Why do the earth and stars and other planets spherical approximately?

Answer 1

Planets (...and also stars) form within immense drifting clouds of gas and dust. Every bit of gas and dust generates a tiny gravitational force. In relatively dense regions of the drifting cloud (...called a 'nebula') two or more bits of gas or dust may be close enough so that they're attracted to each other by their gravity. They clump together, which increases their overall gravity. This larger clump is surrounded by more bits and pieces which are drawn in from all directions. The original clump grows in size and produces more gravity, which in turn pulls in even more material from all directions. The result is a growing sphere.

Answer 2

Gravity pulling everything toward their centers. And centrifugal force pulling everything away from the center. The two balance out and the result is a sphere. (actually, only an approximation of a sphere, as there are a few other forces like magnetism, and variances in the hardness and viscosity of the composite materials of a stellar or planetary body).

Answer 3

Because gravity can't pull spherical blobs together any more compactly. You try it. Mathematically speaking, it's the solid shape of minimum gravitational potential. It's similiar to why free water droplets (not falling through air) are also spherical as well, as they are shapes of minimum surface tension.

This has got nothing to do with spinning or orbiting or anything like that.

Answer 4

it's just like the water when its on the air.
the gravitational full are equal toward the center of the gravity of an object.