soap bubbles, gum bubbles, snot bubbles, champagne bubbles a stable form in a rotating universe all gods are round
None of which are stable , long enough . Interesting ; why a rotating Universe ? And from what direction ? North , South or West , East ? Realitive to Earth . Which direction takes priority ? Why would the Universe rotate ?
Bingo, some galaxies of course are spiral flattened disks....and we have no evidence that the universe spins.
How long is "enough"? Round bubbles last longer than square, triangular or star-shaped - in fact, of all bubbles, the spherical are the only ones that last long enough to be seen and recorded. Why not? Everything in a galaxy does. from the Big Bang outward in all directions: an infinite number of radii Has no-one told you? Earth isn't the center of the universe anymore, and God doesn't live on Mt Ararat.
Quasars, not spheres Galaxies, not spheres Stars, not spheres Planets, not spheres. It seems like if you want answers, just ask river, the correct answer is the opposite of rivers reply.
Many massive objects in the universe tend toward spheres - planets and stars being the most obvious. There's good reason for this. Gravity. While gravity is a tiny, tiny force, it is infinite in extent - and entirely cumulative. Every single atom in every massive compact object is all pulling together. The gross forces tend to cancel, leaving a net force pointing toward the centre of the mass. The one shape that best facilitates this is a sphere. Start with any non-spherical shape. Imagine Earth, smooth as a cueball, with only Mt. Everest sticking up. The pull of every single atom in the entire Earth wants to bring Mt. Everest down to the surface. Imagine Earth, smooth as a cueball, with only the Marianas Trench cut into it. The pull of (nearly) every single atom in the entire Earth wants atoms near the edge fall down into the crevasse. No matter how you cut it, this is effect dominates all others. And it results in every atom trying equally to get to the centre. This effect discourages the formation and life-expectancy of hills, valleys, or even vertices on a cube, etc. That is, excluding rotational momentum. Add in rotation, and it will partially offset the gravitational forces, resulting in an oblate spheroid. Pretty much all compact objects in the universe are dominated by these two forces.
Is a balloon spherical(ish) due to gravity or contained pressure? The topic of this thread is more about "Why do three dimensional spheres exist" which as a question on its own is unrelated to stars, planets, etc. Even without containment like in a balloon. If matter came from a source without wind etc(external forces of any kind). It would expand in areas of least resistance to get some "elbow room". Would that shape take on a spherical structure? or be more random? There is too many variables to calculate successfully and especially the energy (including gravity) contained in the matter itself.
A balloon is roughly spherical. Another balloon looks like a fat surgical glove. Another balloon is shaped like a pig's curly tail. Balloons are manufactured containers; like water bottles or cardboard boxes, they can come in all kinds of shapes; the blown air inside fills whatever space is available. Why does any shape exist? Because it's deliberately designed and contrived for a purpose, or because it's the easiest - that is, least energy-consuming to maintain; most restful, most stable - configuration for the molecules in a substance. Calcium carbonate and cholesterol, for example, never form into a spherical chrystal.
Presumably you know the answer to that. The opening post and followup post #3 referenced only natural celestial objects. Until the OP expands that to terrestrial/artificial, I'm good with addressing celestial objects.
Well, there are too many variables to calculate the simplistic answer that some people seem to be looking for.
Why would matter expand and take up more space? A small asteroid doesn't. A rock in my garden doesn't. You have to specify your starting conditions if you're going to make such a statement. The OP refers to stars and planets, so, implicitly there is an assumption that the starting state is "whatever was there before those stars and planets became spheroid". And what was there was a large, diffuse cloud of dust and gas. This condensed under gravity.
from a great enough distance, everything looks flat, even the earth. From a small enough distance, every surface feels flat, even the earth.
Hmm to me these spheres exit because the sphere the most efficient form of energy . The energy flows around it . And in it . The energy is in fluid form . In any other shape would produce collisions . Reducing energy .