# Gravitational field

The concept of "gravitational field" appeared in physicsnot right away. At first this type of interaction was considered within the framework of the law of World gravitation. The modern term appeared much later. There is this concept for several centuries.

Under gravity is meant the property of bodies is mutuallyAttach, and the property itself is associated with the mass of these bodies. Today in physics, gravity is seen as a curvature of time-space near massive bodies.

Bodies create around themselves force fields. The tension of such a gravitational field at any point characterizes the force that acts on another body located at that particular point. The intensity of the gravitational field g is equal to the ratio of the force F acting on the body of a certain mass m to the mass of the body in the gravitational field.

The field strength coincides in the direction,magnitude and units of measurement with a known acceleration of gravity, but in terms of physical meaning, these are different values. The 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 bodiesattracted with a force directly proportional to the square of the distance on which they are located from each other. Such a conclusion was made by him on the basis of experience of the laws of planetary motion.

The gravitational field is one of the typesThe physical field with which the attraction of bodies (gravitational interaction) is carried out. This can be the interaction between the planets of the solar system, the planets and their satellites, the Earth and bodies that are near it.

The gravitational field of the Earth is a force field,which is due to the attraction of its mass and the centrifugal force arising as a consequence of the rotation of the Earth. It depends (albeit to an insignificant degree) 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 bygravity, potential and a number of different derivatives. Part of the potential is called geopotential (it is due only to the attraction of the Earth). In order to solve various problems, it is represented as an expansion in terms of 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 the schematized model of the planet, which is depicted as an ellipsoid of revolution. It is consistent with the real planet. The anomalous part is smaller in magnitude and is measured in a very complicated manner. Once the position of the Moon and the Sun with respect to the Earth is constantly changing, then periodically there is a variation of its gravitational field. This contributes to tidal deformations of the Earth and, in particular, causes sea tides.

In addition, there are indecent changesEarth's gravitational field, arising from the redistribution of masses in the interior, earthquakes, tectonic movements, the movement of water and atmospheric masses, volcanic eruptions, changes in the instantaneous axis of rotation of the Earth per day, as well as its angular velocity. Many values of such changes can not be observed, therefore they are estimated only theoretically.

The gravitational field of the Earth is the basis forThe definition of a geoid that characterizes the gravimetric figure of the Earth. This figure sets the height of the planet's surface. On the gravitational field, a conclusion is made about the hydrostatic equilibrium state of the planet and the resulting stresses in its interior, investigating the elastic properties of the Earth.

The gravitational field of the Earth helps to producecalculations of the orbits of artificial satellites, trajectories of the movement of missiles. Anomalies of the field help to recognize the distribution of inhomogeneities in density in the earth's crust, the upper part of the mantle, conduct tectonic zoning, and search for minerals.