Eric Gibson Jr., age 14, of Bessemer, Ala., for his question:
WHAT DO WE KNOW ABOUT MERCURY?
In Roman mythology, Mercury was the god who served as the other gods' messenger; he was also the god of commerce, thievery, eloquence and science. In chemistry, mercury is a heavy metallic element that is noted for its fluidity. Astronomically, Mercury is the smallest planet in the solar system and also the closest to the sun.
The worship of the mythological Mercury was introduced into Rome in 495 B.C. when a temple was dedicated to him near the Circus Maximus. He is depicted in sculpture as a slender young man with wings on his heels.
Mercury, the metallic element, is the only metal that is liquid at ordinary temperatures. It is also the heaviest liquid substance known. It was named for the swift messenger.
Mercury occurs in its pure form or combined with silver in small amounts but is found most often in the form of the sulfide, the ore cinnabar. To obtain mercury from cinnabar, the ore is roasted with air and the gases produced are passed through a condensing system in which the mercury is collected.
Mercury is used in thermometers because its coefficient of expansion is nearly constant. The change in volume for each degree of rise or fail in temperature is the same.
Mercury is also used in other types of scientific apparatus such as vacuum pumps, barometers and electric rectifiers and switches. Mercury vapor lamps are used as a source of ultraviolet rays in homes and for sterilizing drinking water and swimming pool water.
The planet Mercury revolves around the sun in a period of 88 days. It moves around the sun faster than any other planet. Its means distance from the sun is approximately 36 miles and its volume and mass are about one eighteenth that of the earth.
The Mariner 10 spacecraft, which passed by Mercury twice in 1974 and once in 1975, sent back pictures of a moonlike, crater pocked surface.
Mariner 10 told us that the planet Mercury has temperatures of about 810 degrees Fahrenheit on the sunlit side and about minus 290 degrees Fahrenheit on the dark side.
Mariner 10 also detected a magnetic field one percent that of the earth. The slow rotation rate of Mercury would seem to preclude the generation of such a field by the planet's iron core and its source remains unknown.
Spectroscopic studies of mercury indicate that little or no atmosphere surrounds the planet. Calculations show that the force of gravity on its surface is only about one third as great as on the surface of the earth. This is too low to hold an atmosphere.
The perihelion (the point closest to the sun) in the orbit of Mercury advances at a slow rate. A small part of this motion cannot be accounted for by calculations based on classical mechanics. The complete explanation of the motion of the orbit according to relativistic concepts was one of the first confirmations of the theory of relativity.
The ancient Romans named the planet Mercury in honor of the swift messenger of their gods.