The universe

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The Universe

“The word universe derives from the Old French word Univers, which in turn derives from the Latin word universum, used by Cicero. unvorsum is everything rotated as one or everything rotated by one".

The universe is everything that exist, contains all of the matter and energy, galaxies, stars, and planets in existence. The most precise estimate age of the universe is13.73±0.12 billion years old and is based on observations of the cosmic microwave background radiation, the diameter of the observable universe is at least 93 billion light years or 8.80×1026 meters, we said observable because we cannot observe space beyond the limitations of light, the exact size of the universe is unknown because it is immensely large and infinite.
In the 1920s, astronomer Edwin Hubblediscovered the universe was not static. Rather, it was expanding.
Long time ago, the universe was expanding more slowly than it is today.
Scientists believe the universe is still expanding outward, because the universe has not been the same at all times some things change like the relative populations of quasars and galaxies, another have been expanded like space. By looking at an object calledelectromagnetic spectrum, scientists can determine If an object is moving away from Earth or towards Earth.
They believe this outward expansion is the result of a violent and powerful explosion that occurred about 13.7 billion years ago.

This explosion is known as the Big Bang which said that “the universe was once in an extremely hot and dense state that expanded rapidly. This rapidexpansion caused the young universe to cool and resulted in its present continuously expanding state.
According to recent measurements, scientific evidence, and observations, the original state happened around 13.7 billion years ago, which can be referred to as the time that the Big Bang occurred?”

In the Universe we can find the solar system which is about 4.6 billion years old. There we can findplanets like Mercury, Venus, Earth, Mars, Jupiter, 
Saturn, Uranus, Neptune and Pluto. Also celestial bodies like Asteroids, 
Constellations, Comets, Black Holes, Moon, etc.

The principal component of the Solar System is the Sun which contains 99.86 percent of the system's known mass and dominates it gravitationally and is the four largest orbiting bodies.

The Sun is the Solar System's starand Its large mass is about 332,900 Earth masses, is the closest star to Earth and is a giant, spinning ball of very hot gas, the Sun is fueled by nuclear fusion reactions. The light from the Sun heats our planet and makes life possible.

The overall structure of the Solar System consists of the Sun, four relatively small inner planets surrounded by a belt of rocky asteroids, and four gas giantssurrounded by the outer Kuiper belt of icy objects.
The sun is composed of roughly 98% hydrogen and helium. The objects of the inner Solar System are composed mostly of rock. Jupiter and Saturn are composed mainly of gases.

The solar system is divided in two:

Inner Solar System, which is the name for the region comprising the terrestrial planets and asteroids. Composed mainlyof silicates and metals, the objects of the inner Solar System are relatively close to the Sun.

Inner planets:
“The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of refractory minerals, such as the silicates, which form their crusts and mantles, and metals such as iron and nickel, which form their cores. Three of the fourinner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features such as rift valleys and volcanoes.

* Mercury:
is the closest planet to the Sun and the smallest planet in the Solar System (0.055 Earth masses). Mercury has no natural satellites  orbiting the Sun once every 87.969 Earth days.
Mercury is...