Black Holes in Outer Space
Have you ever pondered the fact that the universe is filled with many very heavy things - really heavy things, like planets much bigger than our own and suns big enough to encompass our entire solar system, for example? Physicists ponder this fact in great depth and detail.
In their pondering, physicists have discovered just how heavy and dense things in the universe can be, by means of a body of ideas termed "physical theory," or, more commonly termed, "theoretical physics." Physicists use this body of ideas for explaining nature and for determining just how heavy and dense things can be because this body of ideas has yet to ever fail to model nature accurately - not even once.
Using this failure-free body of ideas, physicists have come to recognize just how heavy and how dense massive objects in nature can become. Indeed, they have discovered what are among the heaviest and unquestionably the densest objects in the universe. Physics has given a special name to these objects, appropriately calling them by the name of "black hole". They are so called, because their weight and corresponding density is so great that their gravity prevents them from emitting hardly any light at all. A black hole is a "dark star" - a star that emits no visible light. In short, they are darker than the darkest night. They are called "holes" instead of stars because these dark objects are like one-way "exits" from the universe around them (hence the tem, "hole").
Black holes are formed when an enormous star "burns up" (that is, exhausts all the nuclear fuel) that is constantly "holding up" the star, keeping it bib. Without sufficient energy being released to counterbalance the immense gravity that is the outcome of its immense mass, gravity overcomes energy and the star collapses inwardly. If the star is massive enough, it collapses into a black hole, "sinking" into space and time, "separating" from the rest of the universe, leaving only a "one-way exit" behind.
There is no other kind of object in the universe that is anything like a black hole. This is because there is no other kind of object in the universe where, at its surface, time does not pass. At the surface of a black hole, which is called its "event horizon," time stands completely still according to the measures of the pace of time for anyone outside, not experiencing the effects of the immense gravity.
Theoretical physics, specifically, the Theory of Relativity, explains why time stops at an event horizon surface. Indeed, it predicts that there must be black holes with surfaces where time actually stops. And this is how and why:
As the distance from a source of gravity (a mass) decreases, gravity increases. And, according to relativity, as the effects (the force) of gravity increases, time progressively slows. This fact has been demonstrated conclusively by repeated scientific testing, and there exists no testing anywhere demonstrating the contrary. Thus, a clock placed upon the summit of Mount Everest will run faster than a clock placed at the bottom of the ocean. A clock "floating weightlessly" in outer space, far from any other mass, will run faster than either.
However, to someone next to each clock watching it tic, time's pace would seem identical, regardless of whether it was the clock in outer space far from any other mass's gravity, or the clock at the bottom of the ocean, very close to the great mass of the earth. On the other hand, for the individual watching the clock "weightless" in space, the clock at the bottom of the ocean, subject to the greater effects of the gravity of the earth by virtue of its close proximity, would tic more slowly. The same is true for a black hole.
A star collapsing into a black hole collapses into a smaller volume, becoming denser as it is compressed. As a matter of fact, when a star is so heavy (i.e. so massive) that it collapses into a black hole, it collapses into such a small volume that (among other effects), according to the measures for anyone outside the enormous gravity, time effectively stops altogether at its event horizon surface. In other words, time "freezes" there, which accounts for why - again, according only to the measure of time for anyone outside - light (effectively) never escapes from a black hole (thus making it 'black'). Rather than simply being redirected back, inwardly, light "never" escapes from a black hole for a completely different reason than that. That reason is that, at the surface (again, according only to the temporal measures of someone far away from the effects of the black hole's gravity), there is simply never any time for the light to move. From the perspective of anyone outside (their measures), the surface is an impenetrable barrier frozen in time because the gravity at the surface overwhelms time itself. Appropriately, one can call the surface of a black hole a one-way ticket to the 'end' of time (lying billions or even trillions of years into the future).
Now, what about anyone who happens to approach the surface, with the intention of crossing it? Would time stand still for them? If time did indeed slow for someone falling into a black hole, then, correspondingly, the laws of physics would have to change appropriately with the change in the pace of time – except that according to physical theory, the laws of physics absolutely never change anywhere, ever. Likewise, neither does the pace of time change. So, according to the measure of time for anyone or anything subjected to the immense gravity at the black hole's surface, time is still passing at the same rate as it ever passed anywhere at any time in the universe for them, no less than it does always for anyone else. This being so, then the measure of time for anyone or anything approaching the event horizon surface will be no different from the pace at which it was passing at any moment during its approach to the surface, no differently than it passed while still far from the hole's immense gravity at the surface. But, even though time would be passing normally for anyone as they fell towards the surface, what would be only a brief moment for them, would be (taking relativity to its 'extreme') infinite according to the measure of time for anyone or anything outside the immense gravity of the black hole.
Now, pondering such a journey, one should consider that in approaching the event-horizon surface, one would be heading into an eternal moment on a hot, compressed star, and just how sensible a journey that would be to make. Even though it would take billions or trillions of years to happen from the perspective of anyone outside, the effects to anyone or anything plunging into it would be no different from crashing into the surface of any other star: you'd burn up.
So, because they are frozen in time at their surface, are black holes eternal objects? That question can be answered in the next issue, along with the question of whether or not there exits something called a "singularity" at the center of a black hole. At relativity's extremes, another physical theory, the theory of energy (quantum theory) applies. It is wholly free of singularities of any kind. Although relativity's space and time may be rich with singularities, abundant everywhere, for that lying within space and time, no energy whatsoever will ever be found there, despite its abundance everywhere and anywhere else.