how come earth is round?
112912
Gravity pulls everything to the center. The larger the object the greater the gravity the more perfect a sphere. Jupiter has a smoother surface than the earth. The earth is smoother than the moon. Asteroids are even smaller and don't always have enough gravity to overcome the structural properties of the mineral it is made of, so smaller asteroids have more unusual shapes and are not always very spherical.
868944
Bodies beyond a certain mass are spherical due to the nature of gravity which pulls them together. But there are many asteroids and comets that are small and irregularly shaped because gravity can not overcom the strength of the material.
605515
It is not exactly round, just looks that way.\n\nSee webpage below for the correct shape.
57491
because of gravity, pulling inward with the same force in all directions, giving them a round shape.\n\nyou look very pretty in your avatar by the way ;)
9937
It's because the world in question is ruled by unicorns and merry elves. In "that" world it's only natural that everything is either square or circle. Here of course we have irregular shapes and other geometrical figures like triangles, trapezoids and such. Must sound very strange to you I believe.\n\nUs earthlings, we have strange ways.
884879
Because the earth is round, and if you made your flat map a oval(circle), the oceans would connect and become one!
1069514
By Newton's law of graitation any mass is attracted by another mass. Since the planets are matter like our Earth, the pull of gravity in all directrion make the planet spherical.\n\nThe spin of the planets about their axes actually make them close to  ellipsoid of revolution and not spherical. Our earth is also  close to ellipsoid of revolution.
384998
Because gravity acts pretty much in a straight line.  As the swirling dust clouds collected into the earth, the particles acted on each other to form clumps, and the clumbs attracted to each other, then you end up with a nucleus of matter imparting a gravity field radially out from the centre.  Things will be colliding with the nucleus from all directions with an equal probability and thus a sphere.
320933
Two reasons:\n\nPrimary = spinning + gravity = natural inclination of the material to slowly reach equilibrium. Anything that is not "round" gets pulled/shifted toward the center of gravity (the center of the Earth). The spinning helps this process over billions of years.\n\nSecondary = weather. Erosion constantly smoothing out "bumps" (mountains).\n\nIf this is the best answer, please vote it the best answer. Thanks!
576059
The earth isn't round. It's a squashed sphere, due to it's rotation.\n\nI wish grass fell from the sky. I have to go find a guy who knows a guy to get my grass.
1003678
I think the world is round. Have you been outside of your room even? If the world was flat, you would be flooded, he he. Why are there mountains if the world is flat? Really you can't even answer my question? Try going to the library and actually do some research. Gotta go. Rock.
524282
There are two possible reasons:\n1. A non-round object has higher surface area than a round object for same volume. This in turn could lead to higher reaction rates in portions that are not round (projections etc), finally leading to the element appearing round.\n2. The surface tension of water and buoyancy keep the element on the surface at the cost of local depression in the surface of water. Surface tension tends to make the depression round, which could make the element appear round.
603151
The Flat Earth Society believes it's flat and the Square Earth Society believes it's square.\nhttp://www.indiana.edu/~ensiweb/lessons/flaterth.html\nhttp://home.netcom.com/~rogermw/square_earth.html
510338
Every body like to kick around, whether on the ground or out of it.You, must have observed it when the match is over.This is true in general life also.\n\nyou see there is another reason also ,earth is round,pizza is round, coin is round. Can I say boobs are round, hips are round------your EYES ARE ROUND ---when you say oooh, your mouth is round ----JUST LIKE FOOTBALL IS.
1115991
The ancient greeks knew the earth was round.  They knew it because they watched ships sail off.  Someone with good eyes could see that the ship was going over the horizon, the bottom of the ship dissappeared first.  Also, they knew that an eclipse of the moon showed the shadow of the earth on the moon.  Erastothenes calculated the diameter of the earth in about 200 bc.  He was accurate to about 3%.
91665
Its more of an elispse, not perfectly round due to the gravitational pull of the oceans by the moon and due to mountains.
457528
It is not just round or oval. It is elliptical. One side is close to the sun and one side is closer to the Oort Cloud, or Kuiper Belt, or maybe the heliosphere, the end of the sun's influence to the galaxy.