How Can We Be Sure About Black Holes and Galaxies?

[DaveC426913]

So, when it collapses further down, I think its a "singularity", about the size of the head of a needle, is the gravitational pull the same as before the collapse or does it decrease as well. I'd say it decreases to, but nothing seems to be apparent out there? Any insight on that?

Simply put, if the mass hasn't changed (which it hasn't), the gravity won't change.

 

[dj1972]

WOW, that would definitely part your hair! So when they say a teaspoon full of matter would weigh something like 40 billion tons, there serious. That is almost incomprehensible! But seriously cool.

 

[DaveC426913]

WOW, that would definitely part your hair! So when they say a teaspoon full of matter would weigh something like 40 billion tons, there serious. That is almost incomprehensible! But seriously cool.

Yep.

In theory of course...

It's that dense because it's under huge pressure. If you literally extracted a teaspoon of it, it would explode like a bomb because of the release in pressure.

 

[dj1972]

Yeah, have to think theoretically. But still, that's some pretty wicked stuff.
So if it starts out roughly around 12 - 15 km, how does it get to the size of a head of a needle? Its already compressed beyond belief, but to compress more... I know its massive pressure, and its getting broken down smaller and smaller, but if your not losing mass, how does it get to a little point like that? I know they release radiation and such, but wouldn't that be from the BH releasing trapped energy and not mass? Or is the energy coming from the mass breaking down creating the energy? But then it would be losing mass. So how do you get one without the other??

 

[Chalnoth]

Yeah, have to think theoretically. But still, that's some pretty wicked stuff.
So if it starts out roughly around 12 - 15 km, how does it get to the size of a head of a needle? Its already compressed beyond belief, but to compress more... I know its massive pressure, and its getting broken down smaller and smaller, but if your not losing mass, how does it get to a little point like that? I know they release radiation and such, but wouldn't that be from the BH releasing trapped energy and not mass? Or is the energy coming from the mass breaking down creating the energy? But then it would be losing mass. So how do you get one without the other??

Are we talking about neutron stars now? Well, under the gravity of the neutron star, the matter gets compressed to such extreme levels that the electrons and the protons combine to produce neutrons (neutrons are slightly higher energy states, but under high pressure scenarios, the energy balance shifts so that neutrons are preferred). And neutrons are much, much smaller than atoms, so the density becomes much higher. Bear in mind that atoms are mostly empty space, so without the electrostatic repulsion of the electron shell, they can be vastly more compact.

If instead you are talking about the degenerate matter that makes up white dwarfs, what's basically going on there is that the atoms are squeezed together so tightly that the quantum mechanical limit that prevents two electrons from being in the same state at the same time prevents them from being squeezed further.

 

[dj1972]

AHHHHHHHHH, that makes sense. Got ya. I knew there was an answer some where's.

OK, so let's back up a bit in time right as the sun starts to do all this. The sun goes through these phases where it loses it outer layers as in collapsing or exploding or what ever it does and the core is left. Right? (Trying to keep it simple, so if you need to be technical OK, let it fly) So why isn't the core being vaporized. Is this from the gravitational effect on itself? "I" would think from the initial explosion it would literally pull the core apart. Let's face it, that is very catastrophic. Or is it because the core expanded rapidly from the explosion then the core pulls itself back with so much force it is causing the initial collapse of the core to be so small then continues to get smaller from pressure? And if all of this is from gravitational effect, then I really don't want nothing to do with it! LOL I know these question might seem to be off the wall or not as technical as you may ask them, but I am not that advanced in the technical side of this. Sorry.

 

[Chalnoth]

Well, I'm not quite sure what you're talking about here, but when a star undergoes an explosive event, it does tend to throw out lots and lots of matter. However, it isn't able to throw out too much matter, as the self gravity is just so strong that there remains a significant portion that is unable to escape.

 

[Nabeshin]

http://en.wikipedia.org/wiki/Supernova

This page should give you an idea of the mechanisms involved in the supernova process and why it is not always enough to prevent collapse into neutron stars or black holes.

 

[dj1972]

Sorry to confuse, had baby girl at same time. Totally thanks for the info Nabeshin, I'm reading it right now.

 

[ElectroBurger]

If instead you are talking about the degenerate matter that makes up white dwarfs, what's basically going on there is that the atoms are squeezed together so tightly that the quantum mechanical limit that prevents two electrons from being in the same state at the same time prevents them from being squeezed further.

It was in my understanding though that all matter, even neutrons obey the rules of degereracy and try to stay apart. Would this come to play in the big bang? Since all of the matter started out as the size of a single proton, was degeneracy what forced the matter ot of its starting position?

 

[DaveC426913]

It was in my understanding though that all matter, even neutrons obey the rules of degereracy and try to stay apart. Would this come to play in the big bang? Since all of the matter started out as the size of a single proton, was degeneracy what forced the matter ot of its starting position?

There were no atoms, or even protons at or even much later* than the BB. It was far, far too hot and energy-dense for any kind of matter. There was only energy.

* about 1 millisecond - an epoch in a BB timeline

 

[v2kkim]

Black hole has no volume but it affects other objects through gravitation, meaning that the gravitation field is so magical that it escapes through horizon of event and announces its existence to all other stars. My question is about electrostatic force. If the BH has some charge, say positively charged, then can we feel that from outside ? Can the electrostatic force can escape BH to reach outside ?

 

[Chalnoth]

It was in my understanding though that all matter, even neutrons obey the rules of degereracy and try to stay apart. Would this come to play in the big bang? Since all of the matter started out as the size of a single proton, was degeneracy what forced the matter ot of its starting position?

Not all matter. Only fermions. But yes, Neutron stars are supported by neutron degeneracy pressure in the same way that white dwarfs are supported by electron degeneracy pressure. It's just that the physics works out such that Neutron degeneracy pressure allows for denser matter (by a very significant amount).

Caveat: this is a rather simplistic view, and is understood not to be completely accurate. Apparently some regions within the neutron star are actually composed of a proton-electron superfluid that is at about the same density, and there may be other complexities. But the basic idea of why a neutron star is so dense can be understood just from neutron degeneracy pressure.

 

[dj1972]

OK I'm back, went did some reading. Everything I'm reading I'm assuming is mostly theory. Understood. So if this is all theory, how can we be certain this is right? I'm not trying to make anyone mad by stating this, I'm just being curious. (I meen come on, once upon a time we thought the Earth was flat, look where that got us) So what if its something totally different? Let's take for example, the sun. We haven't been there, not walk on it (Which would be totally cool) let alone touched any of it. We can only assume we know what is going on from the things that happen here on earth. So what if our data is wrong from what is really going on? I just read an article that they just realized that our galaxy is bigger then once believed. So again, if we haven't been outside of it looking back how can we really know? I know they plotted out where some stars are at. But wouldn't that be a small portion of what were looking at? I understand the deal with the red shift and all, but that isn't answering anything that is physically going on with galaxies and BH and super novas. I know this is probably where its going to get heavy in the math area. So if you have to let it fly. Again, I'M really intrigued by all this don't get me wrong and if I offend someone I'M sorry, I did not mean too.

 

[DaveC426913]

OK I'm back, went did some reading. Everything I'm reading I'm assuming is mostly theory. Understood. So if this is all theory, how can we be certain this is right? I'm not trying to make anyone mad by stating this, I'm just being curious. (I meen come on, once upon a time we thought the Earth was flat, look where that got us) So what if its something totally different? Let's take for example, the sun. We haven't been there, not walk on it (Which would be totally cool) let alone touched any of it. We can only assume we know what is going on from the things that happen here on earth. So what if our data is wrong from what is really going on? I just read an article that they just realized that our galaxy is bigger then once believed. So again, if we haven't been outside of it looking back how can we really know? I know they plotted out where some stars are at. But wouldn't that be a small portion of what were looking at? I understand the deal with the red shift and all, but that isn't answering anything that is physically going on with galaxies and BH and super novas. I know this is probably where its going to get heavy in the math area. So if you have to let it fly. Again, I'M really intrigued by all this don't get me wrong and if I offend someone I'M sorry, I did not mean too.

Science is based on building models that fit our observations. The model we've created does so.

Anyone, anywhere is free to create a different model based on a different theory to challenge it. But their model has to explain our observations at least as good as if not better than the generally-accepted model.

It is as easy as that.

And as hard as that.

Our current models explain what we see exquisitely well. So well in fact, that we can be pretty confident enough to extraploate into areas we're less sure about.

 

[Nabeshin]

OK I'm back, went did some reading. Everything I'm reading I'm assuming is mostly theory. Understood. So if this is all theory, how can we be certain this is right? I'm not trying to make anyone mad by stating this, I'm just being curious. (I meen come on, once upon a time we thought the Earth was flat, look where that got us) So what if its something totally different? Let's take for example, the sun. We haven't been there, not walk on it (Which would be totally cool) let alone touched any of it. We can only assume we know what is going on from the things that happen here on earth. So what if our data is wrong from what is really going on? I just read an article that they just realized that our galaxy is bigger then once believed. So again, if we haven't been outside of it looking back how can we really know? I know they plotted out where some stars are at. But wouldn't that be a small portion of what were looking at? I understand the deal with the red shift and all, but that isn't answering anything that is physically going on with galaxies and BH and super novas. I know this is probably where its going to get heavy in the math area. So if you have to let it fly. Again, I'M really intrigued by all this don't get me wrong and if I offend someone I'M sorry, I did not mean too.

You're putting far too much speculation into a lot of things. If you want to go this route, we don't know anything. Yet your cell phone continues to work, your computer boots up, we communicate with satellites, etc. Our understanding of a lot of physics is, at the very least, a very good approximation of reality. Our knowledge of our own sun is quite extensive in most areas, although lacking in a few. Fundamental things such as the composition of the sun and its mechanism for energy production are so well established that I would call them fact.

As far as BH's are concerned, which is really what this thread is about, they seem to be purely theoretical constructs to most people. However, there is a lot of evidence for their existence in the universe. For one, the observed high-intensity x-ray radiation spectra from certain objects conforms almost exactly to what is predicted in the situation of a BH accretion matter. More direct evidence (I would consider) comes from observations of gravitational interactions where we deduce there are x solar masses of material in a space of y, so the density must be z, where z corresponds to densities that result in a black hole.

As far as galactic modelling is concerned it is notoriously difficult to study our own galaxy because of the massive amount of dust which interferes with measurements. We did discover that our galaxy was bigger than previously thought, but not so much so that it drastically changed our concept of the Milky Way. We also recently discovered that the milky way is probably a barred spiral galaxy instead of a normal spiral galaxy. The refinement of measurements leads to more and more accurate data which allow us to refine our models, but in general they are not terribly far off.

Like I said at the beginning of this post, I think you are introducing far more uncertainty than actually exists into a realm of study where (although we cannot directly manipulate objects), many things are quite well understood.