system
Given the following post, respond as if you're commenting on Reddit:
human
Are all planets we have observed generally a similar shape as Earth ?

Are planets any other shapes for example triangular or square ? If not why ?
gpt
Gravity forces all planets that are larger than about 300 km in diameter into a spherical shape.

However, many are not perfect spheres, due to the centripetal force of their rotation making the equator bulge slightly (this is more pronounced in gas giants such as Jupiter).