Laura Wigging, age 12, of Louisville, Ky., for her question:

WHAT MAKES THE SEASONS CHANGE?

Every morning the sun rises and, even after a severe winter, the spring growing season is sure to return. Then comes the flowery summer, followed by autumn with rainbows of colored leaves. All sorts of man made things go wrong. But every morning the sun rises, and every year we can count on the orderly parade of the seasons.

The wise men of ancient Egypt predicted when the Nile would flood its banks from the position of Sirius, the Dog Star. They knew that the earth's changing seasons matched certain changing patterns in the starry heavens. They were right, though most likely they did not understand why this is so. We space¬agers view our earth as a spinning, orbiting spaceship. We know that the sky is our view of the vast reaches of space on all sides. As the earth turns, our view changes.

We also get different views of the heavens from different    places on our round globe. For example, we do not seethe North Star south of the equator.    From month to month, the starry view changes as we travel our 600 million mile orbit around the sun.

However, the earth does not go around the sun in an upright position. Its axis is tilted 23.5 degrees to its orbital path. This makes a great difference to our view of the sky  and it also causes the yearly seasons. It means that during the year first the north polar axis, then the south polar axis tips or bows toward the sun.

In December, the North Pole tilts away from the sun. The Arctic suffers through a long dark night, and the winter season comes to the Northern Hemisphere. In July, six months later and halfway round the orbit, the North Pole is tilted toward the sun. The Arctic enjoys a long sunny day, and the summer season comes to the Northern Hemisphere.

Spring and fall are halfway between the two extremes, when neither of the poles is bowing toward the sun. Meantime, south of the equator, the seasons are reversed. There, Christmas arrives in midsummer and the fall season arrives when we are enjoying the first breath of spring.