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SPECIAL RELATIVITY |
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The two theories of relativity, special relativity and general relativity, were developed by Albert Einstein in the early part of the 20th century. Einstein made substantial contributions to numerous other branches of physics, but his works on relativity remains his best known and most important works. Conceptually, special relativity is the simpler of the two theories, and this is the subject of the articles presented here. |
Perhaps the most well-known "result" from the theory of special relativity is the formula E = mc2, which defines an equivalence between the mass m of an object and its energy E. This formula is one of the most important results to emerge from the theory of special relativity, and many people will have at least heard of this formula, even if the precise meaning is unclear.
Special relativity is based on the idea that all motion is relative - that is, one can only judge the state of motion of an object by comparing it with some other reference point or object. For example, cars move relative to the surface of the earth. Special relativity shows that this apparently simple and obvious assertion has far-reaching consequences, especially when considering very fast-moving objects. Einstein based his theory of special relativity on two basic postulates, one of which is that all motion is relative, and then proceeded to determine the consequences of those postulates. As with quantum physics, the consequences can be surprising and somewhat non-intuitive.
In the first article, the basic postulates of relativity are discussed. In the second and third articles, two of the basic consequences of the postulates are considered, namely time dilation and length contraction. The fourth article considers the origin of the formula E = mc2, what it means, and how it arises from the postulates of relativity. The next article considers one of the most important paradoxes that arises in special relativity, known as the "twin paradox". Finally, we will take a look at how relativity explains a very familiar effect in electricity and magnetism.
In what follows, the views given here are my own interpretation of the results of special relativity. I have made no attempt at a rigorous treatment, such as you might find in a textbook about the subject, and I have kept the maths to a minimum.
Frames of Reference and Postulates of Relativity