-H.S.Varun
“Put your hand on a hot stove for one minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. That’s relativity. “
Albert Einstein.
INTRODUCTION:
Einstein’s theory of relativity has caught the imagination of the average man more than any other physics theory in history. Yet the theory of relativity unlike many other results of physics is not easily understood by the average man. We can understand the relativity theory fully only by the means of mathematical formulas which make it up. I am here trying to explain the relativity without a lot of mathematics. Without mathematics, we can only state some of its basic ideas and quote, but not prove, some of its conclusions. I have tried my level best to make this article error free and any mistake from my side is regretted. This article is just a basic attempt to explain Einstein’s Relativity in simple language and I am in no way an expert on this subject. Now that the nature of the article is clear, let us fasten the seat belts. It is going to be a bumpy ride folks.
So, what exactly is relativity theory? Yes I have quoted Einstein in the beginning, but that maybe hardly making sense, “Where do a girl and a stove come in physics?” Well relativity theory deals with fundamental ideas of time, space, mass, motion and gravitation, which we use to describe the most fundamental happenings. It gives new meaning to the age old ideas that these words represent. The relativity theory by Einstein is basically made up of two parts:
1. The Special Theory of Relativity (1905),
2. The General Theory of Relativity (1915).
I here will be here mainly be explaining the first one, The Special Theory Of Relativity (STR). This theory is called special since it refers to a special kind of motion, Uniform motion in a straight line (constant velocity).
SPECIAL THEORY of RELATIVITY:
The STR (Special Theory of Relativity) was a major blow to the Newtonian Physics. The STR can be best understood by doing a few experiments in one’s own mind. The important 5 special relativistic effects of The STR are:
1. The relativity of simultaneity.
2. Time dilation.
3. Length contraction as speeds approach lights speed.
4. Increase in mass of a moving body.
5. Relationship between mass and energy.
What The STR says is
§ The speed of light is always a constant,
§ At the speed of light, time comes to standstill,
§ At the speed of light mass is infinite,
§ E=MC2 where E is energy, M is mass, and C is speed of light a constant.
We must here get it clear that The STR doesn’t claim that everything in universe is relative. It just clarifies that what we thought as absolute (Time and Space) are not absolute, and things that we presumed as relative (Speed of Light) are absolute. Now these statements may seem simple, but the implications are profound.
WHAT IS MEANT BY RELATIVITY?:
Size, speed and motion are all relative terms. We can see that a vehicle faster or slower only as compared to another vehicle. Thus a car is slower than an airplane but faster than a scooter. Similarly, motion is also a relative term. You maybe sitting still and reading my article, but you are only still when the reference is made to the room or the building, which we take to be as a constant. But the building is on earth, which rotates around in its axis, revolves around the sun, and is moving with the galaxy. So you are actually moving in 3 different directions when you are reading my article.
RELATIVITY of SIMULTANEITY:
Relativity of Simultaneity is nothing but Relativity of Time.
Einstein gave an example of two bolts of lightning striking near a railway line. Suppose if a person were standing close to the track and midway between the two strikes, he would feel that the two strikes occurred at the same time. But if a person were observing this from a fast moving train, he would see the lightning bolt ahead (towards which the train was moving) as the first one to strike. Now if a train goes in the opposite direction, it would be exactly the opposite of the observer on the first train.
Now, they are all correct. In one frame of reference, the strikes appear at the same time, while in another, the bolts strike at different times.
We can here unmistakably see here that time is a relative happening. You have to keep in mind that The STR is right as long as the speed of light is a constant.
TIME DILATION:
After relativity of time, The STR comes up with the amazing concept of Time Dilation. Einstein said that Relativity permits events to take place more slowly for one observer than for another observer. These events also include events of life like ageing. The Famous Twin Paradox is the result of high speed motion on time. It is of course just theoretical. A young astronaut goes on a space trip to distant stars. His twin brother stays back. Now the astronaut goes to different stars at the speed of light. He finds on return that his brother is an old man, while he is still a young man! The astronaut’s biological clock has ticked of fewer hours as compared to clocks on the earth.
There is also the famous Clock Paradox. A spaceship travels to Arcturus (a star 33 light years away), at the speed of light. So the to and fro trip should take 66 years. But because the spaceship travelled at the speed of light, all time processes on board slows down. The crew hardly feels that the to and fro trip took 66 years. They may feel that only a day has passed. But on return they find everything 66 years older!
Such weird possibilities have generated curiosity and controversy more than any other idea in The STR. An experiment at CERN, where a muon particle travelled almost at the speed of light had its life extended almost 30 times. This proves the twin paradox.
LENGTH CONTRACTION AT HIGH SPEEDS:
The STR also states that if an object moves at the speed of light, it would seem to a fixed observer to shorten in the direction of motion. This simply meant that a 100 cm stick would appear less than 100 cm. Such contraction of length is a relative phenomenon that can be demonstrated by thought experiment.
INCREASED MASS WITH SPEED:
Here is yet another feature of The STR, which you may find hard to digest. While time slows down with speeds nearing the speed of light, the mass of an object increases. Finally at the speed of light mass = infinity! This magical concept has been proved in particle accelerators. But the change in mass is only significant at speeds near the speed of light.
E=MC2:
The STR provides with a mathematical formula which defines the relationship between Energy, Mass and Speed of Light. E=MC2. This famous relationship shows us that an enormous amount of energy is in a small amount of mass. Today the equation is thought as the inspiration behind the atom bomb. But this is the formula that is the energy source of most of the universe.
CONCLUSION:
The STR is now accepted as matter-of-fact statement. It is as basic to present day science as the existence of atoms and quarks.
With this, comes the end of our journey. I have tried my level best to get the best possible accurate information, though there maybe mistakes. Like Einstein said:
“Anyone who has never made a mistake has never tried anything new.”
Here I have just given a basic sketch of The STR. And you have to realize that The STR like all theories is just a creation of a human mind. New theories may eventually show the limitations of The STR and deal with problems that The STR doesn’t cover. But no doubt The STR is one of the greatest theories of all times and has bought much progress in the world of science (and also a few marks for me :D).
REFERENCES AND ACKNOWLEDGEMENTS:
This artcile woudn't have been possible without the gracious help of a few individuals and organisations.
- I would like to thank our Physcis Teacher Mr. Mathew Abraham for the oppurtunity to express my thoughts on The STR at this platform.
- Also My parents for all the guidance and support they gave me.
- Albert Einstein for giving us such a wonderfull theory, without which this artcile would have been impossible.
- And God, without whom nothing is possible.Like Einstein said:
“Science without religion is lame, religion without science is blind. "
Lastly, you the reader for whom I have written this article.I hope you have enjoyed reading my article.
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