Why is the earth round? Gravity

No man will doubt and ask why the earth is round. After all, we are all amused to hear stories about how ancient people represented the structure and form of the planet on which they live. Flat Earth, elephants, tortoise and the world ocean ... Now, since childhood, everyone knows about the spherical shape of the Earth. But what is surprising is that only one can explain the reason for this. The rest accept the statement that "the earth is round," for an axiom. Fortunately, such people every year is becoming less: natural curiosity and the availability of information are doing their job.

So, why is the earth round? To answer this question, it is necessary to remember what is known about the formation of the solar system. The working hypothesis that most astrophysicists adhere to is that at first a central star-the Sun and then the planets-was formed from a rotating gas-dust cloud. All the particles rotating in circular orbits were acted upon by the force of gravity, which collected them into a single heavenly body. However, this does not explain why the earth is round, not any other form. The fact is that one of the fundamental laws of the universe is the desire of absolutely all material bodies to expend as little energy as possible. In other words: everything in the universe tends to rest. The same is true for the spherical shape. The vectors of the intensity of the gravitational field propagate in all directions from the source (in this case - the center of the planet). Since they are practically 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 is restored in one way or another (weathering, mechanical destruction). So, one of the main reasons why the earth is round is the action of gravitational forces. They are all the more pronounced, the heavier the celestial body. In addition, the liquid nature of the earth's core contributes to the formation of a spherical shape . As is known, the shape of a ball is much easier to inject gas and liquid. Near the Earth, under a relatively thin layer of crust (the surface visible to us) is an entire ocean of liquid hot magma. When eruptions of volcanoes 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-current currents in the center of the Earth.

By the way, if you look at the shape of large celestial bodies of the solar system, it becomes obvious that all planets are spherical. Sometimes there is a slight distortion of shape due to flattening from the poles. Its origin is due 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 that promotes the formation of the sphere is either absent or insufficient.

Sometimes on the forums you can meet the question of what are the stars of the solar system. Until recently, it was generally accepted that there is only one star in the system - the Sun. However, it is increasingly suggested that our system is double. In addition to the Sun, there is a second star, the existence of which has so far been proven only indirectly, but the name is already given - Nemesis. Because of its elongated orbit, the approach to the Earth does not occur more than once in several thousand years.