Susan Bolon, age i2, of Albany, N.Y., for her question:

What makes the Milky Way look milky?

This pale, ghostly loop over the sky is a thing of wonderous beauty, and mankind has admired it since ancient days. The Greeks and Romans compared it to a trail of spilled milk. The American Indians thought of it as a stairway for departed souls to walk from earth to heaven. The Milky Way is not milk or stairs, but mankind needed the telescope to learn this.

The Milky Way has been a fixture in our night skies since the earth began. But no one guessed and certainly no one knew what it really is until 1609. In that year, the great astronomer Galileo made a telescope and turned it upward to the heavens. Mankind for the first time had a mechanical eye to improve his vision of distant objects.

If you own a telescope, you can remember the excitement of those first few weeks or months. You could not wait for sunset, and you wanted to sit up studying your close up Views of the heavens night after night. Galileo was one of those gifted men who felt this thrill of probing curiously through all his life.

Night after night, on a rooftop in Italy, he used his little telescope to probe the heavens. Through the winter of 1609 and 1610 he saw sights that man had never seen before, and he kept careful notes of his observations. He saw that Venus had phases like the moon. He saw the dazzling rings of Saturn and four of Jupiter's moons He also saw that the Milky Way is not a glowing cloud, a trail of milk or a stairway to heaven.

Galileo's little telescope magnified only 32 times. But it showed him that the Milky Way is made of stars, of teeming crowds of distant stars. All these swarming pinpoints are seething stars like our sun. Their dazzling light becomes dim and hazy as it reaches us across the immense oceans of space. Their brilliant sparkles fade to a milky glow.

The Milky Way is our view of our galaxy, the starry pinwheel which is our home in the heavens. From the earth We get an edgewise view Of the Big wheel, and the stars look crowded because they are more or less on a level, one behind another. Actually, the teeming stars are all separated by light years of space.

The hazy hoop of the Milky Way looks like a ragged scarf. Vast areas are hidden by dark clouds of cosmic dust between us and the crowded stars. Some of the streamers show us the spiraling arms of the great pinwheel.