system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: why do things in space orbit other things in horizontal planes? Why is everything in our solar system essentially in a flat plane?
gpt
As a solar system comes together from gas and dust, it forms a disc shape called an *accretion disc*. Anything going too slow will "fall" into the star, anything going too fast will spin away. Gravity causes the diffuse stuff to start forming into a spiral and it's the residual spinning of that disc shape of dust and gas that led to turning orbits. When things form into solid planets, they can later be knocked around or nudged into other angles.