Planet Earth Information: We explain everything about planet Earth, its origin, the emergence of life, its structure, movement, and other characteristics.
Planet Earth
We call Earth, planet Earth, or simply Earth, the planet we live on. It is the third planet in the solar system from the Sun, located between Venus and Mars. According to our current knowledge, it is the only one that supports life in the entire solar system. It is designated astronomically with the symbol ♁.
Its name comes from the Latin Terra, a Roman deity equivalent to the ancient Greek Gaia, associated with fertility and fecundity. She was popularly known as Tellus mater or Terra mater (Mother Earth), because all living beings came from her womb.
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In other languages, such as English, the name of our planet can have non-Greco-Latin connotations, like the Anglo-Saxon word “earth.”
Since time immemorial, humankind has dreamed of knowing the limits of the Earth and exploring all its nooks and crannies. Ancient cultures believed it to be infinite, or perhaps to end in 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 now have beautiful images of our planet. We also know what its internal layers are made of, as well as what existed before humans appeared on its surface.
Origin and Formation of Planet Earth
The Earth formed around 4.55 billion years ago from the material that formed the rest of the solar system, which was initially a stellar cloud of gases and cosmic dust. The planet’s formation took between 10 and 20 million years, as its surface cooled and the gas cloud that is now the atmosphere accumulated around it.
Eventually, through a long period of seismic activity and possibly due to the constant impact of meteorites, the Earth acquired the necessary elements and physical conditions necessary for the emergence of liquid water.
Thanks to this, the hydrological cycle was able to begin, helping to cool the planet more rapidly 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.
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Characteristics of Planet Earth
Earth is the fifth largest planet in the solar system and the only one capable of supporting life. It has a spherical shape with a slight flattening at the poles and is 12,756 km in diameter at the equator (an equatorial radius of 6,378.1 kilometers).
Its mass is 5.9736 x 1024 kilograms and its density is 5.515 g/cm3, the highest in the solar system. It also has a gravitational acceleration of 9.780327 m/s2.
Like other inner planets such as Mars and Mercury, Earth is a rocky planet with a solid surface and a liquid metallic core (due to the heat and pressure of its own gravity), unlike other gaseous planets such as Venus or Jupiter. Its surface is divided between a gaseous atmosphere, a liquid hydrosphere, and a solid geosphere.
Composition and Structure of Planet Earth
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 remaining elements.
It is estimated that its inner layers are rich in iron and nickel, which would be responsible for the generation of its magnetic field, or magnetosphere.
The planet is composed of concentric layers of matter that extend from the surface toward the core. These layers are:
Lithosphere
It extends from the surface (0 kilometers deep) to about 60 kilometers inward. It is the least dense layer of all and the only one we can access with specific physical means. This is where the tectonic plates are, for example. The lithosphere is divided into two distinct layers:
Crust: It extends from 0 to 35 kilometers deep, and is the layer where life resides, composed primarily of solid silicates.
Upper mantle: It extends from 35 to 60 kilometers deep and is composed mostly of highly basic peridotite rocks, from which basalts may originate.
- Earth’s mantle: The Earth’s mantle extends from a depth of 35 kilometers to 2,890 kilometers, 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 varying viscosity. Within the mantle is the inner mantle and also the asthenosphere.
- Asthenosphere: A low-viscosity layer comprising the upper zone of the Earth’s mantle, composed of silicate materials in a solid, semi-molten, or partially molten state, depending on its proximity to boiling magma. Tectonic plates move above the asthenosphere. This layer extends 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:
- Outer core: Extending from a depth of 2,890 kilometers to 5,100 kilometers, this highly viscous liquid layer of 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 at a slightly higher angular velocity than the rest of the planet and is responsible for generating its magnetosphere. It has a radius of approximately 1,255 kilometers and is believed to be composed of 70% iron and 30% nickel, along with tiny amounts of other heavy metals such as iridium, lead, and titanium.
Movements of Planet Earth
The Earth periodically undergoes two main types of movements:
- Rotation: A rotational motion on its own axis, which intermittently exposes its surface to the sun and is responsible for day and night.
- Translation: This is the movement of the planet along its solar orbit, roughly describing an elliptical path. Every time we celebrate a birthday, the planet completes one more revolution around the sun.
Furthermore, the Earth’s rotational axis is tilted by approximately 23.5 degrees. Because of this tilt, each hemisphere receives more direct sunlight every six months (thus causing the change of seasons).
There are two other types of movements that, although we cannot perceive in our everyday experience, are scientifically proven:
- Precession: This is a very slight movement of the Earth’s axis. Every 25,776 years, the tilt of the axis changes enough for the seasons to reverse.
- Nutation: This is a slight oscillation of the rotational axis. It is due to the effect of the combined forces of gravity of the Earth, the Moon and the Sun.
Planet Earth’s Magnetic Field
Our planet has a magnetosphere, created by the motion of its metallic core. This magnetic field has protected us from the damaging solar wind since early times. Without this protection, the Sun’s forces would have destroyed the atmosphere millions of years ago.
It is also the magnetic north, according to which compasses and migratory animals orient themselves on their long journeys.
The Earth’s magnetosphere extends beyond the ionosphere, about 500 km high, completely enveloping our planet. At the poles, it is closest to Earth, and its effects can be seen, such as the famous auroras.
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Emergence of Life on Planet Earth
Life appeared during the Precambrian Period, the first and longest geological period on our planet. It dates back to the very beginning of the planet, amidst torrential volcanic and electrical activity, some 4 billion years ago.
At some remote moment, certain particular chemical conditions, thanks to the presence of liquid water on the planet, allowed for the creation of self-replicating molecules, which grew in complexity and abundance, leading to the formation of the first cells some 3.8 to 3.5 billion years ago.
These first organisms embarked on an evolutionary race based on the diversification of the so-called LUCA (Last Universal Common Ancestor), the first common ancestor of all life forms existing today. Thus, the basic energy processes that changed the world were born.
For example, photosynthesis filled the atmosphere with oxygen and led to the subsequent emergence of respiration. All of this occurred under the protection of the atmospheric ozone layer, without which ultraviolet radiation would have made the molecular preservation of DNA very difficult, and without it, life as we understand it today.
The Moon
The Moon is our planet’s only natural satellite. Its origin dates back to the very formation of the Earth, with which it shares some geochemical similarities. It has a radius of 1,738 kilometers and a rotation period identical to its orbit around Earth. Therefore, we always see the same side of the Moon.
The Moon has a mass of 7.349 x 1022 kg, 1/81 of the mass of Earth, making it the largest satellite in the solar system in relation to its ruling planet. Its pull on our planet triggers the phenomenon of tides, which suggests that it played some role in the climatic patterns that facilitated the emergence of life.
The most widely accepted theory about its origin is called The Great Impact. It assumes the existence of a protoplanet called Theia, whose orbit coincided with Earth’s enough for them to eventually collide, merging and leaving behind a trail of debris that, over the coming years, gave rise to the Moon.
Solar System
Our planet is part of the solar system, which is the stellar system of bodies orbiting the Sun in concentric elliptical trajectories, each of which contains 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 the Sun, separating them into two groups: inner planets (the first four) and outer planets (the last four). Beyond this, a group of trans-Neptunian objects (including the former planet Pluto) in the so-called Oort Cloud and the Kuiper Belt.
Milky Way
The Milky Way is the galaxy in which our solar system is located. It is a barred spiral galaxy, with a mass 1012 times that of the Sun, within an estimated diameter of 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, approximately 28,000 light-years from the galactic center.
References
All the information we offer is supported by authoritative and up-to-date bibliographic sources, ensuring reliable content in line with our editorial principles.
- Planet Earth in National Geographic (Spanish).
- Earth is our planet in AstroMía
- Earth in NASA Space Place
- Earth in The Encyclopaedia Britannica
