[caption id="" align="alignright" width="300" caption="Illustration of a black hole with an accretion disc at its periphery and a relativistic jet"]
[/caption]This article is not that well-structured. It is, in fact, a traipse.
Black holes are a difficult topic to deal with in physics, thermodynamics and philosophy. That is because, in each field of study, it presents certain paradoxes that violate established theorems and principles, making it hard to find a place or itself in our intuitive understanding of nature and the Universe.
The step in understanding a black hole is to understand what a singularity is. For this, understanding the mathematical definition is sufficient: a singularity is a point in space where the quantities used to measure (or, understand) space-time change in a way that is independent of the coordinate system. Essentially, this means that the space-time fabric at this point is distorted in a way that the laws of physics are modified within its limits.
A black hole is a point in space, whereas the large black spheres we imagine them to be are true if only because that is the region around which the black hole exerts its influence. This 'sphere of influence' does not have a definite boundary, but one can be postulated ideally: the event horizon - a hypothetical sphere whose surface marks the point of no-return. Of course, black holes are called so because they absorb all the light in its area of effect, and so the event horizon is the point beyond which light is lost, leading to the characterization as a "black sphere".
Since all light is lost, what about information that the light contains? Let's say that there are two jets of light coming from two different stars far away in outer space. Both these jets encounter this black hole in their path and are sucked in, leading to the information being... what? What happens to the information in the light? Is that lost, too? Perhaps, perhaps not.
The first step in considering the answer to this question would be the Liouville principle. Before that, let's understand what phase-space is: phase-space is a system in which all the states of an object are represented, and each point in the system corresponds to a unique state of the object. Now, the Liouville principle states that the function that defines this distribution is the same for all points on the curve.
Inside a black hole, the Liouville principle is clearly violated when the beam of light hits the singularity.
[caption id="" align="aligncenter" width="240" caption="Gravitational lensing of a black hole passing against a background galaxy"]
[/caption]How do you account for this apparent loss of information? If you went on to say that the info is irretrievably lost, then it's a violation of the law of conservation of energy as well as the truism that the sum of all probabilities of an event's occurrence within a given space is one (unitarity principle). "The information gradually evaporates during the evaporation of a black hole" - violates the classical theory of gravity. "The information escapes at the last phase of evaporation" - violates the Bekenstein bound. "The information defects into a 'baby universe'" - violates the law of conservation of energy. There more such postulates; however, each comes with the sort of disadvantage that cannot be ignored.
It becomes hard to understand what really is inside a black hole. All that has been known about the behaviour of matter inside a black hole is from the interaction of a black hole with the space around it (reactive observation). Since the black hole pulls in light, it must be infinitely massive. If entropy-loaded objects enter the black hole, and if a black hole is characterized by zero entropy, then the second law of thermodynamics is violated. Therefore, the event horizon must possess a relationship with the black hole's entropy, and so forth.
Black holes have been the subject of many debates, more recently during and after the construction of the CERN supercollider. That they are points in the Universe at which the physical laws of the Universe collapse is something blasphemous, and understandably so. However, in trying to understand the nature of such an entity with the laws of physics seems like a futile exercise to me. Since the laws of physics are conspicuously struggling to fathom the idea, leaving in their wake a string of unsolved problems, an alternative would be to approach the enemy from the other direction (and I'm still talking physics).
There is still a lot about the Universe that we don't know, a lot of which we are in a position to identify, classify and understand with the tools we have, unlike the case with the singularities. Therefore, it would be wiser to classify the understandable universe first, to piece most of the puzzle together, and then look at the black hole with all the clean windows we can muster. That would also be due diligence done to the scientific method as well as, in the case of said diligence not being done, saving some for the bills.
Till then, they remain one of the most faithful and idyllic servants at the feet of the science-fiction writer. Cherish them now, for the moment they are taken apart, they are understood, and the mystery is lost forever. There have been sporadic issues dotting the landscape of investigations in physics and they have promptly been put to good use as fodder for science-fiction. It's of no use to speculate on what happens inside the sun when it's all been laid out for all to see. In much the same way, in the absence of any conclusive information, infinite speculation is assured.
The black hole has appeared as part of sub-plots in many works, notably in Arthur C. Clarke's The City and the Stars, in SG-1 and in the anime, Inuyasha, amongst others. Because of its tie-ins with the pan-galactic continuum, not only does incomplete knowledge regarding the phenomenon present the possibility of a crazy adventure into other dimensions but also completely unrestricted distortions of the known four-dimensional space-time without having to seem far-fetched.
Despite the existence of a clear distinction between the different stars that are allowed to collapse into a black hole, one can simply be conjured as need be, a deus ex machina, a god out of a machine, and made to swallow at the slightest instance of villainy the bad guys out of the plot. Damsel's no longer in distress, game over.
There is a cornucopia of ideas both plausible and implausible stemming from science-fiction; the likes of Asimov, Wells, Gernsback, Verne and Hamilton have advanced the acceptability of the idea that there is something to expect from such works of fiction towards the enhancement of our understanding. However, it must be remembered that their "duty" to science is only conjectural, quite unlike those who are bound to the truth's noble and ennobling righteousness.
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