# Relativity

Einstein invented Relativity Theory for moving object. The theory says that when A moves away from a box, it can mean:
1. A moves away from the box
2. The box moves away from A
3. Both the box and A move away from B who also moves away from the box in opposite direction of A

So Einstein Relativity’s Theory actually want to say that we need to define a base point to know the movement of an object. For the case above, when we have the box as the base point, we can say opinion no 1. When we see A as the base point, then we will say opinion no 2. And if the base point is the B, then come opinion no 3.

A simple theory, but I want elaborate more about relativity that even exist before this movement relativity invented. It’s about position relativity.

The easy example is by looking at this picture:

These two person don’t move one another. They just sit. So what will you say about their position? The easiest answer will be A sit on the left of B. It’s correct if you see it from the front, but it actually have several facts:
1. A sit on the left of B (the watcher see them from the front)
2. A sit on the right of B (the watcher see them from the back)
3. A sit in front of B (the watcher see them from the right side of the picture)
4. A sit behind B (the watcher see them from the left side of the picture)
5. A sit in front of me and B sit behind me (the watcher stay between them)

This old theory is actually have same point with Einstein’s theory. About base point.  On above case, the base point is the watcher position. In mathematics this base point is called as zero coordinate, and 2 other positions will be compare with this zero coordinate before we can say their position one another.

So in our life, we sometime need to mention about position of a place. When you say that building A is on the left of building B, I will be the first one that argue it. I will ask you where you are when you say about left.
Are you in front of of the buildings or behind them?

The easiest way to make a clear answer is by notate it in NSEW (North South East West) direction. I would better say that building A is on the west of building B. However this argument is not 100% correct since we have a round earth. Yes building A is right on the west of building B. But then after thinking several seconds you may say, building A is far away on the east of building B.

On this round world, linear argument doesn’t work, that’s why in mathematics we will find another coordinate system that is called polar coordinate. Using it mathematicians will say that building A and B are on radius 40000 km from center of earth but building A is on 20 degree before building B.

If you getting dizzy after reading this article, I wouldn’t blame you, because I also got dizzy when thinking about it. But one thing for sure, when we talk about coordinate system we need to know what is the shape of world we live in. Is it a plain world (absolutely not), or a ball (we don’t know); which point is the center, where is the zero coordinate point. I think we  don’t pretty much understand about that. So my suggestion is: Let decide the position with the best way we can do :).

Just before I end my writing, I just want to add a background story why I write about this topic. I remember one of my college show me the world map and he said that cartographer now days want to change the position of world map inversely north to south. So he said that the south pole will be on top of map and the north pole on the bottom. My question is, why we should bother about that. We don’t exactly know which one in this world that is called as top and which one is bottom.

Do really we are stand on the earth, or do we hang on the earth? For me many unsolved question we still have in this world…