Gravity

gravitationgravitationalgravitational forcegravitational pullgravitational physicsgravitational attractiongravitationallyforce of gravitygravitational forceslaw of gravity
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light —are brought toward (or gravitate toward) one another.wikipedia
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Planet

planetsFormer classification of planetsplanemo
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light —are brought toward (or gravitate toward) one another.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.

Star

starsstellarmassive star
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light —are brought toward (or gravitate toward) one another.
A star is an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity.

Galaxy

galaxiesgalacticgalactic nuclei
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light —are brought toward (or gravitate toward) one another.
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.

Mass

inertial massgravitational massweight
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light —are brought toward (or gravitate toward) one another.
An object's mass also determines the strength of its gravitational attraction to other bodies.

Earth

Earth's surfaceterrestrialworld
On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.
The gravitational interaction between Earth and the Moon causes tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation.

Tide

tidalhigh tidelow tide
On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.

Weight

gross weightweighingweigh
On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.
In science and engineering, the weight of an object is related to the force acting on the object, either due to gravity or to a reaction force that holds it in place.

Black hole

black holesblack-holeblack hole physics
Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915) which describes gravity not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon.
A black hole is a region of spacetime exhibiting gravitational acceleration so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it.

Universe

physical worldThe Universeuniverses
The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing, forming stars—and for the stars to group together into galaxies—so gravity is responsible for many of the large-scale structures in the Universe.
Dark matter gradually gathered, forming a foam-like structure of filaments and voids under the influence of gravity.

Fundamental interaction

fundamental forcesfundamental forcefundamental interactions
Gravity is the weakest of the four fundamental interactions of physics, 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.
There are four fundamental interactions known to exist: the gravitational and electromagnetic interactions, which produce significant long-range forces whose effects can be seen directly in everyday life, and the strong and weak interactions, which produce forces at minuscule, subatomic distances and govern nuclear interactions.

Gravitation of the Moon

lunar gravityMoon's gravitygravity
On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.
The gravitational field of the Moon has been measured by tracking the radio signals emitted by orbiting spacecraft.

Orbit

orbitsorbital motionplanetary motion
In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies.
In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet.

List of natural phenomena

natural phenomenanatural phenomenonforces of nature
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light —are brought toward (or gravitate toward) one another.

Force

forcesattractiveelastic force
Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915) which describes gravity not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon.
Only four main interactions are known: in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational.

Quantum gravity

quantum theory of gravityquantum theories of gravityQuantization of gravity
The earliest instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10 −43 seconds after the birth of the Universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner. Attempts to develop a theory of gravity consistent with quantum mechanics, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics, are a current area of research.
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics, and where quantum effects cannot be ignored, such as near compact astrophysical objects where the effects of gravity are strong.

Strong interaction

strong forcestrongstrong interactions
Gravity is the weakest of the four fundamental interactions of physics, 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.
In particle physics, the strong interaction is the mechanism responsible for the strong nuclear force, and is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation.

Gravitational singularity

singularitysingularitiesgravitational singularities
The earliest instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10 −43 seconds after the birth of the Universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner.
A gravitational singularity, spacetime singularity or simply singularity is a location in spacetime where the gravitational field of a celestial body is predicted to become infinite by general relativity in a way that does not depend on the coordinate system.

Weak interaction

weak forceweakweak nuclear force
Gravity is the weakest of the four fundamental interactions of physics, 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.
It is one of the four known force-related fundamental interactions of nature, alongside the strong interaction, electromagnetism, and gravitation.

Electromagnetism

electromagneticelectrodynamicselectromagnetic force
Gravity is the weakest of the four fundamental interactions of physics, 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.
It is one of the four fundamental interactions (commonly called forces) in nature, together with the strong interaction, the weak interaction, and gravitation.

Theory of everything

theories of everythingeverythingattempt to explain all
Attempts to develop a theory of gravity consistent with quantum mechanics, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics, are a current area of research.
GR is a theoretical framework that only focuses on gravity for understanding the universe in regions of both large scale and high mass: stars, galaxies, clusters of galaxies, etc. On the other hand, QFT is a theoretical framework that only focuses on three non-gravitational forces for understanding the universe in regions of both small scale and low mass: sub-atomic particles, atoms, molecules, etc. QFT successfully implemented the Standard Model that describes the three non-gravitational forces -- strong, weak, and electromagnetic force -- as well as all observed elementary particles.

Supergravity

supergravity theorySUGRAmSUGRA
The earliest instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10 −43 seconds after the birth of the Universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner.
They are electromagnetic force (the reason why electricity is produced or medicines give us relief), weak force (which relates to radioactivity), strong force (the force that binds up protons and neutrons within the atom) and gravitational force (the reason why apples fall to the ground and the moon revolves around the Earth).

Big Bang

Big Bang theoryThe Big Bangbig-bang
The earliest instance of gravity in the Universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10 −43 seconds after the birth of the Universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner.
Giant clouds of these primordial elements (mostly hydrogen, with some helium and lithium) later coalesced through gravity, eventually forming early stars and galaxies, the descendants of which are visible today.

Newton's law of universal gravitation

law of universal gravitationuniversal gravitationNewtonian gravity
However, for most applications, gravity is well approximated by Newton's law of universal gravitation, which describes gravity as a force which causes any two bodies to be attracted to each other, with the force proportional to the product of their masses and inversely proportional to the square of the distance between them.
Newton's law of gravitation resembles Coulomb's law of electrical forces, which is used to calculate the magnitude of the electrical force arising between two charged bodies.

Galileo Galilei

GalileoGalileanGalilei
Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries.
Galileo studied speed and velocity, gravity and free fall, the principle of relativity, inertia, projectile motion and also worked in applied science and technology, describing the properties of pendulums and "hydrostatic balances", inventing the thermoscope and various military compasses, and using the telescope for scientific observations of celestial objects.

Star formation

star-forming regionnew starsstar-forming
The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing, forming stars—and for the stars to group together into galaxies—so gravity is responsible for many of the large-scale structures in the Universe.
An interstellar cloud of gas will remain in hydrostatic equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force.