Alan Browning, age 15, of Cleveland, Ohio, for his question:

WHAT ARE THE TROPICS OF CANCER AND CAPRICORN?

The tropic of Cancer is a parallel of latitude that is 23 degrees and 27 minutes north of the Equator. It delineates or marks the limits of the northernmost points at which the sun can appear directly overheard at noon.

The tropic of Capricorn is a parallel of latitude located at 23 degrees and 27 minutes south of the Equator, delineating the southernmost point at which the sun can appear directly overhead at noon.

At the tropic of Cancer, the sun's rays strike the earth vertically on one day a year: on the summer solstice which is on or about June 21. At the tropic of Capricorn, the sun's rays strike the earth vertically on the winter solstice on or about December 21.

Between these latitudes are all those points on the earth's surface over which the sun is almost directly overhead during the entire year. The tropic north of the Equator is called the tropic of Cancer because the sun at the summer solstice enters the constellation of Cancer. The southern one, for a similar reason, enters the constellation Capricorn on the winter solstice.