[tangoblue (OP)]

Why is it that if you let a bit of liquid go in a zero gravity environment it will form a perfect sphere, no matter if it is water, juice, acid etc.  Whatever liquid it is it will form a perfect sphere.  If you know please tell me because it is really annoying me now.

[Chemistry4me]

Because of it's surface tension. Just imagine if it was a square!

[tangoblue (OP)]

but how come the sphere is perfect and not just a rough square.

[Chemistry4me]

It is the best and only shape that it can...Oh what the heck, I'll let the physicists tell you, I'll just make a fool of myself.

[Bored chemist]

What other shape would it form? Imagine that it "chose" to form a cube; how would it know where to put the corners?

[Vern]

This Wiki article explains the surface attraction force pretty well.

Surface-tension is caused by the attraction between the liquid's molecules by various intermolecular forces. In the bulk of the liquid, each molecule is pulled equally in all directions by neighbouring liquid molecules, resulting in a net force of zero. At the surface of the liquid, the molecules are pulled inwards by other molecules deeper inside the liquid and are not attracted as intensely by the molecules in the neighbouring medium (be it vacuum, air or another liquid). Therefore, all of the molecules at the surface are subject to an inward force of molecular attraction which is balanced only by the liquid's resistance to compression, meaning there is no net inward force. However, there is a driving force to diminish the surface area, and in this respect a liquid surface resembles a stretched elastic membrane. Thus the liquid squeezes itself together until it has the locally lowest surface area possible.

[lightarrow]

What other shape would it form? Imagine that it "chose" to form a cube; how would it know where to put the corners?

This is a kind of explanation I've never thought about, and I like it very much. Symmetries are a very important concept in physics.

[lyner]

A sphere is the lowest energy shape. And other shape would mean that there was some potential energy 'to spare' and, for instance, the corners of a cube would 'fall down' and a sphere would result. Where would the excess energy go? After some sloshing about, it would be dissipated by internal friction.

[Vern]

Because of it's surface tension. Just imagine if it was a square!

This appears to be the exactly correct answer to the question. The surface of the liquid is pulling itself into as tight an area as it can muster. This turns out to be a sphere.

[Ethos]

Why is it that if you let a bit of liquid go in a zero gravity environment it will form a perfect sphere,

Because the droplet will seek a radial equilibrium. That is to say, from the center of the drop to it's circumference, an equal distance will be the simplest form to take requiring the least physical and informational input.

[lyner]

Because of it's surface tension. Just imagine if it was a square!

It would still be a sphere without surface tension and just with gravity holding it together. Imagine a handfull of sand, for instance.

[Chemistry4me]

So you're saying that if I let go of some sand in space, they would form into a sphere too?

[Ethos]

So you're saying that if I let go of some sand in space, they would form into a sphere too?

As long as the sand is not perturbed by other forces, gravity will eventully form the sand into a sphere. Same process that formed the earth is a work here...................Ethos

[Chemistry4me]

Yes, why yes of course, I should have realised earlier. []

[syhprum]

Allthough in theory it is possible for a few kilos of sand in free fall to form into a sphere I think in view of the weakness of the gravitational attraction between the particles it is very unlikely than the perturbing forces will ever be low enough to let this happen

[lightarrow]

Allthough in theory it is possible for a few kilos of sand in free fall to form into a sphere I think in view of the weakness of the gravitational attraction between the particles it is very unlikely than the perturbing forces will ever be low enough to let this happen

I'm not so sure about it because gravity would be applied constantly, while other perturbing forces wouldn't. At the end, the shape would become spherical.

[Bored chemist]

Of course, if the water or the handfull of sand were spinning...

[tangoblue (OP)]

So you're saying that if I let go of some sand in space, they would form into a sphere too?

That would be so cool

[lightarrow]

Right. Even a small initial angular speed would prevent it.

Edit: I was answering to the last post of Bored Chemist.

[lyner]

So - an oblate spheroid? Will that do?