20 18 what are the ups and downs of Tianjin Hangu Dagang today?

The law of seawater fluctuation is: there are two high tides every day, with an interval of 12 hours. The high tide generally lasts for more than an hour before the low tide begins, and the low tide time is at least between the two high tides.

High tide is a natural phenomenon. There are high tides and low tides in seawater. At high tide, the sea rises, the waves roll and the scenery is spectacular. At low tide, the sea receded quietly, revealing a beach. High tide and low tide are generally twice a day.

The fluctuation of sea water is called tide during the day and sunseeker at night, so it is also called tide. China's ancient book says, "The sea is a tide in the morning and a sunseeker at night". There is a period between high tide and low tide when the water level does not rise or fall, which is called flat tide.

The fluctuation of sea water is called "sunseeker". This phenomenon once puzzled the ancients and I don't know what caused it. Later, careful people found that the tide is delayed for a period of time every day, which is the same as the time when the moon is late every day, so the tide is inevitably related to the moon.

Extended data:

Tides usually come twice a day. In one day, except for the north and south poles and some areas, the tides in all parts of the earth fluctuate twice, each with a period of 12 hours and 25 minutes, twice a day, totaling 24 hours and 50 minutes, so the tide fluctuation time is delayed by 50 minutes every day.

It is precisely because of this fluctuation that when the seawater in one place rises, the stagnant water in other places will be temporarily replenished, thus forming a trend, which is conducive to the exchange of seawater environment. The tide rises, not because there is more water, but because the offshore sea water moves to the land in waves under the gravity of the moon, so that you can see the tide on the land as if the sea water had risen.