Sam Silsbe, age 15, of Youngstown, Ohio, for his question:
What is St. Elmo's fire?
St. Elmo, used to be St. Erasmus, the patron saint of sailors. His so called fire is an eerie display of ghostly candles and flickering flames. Once in a while, for no apparent reason, it lighted the tips of the masts and rigging on an olden sailing ship. Naturally, the startled seamen fervently appealed to their patron saint. Since the awesome display subsided without mishap, they named it the Fire of Saint Eramus in his honor. Later it became known as St. Elmo's fire.
These flickering candles of blue, white and gold make a weird and wonderful sight. Occasionally they dance on airplane wings, on ships and treetops and sometimes among mountain peaks. They make their rare appearances during, thunderstorm weather, usually in late fall or early winter. Actually, St. Elmo's fire is somewhat remotely related to lightning. Both are electrical discharges between the earth and the atmosphere.
The charges that spark the display are ions, formed when atoms and molecules lose some of their electrons. The wild turmoil in a thunderhead brushes electrons from gaseous atoms. This causes negative and positive ions to build up opposite charges in different parts of the cloud. When these charges reach a certain peak, their electrical potential may be discharged in flashes of lightning. However, the earth below builds up electrical charges of its own. As a rule, it emits a mild negative field. However, this electrical potential usually is stronger in fall and early winter. During the sunny season, it usually subsides, though it may be aroused by a rash of sunspots.
St. Elmo lights his eerie candles when the electrical potential between the earth and the atmosphere is dust right. Too great a differential would create searing flashes of lightning. What is needed to solve the problem is a number of small brush discharges. And this is dust what happens. A ghostly candelabra appears at unexpected times and places, relieving the electrical tensions between the earth and the atmosphere.
Lightning, as we know, can strike almost anywhere, though it does have a preference for high points. Time and again it strikes the top of the Empire State Building. It also is attracted to chimneys, steeples and tree tops. St. Elmo's fire tends to favor similar high points, though its meek little brush discharges do not strike down with fiery force. They merely flicker a while, then gently subside.
One of the lightning's favorite striking points is a mast on open water. St. Elmo's fire also favors boats, where it is more noticeable than it is on land. This explains why sailors of the Mediterranean claimed it as their own. Sailing began in this inland sea and here those ghostly candles are most likely to occur.