title: Black Hole Essay type: Research Paper body: Black Holes are considered a recent discovery in the almost age-old study of our universe. Since the beginning of our time here on earth, Man has always expressed fascination and interest in the sky above us and everything beyond. We look out to the unknown in times of awe, happiness, sadness and confusion. It is only recently that our study and understanding of the universe has begun to increase almost exponentially both in pace and possibilities. The concept of black holes has been around in loose theory since the late 1700's, when the French Mathematician Pierre Simon wrote about black stars that he called "dark bodies." The more commonly used term these days is "black hole"- a result of more recent work by the American scientist John Wheeler, among others. Stephen Hawking has also done a great amount of work on black holes since the 1960's.
About the same time as Einstein's Theory of General Relativity came out (about 1915), Karl Schwarzchild derived a system that describes the spacetime geometry of empty space surrounding any spherical mass. One of the more remarkable predictions of Schwarzchild's geometry was that if a mass (M) were compressed inside a critical radius (rs) then its gravity would become so strong that not even light could escape. The Schwarzchild radius (or event horizon) rs of mass M is given in mathematical formula like so: rs = 2 G M / c 2 where G represents Newton's gravitational constant, and c being the speed of light. A star is defined as a self-illuminating body. When a star runs out of light, it dies. A dead star may do one of many things after its demise.
It may shrink until it is a white dwarf (only a few thousand miles or so across- about the size of the earth), it may shrink until it is smaller than a white dwarf and become a neutron star- about 20 miles across (neutron star have incredible density, about a million tons per square inch). Or, a dead star may continue to shrink until it is simply a point in space with infinite density. This is a black hole. A star shrinks because gravity tries to pull the particles in the star together to make it collapse. If the star is less than two or three solar masses, it usually means that there is enough expulsion principle repulsion to support the star against the pull of gravity.
Stars that have masses greater than 3 times the mass of the sun, on the other hand, will most likely turn into black holes. Within the gravitational force of a body in space, it takes a certain speed of an object propelled outward from that body for it to be able to escape, at what is called the "escape velocity." On earth, the escape velocity is about 24 thousand miles per hour- that is, the relative speed that any object (say a baseball) would need to reach so that the ever famous saying, "what goes up must come down again" would no longer apply. If the escape velocity of a star is greater than the speed of light (approximately 300, 000 kilometers per second) then nothing, not even light itself, can escape from the star. The limits of anything within a black hole- the "point of no return," is called the Event Horizon. Black Holes only suck in everything within this certain distance from its center. Anything outside this horizon would, however, be perfectly safe and could orbit the black hole quite successfully without fear of being sucked in.
Aside from the event horizon, the other major "feature" of a black hole is in the center. It is the point of singularity. Stephen Hawking says that falling into a black hole would bring you to a "region of infinite density and the end of time." Singularity is a point where all the known and understood laws of nature cease to exist. Scientists believe that black holes do strange things to the time and space around them. Outside of a black hole the warping of space causes time itself to slow down. If you were to watch a clock fall in to a black hole, the passing of seconds on that clock would slow down as it fell until it passes the event horizon, where you would essentially see time stop.
If, however, a person fell into a black hole, they would not notice any passing of time because literally everything slows down within this area- the person's breathing, thoughts, perception. The person would fall until they reached the point of singularity- where they would explode because o! f the density. (Despite this, when I die I can't help but think it would be a much better eternal fate than a cemetery- and more interesting, too). Gravity is a constant force throughout our universe. All objects in space have gravity. While we tend to think of gravity as being a force that attracts or pulls inwards, the actual implications of gravity are a little different.
Gravity directly depends on (or is a function of! ) the mass of a body in space. The effect of gravity on space is that it becomes curved. The stronger the gravity, the stronger the warping of the space surrounding it. Says British mathematician John Taylor, "We notice this curvature when we travel past these stars, since we then move not in straight, but in curved lines around them." Until the mid-nineties, there was no actual proof of black holes. Yet the theories surrounding them were so strong that most scientists did not need physical proof to believe in what their equations and formulas told them.
When the first real proof of black holes was uncovered, it was seen more as a validation of long held beliefs than as a groundbreaking new discovery. Although different sources quoted different exact dates, it appears that the first proof came in 1992 when NASA's Hubbell Space Telescope brought home the fist picture of one. The picture was not actually of a black hole, but rather it was an image of a giant disc of cold gas and dust, which scientists believe fuel a black hole. It seems that with all this information on black holes, we should understand them with clarity. And yet, full comprehension of black holes has eluded us, as has much other knowledge concerning the vastness that surrounds us. Some people think black holes are frightening, while others think them marvelous.
Some believe black holes contain the ultimate fate of the universe- that is, that everything will eventually end up being swallowed by a black hole, while still others believe that the radiation leakage from a black hole will eventually allow them to spread out and disappear. Keep in mind, though, that the "disappearance" of a black hole is not the disappearance of the matter, it is simply the matter in a much less compressed, dense form. The possibilities that come with black holes and the relevant theoretical implications are inspiring. Much of it is the stuff of science fiction novels and movies. They bring us a little closer to understanding the makeup of our universe, ! as well as presenting us with difficult questions about time- a phenomenon which, in a deep understanding, seems to always be just a little beyond our grasp. I am left wondering things like, What exactly is time Do black holes last forever Do they eventually collapse on themselves Can one black hole swallow another What would the physical implications of that be Or would they simply mold into one big black hole While we may not know everything about black holes, what we do know is encouraging.
As a race, we have embarked on a mission to understand our environments. The more we learn, the more our knowledge expands and contributes to new levels of comprehension. And while science has led us to many of these discoveries, and even broken down countless boundaries for us, I can't help but feel that there are some things that are not mean to be understood by scientific laws or formulas. For me, this is where faith comes in. Even in science, there are certain basic principles that we all accept. Why do we need oxygen to live Because it nourishes us and keeps us alive.
Why does it keep us alive Because it provides us with what our bodies need. Why can oxygen do that and not other things It just can. Why does the universe exist Maybe it just does.