As the humans advanced through times, our technology started to become far more complex and there as a need for a standardized set of units for the whole world to follow. A set of unit that is universal and anyone in the world using those standard would be able to achieve the same results.
In the early of times the unit of length was based on human bodies. For example the Egyptians used cubits as the measurement of length, a cubit is about 52 centimetres or about the size of a human forearms. In the United Kingdoms, the British imperial system standard measurement for anything was set by the ruler of time, for example, a foot would be how far the king would move in one step, or the size of their feet or arm.
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