Why isn't the Earth perfectly round?

In fact, most planets and moons are not perfectly round, but are often distorted in one way or another.

Normally, when a planet rotates, it will be affected by centrifugal force. We can clearly feel how they work if we try to rotate in a chair, or sit on a roller coaster. At this point, you will feel pulled out of your center.

Although the effect is very small, the Earth is slightly flattened and bulged at the equator.

So are the planets and moons. Centrifugal forces often cause them to bulge at the equator, most notably Jupiter and Saturn. If you look at the panorama of these 2 gas giants, you will see that they are slightly shrunk, and the middle part is bulging.

To explain this, scientists say the degree of distortion of each planet depends on their rotation speed. It is easy to prove that Jupiter and Saturn are the fastest rotating planets in the Solar System. Obviously, the faster an object rotates, the greater the centrifugal force acting on that object.

Our Earth is no exception to this trend. If you sit on an artificial satellite or a spacecraft looking down at Earth, you will see that our blue planet is actually a flattened sphere at the North and South poles, with a larger equator radius than the middle radius. the two poles are about 21,385 km.

Dwarf planet Haumea is subjected to such great centrifugal force that it is almost egg-shaped.

During its rotation around its axis, every part of the Earth is subjected to centrifugal inertia forces and tends to be thrown outwards. On the other hand, the centrifugal force is proportional to the distance from that place to the Earth's axis, that is, the farther away from the Earth's crust is from the axis, the greater the centrifugal force. Therefore, the part of the Earth's crust near the equator experiences more centrifugal force than the part at the poles.

Therefore, during the formation of the Earth, due to the different effects of centrifugal force, the "belly" of the Earth swelled, and the two poles flattened. The radius at the equator is larger than the radius at the poles.

Another good example of a centrifugal force acting on an object in the universe is the dwarf planet Haumea. The planet is in the Kuiper Belt, a region of icy objects beyond the orbit of Neptune, and rotates very rapidly (one complete revolution every 4 hours). It was because of such high speed that it flattened to the point that it was almost like a horizontal egg.