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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.
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.
Michael Foale can be seen exercising in the foreground. Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g (named after the g-force) [1] or, incorrectly, zero gravity.
The graviton's Compton wavelength is at least 1.6 × 10 16 m, or about 1.6 light-years, corresponding to a graviton mass of no more than 7.7 × 10 −23 eV/c 2. [18] This relation between wavelength and mass-energy is calculated with the Planck–Einstein relation, the same formula that relates electromagnetic wavelength to photon energy.
In an environment without gravity, it was concluded that the response of white blood cells and muscle mass decreased. Additionally, within the first 24 hours spent in a weightless environment, blood volume decreased by 10%. [14] [4] [1] Long weightless periods can cause brain swelling and eyesight problems. [15]
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.
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.
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.