section_path: Orbital planes
section_name: Orbital planes
paragraph_text: Orbital planes
  
  The analysis so far has been two dimensional; it turns out that an unperturbed orbit is two-dimensional in a plane fixed in space, and thus the extension to three dimensions requires simply rotating the two-dimensional plane into the required angle relative to the poles of the planetary body involved.
  
  The rotation to do this in three dimensions requires three numbers to uniquely determine; traditionally these are expressed as three angles.