What makes dialects different?

This problem is very complicated, and the landlord can further refer to relevant research materials. I can only talk about some personal views here:

Generally speaking, the dialect we usually speak is a regional language variety. Due to the comprehensive influence of regional differences, underdeveloped ancient traffic, immigration, war, the shift of political center, national integration and the development law of language itself, the language differences between different places are getting bigger and bigger, resulting in a variety of dialects, even to the point of not understanding each other. However, various dialects of Chinese are variants of Chinese in the general direction. You can't say that there is a big difference in dialects, so it is not a Chinese nation. Chinese characters that record Chinese transcend dialects, and our writing style has been maintained for thousands of years.

Language is driven by social development, but it also has its own laws of development. The language of the Han nationality develops rapidly in some places and slowly in others, which leads to differences in dialects. The landlord said: "immigrants should do as the Romans do, and what the locals say will be passed on in the future." This statement is not entirely correct. Because the change of language is influenced by many factors, as far as the language of immigrants is concerned, it is not necessarily to do as the Romans do and follow the locals. When immigrants move to a new place, one force keeps the original language unchanged, and another force changes its original language to follow the local language. Perhaps these two forces will prevail, or they may find a balance point and have merged. For example, when Europeans immigrated to North America, they did not follow the language of the local North American Indians, but continued to use English. After hundreds of years of use in North America, English will also change. There are some differences between American English and English now. Another example is Hakka dialect, which stubbornly maintains its own characteristics in various places, but it is bound to be influenced by the local language and will be integrated.

The promotion of Putonghua is not to eliminate dialects, which retain many unique elements of archaism and local culture and should not be extinct. More and more urban people speak Mandarin, but in our vast rural areas, they still speak dialects.