system
Given the following post, respond as if you're commenting on Reddit:
human
Why do all the planets revolve around the Sun in the same direction?
gpt
Conservation of angular momentum.  As has been noted by u_pcliv, the planets in our solar system were formed from our sun's accretion disk and since that disk happened to be rotating in a particular direction, so were the planets when they were formed.  Of course you will see exceptions like Venus and Uranus but those are thought to be caused by massive celestial collisions billions of years ago.  Most moons in the solar system orbit in the same direction as their parent planet's spin as well.  The exceptions are often captured objects such as Triton.  It should be noted that objects that have retrograde orbits tend to experience tidal drag which causes their orbits to degrade.