Planet Earth

We explain everything about planet Earth, its origin, the emergence of life, its structure, movement and other characteristics.

planet earth
Planet Earth is the third closest to the Sun in the Solar System.

planet earth

We call Earth, planet Earth or simply The Earth, the planet we live on. It is the third planet in the solar system starting 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 designated astronomically with the symbol ♁.

Its name comes from Latin Terraa Roman deity equivalent to Gaia of the ancient Greeks, associated with fertility and fecundity. It was popularly known as Tellus mater either Terra mater (Mother Earth), since all living beings would come from her womb.

In other languages, such as English, the name of our planet can have non-Greek-Latin connotations, such as earth of the Anglo-Saxons.

Since time immemorial, human beings have dreamed of knowing the limits of the Earth and exploring all its corners. Ancient cultures thought it was infinite, or perhaps with an end that would be a fall into the abyss. Even today there are those who maintain 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 internal layers are composed, as well as what was there before human beings appeared on its surface.

Origin and formation of planet Earth

The Earth It was formed around 4.55 billion years ago from the material from which the rest of the solar system was made up, which was initially a stellar cloud of gases and cosmic dust. The formation of the planet took between 10 and 20 million years as its surface cooled and the cloud of gases that is today 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 essential for the appearance of liquid water.

Thanks to this, the hydrological cycle could have begun, contributing to cooling 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 observed from space.

Characteristics of planet Earth

The Earth It 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 the equator (an equatorial radius of 6,378.1 kilometers).

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Its mass is 5.9736 x 1024 kilograms and its density of 5.515 g/cm3the highest in the solar system. It also has an acceleration of gravity of 9.780327 m/s2.

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

Composition and structure of planet Earth

layers of the earth
The Earth is made up of increasingly dense layers as they get closer to the core.

The Earth's mass is made up 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 are abundant in its inner layers, which would be responsible for the generation of its magnetic field or magnetosphere.

the planet It is composed of concentric layers of matter extending into the core from the surface. These layers are:

  • Lithosphere It extends from the surface (0 kilometers deep) to about 60 kilometers inward, being the least dense layer of all and the only one that we can visit with concrete physical means. That is where the tectonic plates are, for example. The lithosphere is divided into two different layers:
    • Crust It goes from 0 to 35 kilometers deep, being the layer where life is located, made up mainly of solid silicates.
    • Upper mantle It ranges from 35 to 60 kilometers deep, and is composed mainly of peridotite rocks, extremely basic, from which basalts could come.
  • Earth mantle The Earth's mantle goes from 35 kilometers deep to 2890, that is, to the outer part of the core. It is the widest layer of the Earth's internal structure, rich in silicates, magnesium and iron, all in a semi-solid state and of variable viscosity. Within the mantle is the inner mantle and also the asthenosphere.
    • Asthenosphere A low viscosity layer that comprises the upper zone of the Earth's mantle, made up of silicate materials in a solid and semi-molten or partially molten state, depending on their proximity to the boiling magma. Tectonic plates move above the asthenosphere. This layer goes from 100 to 700 kilometers deep.
  • Core The Earth's core is the “heart” of the planet, and is composed mostly of ferromagnetic metals (iron and nickel), divided into two stages:
    • External core Stretching from 2,890 kilometers deep to 5,100, this liquid layer of highly viscous metal rests on the inner core and comprises mostly iron, with traces of lighter elements.
    • Inner 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 which is responsible for the generation of its magnetosphere. It has a radius of approximately 1,255 kilometers and its composition is believed to be 70% iron and 30% nickel, along with tiny portions of other heavy metals such as iridium, lead and titanium.
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Continue in: Layers of the Earth

Movements of planet Earth

planet earth tilt axis seasons 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 movement of the planet along its solar orbit, describing more or less an ellipse as a path. Every time we celebrate a year, one more revolution of the planet around the Sun is completed.

On the other hand, Earth's axis of rotation is tilted at approximately 23.5 degrees. It is due to this inclination that each hemisphere receives the Sun's rays more directly every six months (thus causing the change in climatic seasons).

There are two other types of movements that, although we cannot perceive them 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 changes enough for the seasons to reverse.
  • Nutation. It is a slight oscillation of the axis of rotation. It is due to the effect of the combined forces of gravity of the Earth, the Moon and the Sun.

Magnetic field of Planet Earth

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

Our planet has a magnetosphere, arising from the movement of its metallic core. This magnetic field It has protected us from early times from the harmful solar wind. If this protection did not exist, the Sun's forces would have destroyed the atmosphere millions of years ago.

Besides It is the magnetic north according to which compasses and migratory animals are oriented in their kilometer-long journeys.

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 You can see its effects such as the famous northern and southern lights.

Emergence of life on planet Earth

Life appeared during the Precambrian that is, the first and longest geological period of our planet. It dates back to the very beginnings of the planet, in the midst of torrential volcanic and electrical activity, about 4 billion 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 grew in complexity and abundance, until giving rise to the formation of the first cells about 3800 years ago. to 3500 million years.

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

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

The Moon

planet earth tides moon satellite natural
The Moon's gravity causes tides on planet Earth.

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

The Moon It has a mass of 7.349 x 1022 kg 1/81 of the Earth's mass, being the largest satellite in the solar system in proportion to its ruling planet. Its attraction on our planet triggers the tidal phenomenon which suggests that it played some type of role in the climatic circuits that facilitated the appearance of life.

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

Solar system

planet earth solar system
All the planets in the solar system orbit the Sun.

Our planet is part of the solar system, which It is the stellar system of bodies orbiting the Sun in concentric elliptical trajectories, in each of which is one of the eight planets (in order of proximity to the Sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

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

Milky Way

planet earth galaxy milky way
Our galaxy, the Milky Way, is shaped like a spiral.

The Milky Way It is the galaxy in which our solar system is located. It is a barred spiral galaxy, which has the mass of 1012 times the Sun, in a diameter that is estimated to be 10,000 light years, equivalent to one and a half trillion kilometers.

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

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References

  • “Earth” in Wikipedia.
  • “Planet Earth” in National Geographic (Spanish).
  • “The Earth is our planet” in AstroMía.
  • “The Earth” at NASA Space Place.
  • “Earth” in The Encyclopaedia Britannica.