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 ==Questions about inclination of orbital planes== 
 The article says: 
 ""All planetary orbital planes wobble around the invariable plane, meaning that they rotate around its axis while their inclinations to it vary, both of which are caused by the gravitational perturbation of the other planets."" 

 Q1: Does this mean that in a hypothetical solar system consisting of only one sun and one planet, the orbital plane would necessarily have an inclination of 0 degrees relative to the invariable plane? 

 Observation: There no orbital planes with really ""big"" inclinations (e.g., 70 degrees). In fact, the maximum inclination seems to belong to Mercury, which tops the charts at a whopping 6.34 degrees (pardon the sarcasm). 

 Q2: So why don't the orbital planes vary more than they do? (It seems obvious that SOME force is pulling the planets' orbital planes towards the invariable plane, but I'd like to understand this mechanism a bit more. 

 Q3: Is there a reason that the planets closest to the sun also have orbits with greatest inclination?"