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 Click here to return to the Weather Archives

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