system
Given the following post, respond as if you're commenting on Reddit:
human
Do all planetary systems have orbital planes? If so, why?

My question is this: does every planetary system (even other than our solar system) have a single orbital plane? That is, for all other stars with orbiting planets, do the planets have orbits that all line up within a certain plane? For instance, our solar system has at least 8 planets that all essentially line up within a single plane.

My second part of the question: Why? (Even if other planetary systems don't follow this rule, why does ours?)
gpt
It's because of the way the system was formed. Picture a spherically symmetric cloud of dust. Something sets the cloud spinning along an axis. Centrifugal force will push it out at the equator, this process feeds back upon itself and the cloud collapses into a disc. Various inhomogeneities cause the dust to collapse into planets/stars/etc., but they all start from the same spinning disk.

I believe the reason some orbits end up not in the plane is gravitational interaction with other systems.