Introduction:

A black hole is an astronomical contradiction – a dark star, an invisible nothing, a prison of light. Its boundary is marked by the so-called Event Horizon, a sphere of darkness that shrouds the inside and defines the point of no return. There is no solid surface beyond, just a bottomless gravitational whirlpool so strong that it sucks everything – even light – relentlessly inward. Oblivion waits at the centre in the form of the Singularity, Gravity's fatal attractor.

Beyond the Bright Star:

To understand the very large in the universe, you need to start with the very small. With the unlocking of the secrets of nuclear energy, scientists finally got a clue to how black holes might form in nature. Stars are born when enormous clouds of cosmic dust and hydrogen begin to clump and condense under their own gravitational weight. Gravity grows stronger by the hour as the increasing density of the protostar curves space more strongly. Faster and faster, the hydrogen gas falls in upon itself in the condensing core. The more it collides the hotter it grows. When the core reaches 10 million degrees, the hydrogen protons begin to fuse into helium. Some of the mass disappears, having being turned into energy and light. Like a giant cosmic light bulb, the star has switched itself on.

Every star we see in the heavens has a giant nuclear reaction raging at its core. It's what makes a star like our sun shine so hot and bright. Gravity is still trying to pull the star's gas tighter and tighter but is matched now by the energy pouring outwards from the nuclear reaction in the core. The star settles into a precarious balance that gravity will always win in the end.

The ultimate fate of a star depends upon its mass. Our sun is middle-aged. It switched on 5 billion years ago and has enough fuel to burn for 5 billion more. But when, in that far distant future, the spent heart of the sun sheds its outer layers and shuts down, gravity will squeeze the core so tight it cannot be squeezed any more. It will become a 'white dwarf', a feeble ember the size of the earth but a hundred thousand times more dense. The more massive the star is, the faster it burns its fuel and the shorter its life expectancy. A star 10 times as massive as the sun may survive only millions, not billions, of years. As it starts to collapse, the crush of in-falling matter slamming into the iron core sends the temperature rocketing to 50 billion degrees. The core has only seconds to respond - and it does so Supernova-style.

A supernova is a massive explosion. Huge quantities of material are blown into space, but only from the outer regions of the star. Most of the star has actually imploded, with the core being given a gravity bear hug so extreme that the protons and electrons have been squeezed into a ball of superdense subatomic particles called neutrons. The resulting 'neutron star' would weigh about one and a half times as much as the sun but would measure only about 20 kilometres across.

A neutron star resist the ongoing crush of gravity, only with its neutrons packed in like sardines in a tin. But if the remnants of the star after supernova weigh more than three times the mass of the sun, even neutrons cannot hold back the inexorable force of gravity. The neutrons are squashed into oblivion. The star's core becomes so dense that gravity overwhelms space itself, distorting it so horribly that it, and time with it, is wrenched off from the outside universe. A darkness forms at the star's heart and moves relentlessly outwards as the stars brilliance is sucked inwards. This is the hungry, growing maw of a black hole: gravity's final triumph. There is no escape, no turning back, until the entire mass of the star has been swallowed and its brilliance completely extinguished.

Visible only by its invisibility, the margin of the black hole is marked by the event horizon, so-called because all events beyond are hidden from view. For a black hole like this the event horizon may be only a few kilometres in diameter but the void beyond impossibly deep to measure. The entire mass of the star has been reduced to a singularity – a point of infinite smallness and infinite density at the very centre of this black malevolence.

The singularity is where science ends and speculation begins. Space and time have ceased to exist, replaced by a seething chaotic mass we call quantum foam. This bizarre conjecture is where Einstein's laws fail. This is where the laws of quantum mechanics fail. This is the realm of something called Quantum Gravity – one of the hottest areas of advanced mathematical research.

It is from a singularity that the Universe is believed to have begun. In many ways the collapse of a star to form a black hole singularity is the reverse of the Big Bang. Is this the way the Universe is going to end? Wilder speculation is that our entire universe might lurk inside someone else's singularity. or even that universes can bud off from each other like this, like some sort of heavenly breeding organism.
It wasn't until 1967 that John Archibald Wheeler slipped the term "Black Hole" into his paper at a scientific conference, and into the lexicon of the late 20th Century.
To Wheeler a black hole is only a rehearsal for the ultimate cataclysm, that he believes will bring down the curtain of creation at the end of the universe. In this so-called "Big Crunch" the bell tolls for us all. Today he refers to black hole as Gates of Time, it is not the blackness of their surface that interests him, it is the utter oblivion at their center. "There is no after after the Big Crunch, just as there is no before before the Big Bang," he says. Therefore, "Space and Time are not fundamental categories of nature," in fact time dies.
"One consequence," says Wheeler, "Is that space is like an ocean, viewed from far above it looks small and flat, but the closer you look the rougher and more violent it seems. The illusion of continuity disappears completely over distances shorter than 10^-33 cm, a hundred million billion times smaller that a proton. Space looks like foam, full of tiny tunnels called wormholes, connecting and disconnecting random points. But no geometry will ever reveal what's going on at these small distances," he explains. (see The Universe: Cosmic Foam.)

New Theory Suggested by Physicist Stephen Hawking:

The English physicist Stephen Hawking has suggested that many black holes may have formed in the early universe. If this were so, many of these black holes could be too far from other matter to form detectable accretion disks, and they could even compose a significant fraction of the total mass of the universe. In reaction to the concept of singularities, Hawking has also proposed that black holes do not collapse in such a manner but instead form so-called "worm holes" to other universes besides our own."

Anatomy of a Black Hole:

Black holes come in all shapes and masses, meaning that they have a wide range of masses. There are at least two main different types of black holes. The types differ by their masses. We are perhaps most familiar with "stellar-size black holes;" these are the black holes which form from the death of a very massive single star. They tend to have masses in the range of a few to a few tens of solar masses. Next, there are what is called the "supermassive black holes;" these objects have the mass of a few billion to hundreds of billions of solar masses. They exist in the centers of galaxies, or so we think.

Another type of black hole is formed upon extreme compression of matter by external forces. This type of black hole is considered a primordial black hole. Additionally, this type of black hole is allowed to have mass less than the sun, since it was not created by the collapse of a star.
One possibility of the existence of such black holes are during the early stages of the universe where high temperatures and pressures existed.
The existence of primordial black holes may also help explain the missing hydrogen and helium that theorists predicted should exist based on calculations of expansion and cooling of the universe after the Big Bang. According to Sasaki and Umemura from the Tokyo Metropolitan University, a great number of black holes with about 100,000 solar masses each would have existed in the early stages of the universe. These black holes could have consumed greater amounts of the gases earlier and then vanished under the event horizon when there was no more gas to consume.

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The Black Hole Family:

All black holes have the same basic structure: an event horizon surrounding a central singularity. But there are different types of holes – stationary, spinning, and those that have an electric charge. And each has different characteristics. While one may be deadly, another may allow a journey into another universe.

The simplest is a Shwarzchild black hole. With no spin and no charge, it consists of just a singularity surrounded by an event horizon. Anything crossing the event horizon will be forced towards the singularity.

In a Reissner-Norstrom black hole, which has charge but no spin, there are two event horizons. The region between them is a one way zone where matter is forced to move inward. Once inside the inner event horizon, matter is no longer sucked inward.

In a Kerr black hole, which has spin, the singularity is elongated into a ring. It, too, is surrounded by two event horizons. Beyond the outer one is the ergosphere – a region like a cosmic whirlpool, where matter is not only dragged inward but also swirled around by the black hole's rotation.

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From the Last Stable Orbit to the Singularity:

In a Kerr black hole the last stable orbit marks the closest that anything can orbit the black hole. Once within this orbit, matter is sucked into the tangerine shaped ergosphere. Because a Kerr black hole rotates it causes it to drag the space-time continuum in its immediate vicinity. This region of space is known as the ergosphere. The outer edge of the ergosphere is known as the static limit an the inner edge as the outer event horizon. The black hole itself begins at the outer event horizon; everything passing this disappears from view for good, unable to pull itself away from the immense gravity. Inside the inner event horizon, however, the spin of the black hole sets up an opposing force to create a region of relatively normal space. Most objects will continue spiraling towards the center, but a rocket with powerful engines could maneuver around (but not out of) this region. At the center is the infinitely dense singularity, where all matter of the original star is concentrated.

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The Event Horizon:

Consider a star that will eventually collapse to a black hole. Initially, when it begins to collapse light rays are only slightly affected by its gravity. As the collapse continues and the density increases, an event horizon may form. The event horizon is not made of matter, it is not, in a sense even made of a warpage of spacetime, it is just a location traced out by light rays that will never escape to infinity away from the star, and will never fall back in. But in a dynamic system like a collapsing star, the event horizon is usually expanding out! As more matter falls in, the expansion of the event horizon slows down as the mass inside it, and hence the gravitational pull on the light rays, increases, eventually the event horizon stops expanding when all the matter has fallen inside.

As a doomed star reaches its critical circumference, an "apparent" event horizon forms suddenly. "Why apparent?" Because it separates light rays that are trapped inside a black hole from those that can move away from it. However, some light rays that are moving away at a given instant of time may find themselves trapped later if more matter or energy falls into the black hole, increasing its gravitational pull. The event horizon is traced out by "critical" light rays that will never escape or fall in.

During the collapse there may be a surface of "outgoing" light rays (light rays that are directed away from the star, not towards it) that at some moment is not expanding due to the pull of gravity inside. This surface may even be contracting! This is called a trapped surface. If that surface is neither expanding nor contracting (it has zero expansion), but is just balanced against the pull of gravity, it is called an apparent horizon. Such a surface is shown in the second picture, and if it exists it cannot be outside the event horizon.

Apparent horizons are convenient in numerical relativity because one only has to test the surface at some instant in time to see if it has no expansion. On the other hand, the event horizon is generally expanding: only at the very end of the dynamical process will it cease to expand. At this point, the event horizon and the apparent horizon will coincide.

The most simple case is known as the Schwarzschild-Solution, which describes the vacuum field of a spherical symmetric, nonrotating and uncharged amount of mass. It is a particularity of this solution to have an event horizon, if the source mass is concentrated within the Schwarzschild-Radius.

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The Schwarzschild-Radius:

How small must an object be to trap light? Einstein's general theory of relativity provides an answer. Just after the general theory's publication, the German astrophysicist Karl Schwarzschild calculated this critical size, now called the Schwarzschild radius. For the sun the Schwarzschild radius is about 3 km, smaller than the typical sunspot. If it were compressed to this size, the sun would have a density of about 1E19 kg/m^3. The mass of any object directly gives its Schwarzschild radius: Radius=3 km M/M sun. For 1 solar mass, it's 3 km; for 2 solar masses, 6 km; for 10 solar masses, 30 km; and so on.
How can a star get as small as its Schwarzschild radius? Two ways are possible. First: runaway gravitational collapse. If you put together more mass than about 3 solar masses, a star must eventually squeeze itself into a black hole. Nothing we know about, not even the hardness of matter itself when it gets to nuclear densities, can stop this final crushing. Second: a supernova, a star's self-destruction, can slam matter into a size smaller than its Schwarzschild radius. The final result of either path is the singularity.

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The Singularity:

Applying the Einstein Field Equations to collapsing stars, Kurt Schwarzschild deduced the critical radius for a given mass at which matter would collapse into an infinitely dense state known as a singularity. For a black hole whose mass equals 10 suns, this radius is about 30 kilometers or 19 miles, which translates into a critical circumference of 189 kilometers or 118 miles.
At the singularity, at the center of a black hole, it is no longer meaningful to speak of space and time, for at the singularity, space and time cease to exist as we know them.

in quantum gravity theory, there are no singularities in the gravitational field. It is simply replaced by a region of spacetime where the graininess of spacetime becomes evident at the so called Planck Scale. Because all fundamental particles are believed to be some kind of 'loops' of spacetime also of about the size of the Planck scale, 10^-33 centimeters, individual particles just dissolve away into the quantum froth of spacetime at these scales.

Newton and Einstein may have looked at the universe very differently, but they would have agreed on one thing: all physical laws are inherently bound up with a coherent fabric of space and time. At the singularity all the known laws of physics, including General Relativity, break down. Enter the strange world of quantum gravity. In this bizarre realm in which space and time are broken apart, cause and effect cannot be unraveled. Even today, there is no satisfactory theory for what happens at and beyond the singularity.

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The Naked Singularity:

It's no surprise that throughout his life Einstein rejected the possibility of singularities. But in the late 1960's scientists investigating black holes became aware of an alarming possibility. When a star collapses into a black hole, an event horizon forms and hides the singularity. But in certain situations, a black hole might form without an event horizon. Then it would be possible to see the singularity – and perhaps even to fly to it and away again. But singularities are places of infinite density, where the laws of physics break down and anything is possible. And without event horizons, there is nothing to protect the universe around them: cosmic anarchy would rule.

A spacecraft gingerly approaches a naked singularity. Formed by the collapse of a spinning star, the singularity takes the shape of a glowing ring. Inside and outside the ring, space is normal. The spacecraft can probe the singularity without being dragged in.

A singularity is gravity's final triumph – the squeezing of matter into infinite density. If the star or object being compressed is not spinning, gravity shrinks the matter symmetrically. The resulting singularity is an infinitely small point. If a spinning object is squeezed, the forces of rotation make it bulge into a doughnut shape. This shrinks, and the resulting singularity is an infinitesimally thin ring.

A ring shaped singularity is not quite an infinitesimally thin line. Magnified a billion trillion trillion times, we would see the structure of space in its vicinity distorted into a "quantum foam" rather like soapsuds. Pace here has no definite shape – only a set of different probable shapes.

British mathematician Roger Penrose proved in 1965 that every black hole contains a singularity. But he was so shocked by the idea of a naked singularity that he proposed a "cosmic censor" who would ensure that singularities are decently clothed with an event horizon. That way, the singularity stays cut off from our universe. But Penrose has not proved that the cosmic censor exists, and other mathematicians believe that naked singularities can exist even if only briefly.

No one has ever seen a naked singularity, but computer simulations suggest they can form in various ways, especially when matter collapses in a very asymmetrical manner. If a long rod collapses under gravity, the simulations produce a thin, elongated naked singularity. However it lasts only briefly before the whole mass cloaks itself in an event horizon.

A singularity forms an edge or boundary to space, where the laws of physics break down. We cannot predict what will happen near one. It might, for example, spontaneously organize a gas cloud into a huge alien cat. If there is just one naked singularity in the universe it cloud cause unpredictable chaos everywhere, even on Earth.

How to make a naked singularity:

The trick is to overcome the forces of gravity that would otherwise create an event horizon. Two forces can achieve this: spin and electric charge. If a body, collapsing to become a black hole, is spinning very fast, or has a strong electric field, the opposing force creates an inner event horizon. Increasing the spin or charge will bring the inner and outer event horizon closer together. If there is enough spin or charge, the two horizons merge and disappear completely, leaving the singularity exposed. In the real universe, a collapsing star cannot build up enough electric charge to counteract gravity, but a very rapidly spinning star might end up as a naked singularity.

A spinning black hole has an inner and outer event horizon, with a one way zone between the two where things can only move inward.

A more rapidly spinning black hole has a larger inner event horizon and a smaller outer event horizon. The one way zone is thinner.

If the hole spins fast enough, the two horizons may merge. The one way zone disappears, and the singularity becomes visible – and accessible.

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The Exploding & Exploitation of Black Hole Evaporation:

Hawking radiation:

Black holes can shine brightly, shrink in size and can even explode! Back in the 1970's, Stephen Hawking came up with theoretical arguments showing that black holes are not really entirely black: due to quantum-mechanical effects, they emit radiation. The energy that produces the radiation comes from the mass of the black hole. Consequently, the black hole gradually shrinks. It turns out that the rate of radiation increases as the mass decreases, so the black hole continues to radiate more and more intensely and to shrink more and more rapidly until it presumably vanishes entirely.

Actually, nobody is really sure what happens at the last stages of black hole evaporation: some researchers think that a tiny, stable remnant is left behind. Our current theories simply aren't good enough to let us tell for sure one way or the other. The entire subject of black hole evaporation is extremely speculative. It involves figuring out how to perform quantum-mechanical (or rather quantum-field-theoretic) calculations in curved spacetime, which is a very difficult task, and which gives results that are essentially impossible to test with experiments. Physicists "think" that we have the correct theories to make predictions about black hole evaporation, but without experimental tests it's impossible to be sure.

Now why do black holes evaporate? Here's one way to look at it, which is only moderately inaccurate. One of the consequences of the uncertainty principle of quantum mechanics is that it is possible for the law of energy conservation to be violated, but only for very short duration's. The Universe is able to produce mass and energy out of nowhere, but only if that mass and energy disappear again very quickly. One particular way in which this strange phenomenon manifests itself goes by the name of vacuum fluctuations. Pairs consisting of a particle and antiparticle can appear out of nowhere, exist for a very short time, and then annihilate each other. Energy conservation is violated when the particles are created, but all of that energy is restored when they annihilate again. As weird as all of this sounds, we have actually confirmed experimentally that these vacuum fluctuations are real.

To understand how all this happens you need to know that the rate at which a black hole shrinks depends on its mass. As I already said, small, low-mass black holes lose energy faster. What is important is the curvature of space around a black hole. A small black hole has a much steeper gravitational well than a large, high-mass black hole. Just as an astronaut approaching a small black hole suffers greater tidal forces effects, so the steeper the well of a small black hole is more effective in splitting a particle from its antiparticle twin. (see Journey into a Black Hole.)

A burst of energy can create a particle and its antiparticle: when they become in close proximity to each other, they annihilate each other in an explosion of equal energy.
Physicists can create particle-antiparticle pairs in particle accelerators. Here a burst of energy produces an electron (green) and its antimatter twin, a positron (red). They spiral in opposite directions. (see Antimatter & Atom and Atomic Theory - Particle Accelerators.)

Now, suppose one of these vacuum fluctuations happens near the horizon of a black hole. It may happen that one of the two particles falls across the horizon, while the other one escapes. The one that escapes carries energy away from the black hole and may be detected by some observer far away. To that observer, it will look like the black hole has just emitted a particle. This process happens repeatedly, and the observer sees a continuous stream of radiation from the black hole.

But exactly how are black holes supposed to evaporate if they always absorb half of the particles that Stephen Hawking says they emit?

Of course no one has verified that 'Hawking Radiation' exists, but the process seems to be so simple, and well motivated that it seems like a sure thing.

Because of the strong tidal gravitational field near a black hole's event horizon, once a pair of particles 'pops' into existence, the gravitational field can do work on these pairs to separate them into a positive-energy and a negative-energy particle. Relative to the event horizon, the positive-energy particle can escape to infinity, at the expense of the negative-energy particle falling back into the black hole.

So, why doesn't the black hole actually grow in mass as it swallows the in-going negative-energy particle? Because the ultimate energy source was the gravitational field of the black hole. When it did the work to create the pair of massive particles, and when one of them escaped, the net loss to the system was the gravitational equivalent of the one particle that escaped to infinity as part of the 'Hawking Radiation'. So, the net effect is that the black hole, through this quantum mechanical process in the physical vacuum, looses mass.

If you drew a diagram of this process, the absorption of the anti-particle back into the black hole and the emission of the ordinary particle can be drawn, quantum mechanically, as an electron emitted from the Singularity, traveling backwards in time out to the event horizon, and then being 'scattered' by the gravitational field into a real physical particle that escapes to infinity.

Black holes for which astronomical evidence exists have masses ranging from stellar-sized black holes of a few solar masses, up to supermassive black holes in the nuclei of galaxies, such as the 3×10⁹ solar mass black hole at the centre of the galaxy Messier 87. The Hawking radiation from such black holes is minuscule. The Hawking temperature of a 30 solar mass black hole is a tiny 2×10^-9 Kelvin, and its Hawking luminosity a miserable 10^-31 Watts. Bigger black holes are colder and dimmer: the Hawking temperature is inversely proportional to the mass, while the Hawking luminosity is inversely proportional to the square of the mass.

Black holes get the energy to radiate Hawking radiation from their rest mass energy. So if a black hole is not accreting mass from outside, it will lose mass by Hawking radiation, and will eventually evaporate. For astronomical black holes, the evaporation time is prodigiously long – about 10⁶¹ times the age of the Universe for a 30 solar mass black hole. However, the evaporation time is shorter for smaller black holes, and black holes with masses less than about 10¹¹ kg (the mass of a small mountain) can evaporate in less than the age of the Universe. The Hawking temperature of such mini black holes is high: a 10¹¹ kg black hole has a temperature of about 10¹² Kelvin, equivalent to the rest mass energy of a proton.

All black holes evaporate, but big ones boil away only very slowly. There radiation is so dim that it is undetectable. But as the hole gradually gets smaller, the process speeds up, and eventually runs away with itself. As he hole shrinks, so the gravitational well deepens, creating more escaping particles and robbing the black hole of ever more energy and mass. The hole shrinks more and more quickly, fuelling an ever faster rate of evaporation. The surrounding halo becomes brighter and hotter. When its temperature reaches a quadrillion degrees, the black hole destroys itself in an explosion.

Evaporation of a mini black hole:

Overview – Steven Hawking found that energy is emitted by the gravitational field around a black hole. When a particle escapes from a black hole without repaying its borrowed energy, the black hole forfeits its amount of energy from its gravitational field. And as Einstein's equation E=mc² says, if you lose energy, you lose mass. The black hole becomes less in mass and shrinks. This "Hawking radiation" is negligible for most black holes, but very small ones radiate energy at a high rate until they explode violently.

It is not well established what an evaporating mini black hole would actually look like in realistic detail. The Hawking radiation itself would consist of fiercely energetic particles, antiparticles, and gamma rays. Such radiation is invisible to the human eye, so optically the evaporating black hole might look like a dud. However, it is also possible that the Hawking radiation, rather than emerging directly, might power a hadronic fireball which would degrade the radiation into particles and gamma rays of less extreme energy, and even though these mini black holes have the mass of a mountain and the size of a nucleus of an atom, this scenario can possibly make the evaporating black hole visible to the eye. Whatever the case, you would not want to go near an evaporating mini black hole, which would be a source of lethal gamma rays and energetic particles, even if it didn't look like much visually.
In the final second of its existence, the mini black hole radiates about 1000 tones of rest mass energy or in other words in less than a millionth of a second with the energy of a billion hydrogen bombs. Such an explosion is large by human standards, but modest by astronomical standards. An evaporating black hole would be detectable from Earth only if it went off within the solar system, or at best no further away than the nearest star.

An assortment of black holes was created by the tremendous forces that existed shortly after the Big Bang that spawned our Universe.

The smallest, weighing million tones - about the weight of a supertanker - exploded within ten years.

Mini black holes - those weighing a billion tones, should be exploding now, about 15 billion years after the Big Bang.

A black hole as heavy as an asteroid will live much longer that the Universe - for more that a one quintillion years (one million, million, million years.)

A mini black hole explodes in large burst of gamma rays, the most energetic radiation of all. Astronomers are looking for this tell-tail burst of radiation, but although many objects in space produce gamma rays, none have been identified as an exploding black hole.

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Energy Extraction:

Black holes have a fearsome reputation for sucking everything in, but it is possible, in theory, to extract vast amounts of energy from a rotating black hole. British mathematician Roger Penrose has formulated a way to extract enormous amounts of energy from the way black holes rotate, at the same time sending great quantities of garbage to oblivion. In the real universe black holes should spin, because the star that formed them would have been spinning as it collapsed. Their massive gravity swirling the fabric of space around like a whirlpool.
Penrose's energy extraction process would require building a power station at a safe distance from the rotating black hole. About 20% of a rotating black holes immense energy is stored in the space being whirled around in the ergosphere.
It is possible for humans to (if we had the means of getting there) harness the rotation of a black hole and use it as a souse of energy. What you would have to do is to aim a payload of rubbish at the ergosphere, from your power station, so that it orbits in the same direction as the black hole is rotating. The tidal forces of the black hole would rip the particles of your rubbish apart. One of the particles carries negative energy into the black hole. And that means the partner has more energy than the one that fell into it.
This process makes energy extraction from black hole seem very simple.
The particles could be any old rubbish you never wanted to see again. Half would disappear into the hole. The whirling gravity around the black hole acts as a sling, accelerating the other half of the rubbish and flinging it away at an incredible speed of gravitational energy that could be used to drive a turbine.
This sort of energy is in effect the slowing down of a black holes rotation, because, as these particles keep falling into the black hole, they gradually slow it down. But since there's usually an enormous amount of rotational energy in a rotating black hole, this would be an extraordinary efficient way of extracting energy.

Proof:

The only thing astronomers can do to confirm that something is a black hole is,
1: the object is too compact and massive to be a star or a planet;
2: Stars and/or gas that come close to it move at speeds too high for the object to be a cluster of optically faint white dwarfs or neutron stars;
3: Matter falling into the object emits radiation that is too high compared to ordinary objects like neutron stars and white dwarfs;
4: the object emits no light of its own considering how massive and compact it is;
5: When matter falls in, it seems to fade away as it comes close to the objects 'event horizon'.

If an object satisfies all of these tests, then scientists are obligated to call it a black hole, but they will never be able to see the object itself because they are too far away and small. The situation is much like our current 'proof' for the existence of quarks. No one can directly see them either, but they can determine that quarks behave just the way the theory predicts, and by this they are identified as quarks.

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