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In [[physics]], an '''orbit''' (or revolution) is the [[Gravity|gravitationally]] curved path of one object around a point or another [[body]], for example the gravitational orbit of a [[planet]] around a [http://www.wikipedia.org/wiki/Star star].

In [[physics]], an '''orbit''' (or revolution) is the [[Gravity|gravitationally]] curved path of one object around a point or another [[body]], for example the gravitational orbit of a [[planet]] around a [https://www.wikipedia.org/wiki/Star star].

[[History|Historically]], the [[apparent]] [[motions]] of the [[planets]] were first understood geometrically (and without regard to [[gravity]]) in terms of [http://en.wikipedia.org/wiki/Epicycles epicycles], which are the sums of numerous [[circular]] motions. [[Theories]] of this kind predicted paths of the planets moderately well, until [http://www.wikipedia.org/wiki/Johannes_Kepler Johannes Kepler] was able to show that the motion of the planets were in [[fact]] (at least approximately) [[elliptical]] motions. In [http://www.wikipedia.org/wiki/Isaac_Newton Isaac Newton]'s ''Principia'' (1687), Newton derived the [[relationships]] now known as [http://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion Kepler's laws of planetary motion] from a [[force]]-based theory of [[universal]] gravitation.[4] Albert [[Einstein]]'s later general theory of [[relativity]] was able to account for [[gravity]] as due to curvature of [[space-time]], with orbits following [http://en.wikipedia.org/wiki/Geodesic geodesics].[http://en.wikipedia.org/wiki/Geodesic]

[[History|Historically]], the [[apparent]] [[motions]] of the [[planets]] were first understood geometrically (and without regard to [[gravity]]) in terms of [https://en.wikipedia.org/wiki/Epicycles epicycles], which are the sums of numerous [[circular]] motions. [[Theories]] of this kind predicted paths of the planets moderately well, until [https://www.wikipedia.org/wiki/Johannes_Kepler Johannes Kepler] was able to show that the motion of the planets were in [[fact]] (at least approximately) [[elliptical]] motions. In [https://www.wikipedia.org/wiki/Isaac_Newton Isaac Newton]'s ''Principia'' (1687), Newton derived the [[relationships]] now known as [https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion Kepler's laws of planetary motion] from a [[force]]-based theory of [[universal]] gravitation.[4] Albert [[Einstein]]'s later general theory of [[relativity]] was able to account for [[gravity]] as due to curvature of [[space-time]], with orbits following [https://en.wikipedia.org/wiki/Geodesic geodesics].[https://en.wikipedia.org/wiki/Geodesic]

[[Category: Physics]]

[[Category: Physics]]