I received a Christmas card last month from some friends who live in Australia. This card depicted a scene that reminded me of one of those puzzles that ask "What's Wrong With This Picture?" Here was jolly old St. Nick all right (or Father Christmas as he is called in Australia), dressed in his bright red, fur-trimmed suit, with a bulging bag of gifts slung over his shoulder. But this bright red suit extended only down to his knees. Good grief, Santa was wearing shorts!

Sometimes it takes a little visual jolt like this to remind us of things we were taught long ago, and even understand quite well, but just don't think about very often. The seasons in Australia are the reverse of our own, and so Santa is wearing shorts because Christmas "down under" happens to occur in the heat of the summer.The 231/2-degree tilt of the Earth's axis points the north pole AWAY from the sun during our winter months, and so we receive the less-intense, glancing rays of the sun while the lands below the equator get the full power of the sun's energy straight on. After the equinox in March, the reverse will be true, and the sun will appear higher in our sky because the Northern Hemisphere will then be pointed TOWARD it. Even though the sun will be millions of miles farther away from the Earth than it is today, the sun's rays traveling through the vacuum of space will have no trouble warming our beaches and our bodies.

Now is a good time for parents and children to think about why Australia's seasons differ from our own, and about how similar our two countries are as well, for this Saturday happens to be Australia Day, which is celebrated there much like July 4th is celebrated here.

Australia Day commemorates the arrival on Jan. 26, 1788, of the first European settlers on the continent of Australia. The 11 ships that anchored in what is now Sydney Harbor carried about 1,000 passengers, three-fourths of them convicts who were being shipped from London to ease the overcrowding in the prisons there and to work off their sentences as laborers in this uncharted wilderness.

Australia was not only uncharted, it was unknown entirely to explorers from the rest of the world well after all the other continents had been located and mapped with some precision. In fact, Australia got its name (Australia is the only country to occupy an entire continent) from the mysterious land that mapmakers back around 1500 had drawn in the South Pacific without any evidence that such a land actually existed. They labeled this imagined land "Terra Australis Incognita," which were the Latin words meaning "the Unknown Southern Land."

"Australis," in Latin, means "southern," and that is why the dazzling visual display we call the "aurora borealis," or "northern lights," is called "aurora australis" in the southern polar regions. ("Aurora" is the Latin word for "dawn.") Australia is very similar in size to the 48 contiguous United States; they are almost identical if we include the land area alone. Indeed, Australia even looks a little like the shape of the U.S., if we flip our country over so that the southern tip of Florida and Texas are pointing north.

This idea was suggested in a classroom I visited recently, where the teacher used black construction-paper cutouts he had made from tracing various countries and continents on a world map. The students learned to identify these regions from their shapes alone, a valuable and pleasurable learning activity that can be carried out equally well in the home.

- 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.