Why is earth round ?

Hundreds of years ago people believed that earth was flat. Well, we can't blame them .
Let's take a walk outside. Do you feel that you are walking on a giant ball that floats around sun ?  Definitely NO !

We know that earth is round (thanks to science),but have you ever wondered why earth is round ?
                       
Two features of Earth that determine its shape are mass and gravity. These features are, in fact, interrelated. Mass attracts other mass, resulting in the force we call gravity. Smaller objects, such as a car or a house, have tiny gravitational force. The amount of mass throughout the Earth, however, is huge and really adds up.
                     
   Scientists theorize that about 4.6 billion years ago, the solar system was a cloud of dust and gas. As gravity pulled the matter in on itself, it began to spin and clump up, forming the sun, planets, moons,and other space objects. Earth's rocky core was the first part of our planet to form, with dense matter sinking to the centre and binding together.Then lighter pieces gathered and formed Earth's crust.
                  
   As Earth's mass added up from all this matter and gravitational forces increased, the matter attempted to take the most efficient shape possible: "a sphere".If Earth was a cube, its corners would be farther away from its centre than other points. Because gravity acts equally on everything, the corners would need to be pulled closer to the centre.
                     
    The result of evening out the uneven places is that you end up with a shape in which every point on the surface is the same distance from the centre. The only shape that fits that definition is the sphere. So, "gravity" is the answer to why Earth is round!
                                
    If you've seen pictures of asteroids that exist in outer space, you may have noticed that some of them are irregular, rocky shapes. That's because they're not big enough to pull themselves into a sphere. If they continue to grow and gain mass, eventually they, too, will form themselves into a sphere. Astronomers have made that ability — the ability to form into a sphere as one of the requirements to be considered a planet!

   Note that earth is not a perfect sphere ! The forces that are formed due to the rotation earth makes equator wider than poles.