This article is about the natural phenomenon. For other uses, seeGravitation (disambiguation). "Gravity" redirects here. For other uses, seeGravity (disambiguation). "Law of Gravity" and "Laws of Gravity" redirect here. For other uses, seeLaw of Gravity (disambiguation).Sorry, your browser either has JavaScript disabled or does not have any supported player.
You candownload the clipordownload a playerto play the clip in your browser.Hammer and Feather Drop-Apollo 15astronautDavid Scotton the Moon recreating Galileo's famous gravity experiment. (1.38MB,ogg/Theoraformat).
Gravitation, orgravity, is thenatural phenomenonby whichphysical bodiesattract each other with aforceproportionalto theirmasses, andinversely proportionalto thesquareof the distance between them. It is most commonly experienced as the agent that givesweightto objects with mass and causes them to fall to the ground when dropped. The phenomenon of gravitation itself, however, is a byproduct of a more fundamental phenomenon described bygeneral relativity, which suggests that spacetime is curved according to theenergyandmomentumof whatevermatterandradiationare present.
Gravitation is one of the fourfundamental interactionsof nature, along withelectromagnetism, and the nuclearstrong forceandweak force. In modernphysics, the phenomenon of gravitation is most accurately described by thegeneral theory of relativitybyEinstein, in which the phenomenon itself is a consequence of the curvature ofspacetimegoverning the motion of inertial objects. The simplerNewton's law of universal gravitationprovides an accurate approximation for most physical situations including calculations as critical as spacecraft trajectory.
From a cosmological perspective, gravitation causes dispersed matter to coalesce, and coalesced matter to remain intact, thus accounting for the existence ofplanets,stars,galaxiesand most of the macroscopic objects in theuniverse. It is responsible for keeping the Earth and the other planets in theirorbitsaround the Sun; for keeping theMoonin its orbit around the Earth; for the formation oftides; for naturalconvection, by which fluid flow occurs under the influence of adensity gradientand gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth and throughout the universe.
