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=   **The Theory Of Relativity** =

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The Theory of Relativity was formulated by physicist Albert Einstein in 1905. The theory explained the be havior of space, matte  r, time and energy  .  The <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;">theory among many things states that the speed of light is constant regardless of an observers speed. The theory allows for things that non- <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;">physicist would describe as bizarre, such as two people observing the same event happening and recording that it occurred at different times, which would happen if o <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;">ne observer was moving faster than the other. Als <span style="font-family: Arial,sans-serif;">o two people meas <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;">urin <span style="font-family: Arial,sans-serif;"> <span style="font-family: Arial,sans-serif;">g the length of the same object can obtain two different lengths and both be cor <span style="font-family: Arial,sans-serif;">rect. Both of those scenarios depend on frames of reference which Einstein describes in his theory. <span style="font-family: Arial,sans-serif;">The theory of relativity is widely accepted by scientists and has been validated by careful scientific experiments, everyday uses and observations of the natural world.

In 1887 Albert Michelson and Edward Morley proved that the Galilean theory of relativity was wrong. The Galilean theory of relativity says that an objects velocity determined by an outside observer is just the sum of its velocities. So a person on a bus traveling at 45 mph that is walking to the front of the bus at 3 mph would appear, to an outside observer, to be moving at 48 mph. Using this principle they assumed that if the Earth was traveling around the sun at a certain speed that the speed of light should be the speed of light minus the speed of the Earth. When they measured the speed of light, they found that the speed was constant regardless of the speed the obje ct was moving <span style="font-family: Arial,sans-serif;"> (    Dine, Michael ). This is part of Einstein's theory that states light has a constant value to all observers no matter how fast they are moving. Later experiments since then have proved the same thing, that no matter how fast an object is moving the speed of light is always the same from all frames of reference.

Global Positioning Systems are used by many people everyday, most don't even realiz e that the time kept by satellites must be corrected because of the effects <span style="font-family: Arial,sans-serif;"> predicted by the Theory of Relativity. Time dilation is caused when two objects with identical clocks move at different speeds relative to each other and experience different lengths of time. So if a there are a pair of twins and one travels away from Earth at or near the speed of light when they return the twin that stayed on Earth will be older than the twin that traveled away from the Earth. This is caused because moving clocks or objects experience time "slower" relative to a stationary object. So the satellites which are orbiting many thousand miles above the Earth they move faster than a person that is standing on the surface of the Earth. This means that the a tomic clocks that are on board the satellites are ticking at a slower speed relative to clocks that are on the surface of the Earth ( Theory: Special Relativity ). Although the differences caused by the relative motion of the satellites are v<span style="font-family: Arial,sans-serif;"> ery small, the GPS that many people use everyday without a thought would be inaccurate at determining the location of a driver on the surface of the Earth.

<span style="font-family: Arial,sans-serif;">T  <span style="font-family: Arial,sans-serif;">h   <span style="font-family: Arial,sans-serif;">e Theory of Relativity says that time is relative to the speed an object travels, so an object traveling very fast would experience time slower relative to an object moving at slower speeds. Although to both <span style="font-family: Arial,sans-serif;"> objects there would be no difference in the rate of time, the time dilation is only measurable by having two identical clocks that record different periods of time. To validate this, physicists knew that when cosmic rays from the sun hit the atmosphere they made particles. One of these  <span style="font-family: Arial,sans-serif;"> particles, a muon, travels very near the speed of light and is also radioactive. Since they knew how long would take for the muon to break apart due to radioactive decay, they knew that there would not be enough time for it to reach the Earth's surface. To see the difference in the number of muons as they traveled to the Earth's surface, they measured the number of muons at the top of a mountain and then at sea level  <span style="font-family: Arial,sans-serif;">  (Stern, David P). As predicted by the Theory of Relativity the decrease in the number of muons was smaller than predicted if time dilation was not taken into effect.

<span style="font-family: Arial,sans-serif;">  <span style="font-family: Arial,sans-serif;"> The theory of relativity is currently one the best theories for describing the physical happenings of our universe. It has been validated in many times since it was published in 1905 by Albert Einstein. Although the theory predicts the actions of large objects the equations break down when they are used for sub-atomic particles, which is where quantum mechanics is much more useful. There are some theories that combine the Theory of General Relativity and quantum mechanics, such as string theory, but many physicists do not agree whether they are valid or not.

Works Cited

"Theory: Special Relativity." __Virtual Visitor Center__. 31 Oct. 2008. Stanford University. 2 Feb. 2009 <http://www2.slac.stanford.edu/vvc/theory/relativity.html>. //Gives a general overview of the the Theory of Relativity. Also gives a brief history of how Einstein formulated the theory. Describes some of the effects that are predicted by Einstein's Theory. This website is credible because it is written by a prestigious university and is also updated regularly.//

Dine, Michael. "NASA - Relativity." __World Online Reference Center__. 2004. NASA. 5 Feb. 2009 <http://www.nasa.gov/worldbook/relativity_worldbook.html>. //This website gives a very good overview of the theory of relativity and explains many of its effects with regards to motion and frames of reference. It is very credible because it was written by a person with a PhD from the university of California.//

Stern, David P. "The Theory of Relativity." __NASA__. 20 May 2008. NASA. 5 Feb. 2009 <http://www-istp.gsfc.nasa.gov/stargaze/Srelativ.htm>. //This website gives a basic explanation of the Theory of Relativity. It gives a brief history of how the theory was vreated and also some of its impacts. This website is credible becasue the author has a PhD in physics.//