# The forces of the planets

**The forces of the planets** play a huge role in the solar system and in the universe. But what is the force of gravity, that is, gravity? What is its nature? The first step in the study of the properties of the can be considered the discovery by Johann Kepler of the laws of the motion of the planets around the sun. He managed to find that the movement of the planets occurs in ellipses. Kepler also found out the law of the change in the velocity of the planet depending on its position in orbit and discovered a relationship linking the orbital periods of the planets with their distances from the Sun.

However, the laws of Kepler still did not say anything about the nature of the forces that bind the planets and the Sun into a coherent system and do not allow them to dissipate in space. The question of why the planets are moving, and what force controls this movement, arose even then. But it was not immediately possible to get an answer to it. In those days, scientists mistakenly believed that any movement, even uniform and rectilinear, can occur only under the action of force. Therefore, Kepler was looking for a force in the solar system that "pushes" planets and does not allow them to stop. The decision came a little later, when Galileo Galilei discovered the law of inertia, according to which when the forces acting on a body are zero, the acceleration of this body is also zero. Therefore, it became obvious that in the Solar System it is necessary to look for not a force "pushing" the planets, but a force that turns their straightforward motion "by inertia" into a curvilinear one.

The law of action of this force, the force of force, was discovered by the great English physicist Isaac Newton, who managed to establish that all bodies on Earth and in the Universe attract each other with a force proportional to their masses and inversely proportional to the square of the distance between them.

The quantitative side of the force of the planets was obtained in exact mathematical calculations and astronomical observations. Suffice it to recall at least the "theoretical discovery" of Neptune, the eighth planet of the solar system. It was noticed that the planets in their movement around the Sun noticeably deviate from Keplerian orbits. At first glance, this seemed to contradict the law of aggression. However, not every contradiction refutes the theory.

If a single planet were moving around the Sun, its path would coincide exactly with the orbit calculated on the basis of the law of aggression. However, in reality, nine major planets are interacting around our daylight, interacting not only with the Sun, but also with each other. These forces of the planets lead to the very deviations mentioned above. Astronomers call them "disturbances".

The movement of any celestial body is ultimately completely determined by the force acting on it and the speed it possesses. It can be said that the future state of the system of celestial bodies is unambiguously concluded. Therefore, the main task is to, knowing the relative position and velocity of any celestial bodies, to calculate their future movements in space. Mathematically, this task is very complex. The fact is that in any system of moving cosmic bodies there is a constant redistribution of masses, and thanks to this the magnitude and direction of the forces acting on each body change. Therefore, even for the simplest case of the motion of three interacting bodies, there is still no complete mathematical solution. The exact solution of this problem, known in "celestial mechanics" as "three-body problems", can only be obtained in certain cases when it is possible to introduce a certain simplification. A similar case takes place, in particular, when the mass of one of the three bodies is insignificant compared with the masses of the others.

But this is exactly the case when calculating rocket orbits, for example, in the case of flight to the Moon. The mass of the spacecraft is so small in comparison with the masses of the Earth and the Moon that it can be ignored. This circumstance makes possible accurate calculations of rocket orbits.

So, the laws of action of the forces of the planets are well known to us, and we have successfully learned to use them to solve a number of practical problems.