2100 words - 8 pages

Albert Einstein's Theory of Special Relativity

The theory of Special Relativity, written by Albert Einstein in 1905, describes the laws of motion at velocities close to and at the speed of light. It was written to make the laws of motion consistent with the laws of electromagnetism. Special relativity makes two postulates: the laws of physics are the same for all non-accelerating observers and the speed of light in a vacuum is constant, regardless of motion. One of the consequences of these postulates is that clocks run slower to an observer in motion, or time slows down. Special relativity also states that objects at high speeds always appear shorter in the direction of motion than they do at rest. However, length measurements transverse to the direction of motion are unaffected. Velocity addition is different for special relativity than for classical mechanics because according to special relativity, nothing can travel faster than the speed of light. Also, in order to retain the conservation of momentum as a general law consistent with Einstein's first postulate, a new definition of momentum must be used at relativistic velocities. The twin paradox is the famous example that uses time dilation and length contraction. Special relativity is not contradictory with classical mechanics because at low speeds, all of the laws of special relativity reduce to the laws of classical mechanics.

In 1905, Albert Einstein wrote his paper on the special theory of relativity (Prosper). This theory has the reputation as being so exotic that few people can understand it. On the contrary, special relativity is simply a system of kinematics and dynamics, based on a set of postulates that is different from those of classical mechanics (Krane). Several of the predictions seem to go against our common sense, but it is actually not more complicated than Newton¡¦s laws. Even though it does go against common sense, the special theory of relativity has been thoroughly tested and found to be correct (Krane).

Before 1905, Newton¡¦s three laws of motion, or classical mechanics, were widely accepted. These three laws included the law of inertia, the law that the force is equal to mass times acceleration, and the law of equal and opposite forces (Tipler). In classical mechanics, if a girl in a car moving at 30 mph throws a ball at 10 mph, a stationary observer will see the ball moving that 40 mph. Maxwell¡¦s laws of electromagnetism were also accepted at that time. Electromagnetism explained electric and magnetic fields and attractive and repulsive forces (Tipler). However, even though both sets of laws were thought to be true, there was a problem with the two laws.

The laws had a contradiction. Newton¡¦s laws of motion predicted that the speed of light depended on the motion of the source and the light source, and so given the right circumstances, light could be observed traveling faster than c, the speed of light. But Maxwell¡¦s laws...

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