Richard Feauto, age 10, of Sioux City, Iowa, for his question:

How many galaxies are there in outer space?

Astronomy is an ancient science but the Space Age is brand new. Most of our super instruments for exploring the outer reaches of space were developed in the twentieth century. We have not had time to use them to the full. Meantime, they are being improved to probe still deeper beyond. The size of the immense cosmos staggers the imagination. Its outside limits are not within range of our exploring instruments. At the present stage of scientific knowledge, the universe seems endless and infinite. But everywhere we probe, we find that its vast reaches are populated with starry galaxies.

Astronomers estimated that the universe within our present probing range con¬tains about a million million galaxies similar to our Milky Way. This is one with a tail of 12 zeros. Most of them appear to cluster together in groups of 20 to several hundred. But the number of galaxies beyond our present range is anybody's guess.