Question: How did all the planets becume round?

Jason Mc Guire answered on 20 Nov 2019:

Gravity. When planets form, the heavy materials pull in the lighter materials, the gravity pull is inwards towards the heavy material and is equal in all directions. This is why the middle of the earth is full of heavy materials and the crust or land we walk upon is usually fully of lighter materials. Also gas which is even lighter clings onto earth via gravity too! This allows our atmosphere to be breathable for us!