black hole

preeth_ag · Oct 3, 2008

hey u guys can u tell me something about blckhole?means  how it is made?what happnes when we go inside it?etc

KickLaBuka · Oct 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>hey u guys can u tell me something about blckhole?means  how it is made?what happnes when we go inside it?etc Posted by preeth_ag</DIV> A black holes is an area of shared magnetic field lines between stars and groups of stars.  There is negative current flow along these lines, which make the stars revolve around it.  The negative current is also flowing towards the poles (use the right hand rule to determine which based on rotation).  Groups of galaxies also align along this axis.When there's a central star or central cluster, the negative flow is going directly through that, compounding the strength of the central star or cluster.Good question,  <div class="Discussion_UserSignature"> -KickLaBuka </div>

MeteorWayne · Oct 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>A black holes is an area of shared magnetic field lines between stars and groups of stars.  There is negative current flow along these lines, which make the stars revolve around it.  The negative current is also flowing towards the poles (use the right hand rule to determine which based on rotation).  Groups of galaxies also align along this axis.When there's a central star or central cluster, the negative flow is going directly through that, compounding the strength of the central star or cluster.Good question,  Posted by KickLaBuka</DIV> I should point out that KickLaBuka's view is his and a few others alone.Everyone else in the serious physics community uses the equations of physics to define a black hole.Don't be misled. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

qzzq · Oct 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>hey u guys can u tell me something about blckhole?means  how it is made?what happnes when we go inside it?etc Posted by preeth_ag</DIV>This may be a useful link: http://cosmology.berkeley.edu/Education/BHfaq.html <div class="Discussion_UserSignature"> *** </div>

weeman · Oct 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>hey u guys can u tell me something about blckhole?means  how it is made?what happnes when we go inside it?etc Posted by preeth_ag</DIV> This is a basic understanding of black hole formation (since I'm not too good with this topic!):The most common formation of black holes is from collapsed stars. Typically, black holes form from high mass stars, much more massive than our Sun. Betelgeuse is an excellent example. Betelgeuse is a Red Super Giant, with a mass that is far greater than the Sun. When one of these colossal stars runs out of nuclear energy, they begin to collapse. Eventually, the star will collapse so far that nothing can prevent itself from collapsing under the pressure of its own gravity. After releasing its guts into interstellar space, the final result will often be a black hole. As for what happens inside a black hole, only theory and mathematics can tell us what may be taking place. Once you cross the event horizon (the point of no return), there is nothing that will stop you from being pulled to the gravitational singularity at the center. The event horizon is the barrier where on the outside, you still have a chance to escape the black hole, yet on the inside, your trip to the singularity is inevitable. Think of it this way: Once inside the event horizon, the roles of time and space are reversed. In other words, in normal 4D space, your forward progression in time is inevitable, there's nothing you can do to stop it; additionally, your movement through space is not dictated by any one direction. Yet, once inside the black hole, these two are reversed: Your forward progression through time will cease, yet your forward progression through space is inevitable, being dictated by the gravitational singularity. Are you following this? <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-cool.gif" border="0" alt="Cool" title="Cool" /> <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

Philotas · Oct 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>This is a basic understanding of black hole formation (since I'm not too good with this topic!):The most common formation of black holes is from collapsed stars. Typically, black holes form from high mass stars, much more massive than our Sun. Betelgeuse is an excellent example. Betelgeuse is a Red Super Giant, with a mass that is far greater than the Sun. When one of these colossal stars runs out of nuclear energy, they begin to collapse. Eventually, the star will collapse so far that nothing can prevent itself from collapsing under the pressure of its own gravity. After releasing its guts into interstellar space, the final result will often be a black hole. As for what happens inside a black hole, only theory and mathematics can tell us what may be taking place. Once you cross the event horizon (the point of no return), there is nothing that will stop you from being pulled to the gravitational singularity at the center. The event horizon is the barrier where on the outside, you still have a chance to escape the black hole, yet on the inside, your trip to the singularity is inevitable. Think of it this way: Once inside the event horizon, the roles of time and space are reversed. In other words, in normal 4D space, your forward progression in time is inevitable, there's nothing you can do to stop it; additionally, your movement through space is not dictated by any one direction. Yet, once inside the black hole, these two are reversed: Your forward progression through time will cease, yet your forward progression through space is inevitable, being dictated by the gravitational singularity. Are you following this? Posted by weeman</DIV> Just testing if I got everything right. The star doesn't really collapse more and more; at first its diameter goes up as fusion moves outwards through new layers. When the core has fused nucleuses to point where it's fusing iron, it can no longer gain energy surplus through fusion (as fusing elements heavier than iron requires energy); and now the core, and the core only, collapses since there is nothing left that now can withstand gravity. At this point, the star is going supernova. Depending on it's current mass, it will transform into either a neutron star or, if it's massive enough, a black hole.The event horizon; that's the point where the escape velocity = c? <div class="Discussion_UserSignature"> </div>

weeman · Oct 3, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Just testing if I got everything right. The star doesn't really collapse more and more; at first its diameter goes up as fusion moves outwards through new layers. When the core has fused nucleuses to point where it's fusing iron, it can no longer gain energy surplus through fusion (as fusing elements heavier than iron requires energy); and now the core, and the core only, collapses since there is nothing left that now can withstand gravity. At this point, the star is going supernova. Depending on it's current mass, it will transform into either a neutron star or, if it's massive enough, a black hole.The event horizon; that's the point where the escape velocity = c? Posted by Philotas</DIV> You're correct.The star will actually go through multiple expansion and contraction phases before it finally collapses as a white dwarf, neutron star, or black hole. Massive stars end very violently as they "burp" their elements into space, which we sometimes see as supernovae. Of course, the most powerful supernovae in the universe, type 1a, are quite rare. Our sun doesn't quite have enough mass to end as a black hole or neutron star; it's predicted it will end as a white dwarf, until billions of years later when it may cool into a black dwarf. Although, it will expand as it begins to use up the last of its hydrogen. The sun will become so large that it will engulf the orbits of Mercury and Venus, and make Earth a very unpleasant place to live. Additionally, as it finally begins to shed its outer layers (in the last gasp of its life) the Sun will blast away the gaseous atmospheres of the outer planets, leaving small, metallic and rocky cores. Stars experience this phase because as they begin to fuse heavier elements, like carbon and iron, their core temperature increases, thus overcoming the hydro-static equilibrium between outward pressure of nuclear fusion and inward pressure of gravity. This is why the star begins to expand. Yet, as the star fuses to iron, it can go no further, and as fusion begins to die off in the core, gravity once again takes over, collapsing the star under its own immense gravity.   <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

Saiph · Oct 6, 2008

In massive stars it is indeed only the core that collapses in the end.  However once the core is Iron, the fusion process shuts off abruptly.  And without the supporting pressure of the core's energy output, the outer envelope does collapse.  In the ensuing collapse the envelope compresses, rebounds off the still collapsing core, and generates a massive shockwave back out through the star (which still has matter falling in...feeding the shockwave).  It's this massive rebound shockwave, and the run-away fusion events fuelled by the insane compression and heat generated by the envelope collapse, and core collapse combined that power the massive explosion that is a supernovae. Also, I'm not sure if Type Ia are the most powerful...I'll see if I can find any information on that subject. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

weeman · Oct 7, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>In massive stars it is indeed only the core that collapses in the end.  However once the core is Iron, the fusion process shuts off abruptly.  And without the supporting pressure of the core's energy output, the outer envelope does collapse.  In the ensuing collapse the envelope compresses, rebounds off the still collapsing core, and generates a massive shockwave back out through the star (which still has matter falling in...feeding the shockwave).  It's this massive rebound shockwave, and the run-away fusion events fuelled by the insane compression and heat generated by the envelope collapse, and core collapse combined that power the massive explosion that is a supernovae. Also, I'm not sure if Type Ia are the most powerful...I'll see if I can find any information on that subject. Posted by Saiph</DIV> Perhaps hypernovae can exceed the power of a type 1a? <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

derekmcd · Oct 7, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Also, I'm not sure if Type Ia are the most powerful...I'll see if I can find any information on that subject. Posted by Saiph</DIV>I'm not sure you will find a completely satisfactory answer to that question.  I see ranges ranges of 10^49 through 10^52 ergs for both SNe Ia and II.  Most commonly, I see both at around 10^51.  Hypernova, on the other hand, I have seen as hight as 10^53.  I don't think there is a simple either/or answer. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

Saiph · Oct 8, 2008

Well, Type Ia are all supposed to be the same, thus their use as a candlestick (reference point) in distance measurements.  Core collapse supernovae are going to vary a lot, yes.  So... the question is what is the typical output of a Type II nova? <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

skeptic · Oct 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>This may be a useful link: http://cosmology.berkeley.edu/Education/BHfaq.html Posted by qzzq</DIV>There is one thing I don't understand about that reference.  Very few people understand this stuff very well and I'm certainly not one of them.  However this reference fails to relate intense gravitational fields to relativistic velocities.   Most of us are familiar with the time dilation and length contraction due to velocities approaching c.  The same thing happens in intense gravitational fields near the event horizon. The dilation and contraction follow the LorentzTransformation which is 1/sqrt(1-v^2/c^2).  In a gravitional field v is the escape velocity.  The effect of a gravitational field is that when an object reaches the event horizon it isexactly the same as if its velocity had reached c.  This means time has stopped and space at the event horizon has cotracted to zero.  How does an object cross the event horizon where space is infinitely contracted and time has stopped?  It seems to me that an observer falling into a black hole would fall forever but never quite reach the event horizon.Crossing the event horizon is the same as exceeding the speed of light.  To me it's odd that enthusiests label anyone who talks about traveling faster than c as a crackpot but regularly discuss crossing the event horizon.

Saiph · Oct 10, 2008

Ahh, you're caught up in a problem with reference frames. The poor soul who falls into a BH will, sadly, go screaming to their deaths rather quickly. Why? because they don't actually hit "C"..they're going at a finite speed.  Also, time for them continues to flow unperturbed. The outside observer doesn't see them cross...but thats really only their image.  The last dregs of light emitted/reflected from the inbound sap right before they cross the event horizon.  The light that is struggling out against the stretched space-time and time dilation.And even then the image of the victim will fade over time, as the remaining light is ever more redshifted. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

weeman · Oct 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Crossing the event horizon is the same as exceeding the speed of light.  To me it's odd that enthusiests label anyone who talks about traveling faster than c as a crackpot but regularly discuss crossing the event horizon. Posted by skeptic</DIV> Where did you hear that crossing the event horizon means exceeding the speed of light? It can't be done. The escape velocity of the black hole, once inside the event horizon, will be equal to the speed of light. But at no time would a doomed astronaut be traveling faster than C. As Saiph stated, an outside observer would never actually see his doomed friend disappear beyond the event horizon. At some point, the inward traveler will emit his last photons, just before he crosses the event horizon. So, to the outside observer, it will take a seemingly infinite amount of time for his friend to cross into the black hole. <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

DrRocket · Oct 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>hey u guys can u tell me something about blckhole?means  how it is made?what happnes when we go inside it?etc Posted by preeth_ag</DIV>For a treatment aimed at a general audience see Black Holes and Time Warps: Einstein's Outrageous Legacy by Kip Thorne.  Thorne is a serious physicist, a specialist in general relativity, a student of John Archibald Wheeler, and the Feynman Professor of Theoretical Physics at Cal Tech.  He is also a co-author with Misner and Wheeler of a standard graduate-level text on general relativity Gravitation.  Not only will Black Holes and Time Warps answer your questions, it is a great read. <div class="Discussion_UserSignature"> </div>

skeptic · Oct 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>For a treatment aimed at a general audience see Black Holes and Time Warps: Einstein's Outrageous Legacy by Kip Thorne.  Thorne is a serious physicist, a specialist in general relativity, a student of John Archibald Wheeler, and the Feynman Professor of Theoretical Physics at Cal Tech.  He is also a co-author with Misner and Wheeler of a standard graduate-level text on general relativity Gravitation.  Not only will Black Holes and Time Warps answer your questions, it is a great read. Posted by DrRocket</DIV> Saiph:  The poor soul who falls into a BH will, sadly, go screaming to their deaths rather quickly. Why? because they don't actually hit "C"..they're going at a finite speed.  Also, time for them continues to flow unperturbed.   First of all c is a finite speed.  Secondly if a freefalling object falls toward a BH from rest and from a distance that is effectively at infinity, its infalling velocity is always equal to the BH’s escape velocity at every point, so at the event horizon the infalling velocity would be equal to c.  Thirdly if the object is free falling, its mass doesn’t increase toward infinity as it approaches c, because even though it is accelerated by gravity, it is at rest.  No energy has been added only converted from potential to kinetic.    True, distant observers never see an object cross the event horizon.  I’m not talking about that.  I’m talking about gravity warping space and time close to the event horizon.  Remember the formula for time dilation sqrt(1 – v^2/c^2).  Check out the time dilation for a massive non-rotating sphere   sqrt(1-2GM/rc^2)   where   sqrt(2GM/2)  is the escape velocity.  Sqrt(2GM/2)^2 takes the place of v^2 in the Lorentz Transformation.  So what is the value for time dilation at the event horizon where the escape velocity is equal to c? http://en.wikipedia.org/wiki/Gravitational_time_dilation   Space also is increasingly contracted as an object approaches the event horizon providing a real life example of Zeno’s runner, getting infinitely close but never quit reaching the finish line.     weeman:  Where did you hear that crossing the event horizon means exceeding the speed of light?   That’s the point, I almost never hear of it.  I remember only one instance – that of some physicists arguing that Hawking’s information paradox doesn’t really exist because matter never really crosses the event horizon.  I realize that never hearing of this point of view means it’s likely that it’s not correct, but I’d at least like to understand why it’s not correct.   weeman:  The escape velocity of the black hole, once inside the event horizon, will be equal to the speed of light.   Think about what you’re saying.  The escape velocity is equal to c at the event horizon.  Inside the event horizon one is closer to the source of gravity so the escape velocity should be even greater.  If we were to solve the Lorentz Transformation for inside the event horizon, both space and time become imaginary.  Some physicists interpret this to mean that time becomes space and space becomes time, but that idea is by no means universally accepted.     To DrRocket, I have the book and it doesn’t discuss this problem.

DrRocket · Oct 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'> Saiph:  The poor soul who falls into a BH will, sadly, go screaming to their deaths rather quickly. Why? because they don't actually hit "C"..they're going at a finite speed.  Also, time for them continues to flow unperturbed.   First of all c is a finite speed.  Secondly if a freefalling object falls toward a BH from rest and from a distance that is effectively at infinity, its infalling velocity is always equal to the BH’s escape velocity at every point, so at the event horizon the infalling velocity would be equal to c.  Thirdly if the object is free falling, its mass doesn’t increase toward infinity as it approaches c, because even though it is accelerated by gravity, it is at rest.  No energy has been added only converted from potential to kinetic.    True, distant observers never see an object cross the event horizon.  I’m not talking about that.  I’m talking about gravity warping space and time close to the event horizon.  Remember the formula for time dilation sqrt(1 – v^2/c^2).  Check out the time dilation for a massive non-rotating sphere   sqrt(1-2GM/rc^2)   where   sqrt(2GM/2)  is the escape velocity.  Sqrt(2GM/2)^2 takes the place of v^2 in the Lorentz Transformation.  So what is the value for time dilation at the event horizon where the escape velocity is equal to c? http://en.wikipedia.org/wiki/Gravitational_time_dilation   Space also is increasingly contracted as an object approaches the event horizon providing a real life example of Zeno’s runner, getting infinitely close but never quit reaching the finish line.     weeman:  Where did you hear that crossing the event horizon means exceeding the speed of light?   That’s the point, I almost never hear of it.  I remember only one instance – that of some physicists arguing that Hawking’s information paradox doesn’t really exist because matter never really crosses the event horizon.  I realize that never hearing of this point of view means it’s likely that it’s not correct, but I’d at least like to understand why it’s not correct.   weeman:  The escape velocity of the black hole, once inside the event horizon, will be equal to the speed of light.   Think about what you’re saying.  The escape velocity is equal to c at the event horizon.  Inside the event horizon one is closer to the source of gravity so the escape velocity should be even greater.  If we were to solve the Lorentz Transformation for inside the event horizon, both space and time become imaginary.  Some physicists interpret this to mean that time becomes space and space becomes time, but that idea is by no means universally accepted.     To DrRocket, I have the book and it doesn’t discuss this problem.    Posted by skeptic</DIV>The problem posed was "can you tell me something about black holes".  Thorne's book most certainly addresses that question.  <div class="Discussion_UserSignature"> </div>

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