Editing Angular momentum (section)

== Angular momentum in orbital mechanics ==
{{Main|Specific angular momentum}}

While in classical mechanics the language of angular momentum can be replaced by Newton's laws of motion, it is particularly useful for motion in [[central potential]] such as planetary motion in the solar system. Thus, the orbit of a planet in the solar system is defined by its energy, angular momentum and angles of the orbit major axis relative to a coordinate frame.

In astrodynamics and [[celestial mechanics]], a quantity closely related to angular momentum is defined as<ref>{{cite book
|last = Battin
|first = Richard H.
|title = An Introduction to the Mathematics and Methods of Astrodynamics, Revised Edition
|publisher = American Institute of Aeronautics and Astronautics, Inc.
|isbn = 978-1-56347-342-5
|date=1999
|page=115}}</ref>
<math display="block">\mathbf{h} = \mathbf{r} \times \mathbf{v}, </math>
called ''[[specific angular momentum]]''. Note that <math>\mathbf{L} = m\mathbf{h}.</math> [[Mass]] is often unimportant in orbital mechanics calculations, because motion of a body is determined by [[gravity]]. The primary body of the system is often so much larger than any bodies in motion about it that the gravitational effect of the smaller bodies on it can be neglected; it maintains, in effect, constant velocity. The motion of all bodies is affected by its gravity in the same way, regardless of mass, and therefore all move approximately the same way under the same conditions.