Grace+K


 * The Theory of Relativity **

Einstein's Special Theory of Relativity describes the motion of particles moving at close to the speed of light. In fact, it gives the correct laws of motion for any particle. This doesn't mean Newton was wrong, his equations are contained within the relativistic equations. Newton's "laws" provide a very good approximate form, valid when //v// is much less than //c//. For particles moving at slow speeds (very much less than the speed of light), the differences between Einstein's laws of motion and those derived by Newton are tiny. That's why relativity doesn't play a large role in everyday life. Einstein's theory supersedes Newton's, but Newton's theory provides a very good approximation for objects moving at everyday speeds. Einstein's theory is now very well established as the correct description of motion of relativistic objects, that is those traveling at a significant fraction of the speed of light. Because most of us have little experience with objects moving at speeds near the speed of light, Einstein's predictions may seem strange. However, many years of high energy physics experiments have thoroughly tested Einstein's theory and shown that it fits all results to date.

Einstein's theory of special relativity results from two statements -- the two basic postulates of special relativity: Given these two statements, Einstein showed how definitions of momentum and energy must be refined and how quantities such as length and time must change from one observer to another in order to get consistent results for physical quantities such as particle half-life.
 * 1) The speed of light is the same for all observers, no matter what their relative speeds.
 * 2) The laws of physics are the same in any inertial (that is, non-accelerated) frame of reference. This means that the laws of physics observed by a hypothetical observer traveling with a relativistic particle must be the same as those observed by an observer who is stationary in the laboratory.

Time and Space
Einstein's general theory of relativity describes gravity as a curvature of spacetime caused by the presence of matter. If the curvature is fairly weak, Newton's laws of gravity can explain most of what is observed. For example, the regular motions of the planets. Very massive or dense objects generate much stronger gravity. The most compact objects imaginable are predicted by General Relativity to have such strong gravity that nothing, not even light, can escape their grip. Scientists today call such an object a black hole. Why black? Though the history of the term is interesting, the main reason is that no light can escape from inside a black hole: it has, in effect, disappeared from the visible universe. Most physicists believe they do, basing their views on a growing body of observations. In fact, present theories of how the cosmos began rest in part on Einstein's work and predict the existence of both singularities and the black holes that contain them. Yet Einstein himself vigorously denied their reality, believing, as did most of his contemporaries, that black holes were a mere mathematical curiosity. He died in 1955, before the term "black hole" was coined or understood and observational evidence for black holes began to mount.

Matter The General Theory of Relativity proposed that matter causes space to curve. The large ball will cause a deformation in the sheet's surface. A baseball dropped onto the sheet will roll toward the bowling ball. Einstein theorized that smaller masses travel toward larger masses not because they are "attracted" by a mysterious force, but because the smaller objects travel through space that is warped by the larger object. Physicists illustrate this idea using embedding diagrams. Contrary to appearances, an embedding diagram does not depict the three-dimensional "space" of our everyday experience. Rather it shows how a 2D slice through familiar 3D space is curved downwards when embedded in flattened hyperspace. We cannot fully envision this hyperspace; it contains seven dimensions, including one for time! Flattening it to 3D allows us to represent the curvature. Embedding diagrams can help us visualize the implications of Einstein's General Theory of Relativity.

Energy Probably the most famous scientific equation of all time, first derived by Einstein is the relationship //E = mc2//. This tells us the energy corresponding to a mass m at rest. What this means is that when mass disappears, for example in a nuclear fission process, this amount of energy must appear in some other form. It also tells us the total energy of a particle of mass m sitting at rest. Einstein also showed that the correct relativistic expression for the energy of a particle of mass m with momentum //p// is //E2 = m2c4 + p2c2//. This is a key equation for any real particle, giving the relationship between its energy (//E)//, momentum ( //p)//, and its rest mass (//m)//. If we substitute the equation for p into the equation for //E// above, with a little algebra, we get //E = gamma mc2//, so energy is gamma times rest energy. (Notice again that if we call the quantity //M =gamma m// the mass of the particle then //E = Mc2// applies for any particle, but remember, particle physicists don't do that.)

Works Cited

1. SLAC. "Theory: Special Relativity (SLAC VVC)." __SLAC Public Website Server__. 31 Oct. 2008. 26 Jan. 2009 . This website explains the theory of relativity. It is publish by a corporation called SLAC National Accelerator Laboratory, which is based and operated at Stanford University. Because the information is operated by SU, the information is legitimate. The set up of the website is easy to navigate which makes understanding the information much easier. 2. Rybczyk, Joseph A. "Millenium Theory of Relativity." __Millenium Theory of Relativity__. 2001. 26 Jan. 2009 . This website is based on the Millenium Theory of Relativity. It gives descriptive statements explaining what the theory is about and relates it to other theories that have developed throughout history. It explains how it was developed and from what theories it branches off of. The website states that the Millenium Theory of Relativity has been developed over four years and is based on the ideas of many scientists. This site is helpful if you want to learn the basics of the Theory of Relativity and learn how to relate it to everyday happenings. Although the website is very texty, it has alot of detailed information.

3. "Theory of Relativity â€“ A Brief History." __Theory of Relativity â€“ A Brief History__. 2002. 26 Jan. 2009 . This website is based on the Theory of Relativity. Although the information correlates with many other websites based on the same theory, this website is run by a Christian group. The statements made by the website may be true, however certain parts of the site may be biased because the religious organization might have different beliefs. Because they are a religious group, their ideas may be opposed to the scientific ideas. This website is set up nicely and is easy to navigate, but the quality of the website may not be quite up to par.