Earths Gravitation

[nhemanth9111]

Hello I have a question.

We all know that the center of earths gravity is ZERO, as we assume earth as 100% spherical, We also know that the earths mass is not uniformly distributed and its not 100% spherical too. Then how can the earths gravity be ZERO at the earth's center still?

[Studiot]

Hello nhemanth, welcome to Physics Forums,

Since the Earth's shape is irregular it does not actually have a geometric centre.

Of course any system of mass in isolation has a centre of gravity, the exact location of this is part of the subject of Geodesy.

Since the Earth's composition is also varied, the resulting variation in gravity is also part of Geodetic work.

However life is never that simple because the Earth does not exist in isolation, it is part of the Earth - Moon system which rotate round a common cente of gravity. This situation is responsible for the tides. In the ultimate, variation in both the Earth's fluid environments (atmosphere and ocean) contribute to (very small) variations in the position of the Earth's own centre of gravity.
There are further weaker interactions with other heavenly bodies.

go well

[markfinn]

Earth's gravitational force is often modeled as though the Earth were an inert sphere of uniform density.
There is a direct relationship between gravitational acceleration and the downwards weight force experienced by objects on Earth.

[AtomicJoe]

Hello I have a question.

We all know that the center of earths gravity is ZERO, as we assume earth as 100% spherical, We also know that the earths mass is not uniformly distributed and its not 100% spherical too. Then how can the earths gravity be ZERO at the earth's center still?

The centre of mass is by definition the centre of the earth.
Everything has a centre of mass as every pair of particles has a centre of mass which can be considered a single particle of the combined mass of the particles. This can be repeated until all the particles are used up.

[Drakkith]

Hello I have a question.

We all know that the center of earths gravity is ZERO, as we assume earth as 100% spherical, We also know that the earths mass is not uniformly distributed and its not 100% spherical too. Then how can the earths gravity be ZERO at the earth's center still?

The net force in any direction near the center of the earth (wherever that might be exactly, due to irregularities) is approximately zero from the force of gravity. The only reason we are pulled to the earths surface by gravity is because almost the entirety of its mass is underneath us. So almost all of the gravity is pulling us DOWN! If you were in the center of the earth you would have near equal amounts of mass on every side of you, so you wouldn't feel a pull in any one direction like you do on the surface.

However, you would feel the pressure of all that mass pulling IN on itself. The matter on the surface is pulling the opposite surface towards it as is all the matter in between. The result of all this is compression.