Absolutely all material bodies, both located directly on Earth and existing in the Universe, are constantly attracted to each other. The fact that this interaction is far from always possible to see or feel, says only that this attraction in these specific cases is relatively weak.
The interaction between material bodies, which consists in their constant desire for each other, according to the 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 to 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 main concept of this law is the force of gravity, which, as mentioned above, is nothing but the result of the influence 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 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 around it. Soon after Newton, another famous scientist - Galileo - convincingly showed that with a free fall, our planet gives all bodies exactly the same acceleration. This is possible only if the gravitational force of the body toward the Earth directly depends on the mass of this body. Indeed, in this case, with an increase in mass by a factor of several, the force of effective gravitation will increase by the same amount, 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”, we can conclude that the same force acts on each of them from the side of our “Mother Earth”. Moreover, relying on the famous law formulated by the same Newton, we can confidently say that the magnitude of this force will directly depend on the mass of the body, therefore the gravitational force 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 attract the moon as an “ally”. It has long been established that the acceleration with which bodies fall to Earth is approximately equal to 9.8 m / s ^ 2, but the centripetal acceleration of the Moon relative 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 taking place both on our planet and in the surrounding space.