Why is the earth round ?

Answer 1

To a first-order approximation the Earth is round. This
is due to gravity. Gravity pulls with equal strength in all
directions; therefore any variations from a spherical
shape will lead to gravitational forces that
bring the shape back into that of a sphere.

This is without considering the rotation of the earth,
however. The rotation of the earth adds centrifugal
effects, which cause the earth to bulge slightly at
its equator and flatten slightly at its poles.
(This is like twirling a rock on the end of a string
and then letting go--the rock flies away from the
twirler.) Because of these centrifugal effects, the
distance from the center of the earth to the surface
of the earth is about 0.33% shorter at the poles
compared to the equator.

Answer 2

To a first-order approximation the Earth is round. This
is due to gravity. Gravity pulls with equal strength in all
directions; therefore any variations from a spherical
shape will lead to gravitational forces that
bring the shape back into that of a sphere.

This is without considering the rotation of the earth,
however. The rotation of the earth adds centrifugal
effects, which cause the earth to bulge slightly at
its equator and flatten slightly at its poles.
(This is like twirling a rock on the end of a string
and then letting go--the rock flies away from the
twirler.) Because of these centrifugal effects, the
distance from the center of the earth to the surface
of the earth is about 0.33% shorter at the poles
compared to the equator.

Answer 3

Seriously though, it's the balance between gravitaional force and the density of the matter. A sphere is the shape which ends up with the lowest energy in terms of the gravitational force. Just visualize it, if it were another shape, some parts of the surface would have a higher force of gravity than others, which would cause it to move. A sphere lets all points on the surface experience the same gravitational force.

BTW, the earth isn't actually a sphere. The rotation creates a 'centrifugal force' which balances with gravity to make it slightly further from pole to pole than through the centre of the earth at the equator.

Answer 4

Because if it were flat we'd fall off the edge.
Think of it this way. Suppose the earth were a cube. Then some points on its surface would be farther away from the center than others. The corners, for example, would be much farther out than the rest.

Since gravity works equally on everything, there would be a tendency to pull those uneven places down. The surface would even itself out.
And the only geometrical object in which every point on the surface is the same distance from the center is a sphere!

And astroids arent big enough for gravity to be a factor therefore they can be all sorts of shapes ...with angles and planes. Thats why they tend to ...just float around in space.

Answer 5

For the same reason that a balloon is round. The earth was formed from a cloud of gas and, as it began to rotate from the uneven pressures, the cloud became more dense and the gravity began to pull in the gas and dust particles until the earth was a semi-solid, round mass which eventually cooled.

Big swirls have little swirls that feed on their velocity
and little swirls have lesser swirls and so on to viscosity.
Bertrand Russel... ABC's of Relativity.

God had nothing to do with it... it was not magic... it was not a miracle... it was just applied physics at work.

Answer 6

Because round is the most efficient shape in the universe. The Earth is really not perfectly round. It is slightly wider at the equator than it is at the poles because of the action of centrifugal force.

Answer 7

When our sun was born the gas clouds around it condensed to form planets including our Earth.The dense gas passes through 3 states viz.,the gaseous state, the molten liquid state and the rigid solid state.When the earth was in the first 2 states it attained a spherical(round) structure due to the cohesive force phenomenon i.e.,force of attraction between the molecules of same element.Later the earth solidified into a rigid planet.

Answer 8

Centrifugal force. The spinning of the earth made it round and keeps it that way.

Answer 9

The earth is shape like an egg. But why? gravity, it has to pull from all places!

Answer 10

It is not round it is spheroidal in shape due to the centrifugal forces caused by rotation.