Planet Earth – WorldAtlas

The Earth is a celestial object and one of the components of the solar system. It is the third planet from the Sun, and the only celestial object capable of supporting life. Earth is the 6th largest object in the solar system, with an average radius of 6,371 kilometers, and the 5th largest planet after Jupiter, Saturn, Uranus and Neptune. About 70% of the Earth’s total surface is water from various sources, with the ocean being the most important source, while the remaining area is land, occupied by about 7.6 billion people. The Earth’s atmosphere is made up of several gases, including oxygen, nitrogen and carbon dioxide. However, the Earth is not just a round object that supports life.

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Origin of the name

Earth is the third planet from the Sun in the solar system.

All of the planets except Earth were named after Roman and Greek gods and goddesses. Earth is a modern English name derived from an Old English word “oerde” or “erda”, which means ground or soil. The early usage of the word came from translations of the Greek word “gē”, the Latin word “terra”, as well as the Hebrew word “‘eretz”, which meant dry land, soil, soil, the surface of the world or the human world. Although Earth was first used to refer to the planet in the 15th century, the Hebrew, Greek, and Latin words may have been used to refer to the sphere much earlier. For example, “’eretz” appeared over 1,400 years ago, in the first chapter of Genesis. The name “terra” is sometimes used in science fiction to distinguish Earth from other planets.

History of the earth

Eons of Earth
The history of compressed earth in 12 hours.

The origin of the Earth has been a hot topic of debate between scientists and religious groups. According to most religious beliefs, the Earth was created by a supernatural being or a deity (God). However, the exploration of the planet by scientists and modern technology has changed the way people perceive the Earth. Until the 16th century, humans did not consider planet Earth to be one of the planets in the solar system. There was also a widely held belief that the planet was flat and floated on a body of water (ocean).

The Geological Time Scale (GTS) highlights events on Earth from the beginning to the present day. These events fall into four main periods called eons. Hadean, the first eon, begins with the formation of the Earth and lasts approximately 600 million years. During this period, temperatures were extremely high and volcanic activity was also quite frequent, which made it impossible for any form of life to exist. Hadean lasted from 4,540 million years (Mya) to 4,000 Mya and the transition to the Archean period.

Evolution of life on Earth
Evolution of life on Earth.

The Archean eon lasted from 4000 to 2500 Mya and was more user-friendly than the previous period. During this period, temperatures were much cooler, while volcanic activity was not as frequent as before. Prokaryotes, the oldest known life forms, appeared at the start of the era through the process of abiogenesis (life from non-living material). Three continents; It is believed that Vaalbara, Ur and Kenorland existed during this period.

The third eon, Proterozoic, began around 2,500 Mya and lasted around 2 billion years. During this time, more complex life forms emerged, collectively referred to as eukaryotes. These organisms produced large amounts of oxygen through the process of photosynthesis, which has become vital for the survival of plants and animals on the planet. The planet may also have experienced extremely low temperatures, dropping below melting point in most places. The continents of Pannotia, Rodinia and Columbia may also have existed during the Proterozoic. The first three aeons form a superereon known as the Precambrian.

The last eon is the Phanerozoic, which has existed since 541 Mya. This period is characterized by complex life forms and marked by the dominance of vertebrate species. Pangea, a former supercontinent, formed during this period and later disintegrated into the current land masses. Several extinction and evolutionary events also took place during the Phanerozoic Eon.

formation of the continent from Pangea
Formation of current continents from Pangea.

Earth formation

Planet Earth was formed about 4,540 million years ago and has been around for about a third of the age of the universe. The formation of the planet is based on two theories; model of nucleus accretion and disc instability. However, the nucleus accretion model is the most popular and widely accepted theory, especially for small planets like Earth, while the disc instability model accounts for the formation of larger and larger planets. other objects.

Birth of a solar system – protoplanetary disc

According to the accretion model, the solar system included clouds of gas and dust known as the solar nebula. Gravity spun these materials, leading to the formation of the Sun. After the Sun formed, the other dust and gases clustered together to form larger objects. Solar winds chased away lighter particles and gases such as helium and hydrogen, leaving larger and heavier rocks to form planet Earth and other celestial objects. The rocky core was the first to form. A lighter material formed the crust while the denser ones sank down the center. The magnetic field, formed around 3500 Mya, prevented the planet from moving away. Gravity also attracted some of the gases that made up the atmosphere.

Volcanic eruptions were common on ancient Earth and shaped the landscape of the planet.

The mantle that runs beneath the crust has caused plate tectonics, giving rise to volcanoes and mountains that have emitted gases into the atmosphere. Over the years, plate tectonics forced the continental crusts to coalesce and form a supercontinent, which later disintegrated to form today’s continents. Rodina began to fall apart around 750 Mya, while Pannotia formed between 600 and 540 Mya. Pangea started to fall apart around 180 Mya. Processes such as volcanic eruptions, tectonic plates, weathering, flooding, glaciation and erosion are constantly reshaping the Earth.

Hydrosphere and atmosphere

4 spheres of the Earth
The hydrosphere and the atmosphere are two of the four spheres of planet Earth.

Unlike other planets, the Earth has abundant surface water, accounting for 70.8% of the total area. The hydrosphere includes oceans, gulfs, lakes, seas, rivers and groundwater. Oceans cover about 71% of the Earth’s surface, with a total volume of about 1.3 billion cubic kilometers. Only 2.5% of the planet’s water resources are fresh water; the rest is saline water. At sea level, the Earth’s average atmospheric pressure is 101.325 kPa, with the atmosphere mainly composed of abundant nitrogen (78%) and 20.9% oxygen. Other traces of gas and water vapor are also present in the atmosphere. The atmosphere is subdivided into layers of thermosphere, mesosphere, stratosphere and troposphere (lower layers). The troposphere makes up about 75% of the total mass of the atmosphere and contains almost all of the water vapor.

Physical characteristics

Planet Earth is spherical and almost flat at the poles, with an equatorial bulge due to centrifugal forces resulting from the Earth’s rotation. Thus, the shape of the Earth can best be described as a flattened spheroid, with an average diameter of 12,742 kilometers. The Earth is approximately 510 million square kilometers, of which only 29.2% is land, while the rest is water.

Earth is made up of many chemical elements and compounds. It is composed of aluminum, calcium, nickel, sulfur, magnesium, silicon, magnesium and iron, totaling 98.8%. Iron makes up 32.1%, while oxygen makes up 30.1% of the total chemical elements. The central region consists mainly of iron, with traces of sulfur, nickel and other trace elements.

layers of the earth
Legend

The Earth is made up of three distinct layers; crust, mantle and core. The core is divided into an outer and inner core made up of iron and nickel. The inner core is approximately 1,221 kilometers thick, while the outer core is 2,259 kilometers thick. The mantle lies between the crust and the core and is approximately 2,800 kilometers thick. The crust, or outer shell, is 1-80 km thick and includes continental and oceanic crust. The crust and the top of the upper mantle form the lithosphere, which is divided into several tectonic plates.

The rotation and revolution of the Earth are responsible for the days, nights and seasons.

The Earth rotates or rotates around the axis when it rotates around the Sun. It rotates counterclockwise once every 24 hours or so. Due to the acceleration of the tides, the Earth’s rotation slowed slightly, with solar days slightly longer by about two milliseconds. On the other hand, the Earth takes approximately 365.26 average solar days to travel approximately 150 million kilometers around the sun. The average orbital speed of the planet is 107,200 km / h.


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