Earth (planet)

Article

October 23, 2021

The Earth is counted from the Sun the third planet of the solar system. In this it belongs to the "terrestrial planets" named after her, of which it is the largest both in mass and volume. Life exists on Earth: it is the habitat of millions of species of organisms. Whether she is alone in this is unclear, but no traces of life have been found in the rest of the universe so far. Radiometric dating has shown that the Earth was formed 4.57 billion years ago and life up to 1 billion years after that. Since the emergence of life on Earth, the Earth's atmosphere has gradually become oxygenated, which has allowed the formation of a protective ozone layer and the development of aerobic organisms. The earth's surface is covered for 71% with water in the form of seas and oceans, the rest consists of continents and Islands. Water is necessary for the survival of all known life forms. The lithosphere, the outermost layer of the solid Earth, is divided into a number of rigid plates that move slowly over the Earth's surface on a geologic time scale (over millions of years). This movement causes the formation of mountain ranges and volcanism. Below the lithosphere is the slowly convective mantle. The current in the mantle causes plate movements and volcanism at the Earth's surface. Under the mantle are a liquid outer core (in which the Earth's magnetic field is generated) and a solid inner core. This magnetic field protects life from the solar wind and cosmic rays. The Earth revolves around the Sun at the same time as it revolves 366.26 times on its own axis. This length of time is called a sidereal year. Because the rotation of the Earth on its axis and the orbit of the Earth around the Sun follow the same direction (anticlockwise as seen from the North Pole), the length of the year measured in solar days is exactly one day shorter, namely 365 ,26 days. The Earth's axis is at an angle of 23.439281° to a line perpendicular to the plane of Earth's orbit, which causes the seasons. The Earth has a natural satellite, the Moon, which must have formed shortly after the formation of the Earth. Sometimes small objects are discovered that temporarily orbit the Earth. The Moon's gravity causes tides in the oceans, stabilizes the tilt of the Earth's axis and slowly decreases the planet's rotational speed.

Astronomical properties

The Earth belongs to the Solar System, the planetary system around the star called the Sun. The Solar System contains seven other planets and a large number of smaller celestial bodies. The Sun is about 109 times the diameter of the Earth and has a mass of 300,000 times. Among the planets, the Earth is of average size. The larger planets, especially Jupiter, have protected the Earth from impacts during its existence by trapping or repelling asteroids and comets with their (larger) gravitational field. The Moon also catches meteorites that would otherwise crash into Earth. The Sun is one of the billions of stars that make up the Milky Way galaxy. Within the Milky Way, the Sun is a relatively inconspicuous star. The Milky Way itself is again part of the Local Group, a group of more than 40 galaxies, of which the Milky Way is one of the larger. This Local Group is part of the Local Supercluster, one of many superclusters of tens of thousands of galaxies that make up the Universe.

Orbit and rotation

Relative to background stars, it takes Earth 23 hours, 56 minutes, and 4.091 seconds (a sidereal day) to rotate once on its axis. Because the Earth rotates counterclockwise when viewed from above the North Pole, it appears to the viewer from the Earth's surface as if other celestial bodies (stars, planets, the Sun and Moon) rise in the east and set in the west. The Earth revolves in a

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