Dear Tom,
I have heard of the troposphere, but what are some other layers of the atmosphere called?
Ron Brianston,
Racine, Wisc.

Dear Ron,
The troposphere is the bottom layer of the atmosphere, extending upward from the Earth’s surface to four to ten miles up. It is the layer in which “weather” occurs and in which temperature usually decreases with increasing height. The next major atmospheric layer is the stratosphere, extending to a height of 30 to 35 miles. It is a layer of increasing temperatures. Then comes the mesosphere, in which temperatures fall and reach the atmosphere’s coldest readings, about -150 degrees F., at 60 miles up. Above that is the outermost layer, extending to several hundred miles up, the thermosphere, with readings of thousands of degrees.