The main reason: the limited knowledge of Chinese people at that time led to backward thinking, short-sightedness and lack of foresight. Gunpowder, for example, was accidentally invented by an alchemist. Through many experiments, it was found that it was composed of saltpeter, sulfur and charcoal. These three substances are combustible drugs, so people in ancient China named them "gunpowder". After the invention of gunpowder, it was only used for acting and celebration (such as firecrackers), and a few were used for military (such as rockets), which shows that its thinking is backward. After the invention of printing, it only replaced the skins and bamboo pieces used to write before, and was invented to write the memorial and letters. The compass was invented only to confirm the direction in the war. Although China had a boat at that time, he didn't think of sailing! ~