The earth-The place of comfort

The history of the Earth indicates that
it was not at all suitable for any form
of life long after its creation . Lack of
water and oxygen,high temperature,continous
bombardments by meteorites , and tens of
other factors made life for any creature
impossible.But after millions of years
a more suitable environment developed
following the processes of degassing,and
the solidification and formation of the
Earth's crust which occured at the same
time.From then on some biological processes
like photosynthesis played a decisive role
in providing a more friendly environment for
life to develop , in such a way that the
atmosphere and the living condition on the
Earth is sharply distinctive from that of
other planets.

As mentioned before,continous bombardment by
meteorites was one of the factors which had
quite decisive effects on the planet Earth.
The bumpy surfaces of such planets a Jupiter
and Satum and also the Moon are themselves
indications of the effects of such continous
bombardments which are 4000000000 years old.
So far more than seventy depressions on the
Earth's surface have been determined to have
formed as a result of the falling of
meteorites . These phenomena are becoming
extinct because of erosion.One of the most
conspicous depressions known is called
Barringer which is located in the state
of Arizona in the United States , and was
created 350000 years ago . Right now the
Earth's atmosphere acts as a barrier to
such events,in such a way that almost all
meteorites burn ,destroy and lose most of
their mass while going through it.

It is worth mentioning that an ocean of air,
called atmosphere , surrounds the Earth ,and
that all living creatures stay at the bottom
of this ocean . The Earth's atmosphere is
made up of different gases such as nitrogen
( 78.08 % ( , oxygen ) 20.95 % ( ,and argon
( 0.93 % ( . The Earth's present atmosphere
has been divided into a few layers . The
lowest layer is called Troposphere which is
in contact with the Earth's surface , all
clouds and the friendly climate for life are
located here.This layer extends up to 12 km.
The second layer is known as Stratosphere
which in some parts extends up to 80 km.
This layer contains a thinner layer which
is made of a special kind of oxygen called
ozone ) O3 (. This thin layer functions as
a shield against harmful short wave cosmic
radiations such as ultraviolet radiation
emitting from the Sun . Without the ozone
layer the life on the Earth would definitely
face a serious danger . The next layer is
named Ionosphere.The X ray and ultraviolet
radiations emitted from the Sun are ionized
in this layer and transformed into charged
atoms and molecules . This layer of the
atmosphere plays a distinctive role in
establishing radio communications. It is
worth mentioning that meteors are small
particles of matter in the solar system
which when entering the upper layers of
the atmosphere are heated by friction ,
against air particles . Then they glow at
about 190 km from the Earth's surface and
at 65 km.Or more burn and turn into ashes.
Looked from other aspect,complex and long
term movements of the Earth which is carried
on slowly and solemn not only does not threat
life on its surface,but is established in
such a way to preserve and stabilize it.
It is worth mentioning that the Earth has
five types of movement :

1 - rotation,every 24 hours the Earth rotates
around its axis at 1667 km/h)in the equator).

2 - revolution, the Earth revolves around the
Sun on its somewhat elliptical orbit ) its
radius is approximately 149.5 million km. )
once every year at a speed of 30 km/s.

3 - nutation,this movement of the Earth is
caused by the change in the direction of
the axis of rotation and takes 26000 years
to complete.

4 - moving along with other planets of the
solar system towards Vega star at 19.5 km/s.

5 - moving along with the milky way galaxy at
270 km/s . This circular movement takes 240
million years to complete.