Why are the planets round?

My daughter was asking me earlier about who made the world, so i took her through the usual theories. When discussing the Big Bang theory a question arose, why is the earth round?

To be honest, i did'nt have an exact answer, so i thought i'd ask the experts. Why are the planets generally round shaped?

Thanks in advance.

CX.

As I understand it.....

It's due to equalling pressure/gravity, etc.

If you think that each square inch of ground has the same amount of gravity acting on it from the centre of the planet, naturally the earth will try to equalise the forces, this produces a spherical shape.

Think about bubbles, they are spherical due to forces acting to equalise themselves.

Hope that makes sence.

Originally posted by Hyacinth
It's due to equalling pressure/gravity, etc.

What about the Moon, where gravity is almost non-existent; as well as other planets with little gravity. What about the gas giants, why are they round?

What do you have for understanding of that? Huh? Huh?

Well ????

lol

I don't recall much of skool, but did it also not have to do with the debri bombardment immediately following the formation of a new planet? Rotating mass of whatever, being shelled by all of it's debri of creation, kind of like sand paper.

Do I win a prize?

NN

they still some gravity. Even you have gravity!!!! There is also still pressure in the gases of the gas giants.

And like I said that's how I understand it, I maybe wrong.

Originally posted by Hyacinth
I maybe wrong.

Well, the first five reslting pages from Google of "why are planets round", says you are right .......... damn, I wanted the prize !!! heh

Even you have gravity!!!!

I know some people that would debate that with you .......... they all say I am full of hot air !! lmao

NN

Another vote for gravity here. Of course, the surface is not very round at all, but from space, anything with an atmosphere will appear more round than it really is. Hope this link helps:

www.pa.msu.edu...





I love Google.

[edit on 7/2/2006 by Cerebral Souldier]

~~

it has to do with the physics...

ac-crete, verb
~to make larger, increase ~

1. To grow together, fuse
2. To grow or increase gradually, as by addition

~~~~~~~~~

all (non-organic) objects in the universe grow & build up mass,
suns, planets, solar systems, galaxies & everything accrete.

i think only crystals grow...

Originally posted by NoNik

Originally posted by Hyacinth
I maybe wrong.

Well, the first five reslting pages from Google of "why are planets round", says you are right .......... damn, I wanted the prize !!! heh

And all that from memory, god it must be 10 years since I did that at school.

Even you have gravity!!!!

I know some people that would debate that with you .......... they all say I am full of hot air !! lmao

It's the most dynamic yet self-sufficient shape. Think of blowing bubbles.
And yes it is caused by the pressure of gravity in the center, and the vaccum outside.

If it was not round, it would crumble. (or disperse, being a gas composed mass)

All of the components of the planet are pulled towards their mutual center of mass by gravity. Those components will arrange themselves over time so that the surface gravity of the whole is similar at any two points on the planet or object. That can only happen if the distance between the center of gravity and the surface of the planet remains somewhat constant and the easiest way to do that is with a spherical shape.

That said, smaller objects like asteroids do not have the gravitational strength to break down their components into smaller pieces to form a spherical planetoid. That's why many asteroids have odd shapes. A planet like the Earth has enough mass and resulting pressure created by gravity to not only crush, but actually melt the solid objects in its interior and of course, a liquid should easily be able to form a spherical shape.

I think it's gravity too.

Isn't it?


Isn't that the same force that keeps our atomic structure from just flying out into nothingness as well? (really, I don't know and am asking ).


I've always wondered about that(the atomic structure thing. Not trying to hijack your thread, just figured if someone answered that you'd have another interesting tidbit to discuss with your daughter!

X

Uh.

Oops


Nothing to see here, move along.


X

[edit on 2-7-2006 by Xatnys]

Actually, there are three different forces that act on the subatomic level. These are the strong and weak nuclear forces, as well as electromagnetism. They are all much, much stronger than gravity, which is the fourth and final fundamental force.

The strength of gravity is so weak that it can easily be broken simply by lifting your hand into the air. You need a very massive object to have any substantial degree of gravity. The others are what keep atoms and molecules bound together. Unlike gravity, the bonds between even something as tiny as two molecules held together by the other three fundamental forces can be nearly impossible to break. Electromagnetism is probably the 2nd most noticeable in daily life and is the reason why a ship can float on water and why your hand does not pass through the keyboard as you type on it.

[edit on 2-7-2006 by vor78]

Wild, thanks for explaining that!


The statement about the keyboard, certainly makes me ponder all sorts of neat stuff not on topic, so I'll shut up for now.


X