Relativity Theory as I Understood

Let us assume that today we are going to travel at light speed in space and we will come back after twenty years. We are carrying a clock which shows date and time. When we come back after twenty years of travel, people here will be 20 years more older than us. If we see our clock, it will show the same date and time which was just before we start traveling.

Everybody might have read this kind of stories about Einsteins relativity theory. Even I heard this story when I was studying in high school from my neighbor who was doing MSc in Physics. I don't know how many of us understood this story, but I was not able to understand this story. I wondered many time how this is possible.

If we are traveling in a train which is moving at 100km/hour speed and if there is a one more train traveling in parallel track with same speed then it looks like second train is not moving. If second train is moving at 150 km/hour speed then we feel like it is moving at 50 km/hour speed. If other train is moving in opposite direction then we feel like it is moving at 200 km/hour speed. These are simple example which can be used to tell basic of the relativity theory. Given example can be explained by using newton classical physics also. Then what is the difference between relativity theory and newton theory. According to relativity theory time, mass and length are not absolute.

Let us understand how time is not absolute. Speed makes clock running slower. If we keep clock in the moving train for an x hour, then the clock kept in the train shows less than the x hour. But this difference is very very negligible. If we want to find the difference then train need to travel at a speed which is comparable with light speed.If train travels at a light speed then clock stops. The story narrated at the beginning explains it. The clock shows the same time which was just before we start traveling.

To understand this let us assume special clock which is a metal sheet. Each second single atom is going to decay. Means each second metal emits a electron and number of atom in the metal sheet will come down by one for each second. There are 100 atoms in the sheet. After x time let us count again. Now if we are seeing 50 atoms it means 50 second has elapsed.Let us use this logic for measuring time.

Let us keep the metal sheet in a train which travels at light speed.If we count after any time the count would not have changed. Means clock has stopped or time stopped. If we are traveling in that train then our aging process would have stopped. So after any year we will be as young as before starting the journey.

Now let us understand how this clock or aging has stopped.Let us assume two points s1 and s2 as shown bellow.

s1--------------------------------s2

Metal sheet has been kept in the position s1. There are 100 atoms in the metal sheet. After one second there will be 99 atoms. There will be one electron at position s2 where the distance between s1 and s2 is equal to speed of light.

What would have happened if we had moved the metal sheet at light speed. After one second metal sheet will be in position s2 and electron also will be in position s2. So electron and metal will be together, means the decaying process has not taken place. It is like pausing the running movie.

Now we might argue that why electron should move in the same direction as metal. So now let us assume the case of moving electron in opposite direction. Moving a electron from position x to y can be explained as moving proton from y to x. There 3 points s0,s1,s2 as shown bellow.

s0--------------------------------s1------------------------------s2

There is a proton at position s0. Now metal is moving towards s2 from s1 at light speed. After one second proton will be in position s1 and metal will be in position s2. So proton is not able to catch the metal. So it is not possible to move electron
or decaying process has stopped.


Japanese average life span is more than anybody in the world. I think it might be because they travel in special train called shinkansen which is high speed train. Now Bangalore has got metro. Let us hope to have high speed train so that we live for more year:-). Till then let us go for jogging and slow our biological clock to slower our aging process.


Recently scientist have found the elements which moves speeder than light. Einstein relativity theory assumes that nothing can travel speeder than light. I don't know what new story will come out now.