Why Is There Gravity Essays - Physics, Theoretical Physics

Why Is There Gravity? When you pick up a stone and release it falls to the ground. This seemingly simple concept has been known throughout history as gravitation. Isaac Newton managed to explain gravity in terms of its effects, but few have come up with a working explanation for the driving force behind it. The mysterious nature of some of the more peculiar effects of gravity, as well as the simple ones, indicate that explaining why there is gravity will be a long, difficult, yet intriguing task. Ohanian (1976) writes that without other forces interfering, mass attracts mass. This is the fundamental concept behind gravitation. Newton explained it as "there is a power of gravity pertaining to all bodies, proportional to the several quantities of matter which they contain? The force of gravity towards the several equal parts of any body is inversely as the square of the distance of places from the particles." This description of gravity creates the simple mathematical explanation of gravity: that the force of attraction, F, equals G * ((m1 * m2) / r^2). This holds true for most gravitational interactions on earth, so any proper theory of gravity would have to include similar results for these interactions. Misner, Thorne, and Wheeler (1973) explain that there are, however, some more complex aspects of gravity that this law does not account for. One of these strange gravitational effects is observed in the "perihelion shift" movement of planets, the most dramatically affected of which is the planet Mercury. Feynman, Leighton, and Sands (1963) contest that another hole in Newton's predictions about gravitation is that repercussions of changes in gravitational state are felt instantaneously. In other words, gravitational effects travel faster than the speed of light, which is in direct contradiction with Albert Einstein's Special Theory of Relativity. This led Einstein to develop a more advanced theory of gravitation. This was known as the General Theory of Relativity and is the closest and only thing that mankind has as an answer to " Why is there gravity?" Einstein's General Theory of Relativity introduces the idea that space itself can be curved. Just as the ground on earth appears to be flat though it is actually curved, Einstein suggested that space may behave much in the same way. Misner et al. (1973) compared the curvature of space to an ant walking on the surface of an apple whose direction was perfectly toward the stem of the apple. The shortest possible path on the surface of the apple to the stem was a curved line. Thus Einstein has theorized that the shortest possible path in a gravitational field is actually a curve, which is contrary to traditional Euclidean geometry. The other basic concept of general relativity is that gravity is essentially indistinguishable from acceleration. A person standing inside of a stationary elevator on earth could drop a ball and it would fall, accelerating at approximately 9.8m/s^2. A person standing in an elevator free from gravitational fields, but accelerating upwardly at 9.8m/s^2 would exp erience the same effect. Einstein used this similarity between gravity and acceleration in the creation of the General Theory of Relativity. One of the most stunning things about Einstein's theories is that they were created with virtually no experimental verification. Only later, after his death, have we been able to prove various aspects of the General Theory of Relativity experimentally. In this sense, Einstein was well ahead of his time. One such prediction that was ahead of its time was that time moves slower in the presence of a gravitational field. In Einstein's day, they simply did not have the resources to test this experimentally. In more recent times, however, through the use of atomic clocks we have shown this to be true. It is certainly amazing to make predictions about something so abstract on a purely theoretical basis and then later have those predictions verified through experimentation. Unfortunately, Einstein's General Theory of Relativity is the only theory of gravity that has never failed experimentally. Other theories that work experimentally are essentially tweaked versions of the same ideas that Einstein had in the General Theory of Relativity. I feel this "theory monopoly" that Relativity has is detrimental to physics in general, being that it has

History of Slavery and Its Impact on Contemporary Society

History of Slavery and Its Impact on Contemporary SocietyMy History of Slavary and its Impact on Contemporary Society is a sample essay for students of English composition, working in the field of public speaking, or just about any area where the importance of correct structure and diction are evident. I am a former English teacher who taught high school English, as well as a writer, copywriter, and editor.This sample essay began life as a memoir by my brother, Robert. Now, the essay has gone through a fair amount of editing, and I have condensed and greatly condensed its content. Nonetheless, I would like to provide some insight into my thinking about the essay, which you will find in the next section. It is important that you understand why I wrote the essay, and what it is trying to convey, before reading the rest of this description.To begin with, I had some misgivings about my past work as an English teacher. Some of my students and colleagues expressed a worry that they were no t able to properly teach English, and that I was actually afraid to speak in front of them. I was not in fact afraid to speak in front of them, but there were many times when I did not feel that I was explaining the material correctly. It is important that the student feels that the material being taught is well understood. Many times, I found myself addressing issues that had no bearing on the learning process, and that I had to resort to remedial homework assignments in order to help my students become more skilled at the subject.One issue that I was quite troubled by was the problem of knowing the history of slavery and its impact on contemporary society. That is to say, I knew that the Renaissance period was one of tremendous change, and that many of the key historical figures of the period were essentially remarkable personalities, but that these individuals did not always enjoy widespread popularity. On the other hand, it could be argued that the generally benign image of Al C apone probably played a role in his continuing popularity. It is no mystery that in the 21st century, many people are not aware of the difficulties that faced many Americans in the middle years of the 20th century. For me, it is important that students are able to appreciate the nuances of these periods, and that they are better able to examine the implications of events that occurred in those periods for the entire course of their lives.There are many who argue that the English language is not a natural language, and that it can only be learned through the study of other languages. I do not share that view. I believe that language can be learned, and that the best way to learn it is to be exposed to English at a very early age. That is why I felt that teaching English as a second language, through immersion in a language that is native to that country, is very important.The History of Slavery and its Impact on Contemporary Society is a sample essay that enables students to have the opportunity to gain first-hand knowledge of the changes that occurred in the culture and the political environment during the middle years of the 20th century. As I was writing the essay, I realized that much of what is used in class today is borrowed from history textbooks and movies. The idea of using such sources does not sound appealing, particularly when it involves facts that are very difficult to access.In the end, I wanted to use the history of slavery and its Impact on Contemporary Society as a vehicle for examining the philosophy of art, the politics of the individual, and the relations between family and society. If you look closely, I believe that this sample essay does an excellent job of demonstrating all of these points.