3 years in Hedong and 3 years in Hexi means: The original meaning is that good feng shui was in the east of the river 3 years ago, but in the west of the river 3 years later, and the river refers to the Yellow River. After metaphor, the fate of the world or people is always in constant change, and there is no fixed number of ups and downs.
"Thirty years east of the river, thirty years west of the river" is generally believed to come from folk stories. In ancient times, due to the high riverbed of the Yellow River, the sediment deposition was serious, the river course was not fixed, and it was often flooded. The Yellow River often changes its course. After the course is changed, the original place in the east of the river is likely to change to the west of the river.
when a river flows through a bend, the water quality points move in a curve to produce centrifugal force. Under the influence of centrifugal force, the surface water tends to the concave bank, while the bottom water flows from the concave bank to the convex bank under the pressure, forming a curved circulation. Under the action of curved circulation, the concave bank erodes and the convex bank accumulates. So that the river is getting more and more curved. Due to the long-term scouring effect on the concave bank, "cutting and bending to get straight" will occur, forming an oxbow lake. The west coast of the past has become the east coast of today.
This view of "Feng Shui takes turns" originally bears the color of feudal superstition, but it is also desirable when it is extended to the rise and fall of the world and changes in turn. It looks at life from the perspective of natural laws, rather than unchanging. It can also be used to observe social and historical phenomena. History is progressive, and we must not look at everything with a static eye; Things are dialectical, and you should never look at everything with stubborn eyes.