# Why does everything in the Universe form a ball or Sphere?

1. May 9, 2013

### blackstar5000

I want to know why everything in the universe forms a Ball or Sphere? Is gravity the cause of this? If so why? For example, If we were to pick the sphere apart can we see the source of gravity? Is gravity also a ball or sphere and can we grasp and see it? Why do we not ever see square planets or hexagon shaped stars etc...? Sorry, I am new to the forum and I tend to ask strange questions.

2. May 9, 2013

### Mordred

Planets and stars are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it. With its large body and internal heating a planet or star behaves like a fluid, and over long periods of time succumbs to the gravitational pull from its center of gravity. The only way to get all the mass as close to planet's center of gravity as possible is to form a sphere.

With much smaller bodies, such as the 20-kilometer asteroids the gravitational pull is too weak to overcome the asteroid's mechanical strength. As a result, these bodies do not form spheres. Rather they maintain irregular, fragmentary shapes.

3. May 9, 2013

### Chronos

A sphere has the lowest possible surface area required to bound any given volume.

4. May 9, 2013

### h6ss

Therefore, it is the most energy-efficient configuration.

5. May 12, 2013

### Abscissas

Are there more energy efficient shapes? Spheres seem to be the most common of course but the universe is a big place and we have much searching to do, is it possible that we find or someone comes up with a shape more efficient than a sphere? Not saying that it is but for example Leonardo's 72 sided figure? What would be the implications of finding this out sort of like aerodynamics but for energy conservation?

6. May 12, 2013

### Jd0g33

I believe differential calculus will tell us that a sphere is the most efficient shape. The taller the mountain gets, the heavier it gets, which means at some point it won't be able to support itself and crash to the surface

7. May 12, 2013

### Fredrik

Staff Emeritus
Right, any other shape is just going to be a spherical planet with some really weird mountains on it. And if there's any kind of disturbance that knocks a piece off, regardless of whether its weather, tectonic activity, meteor impacts, the result is going to be that pieces roll downhill. Give it enough time, and you get a sphere (that's flattened a bit because of its rotation).