system
Given the following post, respond as if you're commenting on Reddit:
human
Why do planets in the solar system rotate around the sun in a single plane of reference?

If you look at pictures of the solar system, you see that their orbits around the sun are drawn in a single plane with respect to the sun. Is that drawn that way for simplicity reasons, or is the orbit of the planets around the sun all in one plane? If they are all in the same plane of reference, why is that so?
gpt
There's a little bit of variation, but they're pretty close to the same plane, within a few degrees.  

The origin of this is that the Sun formed from a collapsing cloud of gas, which had a little bit of rotation.  As the cloud collapsed, it rotated much faster (think of figure skaters drawing their arms in).  Some of it was rotating too fast to collapse into the central point (the Sun), and because the gas molecules collided with one another, that gas took on the form where the gas molecules collide the least, a disk.  The planets formed out of that disk, and preserved its orientation.