Elaine Czohara, age 12, of Newport News, Virginia, for her question:

How can Alaskan summers be so warm?

Our globe is tilted on its axis, and this is why the summers up in Alaska can be so warm. It is also the reason why winters up there are so cold. The axis as all of us know is the line through the globe from pole to pole. It is the center around which the earth rotates once each calendar day. The earth also revolves once each year on an orbit around the sun. However, as it revolves, the axis does not change. Its two poles continue to point in the same directions out in space. During the yearly orbit, this brings the poles into different positions in relation to the sun.

When summer comes to the northern hemisphere, the north polar region is tipped towards the sun. The days grow longer and the midsummer sun does not set at all. These long daylight hours of summer sunshine warm Alaska. The warmth builds up in the ground because little or none of it has a chance to escape during the night. When winter comes north of the equator, the South Pole bows toward the sun. The north polar region tips the other way. The days in Alaska grow shorter and the ground grows colder through the long polar night. Various directions we have about 20 close star neighbors, but our bright North Star is some 300 light years away and billions of blurry stars in the Milky Way are 26,000 light years from the earth.

Sooner or later, the distances of the whopping stars makes us think about the vast reaches of space between them. Actually, they really are tiny objects widely scattered through the immense heavens. Astronomers now assure us that the majority of stars most likely have planet systems more or less like our own. Space travelers, however, will have to span breathtaking distances to reach these other worlds. If our spacecraft could travel at a steady speed of 669,600,000 miles per hour they could reach Alpha Centauri in about four years and four months.