The Ground , is the third Planet the most brought closer to the Sun, as well as largest of telluric planets, in diameter just like in Masse. It can be named " Terre" , " Terre" planet; , " Gaïa ", " Monde" or " Planet bleue".
Habitat of several million species, including the human , the Earth is the only place known in the Univers to shelter the life. The planet was formed there is approximately 4,57 billion years, and the life appeared there on its surface in the space of a billion years. Since this time, the Biosphère of the Earth largely modified the atmosphere and other abiotic conditions. Oxygenic photosynthesis evolved/moved 2,7 billion years of today, forming the atmosphere of Oxygène and Azote which exists today. This change allowed the proliferation of aerobic organizations just like the formation of the Couche of ozone which, with the Magnetic field of the Earth, blocks radiations coming from space, thus allowing the life on ground.
The external surface of the Earth is divided into several rigid segments, or Tectonic plates, which migrates gradually on surface over one duration of several million years. Approximately 71% of surface east covered with Ocean S of salt water, the consistent remainder in Unintermitting S and island S. water liquid, necessary for form of life such as we know it, are present on the Earth, and no another planet was still discovered with water on its surface. The interior of the Earth is composed of a layer of magma, a external core liquid which generates the magnetic field, and a core interns made up of Fer.
The Earth interacts with objects of space, including the Sun and the the Moon.
Time that the Earth puts to turn around the Sun with locates the starry sky of it (its period of sidereal revolution) is 365,26 days, rounded figure, (day of 24:00). However if one measures this same period with the sidereal rotation of the Earth (who is 23:56 min) the sidereal year is equal to 366,26 days sidereal. In calculations of years, one uses value 1 year is equal to 365,25 days.
The axis of rotation of the Earth is tilted of 23,4° in the field of the ecliptic , which produces the variations of season on the surface of the sphere. The only known natural satellite of the Earth, the Moon, which started to orbit there is that more than 4,53 billion years, creates the Marées, stabilizes the axis of rotation of the Earth and slows down the rotation of planet. A broad bombardment of Comet S during the first times of planet played a big role in the formation of the oceans. Later, impact of Asteroid S.A. caused of many changes on the environment on the surface. Periodic changes in the long run of the orbit of the Earth, caused by the gravitational influence of the others Star S, are probably one of the causes of the Glaciations which covered a good part of planet.
See also: History of the Earth
The scientists were able to reconstitute certain information on the past of our planet. The Earth as well as another planets of the Solar system were formed there is that 4.57 billion years apart from a solar Nébuleuse, a Masse of dust and gas in the shape of disc released by the formation of the Sun. Initially in fusion, the external layer of the Earth cools to form a solid crust when water started to accumulate in the atmosphere. The the Moon was made little of time afterwards, undoubtedly following a collision between an object of the size of Mars (sometimes called Théia) with approximately 10% of the total mass of the Earth. Part of the mass of this object remained after the Earth whereas another portion was ejected in the space, which would have then formed the Moon.
The volcanic activity produced a primitive atmosphere. Condensed steam, in addition to Ice brought on planet by comets, produced the oceans. Highly energy chemistry supposément produced a Molécule being able to reproduce itself there is that more than 4 billion years, so that 500 million years later, the last common ancestor of all lives existed.
The development of the Photosynthèse allowed energy coming from the Sun to be cultivated by certain forms of life; the result being an accumulation of Oxygen in the atmosphere and in a Layer of ozone (the molecular oxygen shape) in the upper atmosphere. The incorporation of smaller cells in larger had like result the development of complex cells, called Eucaryotes. Helped by the absorption of the Ultraviolet rays by the layer of ozone, the life started to be increasingly developed on Earth.
As the surface of the sphere is reformed continuously, over periods of several hundreds of million years, continents were formed for then separating. The continents migrate on surface, causing a Supercontinent sometimes. Approximately 750 million the years ago, oldest of the known supercontinents, Rodinia, started to break. The continents recombined later to form Pannotia, there is 650-540 million years, then finally Pangée, which split up 180 million years ago.
Since the years 1960, many assumptions were put forth of which one which affirms that a great glaciation took place there are 750 and 580 million years, during the Néoprotérozoïque, and who covered planet of a layer of ice. This assumption was named Snowball Earth (Ground Snowball), and is of an private interest because it precedes the Explosion cambrienne, when forms of life multicellular started to proliferate.
Following the explosion cambrienne, it has 535 million years, 5 massive extinctions were necessary. The last major extinction goes back to 65 million years, when one supposed meteorite entered in collision with the Earth, thus killing the dinosaurs and other broad reptiles, saver of smaller animals like the mammals. In the 65 million years which were passed since, the mammals diversified, and there is that a few million years, a being resembling a Singe in Africa developed the aptitude to be held right. This allowed the use of tools and encouraged the communication which asked nutrition and stimulation for a Cerveau more developed. The development of the Agriculture, and then of civilizations, made it possible human to modify surface Ground during one short period of time, like any other species, affecting the Nature just like the other forms of life.
Composition and structure
The Earth is a telluric planet, or in other words a solid planet, contrary to the gas giants like Jupiter. It is about largest of four telluric planets, than it is in terms of size or mass. Of these four planets, the Earth has also the greatest density, strongest gravity and the most powerful magnetic field.
The shape of the Earth resembles much has a sheet of paper what wants to say of a completely FLATTENED form. The approximate diameter of plate is of 12.742 km given emitted by the scientist who have to measure it with a slap has to measure (7,913 semi).
The rotation of the Earth which does not exist creates a light equatorial pad, which makes so that the diameter at the equator east 43 km longer than the diameter north pole and south pole. The greatest deviations of the ground of the Earth are the Mount Everest (8,848 m with the top of the sea level) and the pit of Mariannes (10,911 m under the sea level). On the other hand, because of flatness, the object furthest away from the heart of the Earth is in fact the volcano Chimborazo in Ecuador.
The mass of the Earth is of roughly 5.98×10 kg. It is made up mainly of iron (32.1%), of oxygen (30.1%), of silicon (15.1%), of magnesium (13.9%), of sulfur (2.9%), of nickel (1.8%), calcium (1.5%) and aluminum (1.4%), the 1.2% consistent remainder in light traces of other elements. Because of the attraction of the heavier elements towards the center of gravity of the Earth, the heart of the Earth is believed to be mainly made up of iron (88.8%), with more an minor amount of nickel (5.8%), sulfur (4.5%) and less than 1% of other elements.
The geochemist F.W. Clarke calculated that 47% of the earth's crust are made of oxygen present mainly in the form of oxides, whose principal ones are the oxides of silicon, aluminum, iron, calcium, magnesium, potassium and sodium. Silica is the constituent major one of the crust in the form of pyroxénoïdes, the most common minerals of the magmatic and metamorphic rocks. After a synthesis based on the analysis of 1672 types of rocks, Clarke obtained the following percentages of composition in mass:
The Earth consists of several identifiable internal layers about concentric: the Earth's crust (oceanic or continental), the higher coat, the lower coat, the external core and intern. The Lithosphère is consisted of the crust and the higher zone of the higher coat. The asthenosphere is the lower zone of the higher coat (in lower part of the lithosphere).
The earth's crust of the Earth is relatively young, compared to the Earth itself. For the relatively short period of 500 million years approximately where the tectonic erosion and processes destroyed, then recreated the majority of the surface layers of rocks on the surface of the Earth, almost the totality of the traces of the geological history of its surface (craters of impact, for example) disappeared. More than 99% of terrestrial surface would have less than 2 billion years.
This structure is known by means of the study of the propagation of the seismic waves between a source and various points of terrestrial surface.
The speed of a seismic wave changes indeed rather brutally in the passing between two layers of different composition or mineral phase. These limits sometimes received particular names, such as the Discontinuité of Mohorovicic, the Discontinuité of Lehmann or the Discontinuité of Gutenberg.
The constitution of the Earth is explained by its mode of formation, by Accrétion of Météorite S, which produced a stratification in liquid phase by Density decreasing since the internal layers towards the external layers.
Tectonic platesAccording to the theory of the plate tectonics, the upper part of the interior of the Earth is composed of 2 layers: the lithosphere, including/understanding the crust, and the solid part of the coat. Below the lithosphere the asthenosphere is, which forms the heart of the coat. The asthenosphere resembles extremely hot and viscous liquid.
The lithosphere floats primarily on the asthenosphere and is broken in parts which are called tectonic plates. These plates are segments rigic which move in relation to the others in three ways: in convergence, in divergence, and by transcurence. Thus the earthquakes, the volcanic activity as well as the mountains are created.
The principal plates are:
Certain plates have a smaller surface like the Indian Plaque, the Arabic Plaque, the Caribbean Plaque and the Plaque of Nazca in the west of the coast of South America. The Australian plate was amalgamated somewhat with the Indian plate there is that 50 to 55 million years. The fastest plates to move are the oceanic plates, moving with approximately 70 millimetres per year. On the other hand, the slowest plate is the Eurasian plate, progressing to approximately 21 millimetres at the year.
Form EarthThe spherical design of the Earth goes back to Greek antiquity, towards, and more specifically with the pythagoricians. One finds this design at Parménide, Plato or Aristote. To, Ératosthène gave terrestrial Rayon an estimate very close to reality. The geographer Ptolémée provides to the 2nd century geographical information which met well the needs for its time, and still until the Renaissance.
The Civilization arabo-Moslem woman preserved the knowledge of a spherical Ground and at the 9th century, Caliph Al-Mamun, with Baghdad, made carry out a measurement of part of a meridian line, leading to a good approximation of the circumference of the Earth. In the Christian world, this idea was sometimes called into question, for example at the 6th century by Cosmas Indicopleustès. Indeed, the Fathers of the Church could not reconcile the spherical vision of the world of Aristote made up of two polar zones and two moderated zones, separated by an insuperable torrid zone, with the universality of the message of Christ, this message which cannot arrive to hypothetical inhabitants of the Antipode S. Until the 12th century, one thus endeavoured to represent the world under form symbolic system, but of the Philosophe S or the monks such Isidore of Seville, Bède Worthy the, Jean Scot Erigène, Gerbert d' Aurillac, Thomas d' Aquin, Albert Large the or Roger Bacon had integrated the spherical one very well.
The accounts of voyages of missionaries, Marco Polo and the explorer Jean de Mandeville (with its Book of the wonders of the world ) spread in the company the image of a spherical ground, around which one could theoretically make a “circumnavigation”. The Imago mundi of the cardinal Pierre d' Ailly retained this spherical representation. It is known that Christophe Colomb was undoubtedly influenced by the Livre of the wonders of the world of Mandeville, and that it had a specimen of the Imago mundi . This last underestimated the terrestrial ray however largely, which made it possible Colomb to consider in a reasonable way the possibility of joining the the Indies by the West. A more precise knowledge of this ray would have discouraged any attempt at crossing of the Ocean.
The voyages of the Portuguese at the beginning it 15th century to join the Indies by sailing round Africa, the redécouverte Greek texts with the Rebirth, in particular the '' Géographie '' of Ptolémée, their diffusion by means of printing works also largely contributed to propagate the modern representations of the Earth, with North to the top of the charts, the Méridien S, the parallel S, the equator and both Tropique the oldest S. Globe known is manufactured by Martin Behaim towards the end of the 15th century, little before Vasco de Gama, Christophe Colomb or Magellan undertakes their voyages. One sees there Europe, Africa and Asia, but of course, neither Americas, nor Oceania.
Mercator, by drawing its charts, mentioned and drew an enormous southern continent: " Terra incognita australis" (southern land (of the south) unknown). This " southern land inconnue" was drawn in the South because Mercator believed that without this weight, the Earth was going to be reversed! The reflections and work in Géographie (raised cartographic, Projection of Mercator) at the 16th century… made it possible to make evolve/move our knowledge of the Earth.
It is only at the 18th century that the flatness of the poles is recognized, with the forwardings led to Peru and in Lapland.
AtmosphereThe Earth is surrounded by a gas envelope which it retains by gravitational attraction: the atmosphere.
This atmosphere gives to planet a bluish reflection since the space, from where its “blue planet” nickname: the constitution and the density of the atmosphere are such as the incidental light of the Sun and reflected light by the continents and the seas are diffracted (giving its color to the Ciel, and by reflection, with extended from Eau). See the treating article of the Color of the sky.
This envelope, whose overall assets are about 5 × 10 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 (of the Sea level until approximately 45 km) is made up of “permanent” gases, gas of which the proportions remain constant, and of gas of variable concentration with the Altitude.
The nitrogenizes, the oxygen and the Argon constitutes, in volume, 99,997% of permanent gases (see table above); the vertical mixing of the air makes it possible to preserve a constant distribution at all the levels, even for the lightest gases, such as the Hélium or the Hydrogène.
The gases with variable concentration are primarily the vapor of Eau; and to a lesser extent the Carbon dioxide, the Sulfur dioxide and the Ozone. The terrestrial atmosphere can be considered, at a given moment, like a thermodynamic mixture of dry air and steam.
The particles liquid, solid, liquid or mixed in suspension in the atmosphere constitute the atmospheric Aérosol.
These particles play a central role in the phenomena of Condensation (clouds) and of crystal formation of Glace, like with various physico processes - chemical in the atmosphere. Their concentration varies several powers of 10 (several orders of magnitude) according to the place and of time; in raised concentration, they constitute a factor of Pollution. The particles are classified in:
- particles of Aitken: 1 Nm < D < 0,1 µm
- large particles: 0,1 µm < D < 5 µm
- giant particles: 5 µm < D < 50 µm approximately
The atmosphere attenuates in an important way the solar Rayonnement received on the ground; according to the importance of the cloud cover, the ground receives from 68% to 28% (or less) of the solar radiation arriving at the atmosphere.
Structure of the atmosphere
The chemical composition of the atmosphere, its temperature, or the phenomena which are observed there have marked discontinuities when altitude increases. These discontinuities correspond to homogeneous layers whose properties evolve/move continuously; it is (by increasing altitude):
Satellites of the Earth
The the Moon is a Natural satellite, located at approximately 380000 km of the Earth. Relatively broad, its diameter is approximately the quarter that of the planet Ground. It is about the broadest natural satellite in the Solar system relative with the size of the planet around of which he orbits. The natural satellites orbiting around another planets are commonly called the moons, according to the Moon of the Earth.
The gravitational attraction between the Earth and the Moon causes the Marée S on Earth. The same effect with place on the Moon, making so that its number of revolutions is the same one as time that it is necessary for him to orbit around the Earth, presenting thus always the same face towards planet. While orbiting around the Earth, various parts on the visible side of the Moon are illuminated by the Sun, causing the lunar Phases.
Because of the force present, the Moon moves away from the Earth at intervals of approximately 38 mm per years. On several million years, these simple small modifications, as well as the lengthening of the terrestrial day of 23 Microseconde S, can create enormous changes. During the period of the Dévonien, roughly 410 million years of today, 400 days ago in one years, each day during 21.8 hours.
Seen Earth, the Moon is just enough distant to have the same apparent size as the Sun. The angular shape of the two bodies are resembling because even if the Diamètre of the Sun is 400 times larger than that of the Moon, this one is 400 times close to the Earth than this last. This allows the total eclipses S on Earth.
The theory accepted on the origins of the Moon is that of a giant impact between an object of the size of Mars called Théia with the lately formed Earth. This assumption explains the fact partly that the composition of the Moon is curiously resembling that of the Earth's crust.
The Earth has also two satellites Co-orbital, the Astéroïde (3753) Cruithne and 2002 AA29.
Acceleration of gravityThe acceleration of gravity (or “field of gravity”) varies slightly on the surface of the Earth for three reasons:
- It depends on altitude, acceleration being 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 perfectly spherical, but is not flattened a little with the poles, the gravitation is stronger with the poles, for the same reason.
- the Earth rotates, with the result that an object at the equator gives the impression to be very small little the lighter (see Centrifugal force).
Other factors can influence in a tiny way the local field of gravity (See Gravimétrie):
The acceleration of gravity can be calculated as follows:
- g=9,780318 × (1 + 5,3024×10-3 × sin2 (L) + 5,9×10-6 × sin2 (2×L) - 3,15×10-7 × H)
altitude in meter.
With the sea level, h=0 m:
- at the equator (L=0°): g=9,7803 m/s ²
- with the latitude (L=45°): g=9,8063 m/s ²
- with the poles (L=90°): g=9,8322 m/s ²
AnecdoteThe Earth is the only planet turning around the Sun whose name does not come from the Greek Mythologie or Roman and where the life is known. The name given to the Earth, like the Sun and the Moon, is function of the languages, unlike the other names of planets and stars which is resulting from a standard given by the scientists of the various times.
The position of the Earth in the Universe was the source of long debates opposing during philosophical, erudite centuries and monk of all edges. For a long time the Earth was regarded as in the center of the Universe, design defended by Aristote or Ptolémée. In this design, the Géocentrisme affirmed that all the celestial objects, Sun, the Moon, planets and stars, (Astre S) revolved around the Earth. Copernic, taking again the model of Aristarque de Samos, argued for the Héliocentrisme, i.e., a Ground orbits of it around the Sun, with the Moon, natural satellite of the Earth (treated published in 1543: Of revolutionibus orbium coelestium libri VI ). Tycho Brahé proposed an analog and digital system in which the Sun turned around the Earth, and another planets around the Sun. The idea of Copernic was supported by Kepler and Galileo. The Keplerian ellipses made there much by allowing tables of a precision ever equalized, and by explaining the variations of latitude of planets compared to the plan of the ecliptic .
The question hardly any more has of direction today, the choice of a reference frame being arbitrary and depend on the convenience that this reference frame will bring to the studied object. The choice of a reference frame in which simply the laws of physics are expressed results in taking at first approximation a reference frame related to the Sun. The choice of a reference frame corresponding to our own vision led to choose a reference frame related to the Earth. The study of the Galaxies will result in taking other reference frames.
|Random links:||Jojoba | SociologÃa de la religiÃ³n | Ferroïque material | Daniel Henriksson | Regional natural park of Alpilles | Tunja|