Physics

Theory of Relativity Special Relativity Explained



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This is the first article of a multi-part series into the realm of Einstein's Theory Of Relativity. In 1905, Albert Einstein developed the Special Theory of Relativity and ten years later, elaborated on that theory and published the General Theory of Relativity.

Special Relativity is an eloquent thesis on how objects behave at high velocities near the speed of light, which is labeled "C" in Einstein's famous equation E=mc^2. However, even though the results of relativity are only noticeable at speeds near C (light speed), relativity effects any object moving at a different velocity in relation to another. Anyway, in order to minimize the confusion, I'll explain the very basis of this theory.

Special Theory of Relativity was formulated to explain these two postulates:

"The laws of physics are the same in every inertial frame of reference."

This postulate introduces the idea of reference frames, or RFs for short. RFs are the very core of Einstein's Theory of Relativity. With a solid understanding of RFs, all other details about relativity will fall into place and not seem as complex as people normally think.

Imagine yourself and a friend on the train traveling at a constant 55mph. Since there is nobody else on the train, you and your friend decide to toss the football around. Before you throw the ball, do you stop to acknowledge that the train is already going 55mph so you may have to throw the ball extra hard for it to reach him? No, you just throw it as hard as you would if you were both stationary. Since you both are traveling with the train, the both of you are already going at a constant 55mph and are in the same "inertial frame of reference". You toss the ball to him at 15mph and he catches it with no problems.

Now imagine another friend standing on the side of the train tracks waiting for you to throw the ball to him. As you the speed towards him, you throw the ball at about 15mph. Your friend catches the ball, but the speed of the throw gives him a huge bruise on the side of his rib. This confuses the both of you. How could he get hurt from a 15mph throw? After thinking about it for awhile, you come to a conclusion that the ball was going a bit faster than 15mph. Actually, it was going much faster than 15mph.

Since your friend was not on the train, he was in another "reference frame" than you. Since he was stationary and you were on the train going 55mph, the ball you threw to him was actually going 70mph (55+15). Make sense? To sum things things up, velocities of objects are relative to individual RFs (reference frames).

Of course, we did have to factor out any resistance to the ball, (like air) in this example. The main objective of the example is to explain the concept of RF's.

Now that I've explained RFs, I will go on to the next postulate of Relativity, which is where things get a little more complicated.

"The speed of light is the same in every inertial frame of reference."

This postulate states that regardless of your reference frame, light will always be measured at the same speed. Light travels at 670 million mph in a vacuum (no resistance).

Imagine yourself and a friend in separate spaceships facing each other. Your friend flashes his lights at you and you measure the speed of that light at approximately 670 million mph, which is correct. In order to test this postulate, you decide to race towards your friend at half the speed of light. When he flashes the beam at you, the light should measure 1.5 times the speed of light, right?

Wrong. You measured the speed of the light at the very same velocity as the first test. 670 million mph. How can this be? Did something slow the light down? Something had to change...

When objects get up to velocities at or near the speed of light, the differential effects between RFs become very complex. At these high speeds, the effects of space-time dilation become noticeable.........

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