f you were to look down on Earth from
outer space， as an astronaut might， the planet
would resemble a watery blue gem
Viewed from the blackness of space，
the orb is not divided by interna- f
tional boundaries into individ-
_4.
ual countries， but appears as
a cohesive， almost lyricall~-~
entity. Indeed， on the I~
J
planet itself， everything is
interrelated. Together，
the atmosphere (the k.~r--
gases that surround the
planet， including those
that make up the air we
breathe)， the hydrosphere
(including the bodies of water
that cover the earth)， and the litho- ~ ~
sphere (the outer hard surtZace of the planet，
generally considered to be about 50 miles thick)
make fife possible on the earth. The word geogra-
phy， derived from the Greek words geo (\"earth\")
andgraptwin (\"to write or carve\")， reters to the sci-
entific study of Earth--its land， water， and air， and
the distribution of plant， animal， and human life.
Geographers study such interrelationships as
cfimate and vegetation， atmosphere and the sun，
water and soil， and human industries and the
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