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=The Theory of Relativity =

 The theory of relativity was developed by Albert Einstein. It is a complex series of set laws of physics that can be applied to explain many paradoxes that are inexplicable by our other accepted physical laws. There are two main branches of the theory of relativity; the Special and the General theories of relativity. The general theory of relativity deals with gravity, electricity, and magnetism, while the Special Theory of Relativity deals with objects in linear motion and the behavior of light (Uchii). The special theory was devoloped by Einstein first, and the general theory was developed about 10 years later.

The General Theory of Relativity
The general theory of relativity deals with gravity, mostly. While it does discuss electricity and magnetism, or more accurately, electromagnetism, the most common use for it is in the explanation of large scale gravity motions.(21st Century) Using The Genereal Theory of Relativity, it can be explained how planets and celestial bodies orbit, and how black holes and stars are formed and destroyed.

Orbits and Black Holes Explained
When Einstein came up with his theory, one of them was about the effect on gravity on larger objects, such as planets. He found that even planets were affected by gravity; so much so, in fact, that gravity alone explained how the planets orbit the Sun. Using the idea that the planets were "falling" //around// the sun, it made sense that they would stay in orbit. (Relativity) This gravity is based mainly on masses, and it was on this foundation that the equation for finding the effect of gravity was found. Generally, the greater the mass of the object, thr greater gravitational pull it has (Takeuchi) If that mass gets so large and the gravitational pull is so great, even light cannot escape the hold of the gravity, creating the ever-popular black hole.

A Complex Look at Black Holes
Another way to look at black holes is by examing the Schwarzschild radius.(Relativity) If all mass was to be compressed below a certain radius, which differs from object to object, the curvature of spacetime becomes infinite and the object is surrounded by an event horizon. (21st Century) Basically, the Schwarzschild radius is the radius below which a gravitational force between two particles must undergo in order for it to cause an irreversible collapse of gravity. In other words, so much mass is being compressed into such a small radius, that the gravity collapses, and is forced into a black hole. Modern physicists believe this to be the final destination for a star's life cycle. (Takeuchi)

If you look at the figure, an easy way to sum up the Schwarzschild radius is by looking at the number 10^-23cm. You would need to put all of the mass of a human into a space of that size (Smaller than an atom) in order to undergo the irreversible collapse of gravity as mentioned above. (Takeuchi)

The Special Theory of Relativity
The special theory of relativity deals with objects travelling in a straight path. Based upon the special theory of relativity, these objects cannot travel faster than the speed of light. This has been proven by many scientists, and can be explained through the use of examples.

**Typical Scenario**
 Usually, when we refer to speed, we see it as relative to some other object. For instance, you can imagine a student riding a bus. Since the bus is travelling at 60km/hr relative to the ground, you can generalize that the student is travelling 60km/hr relative to the ground as well. Now, say the student is walking forward at 5 km/hr. Now, that student is travelling at 65km/hr relative to the ground. This holds true for many scenarios. But, it does not hold true for light. Because, if you say that the bus is travelling at c, the speed of light, and the student is travelling at 5km/hr relative to the bus, the student has exceeded the speed of light.(Uchii) This is simply not possible. The "what you expect" vs. "What Happens" is summed up in the figure to the right, courtesy of Tatsu Takeuchi.

What occurs as you near the speed of light
As an object gets closer and closer to the speed of light, many phenomena occur, explained through the special theory of relativity. One thing that occurs is that time will actually elapse more slowly (Takeuchi). This is known as **time dilation** Time dilation leads to a famous event known as the Twin Paradox (Uchii). This paradox is summed up better below.

The Twin Paradox occurs when you have two theoretical twins. One goes off to space, travelling at .75c (c being the speed of light), the other stays on Earth. After 60 years, the twin on Earth has aged 60 years, while twin in space has only aged 40. (21st Century) This is owed to the fact that time runs slower at higher velocities.
 * [[image:twin_paradox.gif align="left"]] Twin Paradox**

The time dilation phenomenon has been confirmed with the use of sub-atomic particles and high energy acclerators. The effects of this are not noticed at day to day speed in vehicles or airplane travel. You must be approaching the speed of light to observe the dramatic effects of time dilation.

The Lorentz contraction is similar to time dilation, only instead of time elapsing more slowly, it is the actaul mass of the object that is contracted.(Uchii) The relationship of the smaller space and shorter time frame leads into another more complex branch of the special theory of relativity known as the **time-space continuum.** Due to the immense scope of the continuum, it will not be discussed in full in this article.
 * Lorentz Contraction**

Mass-Energy Equivalence
One of the most important parts of the special theory of relativity is the discovery that since time and space are variable concepts, so too are velocities (Which are just ratios of space over time). If velocities change from one point of reference to another, then velocity must also be relative, just as space and time are. (Takeuchi) Thus, momentum is born. Momentum was defined by Newton, but according to him, momentum is contant, and cannot change from reference frame to reference frame. So Einstein found a way to prove that **relativistic momentum** is conserved, but only of the mass is added into the equation. This is all shown in Einstein's most famous formula:

E=mc^2
The importance of this equation was significant at the time because it meant that there was an equivalence between mass and energy. (As seen in the general theory of relativity. Remember that the Special Theory came //before// the general theory) But, the implication of the formula was not fully realized until many years later. (Takeuchi) Using the basis of Einstein's equation, nuclear energy was discovered, and thus led the invention of nuclear weapons and power.

// *Entire section cited from Takeuchi //

=Summing Up= The Theory of relativity is seen more and more as you near the speed of light. As you add more energy to an object, its velocity does not truly increase, as there is a limit to the velocity of an object. (21st Century) That energy must be applied to //something// however, and the theory of relativity tells us that it is added to the mass. Thanks to Einstein's Mass-Energy equivalence, we see that the energy is added to the mass, and more mass is obtained as an object gets closer and closer to the speed of light. So a spaceship going faster and faster appears to obtain the mass of a building, then a planet, and so on, as its velocity increases.(Takeuchi) The theory of relativity will long have its roots in modern physics, and will continue to be proven or disproven as science expands its horizons to new depths.

Impact on Society
The theory of relativity has far reaching applications to society. While much of the applications deal with the explanation of the phenomena around us all the time, much of it goes unnoticed. We all see the rising and setting sun every day, yet most don't appreciate it. The theory of relativity explains why it rises and sets, and why the moon has its phases around us, and many other things. It also explains why NASA is so important, and how the science is so complex behind getting the astonauts to space. The theory of relativity is nothing without people to appreciate it, and, just like the theory itself, it is all relative to the eyes of the beholder.

Annotated Works Cited
  "21st Century Science." __abyss.uoregon.edu Web Server__. 5 Feb. 2009 < http://abyss.uoregon.edu/~js/21st_century_science/index.html >. //This site contains information on many of Einstein's works. It is an archive of lectures and discussions at a lecture hall in the University of Oregon. Among the topics discussed are Einstein's theory of Relativity, as well as many other complex physical explanations.// "Relativity (physics) -- Britannica Online Encyclopedia." __Encyclopedia - Britannica Online Encyclopedia__. 5 Feb. 2009 < http://www.britannica.com/EBchecked/topic/496904/relativity  >. // The Britannica article is great for getting an idea on the subject. It includes many specific dates and names, and is great for citing and fact checking specific details. // Takeuchi, Tatsu. "Virginia Tech Physics Lecture." __Virginia Tech Department of Physics__. 8 Feb. 2009 < http://www.phys.vt.edu/~takeuchi >. //This article includes many many detailed descriptions and explantions in a more generalized tone. The concepts are still complex, but the mode of delivery is exceptional, and provides an easy understanding of the topic at hand.//

Uchii, Soshichi. "Einstein Seminar." __University of Japan__. 8 Feb. 2009 http://www.bun.kyoto-u.ac.jp/~suchii/Einstein/index.html. //This site is for students at the university of Japan in Tokyo. It includes many examples and counterexamples of the various theories, and includes illustrations to help explain the theories.//