Why is the earth called the earth?

Ordinary: among the nine planets in the solar system, the mass, volume, average density and revolution and rotation of the earth have their own characteristics, but they are not special;

Special: The earth is in a relatively stable and safe cosmic environment, with the necessary conditions of temperature, atmosphere, water and so on, so the earth is special.

There are core, mantle and shell structures inside the earth, and hydrosphere, atmosphere and magnetic field outside the earth. The earth is the only known celestial body with life in the universe at present, and it is the home of millions of creatures, including human beings.

In the process of earth evolution, some astronomical and geological events will occur, and the time period of these events is called geological period.

In various geological periods, major events related to the earth, the solar system and the earth in space have left records on the earth itself, crustal movement, strata, rocks, structures, paleontology, paleomagnetism, glaciers, paleoclimate and many other aspects.

In different geological periods, different geological processes have different characteristics.

Extended data:

The position of the earth in the universe has been fundamentally expanded in the last century. At first, the earth was considered as the center of the universe, but at that time, the understanding of the universe only included those planets visible to the naked eye and seemingly fixed stars on the celestial sphere. Heliocentrism was widely accepted in the17th century. Later, William Herschel and other astronomers discovered that the sun was located in a disk galaxy composed of stars.

By the 20th century, the observation of spiral nebulae showed that our Milky Way was just one of billions of galaxies in the expanding universe. 2 1 century, the overall structure of Hubble volume began to become clear-supercluster formed a huge network structure containing large-scale fibers and holes.

Supergalaxy clusters, large-scale fiber structures and holes may be the largest coherent structures in the universe. On a larger scale (more than one billion parsec), the universe is homogeneous, that is, its parts have the same density, composition and structure on average.

The universe has no "center" or "boundary", so we can't mark the absolute position of the earth in the whole universe. The earth is located in the center of Hubble volume, because observability is determined by the distance from the earth. At various scales, we can give the relative position of the earth with a specific structure as the frame of reference. Whether the universe is infinite is uncertain.

Planets are celestial bodies that do not emit light by themselves and surround stars. Generally speaking, a planet needs to have a certain mass, and the mass of the planet should be large enough to make its shape approximately spherical. Those with insufficient mass are called asteroids. The name "planets" comes from the fact that their positions in the sky are not fixed, just like they are walking.

The five planets visible to the naked eye in the solar system are Mercury, Venus, Mars, Jupiter and Saturn. After thousands of years of exploration, it was not until Copernicus established the Heliocentrism in16th century that people generally realized that the earth is one of the planets revolving around the sun, and the eight planets including the earth constitute the main members of the planetary system revolving around the sun-the solar system. Planets themselves generally do not emit light, but emit light by reflecting the light of stars to their surfaces.

On the sky background mainly composed of stars, the planets have obvious relative motion. The planet closest to the sun is Mercury, followed by Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Starting from the fact that planets originate from different forms of matter, the eight planets can be divided into three categories: terrestrial planets (including water, gold, earth and fire), giant planets (wood and earth) and distant planets (heavenly kings and Neptune).

The motion of the planet around the star is called revolution, and the orbit of the planet revolution has three characteristics: * * areal, isotropic and nearly circular. The so-called * * * planarity means that the orbital planes of the eight planets are almost on the same plane; Isotropy means that they revolve around the star in the same direction; Nearly circular means that their orbits are very close to circular.

References:

Baidu Encyclopedia-Earth