Black Holes... They are some of the most mysterious objects in our universe. Technically, they have infinite density because their actual size is infinitely small. Any comments on this infinite density. Do you think it is actually possible to have infinite density or is it finite, but very large? Will it ever be possible to measure this density or size? And to clear things up for those who may not understand, if our sun collapsed into a black hole tomorrow, we would still be here, because the gravity does not change at distance.
Black Holes
Our sun couldn't collapse into a black hole as it's not massive enough.
The infinities involved are anathema to many physicists and they're rather glad that singularities are hidden behind event horizons; it saves having to face them full on.
As for being able to measure infinites, that is inherently impossible. In order for anything to be measured, it must have a finite value. In the case of singularities, infinite values are purely hypothetical. We can't see what goes on behind the event horizon so there is no way of ever knowing if such theories are accurate.
The infinities involved are anathema to many physicists and they're rather glad that singularities are hidden behind event horizons; it saves having to face them full on.
As for being able to measure infinites, that is inherently impossible. In order for anything to be measured, it must have a finite value. In the case of singularities, infinite values are purely hypothetical. We can't see what goes on behind the event horizon so there is no way of ever knowing if such theories are accurate.
Since you seem to know much more than me...probably because i haven't really researched much, just thought about it...Do we know what the gravity is at the event horizon...I could go to my physics book and probably find the equation. Do you think it would be possible to develop a strong enough material that could actually act as a connector into a black hole?
I doubt it as even light has trouble escaping the strong gravity.
The topic "Black Holes" has always remained a matter of excitment for me from the very beginning. So, I explored a great extent of archives relating to the knowledge of these black holes. Black holes are something formed as a leftover of the Nova or Supernova explosion of a star and I must mention that our sun and in fact every star in the universe has to become a black hole int he future. Talking about the density of a Black hole, yes, it is so much huge that it approaches infinity, but is still finite. If sun were to collapse to a black hole tomorrow, then we wouldn't be alive before more than thousands of year before it becoming a hole, before the supernove stage, the star has to pass through another stage when it gains a huge structure and mass due to the uncontrolled nuclear fusion reactions that break out on the surface of star. In that stage, the star is known as the Red Giant and it has been predicted that in its Red Giant stage, the sun will gallop the inner four planets, including Earth, and not to be mentioned, the whole civilization will destrot due to the immense heat.
Regarding Black holes, you may prefer certain "Best" books, two of these written by the renowned Scientist(and the greatest of present) : Stephen Hawking. His works - Black Holes & Baby Universes and A Breif History Of Time. Do read them. You will certainle enjoy.
Regarding Black holes, you may prefer certain "Best" books, two of these written by the renowned Scientist(and the greatest of present) : Stephen Hawking. His works - Black Holes & Baby Universes and A Breif History Of Time. Do read them. You will certainle enjoy.
yeah , even light was trapped so i guess nothing in this world cannot be suk into black hole .
| anurag_bhd wrote: |
| Black holes are something formed as a leftover of the Nova or Supernova explosion of a star and I must mention that our sun and in fact every star in the universe has to become a black hole int he future. |
Just to correct a couple of misconceptions. Black holes can be formed other than by novae or supernovae. A block hole can form from gas, water or even milk if there is enough of it. One has to remember that gravity acts as if from a central point. Therefore any mass aggregated will increase the gravitational field. It doesn't matter over how large an area that aggregation occurs. It is quite possible that the overall gravitational force of our universe is enough to make it a black hole.
Not every star in the universe has to become a black hole in the future. A black hole will suck in matter that falls within its gravitational field, and by so-doing will increase its mass hence making its field stronger and further-reaching. However, one has to take into account the expansion of the universe. As space expands, the distance between black holes must become greater. If our universe is truly open, it will keep expanding. Once stars have used up their fuel and all novae & supernovae have gone phut,the distances between any remaining objects will be so vast that their gravitational attraction will have no effect. All that will be left is a dark universe with nothing whatsoever happening. Particles will lose their energy and entropy will reign supreme.
A common misconception about black holes is that nothing can escape from it. This is only valid in a classical conception of a black hole, not considering quantum physics.
According to quantum physics every particle is able to escape from a black hole, the chance is just very very very low, next to nothing. However, it does happen all the time and if I'm not mistaken it has already been observed in reality. In fact, statistically every particle will eventually 'escape' from a black hole.
However this theory is still in a very early stage.
According to quantum physics every particle is able to escape from a black hole, the chance is just very very very low, next to nothing. However, it does happen all the time and if I'm not mistaken it has already been observed in reality. In fact, statistically every particle will eventually 'escape' from a black hole.
However this theory is still in a very early stage.
My ex-wife was definitely a black hole where the contents of my wallet were concerned. She would suck out the contents for them never to be seen again. 
It is true about the escaping...
The particle jets on it are explained with this. Also the Consept of warmholes in Black Holes is way down on prablity becasue you would need negitive energy to stay alive inside of it, and pass in a timely manner. It is easier to create a Anitmatter ray, than make negitive energy!
The particle jets on it are explained with this. Also the Consept of warmholes in Black Holes is way down on prablity becasue you would need negitive energy to stay alive inside of it, and pass in a timely manner. It is easier to create a Anitmatter ray, than make negitive energy!
Don't forget dark matter
This unidentified missing energy in the universe could have serious affects on the theory of blackholes.
we don't yet have a quantum gravity principle, which in the future will describe accurately the formation of blackholes.
This unidentified missing energy in the universe could have serious affects on the theory of blackholes.
we don't yet have a quantum gravity principle, which in the future will describe accurately the formation of blackholes.
I think blackhole is some kind of assumption that scientists use to explain things. If a star exploses, why does it have to become blackhole? why can't it just 'vanish'? I think there must be something weird/interesting around the star after it exploded. I wish to discover more about that.
time_ar - Not all stars that explode become black holes. Nebulae are the gaseous residue of stars that have exploded.
To explain why some become black holes and others don't is a bit complex. Our sun is about half way through its lifespan. It's still converting hydrogen to helium. However, when all the hydrogen has gone the fission process will continue. The helium will be converted to something else and so on. Eventually the star is fissioning iron and other heavy elements.
There will come a time when the heat produced is no longer sufficent to overcome the star's own gravity & the surface will collapse towards the center. This causes a bit of a bang & much of the star's remaining mass is blasted of into space as a shell. This is called a nova. If the star is massive enough, the blast is unbelievably intense and can glow brighter than all the other stars in the galaxy added together. This is called a supernova. (All heavy elements that exist in the universe are the result of supernovae explosions.)
OK, so the star's had a tantrum & chucked its toys (in the form of the shell explosion) out of its pram. The bit that's left, the core, continues to contract due to gravity. All stars will eventually contract, not just those that have gone nova. Below a certain total mass, the star will become a brown dwarf - it will simply cease to shine. A bit more mass, and it will turn into a neutron star. Those with sufficient mass will continue to contract. As the star contracts its surface gravity becomes more intense (due to the mass becoming more compact) and the escape velocity at the surface will keep increasing until, in extreme cases, it becomes equal to or greater than the speed of light. The distance from the centre of the collapsing star where the escape velocity is equal to the speed of light is called the event horizon. Anything that passes through that horizon can never again leave (although that's not strictly true due to quantum effects). The star itself can continue to shrink until it becomes a point of no size & infinite density. That is the singularity.
Many scientists don't like infinite values so they're scrabbling around like mad things trying to devise ways where the singularity is avoided.
My brain hurts now so I'm going for a lie down!
To explain why some become black holes and others don't is a bit complex. Our sun is about half way through its lifespan. It's still converting hydrogen to helium. However, when all the hydrogen has gone the fission process will continue. The helium will be converted to something else and so on. Eventually the star is fissioning iron and other heavy elements.
There will come a time when the heat produced is no longer sufficent to overcome the star's own gravity & the surface will collapse towards the center. This causes a bit of a bang & much of the star's remaining mass is blasted of into space as a shell. This is called a nova. If the star is massive enough, the blast is unbelievably intense and can glow brighter than all the other stars in the galaxy added together. This is called a supernova. (All heavy elements that exist in the universe are the result of supernovae explosions.)
OK, so the star's had a tantrum & chucked its toys (in the form of the shell explosion) out of its pram. The bit that's left, the core, continues to contract due to gravity. All stars will eventually contract, not just those that have gone nova. Below a certain total mass, the star will become a brown dwarf - it will simply cease to shine. A bit more mass, and it will turn into a neutron star. Those with sufficient mass will continue to contract. As the star contracts its surface gravity becomes more intense (due to the mass becoming more compact) and the escape velocity at the surface will keep increasing until, in extreme cases, it becomes equal to or greater than the speed of light. The distance from the centre of the collapsing star where the escape velocity is equal to the speed of light is called the event horizon. Anything that passes through that horizon can never again leave (although that's not strictly true due to quantum effects). The star itself can continue to shrink until it becomes a point of no size & infinite density. That is the singularity.
Many scientists don't like infinite values so they're scrabbling around like mad things trying to devise ways where the singularity is avoided.
My brain hurts now so I'm going for a lie down!
My great friend said: "Ajmo napravit šatl i odletit do crne rupe"
trans. Lets make a shuttle and fly up to the black hole
I have been facionated by blackholes since I was young. BLack hole is some kind of material that expands and eat everything around it.
I like blackholes
Blackholes are my idols
trans. Lets make a shuttle and fly up to the black hole
I have been facionated by blackholes since I was young. BLack hole is some kind of material that expands and eat everything around it.
I like blackholes
Blackholes are my idols
No, BlackHoles does not have infinite density, because its imposible. One of Einshtains aproval - energy eqvivalate to mass. Infinite density mean infinite mass and energy.
| Kafka wrote: |
| No, BlackHoles does not have infinite density, because its imposible. One of Einshtains aproval - energy eqvivalate to mass. Infinite density mean infinite mass and energy. |
That is exactly the problem with singularities that physicists don't like. In theory, infinite density is not only possible, it is essential.
Its wrong theory I use to trust Einstains postulats
density of BH is M/R^3, R=2GM/c^2
M mass of BH
R radius of BH
G grav. const
c speed of light
I use to trust Einstains postulats
density of BH is M/R^3, R=2GM/c^2
M mass of BH
R radius of BH
G grav. const
c speed of light
Isn't it that inside black holes, the density is the maximal possible density of energy in a given space? Which is almost, but not completely, infinit.
And I can add - small BH is unstable, because where is quantum effect which destroy small BH.
THERE IS NO DARK MATTER, the plasma contanment theory killed it dead, don't yall watch tv, on the space missions the way things clump togater at a deslerating pace is not gravity because it is desceleating, its the plasma theory at its worst, but it is there, there are more powerful forces thatn gavity, it you think about galaxys are blackholes in a plasm sense.
No one actually experience this. Maybe it is just some equipment made by creatrue on other planet make light works differently for our dumb equipment.
Blackholes are massive sun collapsing on itself and sucking in all other matters on its vicinity. The gravity created is so strong that nothing can escape. Imagine our milky way galaxy collapsing on itself, until all are one huge lump of energy.
I think there is maximum threshold a black hole can take. It can only take in so much until it explodes, releasing vast amount of energy.
I think there is maximum threshold a black hole can take. It can only take in so much until it explodes, releasing vast amount of energy.
I may be wrong, but I thought a black hole was anything that had a radius smaller that its Schwartzchild Radius. I don't think a black hole needs an infinite density, or that one would actually have one. It's just a mathematical quirk, the same way that the escape velocity at the center of the Earth, if calculated naďvely, is infinite. I guess I'd better explain a few things.
You're probably all familiar with the concept of escape velocity. The escape velocity for a given body at a given altitude is the speed you have to be moving at away from the body to be able to escape its gravitational pull. Or to put it more simply, imagine you're in a rocket going up and away from the Earth and you shut off your engines. If your speed was less than the escape velocity, you will fall back to Earth. If your speed is more than the escape velocity, you will keep going out into space. If your speed was equal to the escape velocity, you will hang there in freefall (which is what space stations and orbital shuttle missions do).
The equation for escape velocity is:
Notice how the escape velocity gets higher as the mass increases. That means you need more speed to escape the pull of Jupiter than Earth, assuming you're at the same distance from the center of the planet. Notice also that the escape velocity gets smaller as the distance from the center of the body increases. That means that the closer you are to the center of the body, the more speed you need to escape (this is only theoretical, because you can't get too close to the body's center, because you'll hit the outside first - as an example, you can't be 10m from the center of the Earth because if you were you would be in the molten core under the surface, you have to be at least ~6400km from the Earth's center on average for this equation to make sense... but stick with it for now).
If we use the Earth as an example, escape velocity at the surface of the Earth (where r = ~6400km) works out to 11.2km/s. If you could possibly jump up that fast, you would fly off into space (but in reality, you would burn up first).
If you go any higher, r increases, and ve decreases. At the altitude of the International Space Station (~250km), r is ~6650km, and ve is 7.6km/s. But we can't go any lower, because if we do, we're puncturing the surface of the Earth and the math fails (because now, not all of the Earth's mass is pulling you towards the center, some is pulling you back to the surface). Using that equation for any r < 6400km yeilds nonsense results. Of course, if you set r = 0, you get an infinite escape velocity. It's not real, but it's how the math works out if you apply it naďvely.
Now consider the next step. Let's set the escape velocity to the speed of light. If we do that for a given mass, we'll see how far away you have to be from the center of that mass in order to be able to get away if you could travel at the speed of light. If we set ve to c in the equation above and rewrite, we get:
rs is called the Schwartzchild radius.
Solving for that rs for the Earth, we get 4.44mm. That's right, less than 5 millimeters. But it's only a theoretical distance, because no distance less than 6400km means anything - it's just mathematical nonsense. Because this is (much) less than 6400km, that means that light can escape from the surface of the Earth. The Earth is thankfully not a black hole.
Now, imagine the mass of the Earth was much, much greater, but the radius was the same (that is, the Earth was much, much more dense, but still not infinitely dense). As you increase m, the escape velocty at the surface of the Earth will increase. Also, rs will increase. By just looking at the formulas, you can see that if you make the mass 4 times bigger, ve will be 2 times bigger (because ve is related to the square root of m) and rs will be 4 times bigger.
Eventually, if you increase the mass enough, ve will be c, and rs will be 6400km. At that point, light on the surface of the Earth cannot escape. You don't have a black hole yet, but you're damn close.
Note that neither the mass, nor the density - nor even the radius - is infinite. The mass is huge, yes, and so is the density, but both are finite, and the radius of the body is still 6400km. The Schwartzchild radius (rs) is the event horizon - which in this case is the same as the radius of the body.
If we increased the mass more, the Schwartzchild radius/event horizon/rs will be larger, but the body's radius within the event horizon is still 6400km. And we can keep increasing the mass, which makes the event horizon bigger and bigger, but still, the core body has the same radius, and finite mass and density.
Now, in reality, you have no way of knowing how big the radius of the body in a black hole is. Anything inside the event horizon doesn't exist in this universe, as far as you're concerned. r can be 6400km, or it can be 6.4mm. You know what the mass is, because you know what the Schwartzchild radius is, but you don't know the density or the actual radius (if you know one, you know the other). Because of that, you might as well just say the radius is 0 and the density is infinite, because it makes the math simpler. It's not really true, but you can't find out what the real density or radius is, so who cares?
You're probably all familiar with the concept of escape velocity. The escape velocity for a given body at a given altitude is the speed you have to be moving at away from the body to be able to escape its gravitational pull. Or to put it more simply, imagine you're in a rocket going up and away from the Earth and you shut off your engines. If your speed was less than the escape velocity, you will fall back to Earth. If your speed is more than the escape velocity, you will keep going out into space. If your speed was equal to the escape velocity, you will hang there in freefall (which is what space stations and orbital shuttle missions do).
The equation for escape velocity is:
Notice how the escape velocity gets higher as the mass increases. That means you need more speed to escape the pull of Jupiter than Earth, assuming you're at the same distance from the center of the planet. Notice also that the escape velocity gets smaller as the distance from the center of the body increases. That means that the closer you are to the center of the body, the more speed you need to escape (this is only theoretical, because you can't get too close to the body's center, because you'll hit the outside first - as an example, you can't be 10m from the center of the Earth because if you were you would be in the molten core under the surface, you have to be at least ~6400km from the Earth's center on average for this equation to make sense... but stick with it for now).
If we use the Earth as an example, escape velocity at the surface of the Earth (where r = ~6400km) works out to 11.2km/s. If you could possibly jump up that fast, you would fly off into space (but in reality, you would burn up first).
If you go any higher, r increases, and ve decreases. At the altitude of the International Space Station (~250km), r is ~6650km, and ve is 7.6km/s. But we can't go any lower, because if we do, we're puncturing the surface of the Earth and the math fails (because now, not all of the Earth's mass is pulling you towards the center, some is pulling you back to the surface). Using that equation for any r < 6400km yeilds nonsense results. Of course, if you set r = 0, you get an infinite escape velocity. It's not real, but it's how the math works out if you apply it naďvely.
Now consider the next step. Let's set the escape velocity to the speed of light. If we do that for a given mass, we'll see how far away you have to be from the center of that mass in order to be able to get away if you could travel at the speed of light. If we set ve to c in the equation above and rewrite, we get:
rs is called the Schwartzchild radius.
Solving for that rs for the Earth, we get 4.44mm. That's right, less than 5 millimeters. But it's only a theoretical distance, because no distance less than 6400km means anything - it's just mathematical nonsense. Because this is (much) less than 6400km, that means that light can escape from the surface of the Earth. The Earth is thankfully not a black hole.
Now, imagine the mass of the Earth was much, much greater, but the radius was the same (that is, the Earth was much, much more dense, but still not infinitely dense). As you increase m, the escape velocty at the surface of the Earth will increase. Also, rs will increase. By just looking at the formulas, you can see that if you make the mass 4 times bigger, ve will be 2 times bigger (because ve is related to the square root of m) and rs will be 4 times bigger.
Eventually, if you increase the mass enough, ve will be c, and rs will be 6400km. At that point, light on the surface of the Earth cannot escape. You don't have a black hole yet, but you're damn close.
Note that neither the mass, nor the density - nor even the radius - is infinite. The mass is huge, yes, and so is the density, but both are finite, and the radius of the body is still 6400km. The Schwartzchild radius (rs) is the event horizon - which in this case is the same as the radius of the body.
If we increased the mass more, the Schwartzchild radius/event horizon/rs will be larger, but the body's radius within the event horizon is still 6400km. And we can keep increasing the mass, which makes the event horizon bigger and bigger, but still, the core body has the same radius, and finite mass and density.
Now, in reality, you have no way of knowing how big the radius of the body in a black hole is. Anything inside the event horizon doesn't exist in this universe, as far as you're concerned. r can be 6400km, or it can be 6.4mm. You know what the mass is, because you know what the Schwartzchild radius is, but you don't know the density or the actual radius (if you know one, you know the other). Because of that, you might as well just say the radius is 0 and the density is infinite, because it makes the math simpler. It's not really true, but you can't find out what the real density or radius is, so who cares?
Its all fake. I wont belive till i see it...
black holes? there is so dificult to know how them work because, we cant even know how we work, so, how we can know the black holes that are billions of billions of light years from earth
Excellent post Indi. Couldn't have said it better myself (For one, I don't have all the knowledge) .
.| s43ros wrote: |
| Black Holes... They are some of the most mysterious objects in our universe. Technically, they have infinite density because their actual size is infinitely small. Any comments on this infinite density. Do you think it is actually possible to have infinite density or is it finite, but very large? Will it ever be possible to measure this density or size? And to clear things up for those who may not understand, if our sun collapsed into a black hole tomorrow, we would still be here, because the gravity does not change at distance. |
I think that the problematics of black hole and the general relativity is very complicated. No one really understand what happens with matter in such situation. Fo example when the star is collapsing in some moment, there must appear a very large force due to Pauli principle (two fermions of the same state are not very happy close to each other) and this force must be much larger than the gravitation. But in this moment we dont have theory that describe buth very small and very massive objects. So nobody knows if the density of singularity is really infinte. From the math of general relativity one could say yes, but the laws of physics are maybe different in this situation.
| BLuDShOT wrote: |
| Its all fake. I wont belive till i see it... |
its impossible to see. well, not really impossible, but highly unlikely. you cant 'see' it in terms of light, because not even light can escape the gravitational pull. but through use of telescopes looking for x-rays, you can detect them, so you know they are there.
but that leads to the question, if light cannot escape, what makes us so sure x-rays can?
but i think the most mind-boggling fact about black holes is, in theory, they exist, but do not exist.
they exist in the sense they affect the universe around them, but they dont exist in the sense its not part of the known universe. black holes are not made of matter or anti-matter, so what left is there?
and with the point of singularity, where all matter, mass, space, and time become 'one' in sort of a quantum 'foam', how do we know this happens?
Black holes are super dense objects that DO NOT contain an infinite amount of gravity despite what scientists say. The 'Event Horizon' Surrounding the Black is only called that due to it's gravity sucking everything in including light...The even horizon means 'The Point of no return' (which there is also a movie called 'The event horizon' staring sam neil). The event horizon would actually get bigger if the mass was larger and it would get smaler if the mass were smaller. The black hole contains a single point of matter called 'A singularity', this is where atoms themsleves get ripped a part in a massive 'spaggetificational' matter.
If you were to somehoe survive when going into a black hole, you would be able to see a friend on the ouside, but he would not be able to see you.
Black Holes are where the laws of phsics don't comprehend, it makes it's own laws (like the matrix).
I'll leave you with this last statement to think about...'Black Holes Don't Have any more gravity than it's Star did.'
If you were to somehoe survive when going into a black hole, you would be able to see a friend on the ouside, but he would not be able to see you.
Black Holes are where the laws of phsics don't comprehend, it makes it's own laws (like the matrix).
I'll leave you with this last statement to think about...'Black Holes Don't Have any more gravity than it's Star did.'
from what i remembered my teacher telling me some years ago, he said that scientist have just realised that in billions and billions years later, the sun would keep on expanding. it would expand till all the planets have been "eaten" up so called eaten up lah. all planets would just be sucked into the sun and when the sun has reached the maximum size, it would just burst. thus it would just be a black hole.
A black hole is not a hole exactly....it is a body with a core....which feeds on radiation and matter waves, and matter itself. since stuff all around is sucked in....it appears like a hole. Though the conception thta a black hole's density is far too great for something to escape it......I am lead to believe that a black hole actually accelerates a particle to a velocity far beyond the visible spectrum of radiation......hence everything around it is black.
Research is tryin to prove that, the black hole spins with a velocity that has the capacity to drag the fabric of matter and time. Since its density is high, it would pull an objct and accelerate to a velocity with with it simply escapes the pull and shoots of with a velocity beyond the capacity of our vision.
Some even believe that, you can travel in time if you are able to decide where in your period of revolution around a black hole, would you shoot out. THis stuff is a bit over the head....if someone can make this clearer.......help!!!
Research is tryin to prove that, the black hole spins with a velocity that has the capacity to drag the fabric of matter and time. Since its density is high, it would pull an objct and accelerate to a velocity with with it simply escapes the pull and shoots of with a velocity beyond the capacity of our vision.
Some even believe that, you can travel in time if you are able to decide where in your period of revolution around a black hole, would you shoot out. THis stuff is a bit over the head....if someone can make this clearer.......help!!!
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