The word "gravity" comes from the Latin "gravitas" and means "heaviness." This is one of the fundamental interactions in the universe between all bodies that have mass. It is she who attracts two material objects with mass to each other. Without gravity, it would be impossible to keep people on the surface of the planet, and the Earth itself could not revolve around the Sun.

What is gravity

Gravity is a special force that attracts two bodies. All material bodies are so powerful. Everything in space is subject to gravitational forces.
At low speeds and under the condition of weak gravity, Newton's theory works. It says that the force of attraction between two points that have mass and are at a certain distance is inversely proportional to the distance squared and is directly proportional to the sum of the masses. The greater the mass of an object, the greater its gravity.


What forces exist in the Universe and what is the place of gravity among them

There are four fundamental interactions in the universe.

Strong. It acts on the scale of the atomic nucleus and smaller, is responsible for the bond between quarks and the attraction between nucleons. Actually, this force compels, atomic nuclei are held as one whole.
Weak. It is responsible for the beta decay of the atomic nucleus.
Electromagnetic. It manifests itself between elementary particles with an electric charge. This interaction exists due to the presence of an electromagnetic field.
Gravitational. It is the weakest and determines the geometry of space-time. The carrier of such interaction is the graviton (until it is experimentally detected).
Actually, gravity is most noticeable on a large scale. She is able to keep not only our planet around the Sun , but also the Sun in the Milky Way . It is also an essential element in the creation of the universe. Gas molecules that exist in space are attracted only by gravity. They also unite into stars.

Researchers of the Universe insist that gravity brought stability to particles after the Big Bang and stopped the collapse of the Universe. This force attracts solar systems and forms galaxies . Galaxies, gravitating, form clusters. Thus, gravity can be considered the main force in the evolution of the cosmos.

What is gravitational field and radiation

This is the distance within which objects in the Universe can interact with each other. And the greater the mass of a cosmic body, the stronger its gravitational field. It is possessed by all material bodies in space that have mass.
Due to the gravitational field, massive objects are formed: black holes, quasars, super-large stars. Any astronomical clusters are formed around them. Our galaxy and solar system are just such clusters.
Interestingly, the law of the expansion of the universe is also based on the laws of gravitational interaction.
The term "gravitational radiation" was first proposed by A. Einstein. According to the theory of relativity, such radiation is generated by the motion of such material objects that have variable acceleration. To date, gravitational radiation has not been directly detected. However, his
can be observed when binary stars approach each other .
Gravitational radiation was confirmed only in 2015.


Other effects of gravity

The theory of relativity assumes that there may be such manifestations of gravity that cannot be observed in terrestrial conditions. Detection of such forces and their verification by experiment are difficult at present.

Among such effects are an increase in inertial reference frames, a gravitomagnetic field. The first effect is observed near massive rotating space objects. In this case, additional accelerations appear. Gravitomagnetic fields appear near rotating objects. In this case, the curvature of space-time is observed.

In 2005-2011. similar phenomena have been studied near the Earth. Research data confirmed the presence of geodesic precession around our planet. These results can be useful in studying the gravitational field of the planet in order to study the features of the motion of objects in the solar system.

What is weightlessness

In a state of weightlessness, the force of interaction of a body with a surface is negligible and can be neglected. It is observed on the surface of a body that has moved a great distance from a massive object. In this case, the gravitational forces will be negligible. However, they will not completely disappear, as the action of gravity extends to the farthest corners of the universe.
It is a mistake to think that weightlessness means a complete absence of gravity. Gravity is everywhere in space. And astronauts are constantly affected by the negligible force of gravity of the Earth, the Sun, the galaxy and other celestial bodies.

Astronauts also experience weightlessness. In a spacecraft, the bodies inside it receive an initial velocity and move with the same acceleration. They do not put mutual pressure on each other. In relation to the cabin of the spacecraft, any body in it remains at rest and seems to hang in space. At the same time, there are no external surface forces that would cause mutual pressure of the particles.

Any body, the dimensions of which relative to the earth's radius can be neglected, and which makes translational motion in the earth's gravitational field, provided that there are no external forces, will be in a weightless state.


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