Earth is the third planet from the Sun and the fifth largest planet in the Solar System with the highest density. Today, it is the only known place where life is present.
Key facts and summary
- The perception that the Earth is a planet, and a planet among many others was established “reasonably” recently, in the 17º century – this perception was achieved by the combined forces of ancient philosophers, mathematicians and astronomers.
- Plato correctly deduced that the Earth is spherical, but this idea would take root and be proven much later.
- The name “Earth” – is at least 1,000 years old and is a Germanic word that simply translates to “earth”. It is not known who created it, but it is the only planet that has not been named after a Greek or Roman god.
- However, the Greek equivalent to Earth is Gaia – terra mater – mother Earth, and the Roman equivalent was Tellus – the fertile soil.
- It is estimated that the Earth formed about 4.5 billion years ago – almost a third of the age of the universe – through the accumulation of the solar nebula.
- Earth is the third planet from the Sun, at a distance of 1 AU or 147 million km / 91 million miles.
- It is the fifth largest planet in the Solar System, being the largest of the terrestrial planets.
- It has an equatorial radius of 6,371 km / 3,958 mi and a polar radius of 6,356 km / 3,949 mi, which means that it is not completely spherical, but rather bulged at the equator due to rotation.
- The Earth has a diameter of 12,742 km / 7,917 mi.
- The Earth has a mass of about 6.6 sextillion tons and a volume of about 260 billion cubic miles / 1 trillion cubic kilometers.
- The Earth’s surface area is about 510 million square kilometers.
- About 71% of the surface is covered by water and 29% by land.
- The water is 3% fresh and 97% salty. Of that 3% fresh water, more than 2% is frozen in layers of ice and glaciers, which means that less than 1% is fresh water found in lakes, rivers and underground.
- Regarding the land, the Asian continent covers about 30% of the entire land, having about 60% of the world’s population.
- The Earth’s atmosphere is composed of approximately 78% nitrogen, 21% oxygen, 0.97% argon and carbon dioxide and about 0.04% other gases and water vapor. The gas mixture is commonly known as air.
- The thickness of the atmosphere is about 96 kilometers.
- The Earth’s atmosphere is divided into 6 layers: troposphere, stratosphere, mesosphere, thermosphere, exosphere and ionosphere.
- The highest temperatures on Earth can reach over 110 degrees Fahrenheit / 48 degrees Celsius, and the lowest around -126 degrees Fahrenheit / -88 degrees Celsius, perhaps even lower.
- The Earth has the highest density of all the planets in the solar system – 5.51 g / cm³ – and a gravity of 9.807 m / s² or 1 g.
- This suggests that the Earth’s core is solid, made of iron and nickel, about 1,221 kilometers in radius. Core temperatures were estimated at about 5,400 degrees Celsius. This is hotter than the surface of the sun.
- Along with the inner core, the Earth also has an outer core, with the crust being the mantle and the thickest layer. It is a viscous mixture of molten rock about 2,900 km thick and has the consistency of caramel.
- The outermost layer – the earth’s crust – covers an average depth of 30 km on land. However, at the bottom of the ocean, the crust is thinner and extends for about 5 km from the seabed to the top of the mantle.
- The Earth has only one satellite – the Moon – and some artificial temporal satellites.
- The Earth’s axis is tilted 23.5 degrees from the plane of its orbit around the Sun. The inclination varies between 22.1 and 24.5 degrees, causing seasons and even chaotic seasons. It changes position once every 40,000 years.
- The Earth completes one rotation / day – from west to east – once every 23.9 hours. One orbit / year – a trip around the Sun – is completed in 365 days. The Earth’s orbit is elliptical or oval.
- The Earth’s magnetosphere acts as a shield against radiation from solar and cosmic particles. It is shaped like a teardrop reaching 36,000 mi / 57,936 km in space, and is one of the reasons why life has managed to develop.
Since ancient times, the Earth has been taught to be at the center of the Universe with the other celestial objects orbiting around it. Some believed that the Earth was flat, while ancient Greeks, like Plato, correctly deduced that the Earth was a sphere.
Soon after, the Greek astronomer Ptolemy proposed the idea that the planets were in small spheres and made circles while orbiting the Earth.
Later, at 17º century, Galileo Galilei observed and discovered Jupiter and that it had its own moons, and that Venus went through phases like the Moon.
The observations continued, the ideas were reached and, finally, it was established that the Earth was a planet among many others. Our planet’s name came from the Anglo-Saxon word “erda” and the Germanic word “erde” – both mean soil or soil.
The old English version of these words became “eor (th) e” or “ertha”, which later became “Earth”. Many other languages use some form of variation or proper naming, such as: Aarde, Terre, Tera, Jorden, Nchi, Bumi and much more. We who inhabit the Earth can be called: Terrans, Terrans, Terrans or Gaians.
The Earth is believed to have formed about 4.5 billion years ago. It is estimated that the duration of this formation lasted about 10 to 20 million years.
The theory states that a solar nebula divides a volume of a molecular cloud by gravitational collapse that begins to rotate and flatten into a circumstellar disc.
The planets grow out of that disk through gravity, swirling dust and gas. Slowly, the Earth’s atmosphere and oceans were formed by volcanic activity and gas depletion.
Condensed water vapor in the oceans is believed to be increased by water and ice from asteroids, protoplanets and comets.
The atmospheric greenhouse prevented the oceans from freezing when the newly formed sun had only 70% of its current luminosity. When the Earth’s magnetic field was established, it helped prevent the atmosphere from being blown off by the solar wind.
A crust formed when the molten outer layer of the Earth cooled to form a solid. There are two models that propose that the land mass constantly grows to current forms, or, more likely, that it grew rapidly at the beginning of Earth’s history, followed by a long-term stable continental area. The continued loss of heat from inside the Earth helped the continents to form through tectonic plates.
Over periods of hundreds of millions of years, supercontinents came together and then separated. About 750 million years ago, the first known supercontinent Rodinia began to separate.
Later, the continents came together again and formed Pannotia about 600 to 540 million years ago. This happened again and the Pangea supercontinent was formed, but it also split about 180 million years ago.
There are patterns that suggest that ice ages began about 40 million years ago and intensified during the Pleistocene, about 3 million years ago. Many high-latitude regions have gone through repeated cycles of glaciation and thawing, repeating every 40,000 to 100,000 years. The last continental glaciation is believed to have ended 10,000 years ago.
Distance, size and mass
Earth is the third planet from the Sun, at a distance of 1 AU or 147 million km / 91 million miles. It is located in the gold zone, where temperatures are perfect for the existence of liquid water and the evolution of life.
Depending on their current orbital positions, Venus or Mercury are the closest planets to Earth. It has an equatorial radius of 6,371 km / 3,958 mi and a polar radius of 6,356 km / 3,949 mi, which means that it is not completely spherical, but rather bulged at the equator due to rotation.
The Earth is so big that, if it were sanctified, almost 50 moons could fit inside it. The Earth has a mass of about 6.6 sextillion tons and a volume of about 260 billion cubic miles / 1 trillion cubic kilometers. It has the highest mass of all terrestrial planets and the highest density of all planets – 5.51 g / cm³. Earth’s mass composition is mainly composed of iron 32.1%, oxygen 30.1%, silicon 15.1%, magnesium 13.9%, sulfur 2.9%, nickel 1.8%, nickel 1.8 %, calcium 1.5% and aluminum 1.4%. The remaining 1.2% consists of trace amounts of other elements.
Orbit and Rotation
The Earth rotates on its axis once every 23.9 hours. Earth takes 265.25 days to complete a trip around the solar year. In order for calendars to maintain consistency with this orbit, a day is added every 4 years – this is called a leap day – and also a leap year.
The Earth’s orbital speed averages 29.78 km / s (107,208 km / h; 66,616 mph), which is fast enough to cover the diameter of the planet in 7 minutes and the distance from the Moon in 4 hours.
Structure – Geology
The Earth has four main main layers: an inner core in the center, an outer core that surrounds it, mantle and crust.
As it has the highest density of all the planets in the solar system – 5.51 g / cm³ – and a gravity of 9.807 m / s² or 1 g, the Earth’s core is solid. It is made of iron and nickel with about 1,221 kilometers in radius. Core temperatures were estimated at about 5,400 degrees Celsius. This is hotter than the surface of the sun.
Along with the inner core, the Earth also has an outer core, with the crust being the mantle and the thickest layer. It is a viscous mixture of molten rock about 2,900 km thick and has the consistency of caramel.
The outermost layer – the earth’s crust – covers an average depth of 30 km on land. However, at the bottom of the ocean, the crust is thinner and extends for about 5 km from the seabed to the top of the mantle. In a sense, the crust floats on the mantle due to the lower density.
It is not a solid piece, but rather divided into huge tectonic plates. These plates move, driven by the flow of rock in the mantle, which in turn is fed by heat.
The core heats the bottom of the mantle, causing convection, leading to an increase in the warmer material. It takes about 50,000 to 60,000 years for a bubble to move a single kilometer.
Although the hot material rises towards the surface, it is blocked by the crust. The magmatic rock pushes the plates, making them slide slowly.
Over millions of years, the geology of the Earth’s surface has changed dramatically because of this. Where the crust is weaker, magma can make its way and erupt on the surface, forming volcanoes.
Because of the volcanoes, the material creates new land and also pumps gas that contributed a lot to the Earth’s atmosphere.
The Earth’s interior is very hot – comparable to the sun’s surface. Most of the heat has remained since the formation of the Earth. As it gained mass, it began to contract under its own gravity – the grip added heat to the material. Elements like uranium also contribute to the Earth’s heat when atoms decay radioactively.
Another source of heat: dense materials, such as iron and nickel, sank in the center, heating up due to friction.
As such, the core is so hot because of:
- Heat remains since the formation of the Earth
- Gravity compression effect
- Radioactive decay of elements such as uranium
The Earth’s surface is in constant motion. The molten lava rises from the surface and moves into the space that is created. The new rock helps to separate the plates and, as it cools, it becomes part of the crust in constant regeneration.
When oceanic plates meet continental plates, they are forced downward. This creates friction underneath and the pressure forces the melted rock upward to burst into the crust like ash and lava.
Many volcanoes formed in this way, but there is a second type of collision: when two continental plates converge when one plate slides under the other, the lighter mass of the surface pushes and bends upwards, forming mountain chains.
The third type of plate interaction occurs when the plates are at oblique angles to each other. Pressure and friction between surfaces prevents slippage and, when the tension becomes too high, the plates change, sliding along a fault line. Sometimes violent tremors result and widespread destruction of an earthquake.
The Earth’s surface area is about 510 million square kilometers. About 71% of the surface is covered by water and 29% by land.
The water is 3% fresh and 97% salty. Of that 3% fresh water, more than 2% is frozen in layers of ice and glaciers, which means that less than 1% is fresh water found in lakes, rivers and underground.
Regarding the land, the Asian continent covers about 30% of the entire land, having about 60% of the world’s population. The Earth is divided into 7 continents that “move” constantly several centimeters a year. In about 250 million years, about four fundamental scenarios for the formation of the next supercontinent have been hypothesized: Novopangea, Pangea Ultima, Aurica and Amasia.
Novopangea seems the most likely scenario based on current assessments. The Americas would collide with northern Antarctica adrift and then enter Africa-Eurasia already collided.
The highest altitude – elevation – on Earth is Mount Everest, with 8,848 m 29,029 feet above sea level. The lowest point on land is at the Dead Sea – 420 m / 1,377 feet below sea level. The average depth of the global ocean is about 4 km. Most volcanoes are hidden under these oceans. Hawaii’s Mauna Kea is a volcano much higher than Mount Everest, and even the largest mountain range on Earth – four times more than the Andes, Rockies and Himalayas – lies underwater at the bottom of the Arctic and Atlantic oceans.
The shape of the Earth is almost spherical. There is a slight flattening at the poles and a bulge around the equator due to the Earth’s rotation speed. This makes the shape of the Earth roughly an oblate spheroid. The point on the most distant surface of the Earth’s center of mass is the summit of the equatorial volcano Chimborazo, in Ecuador.
The Earth’s atmosphere is a gas layer above the crust. It is not solid and therefore disappears with height. The line between the Earth’s atmosphere and space is established 100 km / 62 miles above. It is called the Kármán line. Technically, anyone who goes beyond that is an “astronaut”.
The atmosphere in volume is about 78% nitrogen, 21% oxygen, 1% argon and the rest a variety of trace gases. Water vapor is also present, almost all below a height of about 8 to 15 km / 4.9 – 9 mi.
This part of the atmosphere is the warmest part at the bottom, creating convection in the air, which in turn creates upward air currents. They carry water, forming clouds, which is why we have time.
The ozone layer is located at an altitude of 25 km / 15.5 mi on average. This is an oxygen molecule that absorbs solar ultraviolet light very well. This type of light is dangerous for biological molecules, so the ozone layer is essential for our protection and survival.
The Earth’s atmosphere can be divided into 6 main layers:
(1) Troposphere – The lowest, starting at ground level and extending upwards to about 10 km / 6.2 miles. Most of the time occurs here and most of the clouds are present.
(2) Stratosphere – It extends from the top of the troposphere to about 50 km / 31 mi above the ground. This is where the ozone layer is present. Unlike the troposphere, it gets warmer upward, which means a lack of turbulence favorable to commercial jet aircraft travel.
(3) Mesosphere – It extends upwards to a height of about 85 km / 53 miles above the planet. Most meteors burn in the mesosphere and, unlike the stratosphere, the temperature drops again with the maximum temperature reaching -90 degrees Celsius / -130 degrees Fahrenheit. The air here is too thin to breathe and the pressure is well below 1% of the pressure at sea level.
(4) Thermosphere – A layer with very rare air and high energy X-rays and radiation from the Sun being present, but absorbed by the thermosphere. This increases temperatures considerably and most satellites orbit the Earth in this layer. Dawns, northern and southern lights, occur in the thermosphere. The top of the thermosphere varies between 500-1,000 km / 311-621 mi above the ground.
(5) Exosphere – Considered the final frontier of the Earth’s gaseous envelope. The air here is extremely thin and leaks into space. The top varies again: 100,000-190,000 km / 62,000-120,000 mi above the Earth’s surface. The last value is halfway to the Moon.
(6) Ionosphere – It is not a separate layer like the previous ones. It is a series of regions in parts of the mesosphere and thermosphere, where the high-energy radiation from the Sun releases the electrons from its atoms and parent molecules. The electrically charged atoms and molecules are called ions, giving this region some special properties.
The Earth’s outer core is made of liquid metal that conducts electricity. The liquid convects and this movement generates magnetic fields. Earth’s rotation helps to organize this movement into huge cylindrical papers that align with the Earth’s axis.
This generates a magnetic field similar to a bar magnet, with a magnetic north pole and a south pole. This field surrounds the Earth and deflects most of the charged particles from the solar wind. Without this geomagnetic field, the solar wind directly hit the Earth’s atmosphere, corroding the air.
Mars does not have a strong magnetic field, and it is believed that, because of this, its atmosphere is practically vanquished.
Some solar particles from the wind are captured by the Earth’s magnetic field and channeled into the atmosphere. There, they are hit by air molecules about 150 km / 93.2 mi above. This energizes the molecules, which respond by emitting light in different colors. This glow is called aurora.
The auroras happen near the geomagnetic poles, in the extreme north and south. They form ribbons and leaves, depending on the shape of the magnetic field.
The analysis revealed that a magnetic inversion occurs once every 40,000 years, on average. When that happens, the compass needles are likely to point in many different directions for a few centuries while the exchange is being made. After that, the south will become north and vice versa.
The Earth orbits the Sun with a pole constantly tilted towards it. This tilt results in how much light reaches a certain point on the Earth’s surface. The Earth’s axis is tilted towards the ecliptic of the Sun at approximately 23.4 degrees. This is responsible for the Earth’s seasonal changes and the daytime cycle.
Currently, Earth is the only planet known to have water on the surface. Referred to as the “Blue Planet”, the Earth’s hydrosphere consists mainly of oceans, inland seas, lakes, rivers and groundwater to a depth of 2,000 m / 6,600 feet.
The deepest underwater location is the Challenger Deep of the Mariana Trench, in the Pacific Ocean, with a depth of 10,911 m / 35,799 feet. The mass of the oceans represents about 1/4400 of the total mass of the Earth.
Habitability – Biosphere
Life forms inhabit ecosystems, the total of which is sometimes said to form a biosphere. It is speculated that the evolution of the biosphere started about 3.5 Gya. The biosphere is divided into biomes, inhabited by widely similar plants and animals. In 2016, scientists reported identifying a set of 335 genes from the last universal common ancestor (LUCA), of all organisms that live on Earth.
The origin of life on Earth is still disputed. There are two major permanent theories that suggest that life developed here from chemical reactions or that life was brought here by a process called panspermia.
Chemical reactions led to the first self-replicating molecules about 4 billion years ago. Half a billion years later, the last common ancestor of all current life emerged.
Photosynthesis allowed the sun’s energy to be directly harvested by life forms. The resulting molecular oxygen accumulated in the atmosphere and due to the interaction with ultraviolet solar radiation formed a protective layer of ozone in the upper atmosphere.
Smaller cells incorporated into larger cells and resulted in the development of complex cells called eukaryotes. Among the earliest fossil evidence for life are microbial fossils found in 3.48 billion-year-old sandstone in Western Australia.
The panspermia theory suggests that life exists throughout the Universe, distributed by space dust, meteoroids, asteroids, comets and also spaceships that carry unintentional contamination by microorganisms.
Basically, organisms like extremophiles can get trapped in debris ejected into space after collisions between planets and other small objects. These organisms can travel inactive until they reach suitable planets that host suitable conditions for life to thrive and evolve.
About 80% of the Earth’s oceans have not been mapped and about 65% of the Earth remains unexplored. There are no maps that can accurately depict the Earth. The best known model – the Mercator – is defective because the linear scale increases with latitude.
This distorts the size of geographic objects away from the equator and conveys a distorted perception of the planet’s overall geometry.
Probably the most accurate map is the AuthaGraph World Map, because it folds the Earth into a three-dimensional globe.
The Earth has a natural satellite, the Moon, and several other artificial satellites, such as asteroids or large rocks captured by Earth’s gravity. They are only temporarily trapped for months or even years before returning to an orbit around the Sun.
The Moon is believed to have formed after a collision billions of years ago. A large piece of rock hit the Earth and displaced part of the Earth’s interior. The resulting pieces came together and formed our Moon. This is at least the most widespread theory, the research continues.
Since ancient times, mankind has used the moon to measure the passage of months due to its phases of change from the full moon to the new moon and vice versa.
It is called the moon because it was used to measure months. The word moon can be attributed to the Old English word “mōna”. He shares his origin with the Latin words “metri”, which means to measure, and “mensis”, which means month.
The Earth’s moon is the fifth largest of all moons in the solar system. The Moon is quite large when compared to Earth, being a quarter of the diameter of the planet. This is the largest proportion, much greater than that of any other moon orbiting a planet.
The Moon has a diameter of about 3,470 km / 2,156 mi and, on average, is 380,000 km / 236,121 mi away from Earth. This means that 30 of Earth could fit together to cover the distance. The moon has a radius of 1,079 mi / 1,737 km. It is not even wider than the United States.
The Moon has a structure similar to that of the Earth: an inner core of solid iron, an outer liquid core, a thick mantle and a crust of lighter materials at the top.
The core is believed to have about 350 km / 217 radius, with hot temperatures present, but not as high as in the Earth’s core. The lower mantle may be a thick fluid, but, unlike the Earth’s mantle, the upper part is solid.
The Moon is locked on Earth, which means that it always shows only one side of its surface to us. The side we see called the near side is divided into two distinct types of regions:
– Highlands, with many craters
– Maria (Latin for seas), which are darker and softer.
The Moon can also act as a shield against space objects. The highlands have been full of impacts over the ages of asteroid and comet collisions. The rocks in these regions date back to around 4 billion years, almost as old as the Moon itself.
The maria region does not have nearly as many craters. They are younger, looking about 3.5 billion years old. The maria are made of darker basalt material, which means that they probably formed from lava flooding older areas.
The dark side of the moon referred to as the “opposite side” has remained a mystery to us for most of our existence. In 1959, the Soviet Union flew the Luna 3 space probe around the moon, photographing the other side.
Expectations were that the opposite side would look like the next side. However, the opposite side was very different, presenting almost no maria. The crust on the opposite side is thicker than on the near side.
The only explanation for this has to do with how the moon was formed. The best known theory is the Giant Impact hypothesis. A Mars-sized planet hit young Earth, not with frontal impact, but with a grazing collision.
The material from both planets was exploded in space and later formed the Moon. Although similar to Earth in composition, some rocks show a peculiar proportion of different types of oxygen atoms called isotopes, possibly being a piece of strong evidence for this theory. In addition, the Moon was probably closer to Earth and suffered from high Earth temperatures at the time, while the other side later suffered during the late heavy bombardment.
There is a possibility that the moon has water in it. Deep craters near the Moon’s poles have floors that never see sunlight. Comet impacts can distribute water across the moon, most of which are destroyed by sunlight, however, they can be collected in these dark craters.
In fact, water has already been discovered on the Moon, but the water at the poles remains somewhat hypothetical, but very likely.
The Moon helps our planet to be more habitable, moderating the Earth’s oscillation on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humanity for thousands of years.
The Moon used to have active volcanoes, but now they are dormant. It also has a thin and weak atmosphere, called the exosphere.
The Earth, along with the Solar System, is located in the Milky Way and orbits about 28,000 light-years from its center. It is about 20 light years above the galactic plane in the Orion Arm.
The Earth is constantly gaining and losing mass with the Moon moving away from us an inch every year. Humanity must continue to strive and colonize other planets for survival, as nothing lasts forever, especially finite materials.
In a billion years, solar luminosity will increase by around 10%, causing the atmosphere to become a “wet greenhouse”, resulting in uncontrolled evaporation from the oceans. In about 2-3 billion years, the Earth’s magnetic dynamo may cease. Future missions for the colonization of the Moon are being prepared by several nations, as well as other important missions for other worlds.
We hope that this will finally end the Earth’s flat conspiracy and the Moon’s flight conspiracy, and perhaps humanity will realize its true capacity and raison d’être, with the hopeful success of future space missions.
Did you know?
- If the entire surface of the earth’s crust were at the same elevation, the resulting ocean depth would be 2.7 km / 1.68 mi.
- The average salinity of Earth’s oceans is about 35 grams of salt per kilogram of seawater – 3.5% salt.
- Earth’s continents move at the same rate as human nails grow.
- The Moon and Earth orbit a common center every 27.32 days in relation to the background stars.
- Earth’s gravitational sphere of influence has a radius of about 1.5 million km (930,000 miles). This is the maximum distance at which the Earth’s gravitational influence is stronger than the Sun and the most distant planets. The objects must orbit the Earth within that radius, or they can be released by the gravitational disturbance of the Sun.
- If space were a vacuum, the Earth’s magnetic field would extend to infinity.
- The Moon orbits the Earth approximately as fast as a rifle bullet.
- The Earth is gradually rotating more slowly at about 17 milliseconds over 1,000 years. The Moon contributes to this and, as the Earth slows down, the Moon creeps.
- The Earth’s magnetic field and its interaction with the solar wind also produce Van Allen belts, a pair of ring-shaped rings of ionized gas (or plasma) trapped in orbit around the Earth.
- Earth is traveling through space at approximately 67,000 miles at 107,826 kilometers per hour.
- The Earth has far fewer craters than the surface of most other planets. This is because the planet has many volcanoes and earthquakes that cause the ups and downs of the surface to sink or wear out over time.
- About 1,300,000 of Earth can fit in the Sun.
- The Sun will eventually turn into a red giant and swallow the Earth.
- The first photo taken of Earth from space was taken by the Apollo 17 team. The original image showed the Earth upside down. The image was later edited.
- Se 7 bilhões de pessoas pularem ao mesmo tempo, ocorrerá um terremoto de magnitude 4 a 8.
- A poluição luminosa impede que um terço da população da Terra veja a Via Láctea no céu noturno.
- A Lua foi visitada por mais de 100 sondas espaciais.
- As rochas trazidas da Lua pela equipe Apollo 11 ainda são estudadas até hoje.
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