why is the earth round?

Question

there is no reason why it can't be a differnt shape. i'm not saying that it has to be a triangle....but why a ball shape. ya know, and please i don't want some dumb 4 page answer. nothing off the internet that is crap

Answer 1

Maintaining a surface requires energy.
So in nature every object tries to minimize it's surface.

A sphere is the 3d object with the smallest surface to volume ratio. So every object tries to reach a spherical shape.

Since earth was liquid once, it was capable of achieving this form. It then became solid after cooling down and kept this form.

You will see that most objects in space that were formed this way are sphere-shaped.

You can also see this behavior in water drops or more clearly in drops of mercury.

UPDATE:
In retrospect, this answer is probably wrong.
The others are right + some more evidence:
http://www.newton.dep.anl.gov/askasci/gen99/gen99251.htm

Answer 2

the actual shape of the earth is called a geoid. its very similar to an oblate spheroid, and it isnt quite round. along the equator the earth is actually has a diameter thats 43 kilometers larger than the diameter along the poles. The shape was determined by gravity when the earth was forming. a gravitational field extends in all directions, so it pulls debris in from all directions. By doing so it naturally formed into a rough sphere. eventually it hit a point where there was no more debris around to pull in. So really i would say there are plenty of natural, mathematical reasons why it cant be too different of a shape.

Answer 3

Let's assume that the earth was originally a cube and contained only water. The center of gravity of the cube would cause all the water to seek the same level (as in a bath tub). On a global scale that would represent a sphere and all the oceans and seas do in fact form a sphere with land masses above and below the surface. It is believed that the earth originally consisted of only molten rock and metals and these also sought their own level forming a sphere due to gravity.

Answer 4

Whenever energy becomes part of mass, that energy must evidence itself in some manner. Were you to have a cube of ice in the space station, and were you to allow that cube of ice to melt, it would become the shape of a sphere. The heat energy contained within the mass of the water would cause it to assume that shape. It is the same for the planets and our sun. If any planet within our solar system were to have no internal heat energy, then it would have no gravitational field, no matter the size of the mass.

This is further seen in the physics trilogy which is: E = mc2, m = E/c2, and c2 = E/m. The last is that for a gravitational field, or a field of time. It describes what has been stated, that the force of gravity is a particular form of energy relationship between energy (heat) and mass. In that the force of gravity is a particular form of energy may be found in Stephen Hawking's “A Brief History of Time,” page 92, paragraph 3, states; “Like light, gravitational waves carry energy away from the objects that emit them.”

Answer 5

when the earth was liquid (like water), the gravity pulled it together. it has to be a sphere because the gravity pulls on everywhere on the surface at once. think about a cube. the corner of it is farther away from the center than the middle of the side. a circle is the only thing where everywhere is the same distance away from the center. thats about as simple as it gets.

Answer 6

Because its weak.

Gravity indeed pulls in all directions equally and so tend to pull things into spherical shapes, but it has to overcome the strength of the materials themselves to do this.

The core of the Earth is liquid and so flows, and the rocks are too weak to resist gravity. So it ends up spherical.

Smaller bodies do not get pulled into spheres because they are strong enough to resist gravity - so asteroids, some moons and minor planets are not necessarily spheres.