# Special Relativity - History, Special Relativity, Space-time, Unusual Effects Of Motion, Speed Of Light Limit

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reference frames theory phenomena

German–American physicist Albert Einstein's (1879–1955) theory of relativity consists of two major portions: the special theory of relativity and the general theory of relativity. Special relativity deals with phenomena that become noticeable when traveling near the speed of **light** and reference frames that are moving at a constant **velocity**, inertial reference frames. General relativity deals with reference frames that are accelerating, noninertial reference frames, and with phenomena that occur in strong gravitational fields. General relativity also uses the curvature of **space** to explain gravity.

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In the seventeenth century, English physicist and mathematician Sir Isaac Newton's (1642–1727) Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) accomplished a grand synthesis of physics that used three laws of motion and the law of gravity to explain motions we observe both on the Earth and in the heavens. These laws worked very well, and c…

To understand many concepts in relativity one first needs to understand the concept of a reference frame. A reference frame is a system for locating an object's (or event's) position in both space and time. It consists of both a set of coordinate axes and a clock. An object's position and motion will vary in different reference frames. Go back to the example above of the boy a…

Imagine a rocket ship traveling close to the speed of light. A number of unusual effects occur: Lorentz contraction, time dilation, and mass increase. These effects are as seen by an outside observer at rest. To the pilot in the reference frame of the rocket ship all appears normal. These effects will occur for objects other than rocket ships and do not depend on there being someone inside the mov…

Think about accelerating the rocket in the above example. To accelerate the rocket (or anything else) an outside force must push on it. As the speed increases, the mass appears to increase as seen by outside observers including the one supplying the force (the one doing the pushing). As the mass increases, the force required to accelerate the rocket also increases. (It takes more force to accelera…

A paradox is an apparent contradiction that upon closer examination has a noncontradictory explanation. Several paradoxes arise from the special theory of relativity. The paradoxes are interesting puzzles, but more importantly, help illustrate some of the concepts of special relativity. Perhaps the most famous is the twin paradox. Two twins are initially the same age. One of the twins becomes an a…

Like any scientific theory, the theory of relativity must be confirmed by experiment. So far, relativity has passed all its experimental tests. The special theory predicts unusual behavior for objects traveling near the speed of light. So far no human has traveled near the speed of light. Physicists do, however, regularly accelerate subatomic particles with large particle accelerators like the rec…

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