Different rotation speeds, different sizes, diverse and even characteristic aspects to identify each one. But the eight planets that make up the Solar System have something in common, each and every one: their round shape..
Mercury, Venus, Earth, and Mars are known as the inner or rocky planets, while Jupiter, Saturn, Uranus, and Neptune are known as the outer or gaseous planets. They do not have the same sphericity, certainly, but neither is square, pyramidal or hexagonal. But why?
According to a report published on the website of natgeoscientists conclude that the planets have a round shape all by the creation of the Solar System itself, combined with the effect of the force of gravity.
Although it is true that 4,600 million years ago the galaxy did not adopt the shape it has today, the equilibrium formed by the enormous cloud of dust and gas was broken by its destabilization and collapse, which caused the matter in suspension queadara congregated in certain areas of the cloud, giving rise to zones of greater density, attracting more matter and creating larger rocky bodies.
The end result: most of the matter and gas was congregated in what is now the Sun, while the smaller clumps would be gravitationally tied to that center and they would line up to orbit around it, giving rise to what is known as a protoplanetary disk..
Why the sphere shape?
It must be taken into account that these rocky clumps really constitute a gravitational center that will try to attract everything possible around it. Therefore, The only distribution that allows all matter to be as close as possible to the center of gravity is the spherical one..
Another thing to note is that although they all seem balls, their spherical shapes really have unique characteristics because they were formed by means of the material accumulation and isostatic adjustment procedure, so the process varied from one to another.
An example of this is that, since the Sun was the point that attracted the most clumps of matter and gas, the inner planets took much longer to form, due to the lack of material, and they acquired a much smaller size.
Finally, it should be mentioned that neither is perfectly round. All the planets rotate on themselves, so that this force of rotation counteracts that of gravity, causing them to flatten slightly and not even deform in the same way because their rotation speed is different.