Weightlessness means a state in which the forces of gravity (see physical, gravitational field) do not affect the interaction of body parts, and also do not create pressure on each other.
It should be emphasized that the effect of the gravitational field of any body, for example, the Earth, extends over any distance. Initially, it decreases in accordance with the law of universal gravitation, but it does not reach zero anywhere. When the effect of gravity cannot be compensated by a force called in classical physics the “support reaction”, a state of weightlessness occurs. The simplest illustration of this condition is the situation that occurs when an elevator falls. Just like the elevator itself, its passengers are in free fall. Therefore, they do not create a load on the elevator floor and can freely hover in it until they reach the bottom of the elevator shaft. There is a complete analogy with a falling elevator, when a spacecraft that was launched into orbit around the Earth is constantly in a state of falling onto it. But, when falling to the Earth, the spacecraft does not always reach its surface and, making a complete revolution around it, moves in an orbit around it.
It is impossible to achieve a state of absolute weightlessness, since the spacecraft is always under the influence of external or internal forces that are not gravitational. Their occurrence may be caused by the functioning of various systems and units of the spacecraft itself, the movement of astronauts and interaction with the atmosphere. You can also imagine that the falling elevator slightly touches the walls of the shaft.
The spacecraft reacts to factors such as vibrations, vibrations, etc., which cause small accelerations. These micro-accelerations account for millionths of the accelerations of free fall on Earth. Despite this, even such small fluctuations can distort the results of some scientific experiments that are carried out on board the device. In particular, these deviations must be taken into account when creating crystals in zero gravity.
Weightlessness
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