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Atmosphere Boundary
Name: Margie C,
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 2000-2001
Question:
I need to know the distance from the earths ground level
to the earth atomsphere surface...in other words....from the ground where
we walk to the surface of the earth....space
Replies:
Margie,
I shall assume your question seeks the distance to the "top" of the
atmosphere.
Otherwise, the atmosphere begins at the earth's surface and diminishes in
density as the distance from earth's surface increases.
As you already know, earth's gravity holds its atmosphere in place. Since the
force of gravity is a function of the mass of the earth and the mass of an
object on earth, as well as the distance between earth's center of mass
and the
object's center of mass, the force of gravity diminishes with increasing
distance. Thus, the gases that represent earth's atmosphere are held less
firmly with increasing distance. That's the reason for the familiar
thinning of
air as one travels up high mountains or flies at great altitudes.
Because gravitational forces extend to infinite distances, there is no abrupt
cut-off altitude at which the forces between the earth and its atmosphere
simply cease to exist. The result is a gradual thinning (decrease in density)
of the atmosphere as one travels further and further from earth's surface.
In a sense, and stretching things a bit, one could say the atmosphere has no upper
limit.
Regards,
ProfHoff
Margie,
That is actually a difficult question to answer.
It is easier to talk about the top of the
different layers of the atmosphere.
However, virtually all of the atmosphere is
located below the base of the Exosphere,
at 500-1000 kilometers. There is a great
variation in this height, depending where
on Earth that you look at it and depending
on the season. Generally the height is greater
at the equator and less at the poles. Air
molecules that reach the Exosphere are not
likely to return to Earth, and it is common
for there to be as many molecules of matter
from the Sun in this region as molecules of
air from the Earth.
The height described above could be called
the beginning of space.
David R. Cook
Atmospheric Section
Environmental Research Division
Argonne National Laboratory
There is no sharp cut-off where the atmosphere ends and space begins. The
atmosphere just tapers off and not in a regular fashion. Solar storms, for
example, can distort the upper atmosphere.
Vince Calder
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