Earth
| Average: | 15 C | |
| Minimum: | -89.2 C | |
|---|---|---|
| Characteristics of the atmosphere | ||
| Atmospheric pressure | 101 325 Pa | |
| Density in soil | 1.217 kg / m 3 | |
| Total mass | 5.1 10 18kg | |
| Scale height | 8.5 km | |
| Molecular weight average | 28.97 g / mol | |
| Nitrogen N 2 | 78.084 % dry volume | |
| Oxygen O 2 | 20.946 % dry volume | |
| Argon Ar | 0.9340 % dry volume | |
| Carbon dioxide CO 2 | 390 ppm dry volume | |
| Neon Do | 18.18 ppm dry volume | |
| Helium He | 5.24 ppm dry volume | |
| Methane CH 4 | 1.79 ppm dry volume | |
| Krypton Kr | 1.14 ppm dry volume | |
| Hydrogen H 2 | 550 ppb dry volume | |
| Nitrous oxide N 2 O | 300 ppb dry volume | |
| Carbon monoxide CO | 100 ppb dry volume | |
| Xenon Xe | 90 ppb dry volume | |
| Ozone O 3 | 0-70 ppb dry volume | |
| Nitrogen dioxide NO 2 | 20 ppb dry volume | |
| Iodine I | 10 ppb dry volume | |
| Water vapor H 2 O | ~ 0.4 % overall volume ~ Jan-Apr % at the surface (typical values) | |
| History | ||
| Discovered by | Nature planetary approached by the Pythagorean school ( Philolaos of Croton ). Attested to the Hellenistic period ( Aristarchus of Samos and Eratosthenes ). | |
| Discovered | V centuryBC. AD third century BC. AD | |
The Earth is the third planet of the solar system in order of increasing distance from the Sun and the fourth by size and weight increasing. It is the largest and most massive of the four terrestrial planets , the other three being Mercury , Venus and March.
She has a natural satellite , the Moon , which is the fifth largest satellite in the solar system.
It has a powerful magnetic field that points to the poles particles carried by the charged solar wind , including causing auroras and generating radiation belts concentric around the world resulting from the accumulation of these particles trapped in the field Earth's magnetic. The magnetosphere acts as a shield protecting our planet in the solar wind.
Commonly called in French Earth, Planet Earth, Blue Planet or World is a planet to coat active, with an atmosphere containing the oxygen , covered with water liquid.
Summary |
The globe turns continuously over periods of several hundred million years. Continent or supercontinent formed and then divide. Thus there are about 750 million years, the oldest known supercontinent, Rodinia , began to disintegrate. Continents between which it had divided itself recombinrent later to form Pannotia there 650-540 million years, then finally Pangaea , the Permian , which breaks up there are 180 million years.
In 1989, the American researcher Joe Kirschvink hypothesized that one (or series) to large (s) Ice Age (s) took place there 750 and 580 million years, during the Neoproterozoic , and covered the planet with a layer of ice. This assumption has been named Snowball Earth ("snowball Earth"), and is of particular interest because it precedes the Cambrian explosion , when multicellular life forms began to proliferate.
Following the Cambrian explosion, there are 535 million years, 5 mass extinctions occurred. The last major extinction date of 65 million years ago, when a suspected meteorite collided with Earth, exterminating the dinosaurs and other large reptiles, sparing of smaller animals such as mammals, birds, lizards, etc.. Within 65 million years that have elapsed since mammals have diversified, the human species had developed over two million years. Periodic changes in the long term the orbit of the Earth, caused by the gravitational influence of other stars , are probably one of the causes of glaciations that covered much of the planet. Following the last glaciation, the development of agriculture and, later, civilization , allowed humans to modify the surface of the Earth in a short period of time, as no other species on earth before him, affecting nature like other life forms.
Composition and Structure
The Earth is a terrestrial planet , that is to say, a planet mostly rock with core metal , unlike the gas giants like Jupiter , made mostly of gas lighter ( hydrogen and helium ).
This is the largest of the four terrestrial planets of the solar system , either in size or mass. Of these four planets, Earth also has the density highest overall, the highest surface gravity and the strongest magnetic field overall. However, several terrestrial planets larger than Earth have been discovered outside the solar system, including the extrasolar planet Gliese 581 c , which has a diameter 50% larger than Earth. Several missions are under way or planned, to discover new planets similar to Earth, called exoterres.
The outer surface of the Earth is divided into several rigid segments, or tectonic plates that move slowly on the surface over a period of several million years. About 71% of the surface is covered with oceans of salt water , the remaining 29% consisting of continents and islands. The water liquid, necessary for life as we know, is very abundant on Earth, and no other planet has been discovered with the bodies of liquid water ( lakes , seas , oceans) on its surface.
Chemical composition
The mass of the Earth is approximately 5.98 10 24 kg. It is composed primarily of iron (32.1% ) of oxygen (30.1%) of silicon (15.1%) of magnesium (19.9%) of sulfur (2.9 %) of nickel (1.8%) of calcium (1.5%) and aluminum (1.4%), the remaining 1.2% consisting of small traces of other elements. The most dense tend to concentrate at the center of the Earth (the phenomenon of planetary differentiation ), it is believed that the heart of the Earth is composed mostly of iron (88.8%), with a smaller amount of nickel ( 5.8%) of sulfur (4.5%) and less than 1% other elements.
The geochemist FW Clarke calculated that 47% (by weight) of the crust is made of oxygen, present mainly as oxides, which are the main oxides of silicon , aluminum , iron , calcium , magnesium , potassium and sodium. The silica is the major constituent of the crust, as pyroxenoid , the most common minerals of igneous and metamorphic. A synthesis based on analysis of 1672 rock types, Clarke won the percentages in the table below.
| Oxides | Percentage (Weight) |
|---|---|
| Silica (SiO 2) | 59,71 |
| Aluminum oxide (Al 2 O 3) | 15,41 |
| Calcium oxide (CaO) | 4,90 |
| Magnesium oxide (MgO) | 4,36 |
| Sodium oxide (Na 2 O) | 3,55 |
| Oxide of iron (II) (FeO) | 3,52 |
| Oxide, potassium (K 2 O) | 2,80 |
| Iron oxide (III) (Fe 2 O 3) | 2,63 |
| Water (H 2 O) | 1,52 |
| Titanium dioxide (TiO 2) | 0,60 |
| Phosphorus pentoxide (P 2 O 5) | 0,22 |
| Total | 99,22 |
Geological structure
1. continental crust
2. oceanic crust
3. upper mantle
4. lower mantle,
5. outer core
6. inner core,
A: Moho ,
B: Gutenberg Discontinuity ,
C: Lehmann discontinuity.
Earth consists of several inner layers identifiable roughly concentric: the crust (oceanic or continental), the mantle above the lower mantle, and core external and internal. The lithosphere consists of crust and upper mantle surface area. The asthenosphere is the deepest area of the upper mantle (below the lithosphere).
The crust is relatively young compared to the Earth itself. During the relatively short period of about 500 million years during which the erosion and tectonic processes have destroyed and recreated, the most superficial layers of the Earth, almost all traces of the geological history of its surface ( impact craters , for example) have disappeared.
Over 99% of the earth's surface would be less than 2 billion years.
The internal structure of the Earth is known by studying the propagation of seismic waves from a source to various points on the surface.
The speed of a seismic wave changes actually quite abruptly in passing between two layers of different composition or mineral phase. These limits are sometimes given specific names, such as the Moho , the discontinuity of Lehmann or the Gutenberg discontinuity.
The constitution of the Earth due to its formation by accretion of meteorites , which produced a stratification phase fluid density decreases from the inner layers to outer layers.
Much of the internal heat of the Earth (87%) is produced by the radioactivity of the rocks that form the crust: radioactivity produced by the natural decay of uranium from thorium and potassium.
Tectonic plates
According to the theory of plate tectonics , the upper part of the interior of the Earth is composed of two layers: the lithosphere comprising the crust and the solid mantle. Below the lithosphere lies the asthenosphere , which forms the heart of the mantle. The asthenosphere is solid extremely hot and may creep.
The lithosphere is mainly based on the asthenosphere and is broken into pieces that are called tectonic plates. These plates are rigid segments which move in relationship with others in three ways: convergence, divergence, and transcurrent. Thus were created the earthquakes , the activity volcano and the mountains.
Some plates have a smaller area as the Indian Plate , the Arabian Plate , the Caribbean plate and the Nazca plate to the west coast of South America. The Australian plate has merged somewhat with the Indian plate there are 50 to 55 million years. Plates the fastest in their movement are the oceanic plates, moving about 70 Millimeters mm / year. In contrast, the slower the plate is the Eurasian Plate, progressing about 21 Millimeters mm / year.
The main tectonic plates are:
| Map | Name Plate | Total area in (10 6 km 2) | Covers |
|---|---|---|---|
 | |||
| African Plate | 61,3 | Africa | |
| Antarctic Plate | 60,9 | Antarctica | |
| Australian plate | 47,2 | Australia | |
| Eurasian plate | 67,8 | Asia and Europe | |
| North American plate | 75,9 | North America and North-Eastern Siberia | |
| South American plate | 43,6 | South America | |
| Pacific plate | 103,3 | Pacific Ocean |
Atmosphere
The Earth is surrounded by a gaseous envelope that holds by gravitational attraction: the atmosphere. The Earth's atmosphere is intermediate between the very thick, Venus, and the very tenuous, Mars: the pressure at sea level is an average of 101 325 Pa , 1 atm by definition. In addition to a variable proportion of water vapor between 0 and 4%, it consists of 78.09% of nitrogen , 20.95% of oxygen , 0.93% of argon and 0.039% 9% dioxide carbon , and various other gases. This high rate of oxygen is unique in the solar system, and results from the photosynthetic organisms chlorophyll : the Earth is, indeed, the only planet known to harbor life , a probable consequence of the fact that it also only star known to have conditions of temperature and pressure allows the existence of liquid water on the surface.
This atmosphere gives the world a blue reflection from the space , hence its nickname of "Blue Planet". The constitution and density of the atmosphere are such that incident light from the Sun and the light reflected by the continents and seas are diffracted , giving its color to the sky , and reflection, to bodies of water.
Constitution
The envelope, whose total mass is about 5 10 18 kg (one millionth of the mass of the Earth), is contained to 99% in the first 30 kilometers (50% in the first 5 kilometers).
The lower atmosphere (from sea level to approximately 45 km) is composed of gas "permanent" gases whose proportions remain constant, and gas concentration varies with altitude.
- The dinitrogen , the oxygen and argon are, by volume, 99.997% of the permanent gases (see table above), the vertical mixing of air keeps a constant distribution at all levels, even for the lightest gases, such as the helium or hydrogen.
- The gas concentration variable are essentially vapor water H 2 O and to a lesser extent carbon dioxide CO 2,sulfur dioxide SO 2 and ozone O 3.
The atmosphere can be considered at a given moment, as a thermodynamic mixture of dry air and water vapor.
Liquid particles, solid or mixed, suspended in the atmosphere are the atmospheric aerosol.
These particles play a crucial role in the phenomena of condensation (clouds) and formation of crystals of ice , as well as various physical and chemical processes in the atmosphere. Their concentration varies by several powers of 10 (several orders of magnitude) depending on location and time, in high concentrations, they are a factor of pollution. The particles fall into:
- Aitken particles: 1 nm <d <0.1 microns
- coarse: 0.1 microns <d <5 microns
- giant particles: 5 microns <d <50 microns around
The atmosphere attenuates significantly the solar radiation received at ground level, depending on the extent of cloud cover, the soil receives 68% to 28% (or less) of solar radiation reaching the atmosphere, a solar flux initial 1370 W / m 2.
Structure of the atmosphere
The chemical composition of the atmosphere, temperature, or phenomena that are observed show sharp discontinuities when the altitude increases. These discontinuities correspond to homogeneous layers whose properties are changing continuously, it is (by increasing altitude):
- the troposphere
- the stratosphere
- the mesosphere
- the thermosphere
- the exosphere
The boundaries of these layers (altitude variable) have received special designations: tropopause , stratopause , mesopause and thermopause.
Physical and astronomical data
Beauty of the Earth
The shape of the Earth is modeled by an ellipsoid , slightly flattened at the poles, and more specifically by the geoid. The approximate diameter of reference is 12 742 km.
The Earth's rotation creates a slight equatorial bulge, so that the diameter at the equator is 43 km longer than the polar diameter (the North Pole to South Pole). The largest irregularities of the soil of the Earth are the Everest (8848 m above sea level) and the Mariana Trench (11 500 m below sea level). By cons, because of the flattening, the object is farthest from the heart of the Earth is in fact the volcano Chimborazo in Ecuador.
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The design of the spherical Earth dates back to ancient Greece , around the fifth century BC. AD , and more specifically to the Pythagoreans. We find this conception in Parmenides , Plato and Aristotle. It relies on the fact that during lunar eclipses, the shadow of the Earth is spherical, and the fact that the constellations vary when one moves from north to south . In the third century BC. BC, Eratosthenes gave an estimate of the radius of the earth that we suppose very close to reality, and Posidonius , in the I centuryBC. AD. Around the same time, Cleomedes definitions for equator, tropics, Arctic and Antarctic to. Taking these notions, the geographer Ptolemy gives the second century of geographic information that were used until the Renaissance.
The Muslim civilization kept the knowledge of a spherical Earth and the ninth century , Caliph Al-Mamun at Baghdad , was able to make a part of a meridian, leading to a good approximation of the circumference Earth. Even more explicit is a figure like Abu Hanifa , founder of one of the four schools of Muslim jurisprudence , had faith in the curvature of the Earth . In the Christian world, this idea was sometimes questioned, for example the sixth century by Cosmas Indicopleustes. Indeed, the Fathers of the Church could not reconcile the worldview ball of Aristotle consists of two polar and two temperate zones, separated by an impassable torrid zone, with the universality of Christ's message, this message can not achieve hypothetical inhabitants of the antipodes. Until the twelfth century , so we endeavored to represent the world in symbolic form , but of philosophers or religious as Isidore of Seville , Venerable Bede , John Scotus Eriugena , Gerbert d'Aurillac , Thomas Aquinas , Albert Greater or Roger Bacon had very well integrated representation spherical. Around 1150, the book imagines mundi, whose author is presumed to Honorius of Autun , describes the universe in a more mythological than scientific, but in which Earth is a sphere of about 35 000 km in circumference. Charlemagne is also shown some illuminations in his hand as a representation of a small terrestrial globe surmounted by a cross.
Travel narratives of missionaries , of Marco Polo and explorer John Mandeville (with its Book of Wonders of the World ) diffused into society's image of a spherical earth, which could theoretically be a "circumnavigation". The Imago Mundi of Cardinal Pierre d'Ailly was holding the spherical representation. We know that Columbus was influenced by the Book of Wonders of Mandeville, and he possessed a copy of the Imago Mundi and commented extensively annotated by him. Greatly underestimating the Earth's radius and devising an Asian continent three times more extended eastward than it actually is, Columbus was able to reasonably consider the possibility of reaching India by the West. A more precise knowledge of distances would have discouraged any attempt to cross the ocean to the means of the time.
The voyages of the Portuguese early in the fifteenth century to reach the Indies around Africa, the rediscovery of Greek texts in the Renaissance , especially the Geography of Ptolemy , dissemination through print have also contributed to spread modern representations of the Earth, with North up the cards, meridians , the parallel , the equator and the two tropics. The oldest terrestrial globe is made known by Martin Behaim the late fifteenth century, shortly before Vasco da Gama , Christopher Columbus or Magellan begin their journeys. It shows Europe, Africa and Asia, but of course neither the Americas or Oceania.
Mercator has in drawing his maps, mentioned and drawn a huge southern continent Terra Australis Incognita (Southern Land (South) unknown). This "unknown southern land" was drawn to the South because Mercator thought, following the Greeks, that without this weight was not balanced the Earth. The thoughts and work in geography (transcripts map , Mercator projection ) in the sixteenth century have helped to change the knowledge of the Earth.
This is the eighteenth century that the flattening of the poles is known, with expeditions to Peru and Lapland.
Orbital data
The semi-major axis of its orbit defines the astronomical unit , which is 149 597 870 700 3 m whichever is currently the most accurate . Its distance from the Sun is between 0.9833 and 1.0167 AU.
Day, season and year
The Earth rotates on itself in a sidereal day to 11:56 p.m., and around the sun in one year about 365 days. Its axis of rotation is tilted relative to the ecliptic , which produces the alternation of four seasons on the Earth's surface.
The periodicity of the seasons as she, through the tropical year , slightly shorter than the sidereal year of the annual value of the precession of the axis of rotation. The period of transition points of the ellipse of the orbit as the perihelion , is the anomalistic year , slightly longer than the sidereal year of the annual value of the recession of the perihelion.
Finally, in astronomical calculations, it uses the Julian year worth exactly 365.25 days.
Acceleration of gravity
The acceleration of gravity (or "gravity field") varies slightly from the surface of the earth for three reasons:
- It depends on the altitude, acceleration is inversely proportional to the square of the distance between the center of gravity of the Earth and the point where it is measured.
- The Earth is not perfectly spherical but slightly flattened at the poles, gravity is greater at the poles, for the same reason.
- The Earth rotates on itself, so an object at the equator is a little lighter (see centrifugal force ).
Other factors may impact minimally on the local gravity field (see Gravity ):
The acceleration of gravity can be calculated as follows:
- g = 9.780318 [m / s 2] (1 + 5.3024 10 -3 sin 2 (L) + 5.9 10 -6 sin 2 (2 L) - 3.15 10 -7 h)
- where:
- L = latitude
- h = altitude in meters.
At sea level, h = 0 m:
- at the equator (L = 0 ): g = 9.7803 m / s
- at latitude (L = 45 ): g = 9.8063 m / s
- the poles (L = 90 ): g = 9.8322 m / s
The force of gravity thus encompasses both the gravity and centrifugal force, that it comes from the rotation. He remains a force from the rotation of the Earth that can not be included in gravity: the Coriolis force , which depends on the speed of the object on Earth. Gravity has been defined to be independent of the motion of the object on Earth.
Earth satellites
The Moon is a natural satellite , located about 380,500 kilometers from Earth. Relatively large, its diameter is about one quarter that of Earth. Within the solar system is one of the largest moons (after Ganymede , Titan , Callisto and Io ), the largest planet of non-carbonated. It is relatively close to the size of the planet Mercury. The natural satellites orbiting other planets are commonly called "moons" in reference to the Moon from Earth.
The gravitational attraction between Earth and the Moon cause the tides on Earth. The same effect occurs on the Moon, by ensuring that its rotation period is identical to the time it takes to orbit the Earth, presenting always the same face toward Earth. By orbiting the Earth, different parts of the visible side of the Moon is illuminated by the Sun, causing the moon phases.
Because the torque of the tides, the moon moves away from Earth at a rate of about 38 mm per year, also producing the elongation of the Earth day by 23 microseconds per year. Over several million years, the cumulative effect of these small changes produced significant changes. During the period from Devonian , approximately 410 million years ago today, there were 400 days in a year, each day during 21.8 hours.
View of the Earth, the Moon is far enough away to have the same apparent size as the Sun. The angular size of the two bodies is almost equal because even if the diameter of the Sun is 400 times larger than the Moon, it is 400 times closer to Earth than the latter. This still allows just the eclipse total on Earth.
Accepted theory about the origins of the Moon is that of a giant impact between a planetoid the size of Mars, known as Theia , and the newly formed Earth. This hypothesis partly explains the fact that the composition of the moon looks especially that of the crust.
Earth also has two co-orbital satellites , the asteroid (3753) Cruithne and 2002 AA 29 , as well as quasi-satellites , 2003 YN 107 (until 2006), 2001 GO 2 and (164207) 2004 GU 9.
Position in the Universe
We now know that Earth rotates on itself and around the Sun. But this formulation implies a number of principles related to the development of astronomy and physics, and have taken several centuries to assert itself.
The position of the Earth in the Universe was the source of much debate between centuries philosophers and religious scholars of all persuasions. For a long time the Earth was considered the center of the universe, view taken by Aristotle or Ptolemy. This theory, the geocentric theory , claimed that all celestial objects, Sun, Moon, planets and stars ( stars ) orbiting around the Earth. The heliocentric this Earth orbits the Sun, the Moon, Earth's natural satellite. Championed by Aristarchus of Samos , this theory was forgotten until Nicolas Copernicus rediscovered and fully in his treatise published in 1543 : the Revolutions of the Heavenly Orbs libri VI.) Tycho Brahe proposed a system in which the sun revolved around the Earth and other planets around the Sun. The idea of Copernicus was supported by Johannes Kepler and Galileo. Keplerian ellipses did much to tables allowing unprecedented precision, and explaining the variations in latitude of the planets relative to the plane of the ecliptic. At the end of the seventeenth, Isaac Newton introduced his mechanics, which explains the movement of the Earth by applying forces on it, putting themselves in a space that he assumed absolute. We then had a mechanical explanation of planetary motion, consistent with the heliocentric theory.
In the current modeling of Newtonian mechanics , it no longer retains the idea of absolute space. The position of objects is defined relative to a reference, a concept already present in Galileo, Huygens and Newton and Newtonian mechanics assumes the existence of a privileged class of reference, the Galilean. In an inertial frame, the movements of planets can be explained only by gravitational forces.
In common parlance, when nothing is specified, it refers to an inertial frame. This is due to the privileged status of Galilean mechanics. That is why the phrase "the Earth rotates" is not considered inaccurate in physics.
It should be noted that under the principle of relativity , including the release of Galilee, the effects induced by the motion of the Earth are extremely low for those who are there. That is why the ancients were able to assume the earth stationary.
More generally, astrophysicists now believe not only that the universe has no center, but even from any vantage point. This conjecture is called the Copernican principle , since the name of Copernicus is associated with the end of the vision of Earth as the center of the universe.
Earth Day
The Earth Day takes place April 22, 1970. It marks the creation of the green movement.
Notes
- The Blue Marble , taken by the crew of Apollo 17 December 7, 1972. The year 2009 marks the 50th anniversary of the first color photograph to have been sent to the area on 1 December ( 1959 Science ).
- The Earth is the only planet orbiting the Sun that is not equipped with a universal name for all languages from Greek or Roman mythology. In French, however, "Earth" is similar to Terra , the Roman goddess of the earth, Gaia in Greek.
- Ozone is a variant of molecular oxygen, O 3.
- The rotation of Venus is retrograde, the tilt of its axis is greater than 90. One could say that its axis is tilted "-2.64 ".
- It actually uses as a basis for its calculation the distance from Alexandria to Syene in stages , the length of the "stage" being the approximate time and distance from Alexandria to Syene could not then be assessed by a period camel walk (Ian Stewart and Jack Cohen The Science of Discworld)
- Augustine of Hippo issues such doubts on the possibility that the Antipodes were inhabited, which shows that the concept was well accepted antipodes.
References
- Temperature measured at El Azizia , Libya , September 13, 1922: (in) Global Measured Extremes of Temperature and Precipitation , National Climatic Data Center . Posted August 20, 2008
- Temperature measured July 21, 1983 at Vostok , Antarctica (ru) Budretsky, AB, "New absolute minimum of air temperature", in Bulletin of the Soviet Antarctic Expedition, Gidrometeoizdat, Leningrad , No. 105, 1984 [ Full text ]
- Who Originated The concept of snowball earth?
- weight percentage
- (en) David R. Williams, " Mercury Fact Sheet , "NASA, National Space Science Data Center., November 2007
- (en) David R. Williams, " Venus Fact Sheet , "NASA, National Space Science Data Center., April 2005
- (en) David R. Williams, " Earth Fact Sheet , "NASA, National Space Science Data Center., April 2007
- (en) David R. Williams, " March Fact Sheet , "NASA, National Space Science Data Center., November 2007
- see for example, Vitruvius , De Architectura, Book IX, ch. VII, trans. Coignard (1673): "I have spoken here of the constellations whose figures were formed into heaven by the divine spirit who is author of Nature, and the philosopher Democritus designated them, I mean only those rise and lie on our horizon. For all the same as those in the north, and which, by their course around the North Pole, not lie down point and never go underground, and there are others under the ground running as around the southern pole, always remaining hidden without ever getting up on the earth, which makes it does not know what their faces, as is proved by the star called Canopus , we know only by the ratio of merchant have traveled to the ends of Egypt, and to land that are at the end of the world. "
- Muhammad Hamidullah. Islam and its original scientific impulse, Third World, 1982, vol. 23, No. 92, pp. 789: "... Finally, Imam Abu Hanifah (d. 767) knew that the earth was spherical ... "
- (en) IAU WG is NSFA - August 10, 2009 "Current Best Estimates"
See also
Related Articles
- Current designs
- Geography
- Earth Science and the Universe
- Old ideas
- Different models
External Links
- (En) GoManips, movements of the Earth, site CNRS Sagascience
- (En) Observe and interact with the Earth 3D : See day and night polar
- (En) Characteristics of Earth's website IMCCE
- (En) On-system-solaire.net
- (En) astrosurf.com
- (En) maps and statistical information
- (En) geology courses online
- (In) search engine coordinates
- (En) Software Google Earth
- (En) video comparing the size of Earth to other planets
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