1. Gravity: Gravity pulls all matter towards the center of the Earth, causing it to become spherical. This is the dominant force shaping the Earth.
2. Rotation: The Earth's rotation creates a centrifugal force that pushes matter away from the axis of rotation. This force is weaker than gravity, but it causes the Earth to bulge slightly at the equator and flatten at the poles.
3. Internal Pressure: The Earth's interior is very hot and under immense pressure from the weight of the overlying layers. This pressure contributes to the Earth's overall shape, particularly in the mantle and core.
It's important to note that the Earth is not a perfect sphere. It is an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator. This shape is due to the combined effects of gravity and rotation.