Absolutely all material bodies, both located directly on the Earth and existing in the Universe, are constantly attracted to each other. The fact that this interaction can not always be seen or felt only means that this attraction is relatively weak in these specific cases.
The interaction between material bodies, which consists in their constant striving for each other, according to basic physical terms, is called gravitational, while the phenomenon of attraction itself is called gravity.
The phenomenon of gravity is possible because there is a gravitational field around absolutely any material body (including around a person). This field is a special kind of matter, from the action of which nothing can be protected, and with the help of which one body acts on another, causing acceleration towards the center of the source of this field. It was the gravitational field that served as the basis for the law of universal gravitation formulated in 1682 by the English naturalist and philosopher I. Newton.
The basic concept of this law is the force of gravity, which, as mentioned above, is nothingotherwise, as a result of the impact of the gravitational field on a particular material body. The law of universal gravitation is that the force with which the mutual attraction of bodies occurs both on Earth and in outer space directly depends on the product of the mass of these bodies and is inversely related to the distance separating these objects.
Thus, the force of gravity, the definition of which was given by Newton himself, depends only on two main factors - the mass of the interacting bodies and the distance between them.
Confirmation that this phenomenon depends on the mass of matter can be found by studying the interaction of the Earth with the bodies surrounding it. Soon after Newton, another famous scientist, Galileo, convincingly showed that in free fall, our planet sets absolutely the same acceleration to all bodies. This is possible only if the gravitational force of the body to the Earth directly depends on the mass of this body. Indeed, in this case, with an increase in mass by several times, the force of acting gravity will increase by exactly the same number of times, while the acceleration will remain unchanged.
If we continue this thought and consider the interaction of any two bodies on the surface of the "blue planet", then we can conclude that the same force acts on each of them from our "mother Earth". At the same time, relying on the famous law formulated by the same Newton, we can say with confidence that the magnitude of this force will directly depend onmasses of the body, so the force of gravity between these bodies is directly dependent on the product of their masses.
To prove that the force of universal gravitation depends on the size of the gap between the bodies, Newton had to involve the Moon as an "ally". It has long been established that the acceleration with which bodies fall to the Earth is approximately equal to 9.8 m / s ^ 2, but the centripetal acceleration of the Moon with respect to our planet as a result of a series of experiments turned out to be only 0. 0027 m / s ^ 2.
Thus, the force of gravity is the most important physical quantity that explains many processes occurring both on our planet and in the surrounding outer space.
