Franklin, Benjamin (1706-1790) (World of Earth Science)
American scientist and statesman
Before serving his fledgling country during time of revolution, Benjamin Franklin also achieved international recognition for his scientific acumen, especially in his experimentation with electricity.
Born in the British colony of Boston, Massachusetts, Franklin was the fifteenth of seventeen children. His father was an impoverished candlemaker, unable to afford to send young Benjamin to school. As a result, he received only two years of formal education. Franklin was working in his father's shop at the age of ten, and later was apprenticed to his brother, a printer, where he developed a love for books. In 1724, he went to London where he became skilled at printing, returning to Philadelphia two years later. In Philadelphia he made a name for himself, as well as a small fortune, publishing the Pennsylvania Gazette and Poor Richard's Almanack.
In addition to his pursuit of printing, Franklin became interested in the study of electricity in 1746. During this period, scientists around the globe, many of whom had advanced degrees, were investigating the phenomena of static electricity. A less confident man might have felt inadequate to compete, but Franklin, who was essentially self-educated, obtained a Leyden jar and began his own research.
The Leyden jar, invented by Musschenbroek, was a water-filled bottle with a stopper in the end. Through the stopper was a metal rod that extended into the water. A machine was used to create a static electric charge, which could be stored in the jar. A person who touched the end of the charged rod received an electrical jolt. Public demonstrations, in which many people joined hands and received a simultaneous shock, were very popular. Franklin saw such a demonstration, and that initiated his interest in electricity.
It was Franklin's originality and tenacity that earned him the reputation as a leading scientist. He was the first person to wonder how the Leyden jar actually worked, and performed a series of experiments to find the answer. He poured the "charged" water out of the jar into another bottle, and discovered the water had lost its charge. This indicated that it was the glass itself, the material that insulated the conductor, which produced the shock. To verify this, Franklin took a windowpane and placed a sheet of lead on each side. He "electrified" the lead, removed each sheet one at a time, and tested for a charge. Neither sheet gave so much as a single spark, but the windowpane had been charged. Franklin had unknowingly invented the electrical condenser. The condenser, also known as a capacitor, was destined to be one of the most important elements in electric circuits. Today the condenser, which received its name from Alessandro Volta, is used in radios, televisions, telephones, radar systems, and many other devices.
Drawing a parallel between the sparking and crackling of the charged Leyden jar and lightning and thunder, Franklin wondered if there was an electrical charge in the sky. He planned to erect a long metal rod atop Christ Church in Philadelphia to conduct electricity to a sentry box in which a man, standing on an insulated platform, would be able to collect an electric charge. Because he was a proponent in the free exchange of ideas, Franklin had written a book outlining his theories, which received wide circulation in Europe. A French scientist named D'Alibard used Franklin's idea and performed the experiment himself on May 10, 1752, charging a Leyden jar with lightning. Franklin generously gave D'Alibard credit for being the first to "draw lightning from the skies." If nothing else, Franklin did receive credit for the invention of the lightning rod.
While waiting for the rod to be installed atop Christ Church, Franklin had come up with an idea of a faster way to get a conductor into the sky. He tied a large silk handkerchief to two crossed wooden sticks, attached a long silken thread with a metal key at the end, and waited for a thunderstorm. The rain made the thread an excellent conductor, and the static charge traveled down to the key. When Franklin brought his knuckle to the key, a spark jumped from the key to his hand, proving the existence of electricity in the sky.
Franklin had been wise enough to connect a ground wire to his key; two other scientists, attempting to duplicate the experiment but neglecting the ground wire, were killed when they were actually struck by lightning. Still, Franklin was lucky he was not hit by lightning himself. Franklin invented the lightning rod from his work with electricity. The lightning rod became indispensable for protecting buildings from the destructive force of lightning. Because he had discovered he could get the Leyden jar to spark over a greater distance with a sharply pointed rod, Franklin's lightning rods had very sharp points. (In 1776, after the conflict between the Colonies and King George III had erupted, the king ordered that lightning rods with blunt ends be installed on his palace.) By 1782, there were four hundred lightning rods in Philadelphia.
His discovery of sky-borne electricity led Franklin to speculate on the nature of the aurora borealis, the "northern lights" that illuminate the sky. Franklin thought they might be electrical in nature, and suggested that conditions in the upper atmosphere might be responsible.
His work on electricity led to a plethora of new words (battery, condenser, conductor, armature, charge, and discharge to name a few) and concepts. He suggested that electrical charge was due to the abundance or lack of "something" that resulted in attraction and repulsion, and he established the concept of positive and negative charges, believing (incorrectly) that electrical flow went from positive to negative. In fact, the opposite is true.
Continuing his observations of the weather, he noticed there was a prevailing pattern as it moved from west to east and suggested the circulation of air masses was responsible, establishing the concept of high and low pressure. He went on to show that the boiling point of water was affected by air pressure; as he created a vacuum in a sealed water bottle, the temperature needed to boil the water dropped. He also charted the flow on the Gulf Stream in the Atlantic Ocean.
Volumes have been written about Franklin's life as a statesman. He founded service organizations, became Postmaster of Philadelphia, and established a college that eventually became the University of Pennsylvania. He returned to London in 1757 as an Agent of the Pennsylvania Assembly and remained there until 1775. After warning that the "Stamp Tax" was not a good way to obtain revenue from the American Colonies, he returned and joined the committee drafting the Declaration of Independence.
During Franklin's long life he developed many inventions (such as bifocal lenses and the Franklin stove), received numerous honors and achieved an international reputation, becoming one of few Americans of colonial days to do so. He died in Philadelphia, at the age of eighty-four.
See also Atmospheric pressure; Electricity and magnetism