The Search for Black Holes:
Both As A Concept And An Understanding
For ages people have been determined to explicate on everything. Our search for explanation rests only when there is a lack of questions. Our skies hold infinite quandaries, so the quest for answers will, as a result, also be infinite. Since its inception, Astronomy as a science speculated heavily upon discovery, and only came to concrete conclusions later with closer inspection. Aspects of the skies which at one time seemed like reasonable explanations are now laughed at as egotistical ventures. Time has shown that as better instrumentation was developed, more accurate understanding was attained. Now it seems, as we advance on scientific frontiers, the new quest of the heavens is to find and explain the phenomenom known as a black hole.
The goal of this paper is to explain how the concept of a black hole came about, and give some insight on how black holes are formed and might be tracked down in our more technologically advanced future. Gaining an understanding of a black hole allows for a greater understanding of the concept of spacetime and maybe give us a grasp of both science fiction and science fact. Hopefully, all the clarification will come by the close of this essay.
A black hole is probably one of the most misunderstood ideas among people outside of the astronomical and physical communities. Before an understanding of how it is formed can take place, a bit of an introduction to stars is necessary. This will shed light (no pun intended) on the black hole philosophy.
A star is an enormous fire ball, fueled by a nuclear reaction at its core which produces massive amounts of heat and pressure. It is formed when two or more enormous gaseous clouds come together which forms the core, and as an aftereffect the conversion, due to that impact, of huge amounts of energy from the two clouds. The clouds come together with a great enough force, that a nuclear reaction ensues. This type of energy is created by fusion wherein the atoms are forced together to form a new one. In turn, heat in excess of millions of degrees farenheit are produced.
This activity goes on for eons until the point at which the nuclear fuel is exhausted. Here is where things get interesting. For the entire life of the star, the nuclear reaction at its core produced an enormous outward force. Interestingly enough, an exactly equal force, namely gravity, was pushing inward toward the center. The equilibrium of the two forces allowed the star to maintain its shape and not break away nor collapse.
Eventually, the fuel for the star runs out, and it this point, the outward force is overpowered by the gravitational force, and the object caves in on itself. This is a gigantic implosion. Depending on the original and final mass of the star, several things might occur. A usual result of such an implosion is a star known as a white dwarf. This star has been pressed together to form a much more massive object. It is said that a teaspoon of matter off a white dwarf would weigh 2-4 tons. Upon the first discovery of a white dwarf, a debate arose as to how far a star can collapse. And in the 1920âs two leading astrophysicists, Subrahmanyan Chandrasekgar and Sir Arthur Eddington came up with different conclusions. Chandrasekhar looked at the relations of mass to radius of the star, and concluded an upper limit beyond which collapse would result in something called a neutron star. This limit of 1.4 solar masses was an accurate measurement and in 1983, the Nobel committee recognized his work and awarded him their prize in Physics. The white dwarf is massive, but not as massive as the next order of imploded star known as a neutron star. Often as the nuclear fuel is burned out, the star will begin to shed its matter in an explosion called a supernovae. When this occurs the star loses an enormous amount of mass, but that which is left behind, if greater than 1.4 solar masses, is a densely packed ball of neutrons. This star is so much more massive that a teaspoon of itâs matter would weigh somewhere in the area of 5 million tons in earthâs gravity. The magnitude of such a dense body is unimaginable. But even a neutron star isnât the extreme when it comes to a starâs collapse. That brings us to the focus of this paper. It is felt, that when a star is massive enough, any where in the area of or larger than 3-3.5 solar masses, the collapse would cause something of a much greater mass. In fact, the mass of this new object is speculated to be infinite. Such an entity is what we call a black hole.
After a black hole is created, the gravitational force continues to pull in space debris and all other types of matter in. This continuous addition makes the hole stronger and more powerful and obviously more massive.
The simplest three dimensional geometry for a black hole is a sphere. This type of black hole is called a Schwarzschild black hole. Kurt Schwarzschild was a German astrophysicist who figured out the critical radius for a given mass which would become a black hole. This calculation showed that at a specific point matter would collapse to an infinitely dense state. This is known as singularity. Here too, the pull of gravity is infinitely strong, and space and time can no longer be thought of in conventional ways. At singularity, the laws defined by Newton and Einstein no longer hold true, and a "myterious" world of quantum gravity exists. In the Schwarzschild black hole, the event horizon, or skin of the black hole, is the boundary beyond which nothing could escape the gravitational pull.
Most black holes would tend to be in a consistent spinning motion, because of the original spin of the star. This motion absorbs various matter and spins it within the ring that is formed around the black hole. This ring is the singularity. The matter keeps within the Event Horizon until it has spun into the center where it is concentrated within the core adding to the mass. Such spinning black holes are known as Kerr Black Holes. Roy P. Kerr, an Australian mathematician happened upon the solution to the Einstein equations for black holes with angular momentums. This black hole is very similar to the previous one. There are, however, some differences which make it more viable for real, existing ones. The singularity in the this hole is more time-like, while the other is more space-like. With this subtle difference, objects would be able to enter the black whole from regions away from the equator of the event horizon and not be destroyed.
The reason it is called a black hole is because any light inside of the singularity would be pulled back by the infinite gravity so that none of it could escape. As a result anything passing beyond the event horizon would dissappear from sight forever, thus making the black hole impossible for humans to see without using technologicalyl advanced instruments for measuring such things like radiation. The second part of the name referring to the "hole" is due to the fact that the actual hole, is where everything is absorbed and where the center core presides. This core is the main part of the black hole where the mass is concentrated and appears purely black on all readings even through the use of radiation detection devices.
The first scientists to really take an in depth look at black holes and the collapsing of stars, were a professor, Robert Oppenheimer and his student Hartland Snyder, in the early nineteen hundreds. They concluded on the basis of Einstein's theory of relativity that if the speed of light was the utmost speed over any massive object, then nothing could escape a black hole once in it's clutches.
It should be noted, all of this information is speculation. In theory, and on Super computers, these things do exist, but as scientists must admit, theyâve never found one. So the question arises, how can we see black holes? Well, there are several approaches to this question. Obviously, as realized from a previous paragraph, by seeing, it isnât necessarily meant to be a visual representation. So weâre left with two approaches. The first deals with X-ray detection. In this precision measuring system, scientists would look for areas that would create enormous shifts in energy levels. Such shifts would result from gases that are sucked into the black hole. The enormous jolt in gravitation would heat the gases by millions of degrees. Such a rise could be evidence of a black hole. The other means of detection lies in another theory altogether. The concept of gravitational waves could point to black holes, and researchers are developing ways to read them.
Gravitational Waves are predicted by Einsteinâs General Theory of Relativity. They are perturbations in the curvature of spacetime. Sir Arthur Eddington was a strong supporter of Einstein, but was skeptical of gravity waves and is reported to have said, "Graviatational waves propagate at the speed of thought." But what they are is important to a theory. Gravitational waves are enormous ripples eminating from the core of the black hole and other large masses and are said to travel at the speed of light, but not through spacetime, but rather as the backbone of spacetime itself. These ripples pass straight through matter, and their strength weakens as it gets farther from the source. The ripples would be similar to a stone dropped in water, with larger ones toward the center and fainter ones along the outer circumference. The only problem is that these ripples are so minute that detecting them would require instrumentation way beyond our present capabilities. Because theyâre unaffected by matter, they carry a pure signal, not like X-rays which are diffused and distorted. In simulations the black hole creates a unique frequency known as it natural mode of vibrations. This fingerprint will undoubtedly point to a black hole, if itâs ever seen.
Just recently a major discovery was found with the help of The Hubble Space Telescope. This telescope has just recently found what many astronomers believe to be a black hole, after being focused on a star orbiting an empty space. Several picture were sent back to Earth from the telescope showing many computer enhanced pictures of various radiation fluctuations and other diverse types of readings that could be read from the area in which the black hole is suspected to be in.
Because a black hole floats wherever the star collapsed, the truth is, it can vastly effect the surrounding area, which might have other stars in it. It could also absorb a star and wipe it out of existance. When a black hole absorbs a star, the star is first pulled into the Ergosphere, this is the area between the event horizon and singularity, which sweeps all the matter into the event horizon, named for it's flat horizontal appearance and critical properties where all transitions take place. The black hole doesnât just pull the star in like a vaccuum, rather it creates what is known as an accretion disk which is a vortex like phenomenom where the starâs material appears to go down the drain of the black hole. When the star is passed on into the event horizon the light that the star ordinarily gives off builds inside the ergosphere of the black hole but doesnât escape. At this exact point in time, high amounts of radiation are given off, and with the proper equipment, this radiation can be detected and seen as an image of emptiness or as preferred, a black hole. Through this technique astronomers now believe that they have found a black hole known as Cygnus X1. This supposed black hole has a huge star orbiting around it, therefore we assume there must be a black hole that it is in orbit with.
Science Fiction has used the black hole to come up with several movies and fantastical events related to the massive beast. Tales of time travel and of parallel universes lie beyond the hole. Passing the event horizon could send you on that fantastical trip. Some think there would be enough gravitational force to possible warp you to an end of the universe or possibly to a completely different one. The theories about what could lie beyond a black hole are endless. The real quest is to first find one. So the question remains, do they exist?
Black holes exist, unfortunately for the scientific community, their life is restricted to formulas and super computers. But, and there is a but, the scientific community is relentless in their quest to build a better means of tracking. Already the advances of hyper-sensitive equipment is showing some good signs, and the accuracy will only get better.
Word Count: 2172
Neither wormholes or black holes have actually ever been seen directly, even with the sophisticated equipment in use today, but both follow inevitably from Albert Einstein�s General Theory of Relativity, and plenty of indirect evidence has been obtained (at least for black holes). The ideas have certainly been more than readily accepted by the science fiction community, for whom they suggest intriguing possibilities.
One of the most famous black hole theorists, the British physicist Stephen Hawking, proposed the four laws of black hole mechanics back in the 1960s, and calculated in 1974 that black holes should thermally create and emit sub-atomic particles, known today as Hawking radiation, until they eventually exhaust their energy and evaporate. Yet, as recently as 2004, he admitted to losing a bet he made with the Caltech physicists Kip Thorne and John Preskill, and overturned his long-held belief that any �information� crossing the event horizon of a black hole is lost to our universe, and is now convinced that black holes will eventually transmit, albeit in a garbled form as we perceive it in our observable universe, information about all matter they swallow (�information� in this sense may be loosely defined as �that which can distinguish one thing from another�, and essentially refers the identity of a thing and all of its properties).
This is a good indication that the theory is far from cut and dried, and research (both theory and observation) into this challenging area proceeds unabated. As an example of the complexity of the subject matter, a short quote from Professor Hawking�s 2004 presentation may suffice: �The Euclidean path integral over all topologically trivial metrics can be done by time slicing and so is unitary when analytically continued to the Lorentzian�. Wow!