The Theory Of Special Relativity
“Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.”
Who was Albert Einstein?
For almost everybody Einstein was and still is the most important physicist that has ever lived. He made world-changing discoveries and has the most influence on our thinking about physics today. Albert Einstein was born on March 14th 1879 in Ulm, a city far in the south of Germany. He went to school in Munich. He was a good student, especially in science; but at this time nobody could tell that he was a highly gifted child. However he had problems with the german school system and left the Luitpold-Gymnasium in 1894 without graduating. With 17 years he left Germany to follow his family to Mailand, Italy. Later, in 1896 he went to Swiss and got his matriculation there. The following years he worked for the swiss patent office, but was fully concentrated on his physical studies. In 1905 he discovered the special theory of relativity, the photoelectric effect and the world-known formula E = mc². These articles made him famous all over the world and also got him the Nobel Price in Physics in 1921. In his life he travelled a lot into different cities and ended finally in Princeton, USA until his death. There Einstein tried to unite the theory of relativity and the one of electromagnetism; the theory of everything, which should explain every physical phenomena. But he failed. Nobody until today could find this formula. He died on April 18th 1955 at an age of 76 because of an internal bleeding.
Special Relativity as first postulate
The relativity principle is the first postulate of Special Relativity. It states: “Special principle of relativity: If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the same laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K”. -Albert Einstein: The Foundation of the General Theory of Relativity, Part A, §1
In other words, the postulate is composed of the idea that a state of absolute rest is not existent. Also the laws of physics should apply and be the same in all Inertial Frames of Reference, but not necessarily to non-Inertial Frames of Reference. Therefore the postulate implies that no absolute speed or direction can be determined and only speed and direction relative to a certain body can be calculated.
Theory of Special Relativity: Speed of Light as a constant and Time Dilation
More than 100 years ago, two physicians, Albert Michelson and Edward Morley, were confronted with a never considered phenomenon, when they tried to measure the speed of light. The scientist at that time believed in the existence of an ether who (would) affect the light rays in their motion: depending on the (cardinal) direction they come from, their velocity should be different. But, no matter what direction the physicians headed their instruments, the speed of light never changed. This discovery that light apparently only has one velocity, disagreed with the laws of physics at the time. The method of measuring velocities namely, is based on the fact that the same motion can be perceived at different rates, relative to the position of the spectator. Thus, a resting person passed by a jet sees it going really fast, while a passenger traveling in another plane sees it passing slowly, because of his own motion. This regularity, that velocities are relative and dependent on the movement of the spectator, was also considered being true for the speed of light - The length of a beam of light seen from a resting position should be different from the length of the same beam seen from motion. But if light always has the same velocity, that can’t be true - In fact it was proved undoubtedly in the following years that light only knows one speed. With 299 792 km/s it always spreads...
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