The phenomenon of tides is the fluctuation of ocean water on Earth caused by the gravitational action of the moon and the sun. The force that attracts the rising tide is called the tidal force.

Anyone who has ever been to the seaside has seen the periodic rise and fall of the sea. At a certain time, the sea rises rapidly and reaches a climax. Sometime later, the rising water receded on its own, leaving a sandy beach and a low tide. And the cycle goes on forever. This movement of the sea is known as the tide. French literature calls it "the breath of the sea."

The tidal phenomenon is characterized by two high tides each day and night instead of one, "a tide rising in the day and a tide rising in the night."

Generally, the place facing the moon has a large tidal force, while the ocean-facing moon has a smaller tidal force, and the centrifugal force becomes larger. Under the action of the centrifugal force, the seawater runs towards the side facing the moon, so there will be a high tide.

During the full moon and new moon, the sun, the Earth and the moon are in the same line. At this time, the gravity of the sun and the moon on the Earth is in two opposite directions or the same direction, so the ocean high tide reaches its peak.

The tidal wave is the first seawater movement phenomenon that attracts people's attention. It is closely related to human beings. Harbor engineering, shipping traffic, military activities, fishing, salt, aquaculture, offshore environmental research, and pollution control, are closely related to the tidal phenomenon. In particular, the endless fluctuation of the sea surface contains enormous energy, and the exploitation and utilization of this energy also arouse people's interest.

Tidal energy is Marine energy in the form of potential energy. Tidal energy refers to the potential energy of water formed by the rise and fall of the sea tide. The tidal phenomenon of the rise and fall of the sea is caused by the motion of the Earth and the celestial bodies and their interaction. In the ocean, the moon's gravity raises the water level of the Earth toward and against the moon.

Due to the rotation of the Earth, this rise in water level is transmitted from east to west in the form of deep-sea waves with periods of 12 hours and 25 minutes and amplitudes of less than 1m. The sun's gravity works in a similar but smaller way, with 12 hours.

Springtides occur when the sun, moon, and Earth are in a straight line. When they are at right angles, they produce neap tides. In addition to variations in semi-diurnal and lunar tides, the rotational motion of the Earth and moon produces many other periodic cycles, which can range from a few days to a few years.

At the same time, the seawater on the surface is affected by the centrifugal force of the earth's motion. The combined force of the moon's gravity and centrifugal force is the tidal force that causes the seawater to rise and fall.

Tides vary from place to place, and there are often different tidal systems in different regions. They all get their energy from deep sea tidal waves, but they have their unique characteristics. Despite the complexity of tides, they can be accurately predicted anywhere.

Ocean tides gain energy from the rotation of the Earth and slow it down as they absorb the energy. But this slowing of the Earth's rotation would be almost imperceptible over a lifetime, and would not be accelerated by the development of tidal energy.

The tides are amazing. The Amazon surges four to five meters high, over 20 kilometers per hour, over 200 kilometers up the river. Minas Bay Tide in Canada's Bay of Fundy is one of the largest tides in the world, reaching a height of 15 meters.