Judith Koenig, age 7, of Philadelphia, Pennsylvania, for her question:

What time of year is the earth closest to the sun?

You would expect us to be closest to the sun in June, when the days are longest  or perhaps in August, when the days are hottest. But no, this is not so. The earth is closest to the sun in January, when our wintery days are short and cold. On January 2 or 3, the distance between the earth and the sun is about 9 1/2 million miles. At this time of year, the people who live south of the equator are enjoying their summer season. We live north of the equator in the Northern Hemisphere. And, strange to say, we are having winter when the earth is closest to the sun.

The earth, of course, takes a year to orbit around the sun. And its orbit path is not a perfect circle with the sun exactly in the middle. After the New Year we move a little farther from the sun each day until July. Then the earth reaches the part of its orbit that is farthest from the sun. On July 1 or 2, the distance between the earth and the sun is about 94 1/2 million miles. This is the time of year when the earth is farthest from the sun. We are about 3 million miles farther from the sun in July than we are in January. This difference equals about 120 trips around the earth's equator. It seems immense., but in sky distance it  is very small  and it does not cause the changing seasons that switch north and south of the earth's equator.