# Black hole density

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#### pyoko

##### Guest
What is wrong with this picture?<br />Mathematically there is a singularity in the middle of a black hole. The density is infinite at the center. Infinite density means infinite mass. Something has to collapse into a black hole. An object of very finite mass forms an onbect with an infinite mass in the middle. MAtter out of nowhere. So the mathematical theory is simply wrong.<br /><br />Also, black holes have a radius. I've read about the horizon etc, but some black holes are 'larger' than others. What keeps the super-dense matter, say, 5 cm away from the singularity from falling into it?<br /><br />Is there a maximum density matter can be crushed into?<br /><br />Please help me understand. <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

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#### pyoko

##### Guest
Clicked on the wrong forum. Please place this in "Ask the astronomer" section. <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

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#### telfrow

##### Guest
Done. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

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#### billslugg

##### Guest
pyoko<br />The mass of a black hole is going to be the same as the matter that collapsed.<br /><br />The density at the center will be infinite, but the size will also be infinitely small. Thus the mathematical conundrum is resolved. <br /><br />At this scale we really do not know what is going on, but we make educated guesses. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

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#### alokmohan

##### Guest
You must know theory of relativity to understand this.Ordinary physics fails.

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#### casualphilosoph

##### Guest
Excuse me but did not hawking disprove the idea of a singularity? I am remember hearing something like that some years ago.

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#### pyoko

##### Guest
Well I do remember learning theory of Relativity in matriculation followed by my one year of physics at university level. Don't assume I don't know it <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

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#### pyoko

##### Guest
I can't be sure and am way too lazy to google it right now, but I believe Hawking changed his mind on the issue of Information loss concerning black holes. <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

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Bingo

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#### oscar1

##### Guest
I have been asking myself the same thing. Of course as such a black hole cannot exert more attraction than the original star did, so black holes do not distort the universe. We have to accept that we will not ever be able to look inside the gravity field of a black hole, for we'd be 'spagettied' (as Hawking puts it) far out from the core already, while light won't reflect to give us a visual at a distance. So the term 'singularity' will have to do. Yet I do find that rather unsatisfactory, so I like to think that matter can indeed be compressed beyond our imagination, be it from a star larger than the Sun to a size football, a size marble, or size pinprick. In addition, I like to think that somehow the mass of a black hole may have a limit, and that when that limit is exceeded, the resulting instability will cause the black hole to explode violently, like the Big Bang. Such occurrence cannot have taken place since the Big Bang, for it would have destroyed the universe, or at least a large part of it, so it must be rare to the extreme. However, if and when galaxies collide, black holes, and also large stars, may get close enough to eachother to 'merge', and form a rather massive black hole. At some point, after numerous 'mergers', one black hole may become critical, and start the whole thing all over again, i.e. it would be the Big Bang again, violently destroying all history before it. Of course, this is merely how I myself see it though.

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#### search

##### Guest
It is a very interesting what you said and the reason I say this is expressed in the bottom article of this post:<br /> <br />Regarding the compression of mass:<br /><br />Stars have different mass but the mass comparison star is our sun.<br /><br />"A white dwarf is an astronomical object which is produced when a low or medium mass star dies. These stars are not heavy enough to generate the core temperatures required to fuse carbon in nucleosynthesis reactions. After such a star has become a red giant during its helium-burning phase, it will shed its outer layers to form a planetary nebula, leaving behind an inert core consisting mostly of carbon and oxygen."<br />http://en.wikipedia.org/wiki/White_dwarf<br /><br />"The Chandrasekhar limit is the maximum mass possible for a white dwarf star (one of the end stages of stars that have exhausted their fuel) supported by electron degeneracy pressure, and is approximately 3 × 1030 kg, around 1.44 times the mass of the Sun. If a white dwarf (normally formed with about 0.6 solar masses) were to exceed this mass through accretion, it would begin to collapse under gravity."<br />http://en.wikipedia.org/wiki/Chandrasekhar_limit<br /> <br />"There are several different types of supernovae and two possible routes to their formation. A massive star may cease to generate fusion energy from fusing the nuclei of atoms in its core, and collapse under the force of its own gravity to form a neutron star or black hole. Alternatively, a white dwarf star may accumulate material from a companion star until it nears its Chandrasekhar limit and undergoes runaway nuclear fusion in its interior, completely disrupting it. This second type of supernova is distinct from a surface thermonuclear explosion on a white dwarf, which is called a nova. In either type of supernova, the resulting explosion expels much or al

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#### oscar1

##### Guest
Thank you for the info and the links. I am glad that there are others thinking more or less along the lines I do. This line could be false, but if it is not, it would explain what triggered the Big Bang. It would in fact explain quite a few other things. We would not have to wonder where and when it all started, for it would just be a cicle that simply 'is'. It would also explain why we don't see the night sky as brightly lit as if the sun was shining (which would be the case if the universe is everywhere and forever), for the super massive black hole would, just before it becomes critical and explodes, suck up distant light rays like an extremely powerful vacuum cleaner, therewith erasing them from detection by anyone within the new sphere of universe during the existence of that sphere of universe.

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#### delster45

##### Guest
Oscar<br /><br />I posted an idea very similar to the one you mentioned, a cycle of big bangs and time not being relevant to a beginning or end, just an infinite being or presence. Someone referred to it as the Universe Oscillation Theory.

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#### search

##### Guest
Sorry but this not about cycling universes it is about our universe or the Big Bang resulting from a singularity but a defined singularity. In this case our universe results from the death (as a supernova) of a gigantic massive star. <br />Strange theory? Yes very, but it would give meaning to what is before the Big Bang although in the end would face the same beggining deferred in time, which is: NOBODY REALLY KNOWS.<br /><br />Its also about Olbers' Paradox. Why is the sky dark?<br />Go through this site:<br />http://www.arachnoid.com/sky/index.html

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#### oscar1

##### Guest
Indeed, I think that delster45 is referring to an oscillating universe where it does so expanding and contracting. If that were the case (and who knows, it might be), the universe would indeed need dark matter and energy to float about somewhere within, for otherwise there cannot be ultimate contraction. Also, if indeed contraction would ultimately lead to the Big Bang [again], time might run backwards during contraction (almost too weird to contemplate). In the underlying scenario however, the universe as we think we know it a littlebit, would keep on expanding until such time that another Big Bang occurs somewhere within it. Through the sheer speed (the speed of light being negligible in comparison) of the explosion of this new Big Bang, anything in the path of the explosion/expansion would be so destroyed/absorbed by it, that it becomes part of the explosion as if it never existed.

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#### search

##### Guest
My mistake I wrote cycling instead of oscillating or oscillatory.<br />Dark matter I believe its a problem to be solved in either case (oscillating universe theory or supernova big bang resulting in universe) and I bet (I may loose like Hawkins though) there is plenty of MACHOS, WIMPS and Neutrinos to fill up the gap. <br />What I never enjoyed is the Dark Energy since its either a distortion of our idea of gravity or there is some strange and misterious force behind the acceleration of the universe and I am not fond of strange and misterious forces unless I am watching a science fiction movie.<br />Oscilatory universe theory has been revived in brane cosmology as the cyclic model, which evades most of the arguments levelled against the oscillatory universe in the sixties. Despite some success, the theory is still controversial, largely because there is no satisfactory string theoretic description of the bounce in this model.<br />This new thought it does not change the universe as we see it in the Lambda CDM model but may be able to explain the Big Bang origin (again just deferring in time the ultimate question which is: How did it all started?). <br />I guess that question will always be unexplainable to human beings since we are mortals and we have difficulties in understanding the concept of eternity.

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#### oscar1

##### Guest
The concept of eternity is indeed incomprehensable to mortals. But I can live with that, for that in itself makes perfect sense (apples and pears). Yet, although we cannot comprehend eternity, we cannot comprehend the alternative(s) either. That is to say, I am perfectly at ease with a tree growing new leafs in spring, and shaking them off again in the fall; a kind of oscillation one could argue. In other words, I do not feel uncomfortable with an oscillating eternity where 'our' universe is concerned. Are there more universes, or portions of an infite universe? Well, that would lie beyond our horizon, and is in any case mostly irrelevant where our understanding of our own environs is concerned. I come to the conclusion therefore, that the question "how did it all start?" is also one of these "over the horizon" questions. If there was no 'time' before 'it' started, than a being that 'is' exactly because of 'time', has no alternative but to accept that 'it' always was/is, even if in some other dimension this would not be the case.

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##### Guest
Black holes is quite an unresolved concept .We exactly don't know what does it exactly made of or what does it consists of.Some scientiests believe that itn might be the way to travel in the other end of universe.

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#### oscar1

##### Guest
Hmm, interesting pic, but it 'warped' this thread into a wider dimension. <img src="/images/icons/smile.gif" />

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##### Guest
As you say that some scientist believe that it is a way <br />to travel to other end of the universe.Can it be the way to travel faster than light? so as to acheive command over the time and to make time travel possible.

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#### oscar1

##### Guest
Our mere existence is based on space-time; that is the dimension we live in. Matter, light and mass are without space and time, but we, the living, need it in order to be. Only at the point of a singularity exploding, is the space-time law broken (that is, only compared to what will be afterwards), therewith creating that space-time, and along with it the universal speed limit, which can not be exceeded by anything until the next singularity goes bang, wiping out everything before it.

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#### derekmcd

##### Guest
<i>"Also, black holes have a radius. I've read about the horizon etc, but some black holes are 'larger' than others. What keeps the super-dense matter, say, 5 cm away from the singularity from falling into it?"</i><br /><br />Blackholes have 2 features... the Event Horizon and the Singularity. The radius is the distance from the singularity to the event horizon. The event horizon is not a physical surface... merely the point where nothing can escape. Once matter is beyond the event horizon, it has a direct, one-way ticket to the singularity.<br /><br /><i>"Is there a maximum density matter can be crushed into?"</i><br /><br />In mathematical terms: No. Since we may never be able to observe and experiment with a singularity, we may never physically know.<br /> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### pyoko

##### Guest
In reply to:<br /><br />In mathematical terms: No. Since we may never be able to observe and experiment with a singularity, we may never physically know.<br />---------------------------------<br /><br />Thanks for all the great replies.<br />I understand that in theory there is a mathematical singularity and a non-matter radius (the 'point of no return') to the black hole model. But I find it hard to swallow (don't ask me why, because I will not be able to give a satisfactory reply).<br /><br />Also, next year (I believe), scientists hope to create miniature and (hopefully) short-lasting black holes in a massive accelerator. We will learn much from this. Perhaps if energy radiates from black holes. To me, it seems this assumption is based on the premise that Hawking radiation is valid? <br /><br />edit: I can find you links for the proposed black hole experiment if someone requests it. <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

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