Edward Ramotowski, age 12, of Spokane, Washington, for his question:
What are the Tropics of Capricorn and Cancer?
The earth's own geographical markers are the North and South Poles. They are the ends of the axis around which it rotates. The.rest of the globe is sectioned in man made geographical markers of latitude and longitude. The Tropics of Capricorn and Cancer can be said to be markers drawn down from the sky.
The torrid zone is a wide belt around the bulging waist of the world. It is about 1600 miles wide and its center is the Equator, that imaginary circle exactly halfway between the two geographic poles. The northern limit of the torrid zone is the Tropic of Cancer and the southern. limit is the Tropic of Capricorn. Each of these Tropics is a global circle about 23.5 degrees of latitude from the equator. The word "tropic" is coined from an older ward meaning "to turn." It refers to the two turnabouts in the seasonal journey of the sun.
In our zone, the sun is never directly overhead:. In summer, however, the noon sun reaches higher than it does in winter. Each noon it climbs higher until it reaches its highest point on June 22. Then each noon, the sun is lower until it reaches its lowest point on December 22. After this, the days grow longer and each noon sun climbs a little bit higher in the sky. This seasonal journey affects the entire globe. But the noon sun is never directly over head outside the tropical belt. And even in this zone, it happens only twice each year.
March 21 is an equinox day, when day and night are equal all over the world. On this day at the equator, the noon sun is directly overhead. Then it creeps northward and on June 22 it is overhead at the Tropic of Cancer. This is the summer solstice, when the sun stands still in its path. From there, it moves south again and reaches the equator again on September 23, in time for the fall equinox. Then the sun's path moves south of the equator and reaches the Tropic of Capricorn on December 21. This is our winter solstice when the sun begins the six months journey back to the Tropic of Cancer.
The sun, the moon and the major planets move within a wide celestial highway called the zodiac. They move against a background of fixed stars that were divided long ago into 12 constellations. Through the years, the sun moves through the constellations of the zodiac, one by one. Cancer the Crab is a leggy constellation that follows Gemini the Twins over our skies in spring. The Tropic of Cancer on the earth is named for the celestial Crab. Capricornus the Goat follows Sagittarius over our autumn skies. The Tropic of Capricorn on the earth is named. for the celestial Goat. In June, when it reaches the northern limit of its journey, the sun is near Cancer. In December, a t the southern limit, the sun is near Capricornus.
Through the year, every spot on earth gets its fair share of sunshine. But the average warmth of the tropical belt is higher than any other zone. Here the sun shines almost straight down through the atmosphere. North and south of the tropics, the sun's rays slope down through a thicker layer of atmosphere and when they strike the earth they have less heat. In the tropics, the days and nights are equal or nearly equal. The high daytime sun is hot and there are no extra long nights for its heat to escape.