Why do planets orbit around the sun in the same plane?
The primordial dust cloud the sun was formed from collapsed in a disk as all the surrounding cloud averaged out velocities into an orbit. When the sun lit, it blew away all the particles what had not been close to the average orbit. Then the dust began collecting together forming chunks, chunks into glumps, glumps into bumps, and many bumps later – planets and such. The velocities all averaged out. However, many objects in the outer solart system are a bit weird. Neptune rotates 90 degreres to orbital plane. Pluto is not quite in the same plane as ‘real’ planets, and there is strong theories that there are many bodies in solar system outside of pluto that aren’t even close to plane.
