How are tides formed?

For the objects on the ground farthest from the moon, the gravity of the moon is less than the corresponding inertia force, and their resultant force is opposite to the gravity of the earth, which also makes the gravity of the objects obviously smaller. Therefore, the part of the sea farthest from the moon will also have a climax.

Think of the earth and the moon as particles and say that the moon moves in a circle around the earth. In fact, both the moon and the earth move in a circle around their common center of mass, but the circular orbit of the earth is much smaller. Taking the center of the earth as a non-inertial reference object, the gravity of the earth particle by the moon particle is the centripetal force of the earth particle moving around the common center of mass, which is equal to and opposite to the inertial force corresponding to this centripetal force. Therefore, the attraction of the moon particles to the earth particles and this inertia force cancel each other out.

Since the earth is regarded as a particle, the trajectory and dynamics of objects on the earth can be regarded as exactly the same as the earth particle. In this way, the gravity of the moon and the corresponding inertia force cancel each other out.

In fact, the earth is very large. On the ground closest to the moon, the orbital radius of an object moving around the common center of mass of the earth and the moon is obviously smaller than that of a particle on the earth, and the attraction of the moon to the object will be greater than the corresponding inertial force. These two forces can no longer be offset, and their resultant force is opposite to the direction in which the object is attracted by the earth, which makes the gravity of the object obviously smaller.

Extended data:

The change of tides is related to the relative position of the earth, the sun and the moon, as well as the influence of the earth's rotation and the depth of the ocean, the Great Lakes and estuaries. Tide-like phenomena will also appear in the space-time system of other gravitational fields.

The actual sea level changes in shallow seas and harbors are not only influenced by astronomical tidal force, but also strongly influenced by meteorology, such as storm surge. Tides have changed the depth of accumulated water in the ocean and estuaries, forming a rapid tidal current, so it is very important to forecast the tidal current in coastal areas during navigation. Intertidal zone, buried in seawater at high tide and exposed at low tide, is an important marine ecology caused by tides.

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