High Quality Content by WIKIPEDIA articles! For most of the problems in astrodynamics involving two bodies m1 and m2 standard assumptions are usually the following: A1: m1 and m2 are the only objects in the universe and thus influence of other objects is disregarded; A2: the mass of the orbiting body (m2) is far smaller than the central body (m1), (m1 m2); A3: the effects of general relativity are so small that they can be ignored. Even just the combination of A1 and A3 keeps the problem relatively simple. If the other assumptions are not fulfilled, many results still apply with a small modification; see gravitational two-body problem.