Gravity fights with quantum theory. It does not fit into the Standard Model. As if it were not enough, nobody detected the particle that is responsible.
So, what is gravity?
The effects of this physical phenomenon are observable. Through this phenomenon, the physical bodies attract each other, with a force whose intensity depends on their masses and the distance between them.
Gravity is one of the four fundamental interactions of known nature.
Gravity is described by the theory of generalized relativity on a macroscopic scale, but it is possible to apply with great precision the law of Newton’s universal attraction in classical mechanics.
The Law of Universal Attraction says that any two bodies act on each other with a force of attraction directly proportional to the masses of the two bodies and inversely proportional to the square of the distance between them.
Which is a mystery, is the nature and reason of the existence of this force.
Although it is observed everywhere, the phenomenon is not elucidated. The value of a body’s weight is directly proportional to its mass and is oriented towards the centre of the Earth.
It is the same force that holds us on Earth, the same force that makes the moon orbit around the Earth or Earth orbit around the Sun. The proportionality coefficient is called gravitational acceleration and is equal to the acceleration of a body that falls freely in the gravitational field of the Earth.
Because of gravity, we exist today. It is the force that led to the emergence of all planets and natural satellites through the mutual attraction of matter particles spinning around a star.
Even within a galaxy, stars and star systems are held together due to gravity, and the evolution of the entire universe is in turn dictated by the gravitational force between the existing matter particles.
Einstein argued that the three dimensions of space and the dimension of time are united in a single space-time structure. The deformation or curvature of the space-time structure, in four-dimensional geometry, creates gravity.
The Earth remains in orbit because it follows the curves of the space structure caused by the presence of the Sun. Einstein called this new image of gravity “general relativity.”
The catastrophe of the Sun’s disappearance produces gravitational waves that move to Earth at the speed of light, and then the trajectory changes.
Einstein’s theory of general relativity (1916) illustrates the macro universe as an elastic fabric that can deform and stretch the stars and planets. These deformations and curves create what we feel is gravity.
The gravitational attraction that holds the Earth in orbit around the Sun is the consequence of our planet following the curves and contours that the Sun creates in the spatial structure.
String theory is the most popular quantum theory of gravity.
According to the string theory, the gravitons responsible for gravity are closed meshes, with no terminations with which they can fix and can pass into other dimensions, weakening the force of gravity relative to the other forces.
In 1984, Michael Green and John Schwarz were convinced that string theory was correct, that strings can describe gravity and other forces, so they can unify different forces.
Theoreticians like Ed Witten considered in 1995 that extra dimensions allow a string to stretch, forming something like a membrane, or a “brain.”
Its energy density is that of a nongravitational field enclosed in a dimensional subspace of space with 9 dimensions of (super) string theory. (Who “live” in a space with 9 spatial and temporal dimensions).
Although the effects of gravity are colossal, at the atomic level, gravitational interactions are much weaker than nuclear or electromagnetic. Gravity is the weakest of the four fundamental forces.
The most popular theory that provides answers to these mysteries is string theory. If this is confirmed or denied, we hope we will see the results of the Large Hadron Collider experiments.
Large Hadron Collider is looking for answers.
The researchers hope to get the particles responsible for gravity artificially called gravitons. If this happens, we could detect their appearance in the three accessible new dimensions. Gravitons, if produced, will not be “in our world” for a few moments, then disappear into the most mysterious dimensions hidden to our senses.
Scientists use the reduced gravity conditions on the International Space Station (370 kilometres tall) to make experiments that are not possible on Earth. Under these “microgravity” conditions, a candle’s flame does not rise vertically but burns slowly and evenly in all directions.
Such experiments allow a better understanding of the combustion process, essential for many applications, both on Earth and in space.
How do satellites stand in orbit?
There are currently about 900 satellites in orbit around the Earth.
But how do I stay there without being propelled by an engine? Satellites do not need propulsion because they are actually in a process of permanent fall.
They are launched into orbit by a rocket that must generate enough power to defeat the gravitational attraction of the planet.
Once in space, the satellite is released on a perpendicular trajectory and begins to “fall” under the exclusive influence of the gravitational attraction of the Earth.
Thus, the trajectory is curved, in the form of an ellipse, which is called orbit. Because the satellites overwhelm the Earth outside the atmosphere, their movement is not overwhelmed by anything and can continue unhindered for many years.