Classification: Education/Science >> Science and Technology

Analysis:

The origin of tides

Tide is a kind of reciprocating and regular seawater movement, which is mainly caused by the gravity of the moon and the sun. Sea water is different from river water. Sometimes the water level drops to a very low level, then rises to a very high level after a few hours, and then drops to a very low level after a few hours. This reciprocating change of seawater occurs twice a day in most areas, and once a day in the south, the Arctic and individual areas. Most coastal areas in China have to go back and forth twice a day. China's ancient book says: "The sea is a tide in the morning and a sunseeker at night." That is, the fluctuation of seawater during the day is called tide, and at night it is called sunseeker. Between high tide and low tide, there is a period when the water level does not rise or fall, which is called flat tide.

Tides are produced by the gravity of the moon, the sun and other celestial bodies. Under the action of gravity, the moon is attractive to the sea water on the earth. People call the force that attracts the high tide of seawater tidal force, and the distance between the earth's surface and the moon is different. Therefore, the tidal force of seawater varies from place to place. Generally, the tidal force is large in the place facing the moon, and the tidal force of the sea water facing away from the moon becomes smaller and the centrifugal force becomes larger. Elephants run with their backs to the moon, so there will be long tides. Because the celestial bodies are in motion, the tidal force exerted by seawater everywhere is constantly changing, which makes the seawater on the earth rise and fall, thus forming a tidal phenomenon.

Tidal characteristics

The tide is very punctual. It is almost as accurate as a clock. The moon revolves around the earth for 24 hours and 48 minutes, and the cycle of tides is also 24 hours and 48 minutes. During the day and at night, most of the sea water faces the moon once and its back faces the moon once, so the sea water naturally fluctuates twice.

At high tide, a huge amount of seawater rushes in, and the seawater has a lot of kinetic energy; During the high tide, the seawater level rises gradually, forming * * *, which converts a lot of kinetic energy into potential energy. At low tide, a large amount of seawater is washed away, and the water level drops one after another, and a large amount of potential energy is converted into kinetic energy. A great deal of kinetic energy and potential energy of seawater in the process of movement is called tidal energy. Scientists believe that the tidal energy in the world is about 65.438+0 billion kilowatts. Most of them are located in narrow and shallow straits, bays and estuaries. The maximum tidal range18m in the Bay of Laudy in the United States and Canada, the tidal energy is 20 million kilowatts, and the Yellow Sea in China is also 55 million kilowatts. China's coastline is very long, with the mainland coastline alone reaching more than 18000 kilometers. There are many small harbors and estuaries along the coast, which are good places for tidal energy utilization. China is rich in tidal energy resources, which provides favorable conditions for the development and utilization of tidal energy.

The influence of tides

Tidal changes directly affect people's lives, such as military affairs, ocean navigation, ocean fishing, mariculture, ocean engineering and various coastal production activities. In order to master the laws of tides, the research on tides has never stopped. There are many large and small ocean stations along the coast of China, which can record the changes of local tides and tidal levels at any time and transmit these information to the National Ocean Information Center in time and accurately. According to this information, experts in marine information make analysis and calculation, and make tidal schedules of China and major ports in the world, so as to know them three years in advance for use by various power generation departments. For example, in the lower reaches of the river, when the tide rises, it is very convenient to irrigate farmland. At high tide, the high salinity seawater in the open sea is pushed to the shore, which is a good opportunity to extract seawater and dry it. At that time, the Yantian sluice gate was opened and the seawater naturally flowed into the Yantian, which not only ensured the quality of seawater, but also saved manpower and material resources. Agronomists suggest planting "halophytes" along the coast, because many "halophytes" can be processed into "natural pickles", so that people can taste traditional pickled pickles and greatly reduce the harm of nitrite; In the coastal areas with gentle terrain and small slope, the tidal fluctuation is slow, the sediment concentration and salt content in large reclamation areas and beaches are moderate, and the seawater cleanliness, geography and climate conditions are very suitable for the growth of "halophytes".

Recently, Russian experts found that the causes of some earthquakes in the Pacific region are related to ocean tides. The spring tide can exert great pressure on the crust in the Pacific region, and cracks will appear in some weak crust. Atomic particles such as neutrons and nuclear rays will be released from cracks, and the normal level of neutron rays will fluctuate accordingly. If this rupture occurs in an earthquake zone, the energy inside the earth in this area will be released violently, so the occurrence of an earthquake is inevitable.

In addition, scientific research shows that wild animals really get angry around the full moon or the full moon. For a long time, it has been thought that the moon will affect the behavior of wild animals during tides and full moons. After a long-term investigation, doctors at the Royal Bradford Hospital in England confirmed that wild animals were really easy to attack humans during this time. They investigated 162 1 people who came to the hospital for emergency treatment between 1997 and 1999, and found that the proportion of people who were bitten by wild animals around the full moon was twice as high as usual. The researchers said in the published British Medical Journal: "There is a link between the behavior of wild animals and the changes in the moon's profit and loss. ..... The nature of wild animals biting people during the full moon becomes more obvious. " "Tides sometimes bring inconvenience to people's lives."