How do I know what is a black hole.?
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Search black hole in the internet.
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We have no idea what happens to any matter inside a black hole. The laws of physics that we know do not apply.
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try this   http://uk.wrs.yahoo.com/_ylt=A0geuljFJktF2mIBr3FLBQx.;_ylu=X3oDMTE5ZTFiZDM5BGNvbG8DZQRsA1dTMQRwb3MDMQRzZWMDc3IEdnRpZANVSzAyNTVfMjU1/SIG=123f2f7rt/EXP=1162639429/**http%3A//curious.astro.cornell.edu/blackholes.php
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click here:http://en.wikipedia.org/wiki/Rotating_black_hole
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It is precisely that the density of a black hole is beyond the scope of reality that makes a black hole what it is - a singularity. In mathematics, a singularity is a point at which an equation cannot be solved. A simple example is 1/x, which is undefined at 0. In a black hole, the laws of physics have no solution.\n\nThe atomic bomb has nothing to do with this. Radioactive material like plutonium will explode in a runaway chain reaction if sufficient mass is brought together. (An explosive mass of radioactive material is called a prompt critical mass.) This only works with highly radioactive materials and involves no compression, whereas anything will form a black hole if sufficiently compressed. Compressing matter to this level is far beyond our current capabilities, however; it takes the collapse of a massive star to make a black hole.
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Let me ask you something.  Since density is defined as the mass divided by the volume, how did you determine the mass of a black hole to be 10^13 kg/m^3?  Since the volume of a black hole is 0 (a singularity is a 0 dimentional point with no volume), then the mass divided by the volume (0) equals infinity.  Therefore, a black hole has an infinite volume, which is a heck of a lot larger than 10^17kg/m^3.\n\nPS Densiest isn't a word, and even if it were, you'd be spelling it wrong.  Grow a brain before you start talking down to people.
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An event horizon is the theoretical visible edge of a black hole.  A black hole is a mass so dense that its gravity will allow nothing to escape, not even an object travelling at the speed of light, not even light itself.  An event horizon is the boundary of a black hole at which light can still escape.  Therefore we could see everything that happens up to an event horizon, in theory.  Beyond this boundary, light is drawn back into the super-dense mass and nothing can be seen.
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The answer to that can fill a book:\n\nIn astronomy, a black hole is a region in time and space within which gravity is so strong that nothing can escape, not even electromagnetic radiation such as visible light. Black holes are thought to surround certain celestial objects. \n\nThe idea of a black hole (if not the term itself) is not new. As the intensity of the gravitational field around an object increases, so does the escape velocity. The escape velocity for a celestial mass (such as a star, planet, or moon) is the vertical speed with which an object must be hurled from the surface in order to fly forever beyond the gravitational influence of the mass. If a substantial celestial body such as a star becomes small enough in diameter, the escape velocity at the surface can theoretically exceed the velocity of light. This idea occurred to astronomers even in Isaac Newton's time. Modern astronomers believe they have observed black holes, consisting of stars that have collapsed under their own gravitation after spending their nuclear fuel. Black holes are also believed to exist at the centers of galaxies, including our own. \n\nA black hole produces bizarre effects on time and space. As seen from outside, an object falling into a black hole would approach the so-called event horizon, which is a spherical "one-way membrane" or "Rubicon" surrounding the black hole itself. If the object were a clock, it would seem to run more and more slowly as it approached the event horizon, and would never quite make it inside the black hole. From the reference frame of the falling object, nothing out of the ordinary would take place in the rate at which time passed, and the entry to the black hole would proceed apace, although the gravitational force near the event horizon might tear the falling object apart. \n\nBlack holes have been fodder for wild ideas and science-fiction stories since the concept became well known in the mid-1900s. Some scenarios are sensational to the point of madness. For example, suppose a tiny black hole, manufactured for use as a doomsday weapon, were dropped onto the surface of the earth? It would, as the story goes, proceed to devour the planet with unstoppable and phenomenal violence. \n\nOn the other hand, a worm hole is :supposedly a connection between white holes and black holes above. Do they exist? There are tons of controversy about these and no one can say for sure that they do exist.
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Black holes as mentioned above are a singularity.  Nobody really knows what happens once you cross the event horizon ( the edge of the black hole).  These are very strange events in that they pull everything including light towards them, which contradicts Newtons second law with mass being proportional inversely proportional to mass ( as light has no mass) and Einstein's theory of relativity and the conservation of mass and energy.  All theory we have breaks down when we encounter black holes.\n\nAn interesting theory is that black holes are a link to another universe, matter passing through a black hole and appearing through a white hole in another universe.  This theory has the assumption that there is more than one universe and that they are all linked.  Stephen Hawking's "A Brief history of time" gives many interesting insights.  \n\nHe has recently changed some of his views however with a new theory that a Universe is created by the bumping of one universe into another with black holes becoming the remanents of the reaction, and thus there is no begining or end to time.  He is publishing his ideas soon.  In short however nobody really knows what happens in a black hole.
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A Black hole is a Quantum Singularity in which so much matter energy, be it solid, liquid, gas, or particle matter evaporated states are attracted to it through the quantum gravitational attraction, and once they enter into the singularity those states are crunched into a quantum compressed state in which matter energy will exist with absolutely no function, and the quantum gravity state is so strong nothing at all, not even light quanta can escape this state so long as it remains stable.\n\nAlso nothing at all can travel through a Black hole it is a supper solid mass, which will crunch any, and everything which enters it, if you here that it is a gateway to another universe, or you can pass through it, the person telling you this is probably watching to many Disney movies.\n\nA worm hole is completely different state of function, and actually folds space with respect to an energy vortex which I believe occurs naturally under specific conditions, and can also be created, however no person has created one to my knowledge at this time, with respect to this time line which we are now living in, and observing, although if they have then I feel positive that it would be labeled top secret, and we would know be the wiser to that knowledge.
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The defining factor of a black hole is that the escape velocity is higher than the speed of light.  This is a function of density and not total mass.  It's possible to have very small black holes.  They can even have masses smaller than that of an atom.  The LHC at CERN, which is expected to come online in 2007, may be capable of producing such microsingularities.  \n\nAs for our universe being a black hole...  from inside it's certainly not.  But, from "outside", if you can define such a thing, maybe it does appear as such, since light cannot escape out universe.  This assumes, however, that there is an outside from which this can be considered, and there's no proof, and perhaps no way to prove, whether or not there is.
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A black hole isn't necessarily big or heavy. Any mass M which is compressed to \n\nSchwarzschild Radius: R = 2*G*M/c²\n\ngravitational constant: G = 6,6742/10^11 m³/(kg*m²)\nspeed of light: c = 2,9979*10^8 m/s\n\n\nwill collapse and form a black hole, theoretically. If you have such a thing and want to carry it around you have to isolate it from surronding matter because everything touching the event horizont R will fall into it. But that's science fiction. Rumours say that romulans use tiny black holes for their warp drives and call them quantum singularities.\n\nHawking Radiation\nhttp://en.wikipedia.org/wiki/Hawking_radiation
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A black hole is a star which has loss most of its mass but retains enough gravity to trap everything including light\n\nA quantum Singularity is close to the same definition of a black hole but it is a point in space that can contain unlimited amounts of mass or things\n\nA wormhole is an unsteady disturbance in the space time continuum that allows for easy journey between two points in space within a reasonable time. Wormholes are sometimes believed to be on the other side of black holes often called white holes for the fact that if they were on the other side of black holes that constantly capture light it would be radiating from the other side
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Another name for a black hole is "Quantum Singularity"\n\nAll the matter in the black hole has collapsed under its own weight to an infinitely small point. (there's the clue)\n\nAn infinitely small point would have no Length width or depth.\nAs time ceases from our perspective, once inside the event horizon, there is no time.\n\nHence a black hole is dimensionless no space/no time.\n\nWell that's how I see it anyway!!\n\nLet the argument rage on
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A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). The gravitational field is so strong that the escape velocity past its event horizon exceeds the speed of light. This implies that nothing, not even light, inside the event horizon can escape its gravity. It is, however, theorized that wormholes can provide an exit path for energy or matter. The term "black hole" is widespread, even though it does not refer to a hole in the usual sense, but rather a region of space from which nothing can return.
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A black hole is an object predicted by general relativity with a gravitational field so strong that nothing can escape it — not even light.\n\nA black hole is defined to be a region of space-time where escape to the outside universe is impossible. The boundary of this region is a surface called the event horizon. This surface is not physical, just an imaginary boundary. Nothing can move from inside the event horizon to the outside, even briefly.\n\nThe existence of black holes in the universe is well supported by astronomical observation, particularly from studying X-ray emission from X-ray binaries and active galactic nuclei. It has also been hypothesized that black holes radiate energy due to quantum mechanical effects known as Hawking radiation. \n\nHistory\n\nThe concept of a body so massive that even light could not escape was put forward by the English geologist John Michell in a 1784 paper sent to the Royal Society. At that time, the Newtonian theory of gravity and the concept of escape velocity were well known. Michell computed that a body with 500 times the radius of the Sun and of the same density would have, at its surface, an escape velocity equal to the speed of light, and therefore would be invisible. In his words:
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I think what you need to do is start looking at the picture in a different way.  \n\nYou're looking at the things that are THERE.  \n\nStart looking for what ISN'T THERE.  \n\nIt may be technically accurate to say that you can't see a black hole, because of the fact that our eyes register things that have light reflected off of them.  However, this doesn't change the fact that we can take a picture that displays the black hole, if only because of its nothingness.