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In physics, gravity (from Latin gravitas 'weight' [1]) is a fundamental interaction primarily observed as mutual attraction between all things that have mass.Gravity is, by far, the weakest of the four fundamental interactions, approximately 10 38 times weaker than the strong interaction, 10 36 times weaker than the electromagnetic force and 10 29 times weaker than the weak interaction.
Gravity field surrounding Earth from a macroscopic perspective. Newton's law of universal gravitation can be written as a vector equation to account for the direction of the gravitational force as well as its magnitude. In this formula, quantities in bold represent vectors.
At the speed of light it would take roughly three and a half hours to reach this micro-gravity environment (a region of space where the acceleration due to gravity is one-millionth of that experienced on the Earth's surface). To reduce the gravity to one-thousandth of that on Earth's surface, however, one needs only to be at a distance of ...
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics.It deals with environments in which neither gravitational nor quantum effects can be ignored, [1] such as in the vicinity of black holes or similar compact astrophysical objects, as well as in the early stages of the universe moments after the Big Bang.
But in a relativistic theory of gravity, mass cannot be the only source of gravity. Relativity links mass with energy, and energy with momentum. The equivalence between mass and energy, as expressed by the formula E = mc 2, is the most famous consequence of special relativity. In relativity, mass and energy are two different ways of describing ...
Gravitational energy from visible matter accounts for 26–37% of the observed total mass–energy density. [15] Therefore, to fit the concept of a "zero-energy universe" to the observed universe, other negative energy reservoirs besides gravity from baryonic matter are necessary. These reservoirs are frequently assumed to be dark matter. [16]
Under general relativity, gravity is the result of following spatial geometry (change in the normal shape of space) caused by local mass-energy. This theory holds that it is the altered shape of space, deformed by massive objects, that causes gravity, which is actually a property of deformed space rather than being a true force.
The graviton is a hypothetical tensor boson proposed to be the carrier of gravitational force in some quantum theories of gravity, but no such theory has been successfully incorporated into the Standard Model, so the Standard Model neither predicts any such particle nor requires it, and no gravitational quantum particle has been indicated by experiment.