It turns out that the ocean is so rough, the moon and the sun. The gravity of the earth on the ground is millions of times that of the moon and the sun. So the ocean stays on the earth and will not be attracted by the moon and the sun. However, although the moon and the sun are far away from the ocean, they attract the ocean like huge magnets. It will suck in nearby seawater and cause tides.
For example, the trend in Hangzhou. Due to the special topography of Hangzhou Bay, its external width is narrow, with a sea width of100km, only 3km west of Haining County. The tide has just entered Hangzhou Bay, and the water surface is very wide. The farther west you go, the more bound you are by the terrain on both sides of the river. Water will accumulate, and the tide will accumulate higher and higher, just like a vertical water wall pushing westward. At the same time, influenced by the tidal current, a large amount of sediment from the Yangtze River has been brought into Hangzhou Bay, and the mouth of Qiantang River has become a huge "Shakan"-shaped threshold river. When the sea pushed the river to the mouth of Qiantang River, the sandbars stopped the rising tide and formed one spectacular scene after another.
What is the law of tides? The relative positions of the moon, the sun and the earth have great influence on the tides. For example, when the moon and the sun are aligned with the earth, the tidal force of the moon and the sun on the earth will increase, thus causing abnormal tides. This tide is called tide, once a month in the lunar calendar and once every fifteen minutes. When the moon and the earth are at right angles to the two straight lines of the sun and the earth, the tides are weak and the tidal range is small. Tidal range refers to the height difference between the sea surface at low tide and the sea surface at low tide. The tide is low. This kind of wave is called small wave. Because the moon is closer to the earth than the sun, the moon has a greater influence on the tides. Therefore, there is a saying in the peasant squad: "The fifteenth tide rises and falls, and beaches can be seen everywhere in the first eighty-three tides."