Seen from Space, earth haS a lot of dark blue and white - throughthe oceanS, ice SheetS at the .poleS and cloudS in the atmoSphere. Physical map of the Earth
Water cycle wasdiscovered, or even guess, very early inhuman history. Even the Bible refers severaltimes to this circuit, especially in relationto flood. The following quote is translatedfrom the Sanskrit text of thebook Indian Manusmrti, book a homeatleast 2500-3000 years: "The water rises toheaven in the form ofvapor from the sky asrain falls, the rain are born theplants, plantsand animals "(Manusmriti - book III, sloka 76).
Among the various theories on the water cycle and the mechanismthat causes are worth mentioning:Meteorogenă theory,Geogenă theory,Genesis theory in the air. Xenophanes of Colophon, the philoso pher around 500 BCdescribed the water cycle in nature
The theory of the genesis of airThe theory was first supported by Anaximene of Miletus and the air is postulated that the initial material, the concentrationchanges in water and stones, and by dilution turns into fire.Diogenes of Apollonia on the theory went, considering that by the concentration of the air occurs and sludge from which life arises.He developed the theory of cycles in which the infinite successionof worlds born. Based on these assumptions, Aristotle theorizedthat the water would be produced from the air through acondensation process that would lead to precipitation falling on the ground and feeds the rivers that drain into the sea. Aristotles theory covers only part of the water cycle as seen today and did not include supplying water evaporation in the atmosphere. Such a return was not necessary because, according to Diogeness theory, the cycle is closed when all the sludge produced by thecondenser was washed into the sea and had generated a new world, Genesis would not have seemed possible in the case of aclosed water cycle . Aristotles theory was considered valid by scientists until the seventeenth century.
Theory meteorogenăThis theory describes the water cycle as accepted concepts ofcontemporary science. It seems that this theory was stated by the Greek philosopher Xenophanes of Colophon. Different studiesfossils, Xenophanes concluded that in the distant past, the waterscovered all the land, which was later called hypothesisNeptunism. Thus he developed the theory of a cycle of soil in which the land would be eroded and led to the oceans, becauseafter complete disappearance of the land, he would regenerate.On the water cycle, he found that the origin of the seas clouds that produce rain water that eventually reaches all the oceans. Sincewater was the origin of the whole process, he hypothesized that the sun and stars would have been generated all of these clouds.Finally, after him, rainbows would be nothing but a special type ofcloud. Although soil cycle and was not subsequently confirmedhis theory of clouds are inaccurate description of the water cycleis generally correct and the vital role oceans they have been correctly guessed.
Theory geogenăPrepared by Hippo of Samos, reverse assumptions meteorogenetheory and claimed that the earth floats on the ocean planet.According to this theory, underground sea, floating on the earth, rises through the ground, through a kind of reverse infiltration.Since the earths surface, water evaporates into the atmosphereand returns to a large precipitate. The theory maintains idea of acycle, but the sense of motion is reversed. The theory wassupported by Thales of Miletus, and later by Platon.
Of the 510 million km ² globe covering almost three-quarters water.Water is everywhere, in Earths crust to a depth of 20km, and theatmosphere as water vapor, up to 15 km high.
Water physical properties - unusual compared to other liquidchemicals. Compared with ordinary liquids become denser whencooled, water reaches its maximum density at 4 degrees Celsius.Below, and above this temperature, water has a lower density.This is why, for example, large and lakes freeze from the surfacedown, and the ice floats on water. Because ice is less dense thanliquid water and the water freezes from the surface down, it was possible that during the glacial deep ocean life to persist in itbeing isolated from the cold.
Water cycleBecause solar heat, water and ocean sea surface (especially inthe tropics) rising evaporates into the atmosphere as water vapor. in the atmosphere are water vapor drift through layers of cold air, where condensation takes place, vapor turns into waterdroplets which, uniting, form larger drops that fall on land, formingrain. Have a permanent phenomenon.A year evaporates from the oceans an amount of 450,000 km ³ of water, of which approximately 400,000 km ³ fall as rain back intothe seas and oceans, forming small flow of water. Evaporatesfrom the surface of land annually about 62,000 km ³ of water, but100 000 km ³ dry falling water, the difference comes from the fall of ocean water on land. Of water fell on the dry, some rivers andstreams flow through the seas and oceans, and some seeps intothe earths crust, giving rise to groundwater.
Wva ater Ice po rs Water is the only substance on Earth that exists in all three states of aggregation: solid, liquid, gas. Is found in liquid form in oceansand lakes or in the glass of water you drink, in solid form-iceinside the earths crust, snow or hanging roof floes in winter andas a gaseous vapor in the atmosphere or removed by a steamkettle. Hydrological cycle describes the journey that makes the water in nature, "disguising the" new and permanent new forms.Changing the state allows him to reach inside the earth in the airas clouds and back to Earth as rain. The sun is the engine of this process, water recycling, again and again. It may, therefore, thatmolecules of water fell as rain in the garden once grandparents,to return today, tomorrow as snow.