It was 31 years ago Tuesday (Aug. 7, 1959) that the very first photo of Earth was transmitted from space. Until this event occurred, every model and likeness we had ever made of our planet had been based upon projections and conjectures.
But 31 years ago, the Explorer VI satellite sent back a picture from 19,500 miles above Mexico that showed us a world very much like the one we had seen represented by our classroom globes. No, the countries of the world and the states of the U.S. weren't separated by differing colors or by artificial boundary lines, nor was there any sign of the equator or the Arctic Circle or the international date line. In fact, as wonderful and as necessary a home learning aid as a globe of the earth is, it can create some confusion for us as well, if we think of it as a perfect representation of how Earth would appear to an observer in space.Look at your globe and try to imagine how it would appear if it depicted the Earth that the astronauts saw on their trips to the moon. (Here is another appeal to have a basketball-size globe around the house. They aren't that expensive, either. I saw a very good model in a discount store the other day for less than $15.) The only surface distinctions you would see would be the different colors of land, water and ice.
You could locate the United States, but could you see the entire outline of any individual state? Yes - Hawaii. Which countries could you trace completely? Island nations like Australia, Greenland, Iceland, Sri Lanka and Madagascar, and others that have rivers and lakes for boundaries, but none whose borders follow a straight line. Nature, herself, does not make long, straight lines.
Globes can confuse us even more if we aren't careful to view them with an accurate sense of proportion. Some models, for instance, have a raised surface to indicate the various mountain ranges of the world. These "relief" globes are usually quite expensive, and they can also lead us to a distorted view of the earth. If a 12-inch diameter globe represents an Earth whose diameter is approximately 8,000 miles, then each 1/4-inch bump on a relief globe would represent a mountain 167 miles high! (That's more than 30 times the height of Mt. Everest.) Our Earth has, in fact, a surprisingly smooth surface when you consider how vast that surface really is. If the earth were reduced, in perfect proportion, to the size of a billiard ball, it would have a smoother surface than any billiard ball ever manufactured.
Children need to develop this sense of proportion about the earth, and you can help them do so. Put your globe in the corner of the living room, and then explain to your child that each globe diameter you move away represents one earth diameter, or 8,000 miles. Our moon is about 30 Earth diameters away (approximately 240,000 miles), so to see how our planet would look to someone on the moon, have your child move back 30 feet and see what features can be recognized on the globe. How would the Earth look to someone standing on Mars? You'd have to move back more than three-quarters of a mile to get this perspective.
Now let's come back a little closer to Earth. The layer of air that sustains all life on Earth and in which all the world's weather occurs (the portion of the atmosphere known as the troposphere) is only 8 or 10 miles deep, and about half that depth over the poles. To put this in proportion, all plant and animal life on Earth depends for its existence upon a layer of gases so thin that it corresponds to the thickness of the wax coating that covers your globe.- Dr. William F. Russell's new book, "Animal Families of the Wild," is available at local bookstores. Send your questions and comments about Family Learning to him at P.O. Box 1279, Menlo Park, CA 94026.