Gravity gives you incredible scope for imagination.
It could be something innocuous, like science fiction. But at the same time it can be a breeding ground for many obscurantists who take advantage of the fact that there is no single theory.
As strange as it may sound, what we know for sure is that we know almost nothing about her. We know that this is what works between all the bodies in the universe. At low speeds (relative to the speed of light), as well as with weak interactions, gravity is described by Newton's theory of universal gravitation. In other cases, it can be described by the General Theory of Relativity (GTR). But the quantum theory of gravity, which could combine the two theories - quantum mechanics and the General theory of relativity - has not yet been developed, and this does not allow to create the so-called "Theory of everything".
And what else we know is that gravity exists. Because without it, there would be no galaxies, no stars, no planets, no you and me, since it is she who plays a key role in maintaining the balance between bodies in the universe.
How can you study gravity?
General relativity says that gravity is scattered in space as waves with a speed equal to the speed of light. These waves are almost impossible. Nowadays, devices have a sensitivity that is enough only to detect waves from extremely large-scale events, for example, the collision of two black holes.
For the first time, such waves were recorded on September 14, 2015. And last year, for the first time, both gravitational waves and light from the same event were detected - the merger of neutron stars. Now researchers are using this data to confirm some basic facts about the universe. Now these data are used by researchers to confirm basic facts about our universe.
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These events allowed scientists to draw several conclusions about gravity:
1. No evidence of the existence of a "gravitational leak" has been found
Prior to this, it was believed that gravity can leave the four changes (the X, Y, Z axes and time). If gravity could do this, then it would lose more energy than the light that travels through space from an event. However, analysis of the waves from the collision of neutron stars showed that this is not happening.
2. Gravity moves exactly as General Relativity says. If the graviton (the particle that carries the gravitational interaction) had mass, like any other particle, then the waves would show signs of momentum, which would violate the theory of relativity. Fortunately, this does not happen, and the graviton remains without mass, and general relativity has once again been confirmed.