Movement

Movement began to be studied in Ancient Greece around the 5th century BC. Dynamics, a science that studies the motion of real (massive) bodies under the action of forces, is already considered in the writings of Aristotle, the great scholar of antiquity (384-322 BC).

The mechanical movement of Aristotle is a change of place. For modern people, the direction of the movement is significant. The ancient Greeks were only interested in the initial and final points of the movement. This caused a certain confusion. For example, how to be with the movement in a circle? After all, it is impossible to clearly name the starting and ending points, without knowing the direction of the movement. Therefore Aristotle defined the circular motion as a movement "from something to the same thing" and emphasized that the circular motion is unlimited.

The movement was divided into two types: natural and violent. The natural movement occurred by itself without the intervention of outside power. Forced, however, required some "engine". Such an engine should be either located in the moving body itself, or be in direct contact with it.

The natural movement, in their opinion, was the desire of the body to take its "natural" place in the world. For heavy objects, such as stones, metal objects, etc., such a natural place was the earth. For light bodies (for example, fire), the natural place was the sky. Therefore, the stone itself fell to the ground, down, and the fire aspired to heaven, up. And to change this movement - in other words, to lift a stone upward or to bring down the flame downwards, it was necessary to exert force. This natural desire of bodies to take their places was called rope. In the lower sublunary world, where everything had a beginning and an end, the natural movement must be rectilinear in order to also have a beginning and an end. In the upper, supra-lunar, world, where everything was eternal and unchanging, the natural movement must also be eternal and unchanged-and, consequently, circular and uniform. Such was the movement of the stars.

As we see, the concept of rope - a natural movement - corresponds to our concept of inertia. The modern concept of inertia is connected with rest or relative rest of a body - uniform rectilinear movement.

In the ancient Greeks, the natural movement began to manifest itself when the moving body encountered an obstacle. If at that time any point of the body was stationary, the inertia of the remaining points forced them to continue their movement, that is, to rotate around the fixed point.

As for the violent movement, then, as we have already said, force is necessary for its emergence. This force was called Aristotle dynamis and is defined in the following cunning way: "If some force moves the body some distance, then this force moves the body half as much or twice as much, or at the same distance, but for half as little time".

Let's not forget that in ancient times such constructions were made, including Egyptian pyramids and other "miracles of light", which even today's technology is hardly under force. But theory was still not enough. The main unresolved problems were, by and large, two: how do the bodies behave, when forces act on them, and how do they behave when the forces do not act on them? And it took about 2 thousand years to bring at least some clarity in these issues.