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Albert Einstein has been a major influence to not just our world of science but also society. His ideas of theory of relativtiy has benefited in many ways. **It has furthered our understanding of gravity and black holes and also lead us to the GPS Navigation System.**

=__**Background Information **__= - Alber Einstein is often called the most influencial physician of modern history and his work on relativity the greatest impact on not only science but also society - There are two types of relativity: Special and General - General theory of relativity may be the biggest leap of the scientific imagination - According to special relativity the speed of light is the same for all observers, no matter what their relative speeds - A black hole is a region of space whose attractive gravitational force is so intense that no matter, light, or communication of any kind can escape - GPS receiver performs the necessary relativistic calculations when determining a user's location

=**__What is Relativity? __**=

Einstein's idea of relativity is put into two parts special theory of relativity and general theory of relativity. Special theory of relativity is the theory of time and space. Special relativity describes the motion of particles moving at close to the speed of light. The speed of light is the same for all observers no matter what their relative speeds. General theory of relativity is the theory of gravity and the behavior of space and time.

=**__Gravity and Black Holes __**= General relativity is also known as the equivalence principle which means when gravity is pulled in one direction it is equivalent to an acceleration in the opposite direction. For example, "A car acceleration forwards feels just like sideways gravity pushing you back against your seat or an elevator acceleration upwards feels just like gravity pushing you into the floor" (Lightman). (click link below to see video animations of the above examples) http://www.pbs.org/wgbh/nova/einstein/rela-i.html

A black hole is an area of space-time with a gravitational field so intense that its escape velocity is equal to or exceeds the speed of light. Einstein believes that black holes are formed from the collapse of stars. "As long as they are emitting heat and light into space, stars are able to support themselves against their own inward gravity with the outward pressure generated by heat from nuclear reactions in their deep interiors" (Lightman). When the star runs out of fuel for nuclear burning in the core it is no longer able to support itself and its self-gravitational attraction becomes unbalaced and causes the star to collapse.

=__Global Positioning System (GPS) __=

Global Positioning Systems are found and used in today's society. GPS receivers can determine you position, speed, and heading on the surface of the Earth. Without Einstein's special and general theory of relativity, navigation probably would not be where it is today. "Satellites are constantly moving relative to observers on the Earth. Satellites are in orbits high above the Earth, where the curvature of spacetime due to the Earth's mass is less than it is at the Earth's surface. A prediction of general relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away. As such, when viewed from the surface of the Earth, the clocks on the satellites appear to be ticking //faster// than identical clocks on the ground" ("Real-World Relativity: The GPS Navigation System"). Special relativity predicts the oppostite, their clocks ticking slower.

  < http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html >.
This web page contains credible information. It talks about the theory of relativity and how it relates to the Global Posting System. This site has alot of good information to refer to. There are examples of how GPS receivers can determine one's location. This web page discusses how it effects both general and special relativity.

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This web page talks about Einstein's discoveries of the theory of relativity. This site contains credible information and many facts and examples. It talks about both general and special relativity. This site also contains information about collapsed stars and black holes and how they relate to relativity.