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This article presents some interesting stuff about special relativity, a theory introduced in 1905 by Albert Einstein. In the article "On the Electrodynamics of Moving Bodies", he proposed that the speed of light is the same for every observer.

First, it is important to note that special relativity proposes a maximum speed for moving objects. The maximum speed is not a consequence but a fundamental hypothesis on which the theory is constructed. One can show that, if the maximum speed is a constant of nature (299 792 458 meters per sec = 670 616 629 miles per hour), then the strange laws of special relativity must happen.

For a brief introduction, the article entitled Travel Faster Than the Speed of Light? Are you kidding? by Ray Joseph presents the basics of relativity. Easy reading, yet very accurate. It explains that, as we approach the speed of light, three strange effects can be used to do usually impossible things, such as : travel in the future, shorten objects or desynchronize the present. These effects are illustrated with simple examples. It is very interesting to note that these effects are completely real and have been mostly measured in laboratory experiments. Some of them are also used on a daily basis in satellites for positionning and communication.

For a more complete -but also more difficult- introduction, the video (below) entitled Einstein Theory of Special Relativity in 2 minutes is interesting enough. It presents good illustrations of the effects of relativity. This more academic introduction resumes what is usually found in scholarly textbooks.

Recently, an experiment called OPERA, involving neutrinos, showed evidence for particles (the neutrinos) moving a little faster than the speed of light. If it is confirmed, it will be a very important result for modern physics, because a new theory will have to be produced to explain the effect. Of course, all previous experiments will continue to be verified, but a shift in our understanding of the laws of nature at extreme speeds will be necessary.

The Theory of Relativity
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