

I have been called many names in the past for not thinking along the Big Bang Theory and in many cases not talked to because of that.

kovil wrote:To go another step further, I think someone has calculated the average density we see locally in the galaxy and for a few billion light years or so. Using that average density number, can you calculate what the total solar masses would be and then what the event horizon diameter would be for that number of masses, and what the average density would be, and does that match the average density of the universe we see? By working it back and forth a little to get things to match up, can this tell us where the border of our awareable universe should be? Does it work out to 15 billion light years?

Well I can only find approximate estimates of the mass of the visible universe, so far, but they all seem to fall about the same range, on the order of 6e51 kg or so. Now, I have no idea if this is just the luminous matter, or if it includes dark matter. Anyway, it works out to an event horizon radius of only 940 million light-years, much smaller than the visible universe, so we're not stuck in a black hole yet.

Or to go the other way, how much mass would be needed to make an event horizon of 30 billion light years in diameter and what would the average density be within that volume? Does this correspond to what we experience???

That works out to a value roughly 100 times the amount of matter currently present in the visible universe, ~1e53kg. The average density would be near 8e-27kg/m^3, which is a little over 100 times more dense than what we observe.

If not, can any numbers we do experience be plugged into this formula and will it calculate what the size of our universe should be, and then will the new super-large telescopes be able to look that far or farther. Will observational astronomy be able to see 'the wall' ! , beyond which we cannot see beyond.

I imagine we won't be able to see the 'edge' of the universe, so to speak. More than likely what we'll observe is simply things becoming dimmer and more and more redshifted, until they're beyond observability.

Which is weirdly like looking at something falling into an event horizon, now that I think of it.

Hello Qev

What is the purpose?

A very interesting train of thought, though Harry's dismissive tone rains on the parade over and over again. I'm sorry, I shouldn't get irritated.

Harry, how do you know "Our universe cannot be a BH and cannot have an event horizon regarless of the mass"?

I'd say the purpose is that it makes lively and interesting discussion. It doesn't need more than that.

I don't know about how others feel, Harry, but I think a little humility in your writing would do you a world of good.

We are seeing well past 5 billion light-years, assuming one takes the red shift measurements to imply distances. I still question this basic assumption, but I'm keeping an open mind. It's interesting that now and again I see distance numbers quoted WELL in excess of 13.7 billion light-years. I've always taken that to mean this red shift = distance theory isn't quite complex enough. It's also why I wonder whether things we regard as constant - e.g., the speed of light - have not always been so.

Oh, and ta152h0, I don't believe I'm mixing up anything. In my view, the universe is not mixed up, it is not running on "Newtonian Physics", specifically, nor "Quantum Mechanics". It is an integrated whole, running on its complex set of rules, and that's how I imagine it. I don't claim to understand 1% of any of these fields, but I really don't need to now, to be able to picture 3 physical dimensions + 1 (time) in my imagination, then develop my own views on how it works.

Can you further describe this "huge difference" you speak of between gravitational forces and mutual attraction? Surely you're not just talking about the other forces (magnetism, nuclear forces, etc.)? Note that I didn't say the perturbation of time by mass density was the only thing operating here.

I imagine we won't be able to see the 'edge' of the universe, so to speak. More than likely what we'll observe is simply things becoming dimmer and more and more redshifted, until they're beyond observability.

I like the way you think, Qev. That sounds very right to me.

And what if time is traveling backwards in this huge black hole in which we live, and what we see as expansion is really in grand sense the collapse of matter inward from material falling into the universal event horizon. And further, what if entire new universes are being created in our own black holes, and universes within them, ad infinitum? Perhaps we're seeing into the future with our telescopes.

-Noel

Qev, let's go one more step in this thought experiment.
(the last paragraph says it best, and I brought all that up front here)

*** We are surrounded by the outside of an event horizon. *** LOL

We aren't inside a black hole we are surrounded by the outside of one !
We are inside of the outside,

Hamlet was correct, " Though my universe would be bounded by a nutshell, I could consider myself a King of Infinite Space." !

*** What would be the size of the event horizon, based on the average density we do see, and how much mass would be required to result in this. ***
(sorry it took so long to say it clearly!)

- - -

<<
Quote:
Or to go the other way, how much mass would be needed to make an event horizon of 30 billion light years in diameter and what would the average density be within that volume? Does this correspond to what we experience???

That works out to a value roughly 100 times the amount of matter currently present in the visible universe, ~1e53kg. The average density would be near 8e-27kg/m^3, which is a little over 100 times more dense than what we observe.

Quote:
If not, can any numbers we do experience be plugged into this formula and will it calculate what the size of our universe should be, and then will the new super-large telescopes be able to look that far or farther. Will observational astronomy be able to see 'the wall' ! , beyond which we cannot see beyond.

I imagine we won't be able to see the 'edge' of the universe, so to speak. More than likely what we'll observe is simply things becoming dimmer and more and more redshifted, until they're beyond observability.

Which is weirdly like looking at something falling into an event horizon, now that I think of it. >>

- - -

So, an event horizon of 30 billion light years requires 100 times more mass than we think our universe contains. And the average density we observe is 100 times more dense than the density an event horizon of 30 billion light years would result in. It sounds like we have some kind of correspondence going on here !!!

*** I'm having trouble saying all this clearly. I'm seeing two calculations here, one for size of the event horizon based on the density we observe, and how much mass would that require.

*** With this as our parameters, what would be the size of the event horizon for the density we do see in our universe? and how much mass would that predict our universe should have?

- - -

We are not inside of a black hole exactly, but there are some similarities.

*** We are surrounded by the outside of a black hole. ***

As we look further it starts to look like we are looking toward a black hole !

How poetic justice !

I haven't read much of this thread, from the little I just scanned:

A black hole (in theory) can be any size object that the escape V is equal or greater than the speed of light. The minimum would be a mass meeting the above criteria with the event horizon exceeding the shortest wavelength of EMF. Or, an object smaller than a wavelength of light and dense enough that light cannot escape. It is both the mass and the density are interrelated in determining if an object is a BH - mostly density. On a small scale, the larger the event horizon becomes the total density within the EH may become less (inverse square law).

The density of a galaxy or cluster, as a whole, does not meet the criteria of the escape V being greater than c, the orbit is too large = the density too small.

Hello All


I agree with Dr Skeptic

Smile

Not much fun when someone agrees.