Paul Tipton, age 10, of Burnsville, N.C., for his question:

WHAT IS TROPOSPHERE?

The layer of the atmosphere closest to the earth is called the troposphere. We actually live in the troposphere, and all of the earth's weather occurs there.

The troposphere continues upward between six and 10 miles. Above this area lies the stratosphere with the mesophere and the thermosphere above the stratosphere.

As you climb up into the troposphere, the temperatures drop. With an average temperature of 60 degrees on the earth's surface, the average temperature at the top of the layer  called the tropopause  is about minus 67 degrees.

The thickness of the troposphere varies from the poles to the equator. It is about six miles deep in the polar regions while it is 10 miles high at the equator.