Gravity

In physics, gravity , also known as gravitation or a gravitational interaction, is a <a href="/facts/Fundamental_interaction/WrFEJaFl">fundamental interaction</a>, a mutual attraction between all massive particles. <a href="/facts/Gravity_of_Earth/IXe9Bh8k">On Earth</a>, gravity takes a slightly different meaning: the observed force between objects and the Earth. This force is dominated by the combined gravitational interactions of particles but also includes effect of the Earth's rotation. Gravity gives <a href="/facts/Weight/9NMHCsQd">weight</a> to <a href="/facts/Physical_object/WhqjK6xo">physical objects</a> and is essential to understanding the mechanisms responsible for surface water <a href="/facts/Gravity_waves/HHazND81">waves</a> and lunar <a href="/facts/Tide/zNstvWPv">tides</a>. Gravity also has many important biological functions, helping to guide the growth of plants through the process of <a href="/facts/Gravitropism/TpLjv6Dc">gravitropism</a> and influencing the <a href="/facts/Circulatory_system/EGs6Y7sI">circulation</a> of fluids in <a href="/facts/Multicellular_organism/rk8QBF7o">multicellular organisms</a>.
The gravitational attraction between primordial <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a> and clumps of <a href="/facts/Dark_matter/y5HgX55N">dark matter</a> in the early <a href="/facts/Universe/lfoqc5m6">universe</a> caused the hydrogen gas to <a href="/facts/Coalescence_(physics)/GK5uqyN8">coalesce</a>, eventually condensing and fusing to <a href="/facts/Star_formation/SMyfVDY6">form stars</a>. At larger scales this results in galaxies and clusters, so gravity is a primary driver for the large-scale structures in the universe. Gravity has an infinite range, although its effects become weaker as objects get farther away.
Gravity is accurately described by the <a href="/facts/General_relativity/jVsoIg8X">general theory of relativity</a>, proposed by <a href="/facts/Albert_Einstein/CNTet8qu">Albert Einstein</a> in 1915, which describes gravity in terms of the <a href="/facts/Curvature/RFCAEsj8">curvature</a> of <a href="/facts/Spacetime/uRIN1x4b">spacetime</a>, caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a <a href="/facts/Black_hole/1r2lmkcF">black hole</a>, from which nothing—not even light—can escape once past the black hole's <a href="/facts/Event_horizon/KXH2ptnI">event horizon</a>. However, for most applications, gravity is well approximated by <a href="/facts/Newton%2527s_law_of_universal_gravitation/F6qH2XC3">Newton's law of universal gravitation</a>, which describes gravity as a <a href="/facts/Force/LNAUWMwK">force</a> causing any two bodies to be attracted toward each other, with magnitude <a href="/facts/Proportionality_(mathematics)/xDQmfh6t">proportional</a> to the product of their masses and <a href="/facts/Inversely_proportional/xDQmfh6t">inversely proportional</a> to the <a href="/facts/Square_(algebra)/Jzpq0R0z">square</a> of the <a href="/facts/Distance/hbXlaEFk">distance</a> between them.
Scientists are currently working to develop a theory of gravity consistent with <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum mechanics</a>, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a <a href="/facts/Theory_of_everything/rpossh4t">theory of everything</a>) with the other three fundamental interactions of physics. Although experiments are now being conducted to prove (or disprove) whether gravity is quantum, it is not known with certainty.

Gravity open-in-new

Gravity