why earth is round?

Question

why not earth is curvy stright or rectangle why it is in round shape?

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.

Mjr

Answer 2

Physically speaking, round is a perfect shape. Think about a bubble. A bubble may start out elongated but air pressure insists that it be confined to the smallest space possible. That would be a sphere. Everything is uniform from the center outward.

Same thing with the earth. The are several things that encourage this shape.

One is gravity, which pulls every particle toward a common center.

Another is atmospheric pressure pushing everything inward from all directions

Another is rotation, centripetal force.

Round is the shape best for traveling through space at high velocity. No sharp corners to get snagged on the universe.

TRY THIS: Take some Playdoh and press it with your hands; equally in all directions. What do you get, a sphere.

Answer 3

Associated with each possible blobby shape of molten rock is an amount of "potential energy".

Nature tries to minimise potential energy - apples fall when you drop them, rubber bands ping back into shape when you let them go. Light bounces off a reflective surface in such a way that it takes a shortest path. And so on.

A SPHERICAL blob of molten rock would have the least potential energy . . . spin it a little as with our Earth, and you get a slightly flattened shape called and oblate spheroid.
(Sounds painful !)

If the Earth had not been molten at some stage, we could be living on an irregular blobby shape - gravity could then be very different at different places on our planet, and life would have been much more exciting !

Answer 4

At one time the earth was a mass of molten material. Molten material spinning in space takes on a round shape. That's how lead shot in made. The melted lead drops down inside a tall tower. By the time it hits the pool of cooling water, it has taken on a perfectly round shape and has solidified enough to hold that shape.

Answer 5

I noticed that the first two posters mentioned some crazy concept known as "centrifugal force" when discussing a rotating reference frame. One should not continue to perpetuate this myth; there is no such thing as centrifugal force!

Please refer to the following site to visualize this:

http://regentsprep.org/Regents/physics/phys06/bcentrif/centrif.htm

Also, that answer ("to a first-order approx...) was copied and pasted from the following site:

http://www.newton.dep.anl.gov/askasci/gen99/gen99251.htm

You can't trust everything you read online: even this site had it wrong.

The true shape of the earth is an oblate ellipsoid. An excellent explanation is provided by the folks at Dynamic Earth:

http://earth.leeds.ac.uk/dynamicearth/internal/shape.htm

Answer 6

When the Earth was still froming the Sun's gravity pressed it into a round shape.

Answer 7

I support Diana's answer, plus spherical is the most natural shape, try releasing water in space gently and it will be shaped the same, unless disturbed off course.

Answer 8

Actually the Earth is oval and tilted so really it is a big oval.