1. 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

4. Water cycle was
discovered, or even guess, very early in
human history. Even the Bible refers several
times to this circuit, especially in relation
to flood. The following quote is translated
from the Sanskrit text of the
book Indian Manusmrti, book a homeat
least 2500-3000 years: "The water rises to
heaven in the form ofvapor from the sky as
rain falls, the rain are born the
plants, plantsand animals "(Manusmriti - boo
k III, sloka 76).

5. 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

6. The theory of the genesis of air
The 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. Aristotle's 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 Diogenes's 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 . Aristotle's theory was considered valid by
scientists until the seventeenth century.

7. Theory meteorogenă
This 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.

8. Theory geogenă
Prepared
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 earth's 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.

9. Of the 510 million km ² globe covering almost three-
quarters water.Water is everywhere, in Earth's crust to a depth of 20
km, and theatmosphere as water vapor, up to 15 km high.

10. Water physical properties - unusual compared to
other liquidchemicals. Compared with ordinary liquid
s 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.

11. Water cycle
Because 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 earth's crust, giving rise to groundwater.

12. W
va 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 earth's 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.