Raw material extraction
manufacturing
distribution
and retail <span />
==> the object's mass; ==> how close you can get to its center.
The main reason for the wall's construction had always been defense. Since China's first dynasty, the empire faced a near-constant threat of attack from the nomadic tribes to the north. This included those famed Mongols as well as lesser-known groups like the Xiongnu and the Göktürks.
