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 *  Einstein's Theory of Relativity   **

 In 1905, German-born scientist, Albert Einstein, questioned Isaac Newton's theories about movement, time, and gravity. His thoughts seemed outlandish at the time and drew up contraversy. Einstein put his thoughts together to form The Theory of Relativity. This theory has been confirmed and will continue to be confirmed by modern scientists and researchers.

There are two parts to Einstein's Theory of Relativity: Special Relativity and General Relativity.

The Special Theory of Relativity was published in 1905. It states that the speed or space between objects is dependant on the reference point. There is no way to tell if an object is really moving. Imagine being the only object in a dark space of nothing: no other people, no ground, no sky, no planets, no stars. There is no way to tell if you are moving. You aren't moving towards or away from anything. Nothing is moving towards or away from you. An object's speed cannot be measured without a reference point. The object has a different speed when measured relative to a stationary object rather than another moving object. This also goes for two moving objects. If one object is moving at a speed of 10mph, and another object is moving towards the first object at 20mph, the second object is moving at 30mph relative to the first object. Light is the only thing that does not go by this rule. The speed of light is the same for all viewers, no matter where they are or what their speed is.  The Theory of General Relativity, published in 1915, concerns gravity. Einstein wanted to answer the question 'what is gravity'. It was understood what gavity does but no one knew how it created the pull towards the earth. Einstein developed the general theory of relativity to modify Newton's law of gravitation so that it would agree with special relativity. The key disagreement lay in descriptions of how objects exert forces on one another. (NASA-Relativity) Consider, for example, an atom of the simplest form of hydrogen. This atom consists of a single electron in orbit around a single proton. The electron carries a negative electric charge, while the proton is positively charged. The position of the proton determines the motion of the electron. It does so by exerting a force of attraction on the electron -- an application of the familiar principle "opposite charges attract." (NASA-Relativity) Einstein's theory predicts that the direction of light propagation should be changed in a gravitational field. Precise observations indicate that Einstein is right, both about the effect and its magnitude. We have already seen a spectacular consequence of the deflection of light in a gravitational field: gravitational lensing. (Gravitation and the General Theory of Relativity)  Tests are being made constantly that prove or disprove Einstein's Theory of Relativity. Here's an example of one that prove's it: The orientation of Mercury's orbit is found to precess in space over time, as indicated in the adjacent figure (the magnitude of the effect is greatly exaggerated for purposes of illustration). This is commonly called the "precession of the perihelion", because it causes the position of the perihelion to move around the center of mass. Only part of this can be accounted for by perturbations in Newton's theory. There is an extra 43 seconds of arc per century in this precession that is predicted by the Theory of General Relativity and observed to occur (recall that a second of arc is 1/3600 of an angular degree). This effect is extremely small, but the measurements are very precise and can detect such small effects very well. (Gravitation and the General Theory of Relativity)

 Albert Einstein developed the Theory of Relativity to explain movement and gravity. He created a theory that would forever be a vital concept to scientists. Not only is this theory interesting and complicated, it requires a truely genius person to be the first to wrap their mind aroun this idea. Although the theory of relativity has caused great contraversies, it has also stood as a huge leap in human knowledge. //

Pysics: Albert Einsteins Theory of Special Relativity MSN Encarta //

Works Cited "NOVA Einstein's Big Idea Relativity PBS." __PBS.org.__ Feb. 3, 2009 http://www.pbs.org/wgbh/nova/einstein/relativity/ The Theory of Relativity is explained on this site with text and videos. It is sponsered by PBS so it is unbias and reliable.

"NASA-Relativity." __NASA.gov.__ Feb. 3, 2009 http://www.nasa.gov/worldbook/relativity_worldbook.html This site explains both the special and general theory of relativity. It goes into detail about some of Einstein's other acomplishments and tests that have been done to confirm his theory. The fact that this article is on NASA's website makes the site reliable and highly informational.

"Gravitation and the General Theory of Relativity." __phys.edu.__ Feb. 3, 2009 http://csep10.phys.utk.edu/astr162/lect/cosmology/gravity.html Diagrams and pictures describe Einstein's theory of relativity. This site has sraight forward information and is an educational site. It is unbias and credible.