Why the planets are round ? Because they are revolving or because they are revolving inside some kind of walls(energy) walls?or because thing move in circular motion when they are inside something else?or some central force?

MAB

Gravity causes the accumulated matter to form a spherical shape because as the planet forms (from the inside out) matter tries to occupy the lowest gravitational energy state, that of resting on the matter below it. Protrusions away from the spherical surface will 'slip' towards the center and thus matter is distributed evenly along the surface of the sphere.

Iirc the matter making up the planets is also trying to assume the lowest gravitational energy state with respect to the sun's gravity well, so they are slightly distorted spheres.

this can be demonstrated by pouring drops of molten lead from a height into a bucket of cold water, it`ll make little spheres (that`s how the old lead shot was made). or hail stones, or chemical prills.

 

granted this exploits cohesive forces as opposed to gravity, but the principal is similar

Also, seeing the spilled drinks in space form spherical bubbles are an example. No rotation required.

 

If I understand correctly, a planet forms in a sphere for the same reason we are stuck on this planet. Gravity pulls us towards the center, so when it was a liquid or semi-liquid, all matter was pulled toward the center somewhat evenly.

thats realy interesting about the lead shots! another little fact for my library!

Gravity would pull the substance together, and continue doing this until the substance was hard as a planet or another, stronger gravity destroys (or at least morphs) the shpere.

simply, spheres are the simplest 3d shapes.

A sphere has the lowest area for its volume of any 3 dimensional shape.

Gravity causes the accumulated matter to form a spherical shape because as the planet forms (from the inside out) matter tries to occupy the lowest gravitational energy state, that of resting on the matter below it. Protrusions away from the spherical surface will 'slip' towards the center and thus matter is distributed evenly along the surface of the sphere.

thas a good way to say it b/c i couldn't explain it... even thought thats technically what i meant