The force of gravity makes planets round, which happens the same way in all directions. Thanks to it, the particles collide with each other, forming a single whole. This is how the planets were born, which eventually increased and became more massive, and the shape turned into a spherical one.
Why are planets round?
As scientists write, planets are formed from world dust and particle collisions. Under the influence of gravity, particles are attracted to each other until they form a single ball.
In the process of formation, the ball becomes more massive and heavier and attracts more and more matter to itself. This is where gravity comes into play. And the more parts are attached to the ball, the more the force of gravity increases.
Due to the fact that gravity is the same in all directions, the planet turns into a ball. New parts join the planet and spread out over its surface, making it round.
Can the planet Earth be considered perfectly round?
The earth is an “oblate ellipsoid”. It's not exactly spherical. The planet has a bulge in the middle (at the equator).
This is due to the fact that the Earth rotates around its axis, moving further in the middle than its policy, that is, the planet at the equator moves faster than at the poles. “After reaching a certain age, a new planet always takes on a bulge around its middle. Accordingly, her “polar” and “equatorial” diameters are different», — noted in a scientific article.
Why aren't asteroids round?
Asteroids and satellites are much smaller than planets in size and mass, so the force of gravity is hardly felt here, which leads to a less round shape, explain scientists.
For example, according to the journal Science Focus, comet 67P/Churyumov-Gerasimenko is a trillionth of the weight of the Earth. In shape, it looks more like a “rubber duck”, but not a ball.
Sources: https://www.sciencefocus.com, http://interesno.cc/