One of the cardinal principles of Family Learning is that there is an abundance of low-cost educational materials available to every home and family, if only we will recognize their potential and then use them to stimulate learning in the home.

One example of this idea is the weather map that is printed in almost every daily newspaper across the country. The styles of weather maps and the arrangement of the information they contain vary from paper to paper; some are highly detailed, while others show only the most basic weather information.But let's think a moment about what is "basic information" on a weather map. What understanding should an educated adult or child be able to take away from a simple newspaper weather map?

As with almost every other area of learning, the understanding you are able to take away from a weather map will depend in large part upon the knowledge you are able to bring to that learning opportunity. If children aren't aware of the basic scientific concepts that govern the movement of air, they can't be expected to learn anything from the letters and symbols that the map uses to describe those movements. Fortunately, these concepts can be learned at home, and the use of a newspaper weather map will enable us to reinforce them and apply them to everyday life.

No matter how limited the detail of a weather map may be, it will always show the centers of high and low pressure around the country, usually labeling them "H" and "L." Yet, an understanding of these two symbols alone requires a level of "scientific literacy" that very few students have, even those in high school and college.

Children need to realize that they are living at the bottom of an ocean of air, which extends several miles above their heads and is held against the earth by gravity. That column of air directly above them weighs a great deal, for although air doesn't feel like it weighs very much, when it is piled up for miles and miles, it exerts a pressure that is tremendous - roughly 15 pounds per square inch or about a ton per square foot! That's about 200 pounds of pressure on the surface of your open hand, but you don't feel the weight because there is air pushing up beneath your hand as well.

Take a sheet of paper and lay it on top of your open hand. Now cover the paper with a piece of cardboard held in your other hand. Lift the cardboard quickly and watch what happens to the paper. For just a moment, the cardboard has carried some of the air away from the top side of the paper, and so the greater air pressure on the bottom pushed the paper toward the cardboard.

This ocean of air, just like an ocean of water, does not have a smooth upper surface. Our atmosphere is constantly moving and forming high peaks of air that spill into low valleys of air (It is easiest to explain and visualize this idea if you have a globe of the earth at hand). As one of these high peaks passes over your head, the column of air above you is taller, weighs more and therefore exerts greater pressure on you than the shorter column would if you were standing beneath a valley of air.

And there you have it: The "H" and "L" symbols on your weather map show the peaks and valleys in our ocean of air. Next week we'll look at what science and a weather map can tell us about the movement and the temperature of that air.

- Dr. William F. Russell's latest book for children is "Animal Families of the Wild." Send your questions and comments about Family Learning to him at P.O. Box 1279, Menlo Park, CA 94026.