In the last part we saw how a point in space, for example, a point in space enclosed by walls in your bed room, is referred by different people with different spatial coordinates.
That is, the coordinates to refer to a point used by someone whose reference frame is the three directions (dimensions) defined by the two corner lines where floor and the two walls meet and the third one where the two adjacent walls meet, is different from someone else who uses the Longitude and Latitudes to refer to the same point..
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Relativity
While the above refers to the different spatial coordinates or reference frames, we will now look Relativity which talks about how an observer in motion sees things differently from a stationary observer.
Relativity is not an uncommon phenomenon as many would think. Relativity is experienced by all of us in day to day life in fact. For example, imagine, you are traveling in a train and you fall asleep. Suddenly you wake up and see through the window and there is another train moving fast on a parallel track. With the moving train blocking your view through the window, you may probably be uncertain for a second as to whether your train was moving or the other. You may, perhaps, have experienced such a situation on road more often while waiting at a signal.
The important thing to notice in the above example is that at this moment we are restricting ourselves to two observers where one is stationary relative to the other.
We will now take another example: A man is riding on a Train and he is standing on the moving train holding a ball in his palm. Imagine you are sitting on a chair in one of the stations and the train approaches the station at 100KM/hr speed. Assume that the train is covered with transparent glass and so you can see everything inside the train.
Now, as the train approaches the station, you see the man standing inside the train and just when the man in the moving train crosses straight in front of you (your straight vision line), he drops the ball from his hand. Within a second, the ball touches the floor of the train.
Now, let’s see how you would have seen the falling of the ball compared to the man riding on the train.
To find out that you both are asked to draw the graph of how the ball traveled from the man’s hand until it touched the floor of the moving train.
In the next part, soon to be published, we will see how you both would have seen the same event:
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