The concept of “gravitational field” did not appear in physics immediately. At first, this type of interaction was considered under the law of universal gravitation. The modern term appeared much later. This concept has existed for several centuries.
Gravity refers to the property of bodies mutually attracted, and the property itself is associated with the mass of these bodies. Today in physics, gravity is considered as a curvature of time-space near massive bodies.
Bodies create force fields around themselves. The tension of such a gravitational field at any point characterizes the force that acts on another body located at this particular point. In this case, the gravitational field strength g is equal to the ratio of the force F acting on the body of a certain mass m to the body mass in the gravitational field.
The field strength coincides in direction, magnitude and units of measurement with the known acceleration of gravity, but in terms of physical meaning these are different values. Field strength characterizes the state of space at a certain point, and acceleration and force appear only when the body is at this point.
Newton in 1687 established that two bodies are attracted with a force directly proportional to the square of the distance at which they are from each other. Such a conclusion was made by him on the basis of the experience of the laws of planetary motion.
The gravitational field is one of the types of the physical field with which the attraction of bodies is carried out (gravitational interaction). This may be the interaction between the planets of the solar system, the planets and their satellites, the Earth and the bodies located near it.
The gravitational field of the Earth is a force field, which is due to the attraction of its mass and centrifugal force arising as a result of the rotation of the Earth. It depends (albeit to a small extent) on the attraction of the moon, the sun and other bodies, as well as the mass of the earth's atmosphere.
The gravitational field of our planet is characterized by gravity, potential and a number of different derivatives. Part of the potential is called geopotential (it is caused only by the gravity of the Earth). In order to solve various problems, it is represented as an expansion in functions (spherical).
The gravitational field of the Earth consists of two parts, which are called normal and abnormal. The first is basic, it corresponds to a schematized model of the planet, depicted as an ellipsoid of revolution. It is consistent with a real planet. The anomalous part is smaller in size and is measured in a very complex way. Once the position of the Moon and the Sun with respect to the Earth is constantly changing, then a variation of its gravitational field periodically occurs. This contributes to tidal deformations of the Earth, and also causes sea tides.
In addition, there are non-tidal changes in the Earth’s gravitational field that occur due to redistribution of masses in the bowels, earthquakes, tectonic movements, movement of water and atmospheric masses, volcanic eruptions, changes in the Earth’s instantaneous rotation axis per day, as well as its angular velocity. Many values of such changes are impossible to observe, therefore, they are estimated only theoretically.
The gravitational field of the Earth is the basis for determining the geoid, which characterizes the gravimetric figure of the Earth. This figure sets the heights of the planet's surface. The gravitational field makes a conclusion about the hydrostatic equilibrium state of the planet and the stresses arising because of this in its bowels, they study the elastic properties of the Earth.
The gravitational field of the Earth helps to calculate the orbits of artificial satellites, the trajectory of rockets. Anomalies of the field help to recognize the distribution of heterogeneities by density in the earth's crust, the upper part of the mantle, conduct tectonic zoning, and search for minerals.