CONCEPTS

Planet Earth

We explain that what is planet earth? its origin, the emergence of life, its structure, movement and other characteristics.

  1. What Is Planet Earth

We call Earth, planet Earth or simply Earth, the planet we inhabit. It is the third planet in the Solar System beginning to count from the Sun , located between Venus and Mars. According to our current knowledge, it is the only one that harbors life in the entire Solar System . It is astronomically designated with the symbol ♁.

Its name comes from the Latin Terra , a Roman deity equivalent to the Gea of ​​the ancient Greeks , associated with fertility and fertility. It was popularly known as Tellus mater or Terra mater (mother Earth), since from her womb would come all living beings .

In other languages, such as English, the name of our planet may have non-Greco-Latin connotations, such as the Earth of the Anglo-Saxons.

Since time immemorial, the human being has dreamed of knowing the limits of the Earth and going through all its corners. Ancient cultures thought it infinite, or perhaps with an ending that would be a fall into the abyss. Even today there are those who argue that the Earth is flat, that it is hollow and other conspiracy theories.

However, thanks to science and technology, we currently have beautiful images of our planet. We also know how its inner layers are composed, as well as what was before the human being appeared on its surface.

  1. Origin and formation of planet Earth

The Earth formed around 4550 million years ago , from the material from which the rest of the Solar System was constituted, which was initially a stellar cloud of cosmic gases and dust. The planet’s formation took between 10 and 20 million years , as its surface cooled and the cloud of gases around the atmosphere accumulated around it .

Eventually, through a long period of seismic activity and possibly due to the constant impact of meteors, the Earth had the necessary elements and physical conditions indispensable for the appearance of liquid water.

Thanks to this, the hydrological cycle could begin, contributing to cool the planet more quickly to levels where life could begin. Over time, the large amount of liquid water on the surface gave our planet its blue hue when viewed from space.

  1. Characteristics of planet Earth

Earth is the fifth planet in the Solar System in terms of size , and the only one capable of harboring life. It has a spherical shape with a slight flattening at the poles, and 12,756 km in diameter at the height of Ecuador (an equatorial radius of 6,378.1 kilometers).

Its mass is 5.9736 x 10 24 kilograms and its density of 5.515 g / cm 3 , the highest in the Solar System. Also has an acceleration of gravity of 9.780327 m / s 2 .

Like other inner planets such as Mars and Mercury, the Earth is a rocky planet , with a solid surface and a liquid metal core (due to the heat and pressure of its own gravity), unlike other gaseous planets like Venus or Jupiter Its surface is divided between the gaseous atmosphere, the liquid hydrosphere and the solid geosphere .

  1. Composition and structure of planet Earth

layers of the Earth
The Earth is made up of increasingly dense layers as they approach the core.

The land mass is composed of a diverse set of chemical elements . The most abundant elements are iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1, 8%), calcium (1.5%) and aluminum (1.4%) , leaving 1.2% for the rest of the elements.

It is estimated that iron and nickel abound in its inner layers, which would be responsible for the generation of its magnetic field or magnetosphere.

The planet is composed of concentric layers of matter that extend to the nucleus from the surface. These layers are:

Lithosphere . It extends from the surface (0 kilometers deep) to about 60 kilometers inwards, being the least dense layer of all and the only one we can visit with specific physical means. It is there where the tectonic plates are, for example. The lithosphere is divided into two distinct layers:

  • Bark . It ranges from 0 to 35 kilometers deep, being the layer where life is located, consisting mainly of solid silicates.
  • Upper mantle . It ranges from 35 to 60 kilometers deep, and is mostly composed of extremely basic peridotitic rocks, from which basalts could come.

Earth ‘s mantle . The mantle of the Earth goes from 35 kilometers deep, to 2890, that is, to the outside of the core. It is the widest layer of the Earth’s internal structure, rich in silicates, magnesium and iron, all in semi-solid state and of variable viscosity. Inside the mantle is the inner mantle and also the asthenosphere.

  • Asthenosphere . A low viscosity layer comprising the upper area of ​​the earth’s mantle, formed by silicate materials in solid state and partially molten or partially molten, depending on its proximity to the boiling magma. Tectonic plates move above the asthenosphere. This layer ranges from 100 to 700 kilometers deep.

Core . The Earth’s core is the “heart” of the planet, and is mostly composed of ferromagnetic metals (iron and nickel), divided into two stages:

  • External core . Extending from 2890 kilometers deep to 5100, this highly viscous liquid metal layer rests on the inner core and comprises mostly iron, with traces of lighter elements.
  • Internal core . The true center of the Earth is a solid metal core, which rotates with an angular velocity slightly higher than the rest of the planet, and is responsible for the generation of its magnetosphere. It has a radius of approximately 1255 kilometers and its composition is believed to be 70% iron and 30% nickel, along with very small portions of other heavy metals such as iridium, lead and titanium.
  1. Earth planet movements

planet earth tilt axis stations movement
The difference in seasons between the hemispheres is due to the inclination of the earth’s axis.

The Earth periodically executes two main types of movements:

  • Rotation . A rotating movement on its own axis, which exposes its surface to the sun intermittently and is the cause of days and nights.
  • Translation . This is the displacement of the planet along its solar orbit, describing more or less an ellipse as a trajectory. Every time we celebrate a year, another round of the planet around the Sun is fulfilled.

On the other hand, the axis of rotation of the Earth is inclined at approximately 23.5 degrees. It is because of this inclination that each hemisphere receives the sun’s rays every six months more directly (thus causing the changing of the climatic seasons).

There are two other types of movements that, although we cannot perceive in our daily experience, are scientifically proven:

  • Precession . It is a very slight movement of the earth’s axis. Every 25,776 years the inclination of the axis is modified enough that the seasons are reversed.
  • Nutación . It is a slight oscillation of the axis of rotation. It is due to the effect of the combination of the gravity forces of the Earth, the Moon and the Sun.
  1. Magnetic Field of Planet Earth

aurora boral polar solar wind magnetosphere
The magnetosphere protects us from solar wind.

Our planet has a magnetosphere, emerged from the movement of its metal core. This magnetic field has protected us since early times from the damaging solar wind . If this protection did not exist, the forces of the Sun would have destroyed the atmosphere millions of years ago.

It is also the magnetic north according to which compasses and migratory animals are oriented in their kilometric movements.

The Earth’s magnetosphere extends beyond the ionosphere, about 500 km high, completely enveloping our planet. At the poles its proximity to the Earth is greater, and its effects can be seen as the famous northern and southern auroras .

  1. Emergence of life on planet Earth

Life appeared during Precambrian , that is, the first and longest geological period of our planet. It goes back to the very beginning of the planet, in the middle of a torrential volcanic and electrical activity, about 4,000 million years ago .

At some remote moment, certain particular chemical conditions, thanks to the presence of liquid water on the planet, allowed the creation of self-replicating molecules, which were growing in complexity and abundance, until giving rise to the formation of the first cells about 3800 to 3500 million years.

These first organisms undertook an evolutionary career from the diversification of the so-called LUCA ( Last Universal Common Ancestor ), the first ancestor common to all life forms existing today. Thus were born the basic energy processes that changed the world.

For example, the photosynthesis filled the oxygen atmosphere and led to the subsequent appearance of the breath . All this under the protection of the ozone layer of the atmosphere, without which ultraviolet radiation would have made the molecular preservation of DNA very difficult , and without it, life as we now understand it.

  1. Moon

planet earth tides moon satellite natural
The gravity of the Moon causes the tides on planet Earth.

The Moon is the only natural satellite on our planet . Its origin dates back to the periods of the Earth’s formation itself, with which it shares some geochemical similarities. It has 1738 kilometers of radius  and a period of rotation identical to that of its translation in orbit around the Earth. Therefore, we always see the same side of the Moon.

The Moon has a mass of 7,349 x 10 22 kg , 1/81 of the Earth’s mass, being the largest satellite in the Solar System in proportion to its ruling planet. His attraction on our planet triggers the phenomenon of the tides , which suggests that he played some role in the climatic circuits that facilitated the emergence of life.

The most accepted theory about its origin is called The Great Impact . It implies the existence of a protoplanet called Tea, whose orbit coincided with the Earth enough to eventually collide with each other, merging and leaving behind a trail of rubble that over the coming years gave rise to the Moon.

  1. Solar system

planet earth solar system
All the planets of the Solar System orbit around the Sun.

Our planet is part of the Solar System, which is the star system of bodies orbiting the Sun , on concentric elliptical paths, on each of which is one of eight planets (in order of proximity to the Sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

In addition, around the Sun orbits a belt of asteroids that separates them into two groups: inner planets (the first four) and outer planet (the last four), and beyond a set of trans-Neptunian objects (including the ancient planet Pluto), in the so-called Oort Cloud and the Kuiper Belt.

  1. Milky Way

planet earth galaxy via milky
Our galaxy, the Milky Way, has a spiral shape.

The Milky Way is the galaxy in which our Solar System is located . It is a barred spiral galaxy, which gathers the mass of 10 12 times the Sun, in a diameter estimated to be 10,000 light years, equivalent to a trillion and a half kilometers.

Its name comes from Greek mythology , and in Latin means “Way of milk”, referring to the breastfeeding of the hero Hercules by the goddess Hera, wife of Zeus. Our Solar System is located in one of the galaxy’s arms, in the Orion Constellation , about 28,000 light years from the galactic center.

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