Not a single person will doubt and ask the question why the earth is round. After all, it’s all fun for us to hear stories about how ancient people imagined the structure and shape of the planet on which they live. Flat Earth, elephants, turtle and oceans ... Now, from childhood, everyone knows about the spherical shape of the Earth. But what is surprising: only a few can explain the reason for this. The rest accept the statement that “the earth is round”, for an axiom. Fortunately, such people are becoming fewer every year: natural curiosity and the availability of information do their job.
So why is the earth round? To answer this question, it is necessary to recall what is known about the formation of the solar system. The working hypothesis, which is held by most astrophysicists, is that at first a central star was formed from a rotating dust cloud, the sun, and then the planets. All particles rotating in circular orbits were affected by the force of gravity, collecting them into a single celestial body. However, this does not explain why the earth is round, and not any other shape. The fact is that one of the fundamental laws of the universe is the desire of absolutely all material bodies to spend as little energy as possible. In other words: in the Universe everything strives for peace. The same is true for the spherical shape. The gravity field vectors propagate in all directions from the source (in this case, the center of the planet). Since they are almost equal, the result is the formation of a spherical body, each point of the surface of which is equidistant from the common center. Any change in this distance (for example, the appearance of a mountain) causes a violation of equality and a change in the intensity of the gravitational field vector. After some time, the inequality will still be eliminated, and the balance restored in one way or another (weathering, mechanical destruction). So, one of the main reasons why the earth is round is the effect of gravitational forces. They are all the more pronounced, the more massive the celestial body. In addition, the liquid nature of the earth’s core contributes to the formation of a spherical shape . As you know, the shape of a ball is much easier to give gas and liquid. Near the Earth, under a relatively thin layer of the crust (the surface visible to us), there is a whole ocean of liquid hot magma. During volcanic eruptions, it splashes out and freezes. There is a theory that in the very center of the planet there is also a liquid core. The prerequisites for this assumption were attempts to explain the occurrence of a magnetic field by the generation of high currents in the center of the Earth.
By the way, if you look at the shape of the large celestial bodies of the solar system, it becomes obvious that all the planets are spherical. Sometimes there is a slight violation of the form due to flattening from the poles. It owes its origin to the rotation of the planets around its axis. But the small bodies of the system - asteroids - can have an almost arbitrary shape. The reason is their insufficient massiveness and, as a consequence, small gravitational forces. In addition, the rotation contributing to the formation of the sphere is also either absent or insufficient.
Sometimes on forums you can come across the question of what stars of the solar system exist. Until recently, it was believed that there is only one star in the system - this is the Sun. However, the assumption that our system is dual is increasingly being heard. In addition to the Sun, there is a second star whose existence has so far been proved only indirectly, but the name has already been given - Nemesis. Due to its elongated orbit, the approach to the Earth does not occur more often than once every several thousand years.