Eli5: Why is the Earth round?



– basically, why is the structure the way it Is. Moreover, what significance can we attribute to this matter of fact? Thanks!

In: Earth Science

Gravity, the pull of gravity pulls it into the smallest shape with the largest volume (a sphere). The gravitational pull of the Sun means that there is a minor bulge around the equator.

Earth (And planets and stars in general) are round because of gravity. Gravity is a force which pulls matter closer together, and the shape which allows the most matter to be nearest to the most other matter, is a sphere!

If the Earth were some other shape instead, like a flat disc, then the edge of the disc, would be much further away from the bulk of Earth’s mass than it could be. If some of the planet’s mass broke off the edge and sat against the middle instead, then it would all be much closer together.

So the end result, when gravity pushes all matter toward its neighbouring matter, is stuff sticks together in spherical blobs.

The Earth is round because gravity pulls everything towards each other. If any part of the Earth is a lot higher then the other parts then it will get pulled down by all the other parts of the Earth and either falls over or sinks into the soft mantle.


Gravity pulls everything towards the center of mass.

This means all matter “wants” to get as close to that center of mass as possible, so for a giant lump of molten material like early earth, which could flow around, the shape that let the most mass get as close to that center as possible is a sphere, where every point on the edge of the sphere is (roughly) the same distance away from the center.

In a cube for example, the corners of the cube would be further away from the center than the faces of the cube.

All the mass on Earth is attracted toward the center by gravity. The way to get it all as close together as possible is to pack it into a sphere.


All the mass of the earth is pulling on all the other mass of the earth. If the earth wasn’t spinning, the only stable shape where everything doesn’t want to move is a ball, so any random assembly of bits floating in space, not spinning, and under the influence of gravity only, will form a ball.

The earth is spinning, so it bulges a little around the equator, but it’s so close to a ball that we usually can’t tell the difference (your GPS knows though).

There’s no significance to this fact, really, other than “because gravity.”

Because of gravity. Gravity pulls everything towards the center of the earth. A ball is the most compact shape. Though that’s not quite true. Earth also spins, and things that spin tend to get more of a pizza shape (that’s why you can make pizzas by spinning the dough). Since earth is very heavy but doesn’t spin fast, it’s still mostly a ball, but not quite.

Gravity. Everything pulled toward everything else (disclaimer, gravity isn’t exactly a force but it does very good impressions of one).

A sphere is the shape that will result from a large mass as it moves towards a state of equilibrium. Same goes for stars, planets and moons.


If you have enough matter the internal forces from gravity will deform it to the shape where it can pull it together any more and that is a sphere

If you build a high enough pile of brick the weight of all bricks on top will crush the brick on the bottom.

On a planetary scale, there is no material that can support the weight of what is on top if there is no anything beside it so it can move away, The pressure in the center of the earth is around 3 million times atmospheric and it can crush and deform everything.

As people said before, it’s gravity and also inertia.

Contrary to belief the Earth is not a perfect round sphere, but rather an “Oblate spheroid”.

The earth takes a round shape because of the dense mass at the center which pulled materials towards it in a uniform pull all around.

However, because of the inertia (the resistance of mass to a change in velocity/motion) caused by the earth’s rotation and orbit around the sun, the earth actually starts to bulge from the sides.

The “oblate spheroid” shape is basically a sphere, where the top and bottom are squished in a little causing the sides to bulge out.