Editing Three-body problem (section)

{{Short description|Physics problem related to laws of motion and gravity}}
{{about|the physics theory}}
[[File:Three-body Problem Animation with COM.gif|thumb|320px|Approximate trajectories of three identical bodies located at the vertices of a scalene triangle and having zero initial velocities. The [[center of mass]], in accordance with the [[law of conservation of momentum]], remains in place.]]
In [[physics]], specifically [[classical mechanics]], the '''three-body problem''' is to take the initial positions and [[velocity|velocities]] (or [[momentum|momenta]]) of three [[point mass]]es orbiting each other in space and then calculate their subsequent trajectories using [[Newton's laws of motion]] and [[Newton's law of universal gravitation]].<ref name="PrincetonCompanion">{{cite encyclopedia
| last  = Barrow-Green
| first = June
| year  = 2008
| title = The Three-Body Problem
| editor-last1  = Gowers
| editor-first1 = Timothy
| editor-last2  = Barrow-Green
| editor-first2 = June
| editor-last3 = Leader
| editor-first3 = Imre
| encyclopedia = The Princeton Companion to Mathematics
| pages  = 726–728
| publisher = Princeton University Press
}}</ref> 

Unlike the [[two-body problem]], the three-body problem has no general [[closed-form expression|closed-form solution]], meaning there is no equation that always solves it.<ref name="PrincetonCompanion"/> When three bodies orbit each other, the resulting [[dynamical system]] is [[chaos theory|chaotic]] for most [[initial condition]]s. Because there are no solvable equations for most three-body systems, the only way to predict the motions of the bodies is to estimate them using [[numerical method]]s. 

The three-body problem is a special case of the [[n-body problem|{{mvar|n}}-body problem]]. Historically, the first specific three-body problem to receive extended study was the one involving the [[Earth]], the [[Moon]], and the [[Sun]].<ref name="first">{{cite web |url=http://www.wolframscience.com/reference/notes/972d |title=Historical Notes: Three-Body Problem |access-date=19 July 2017}}</ref> In an extended modern sense, a three-body problem is any problem in [[classical mechanics]] or [[quantum mechanics]] that models the motion of three particles.