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