Weathervanes, Lightning Rods

Lightning is an atmospheric discharge of electricity, usually, but not always, during a rain storm. more...

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Early research

During early investigations into electricity via Leyden jars and other instruments, a number of people (D. William Wall (1708), Stephen Gray (1735), and Abbé Nollet) proposed that small-scale sparks shared some similarity with lightning.

Benjamin Franklin also invented the lightning rod, endeavouring to test this theory using a spire which was being erected in Philadelphia. While he was waiting for the spire completion, some others (Thomas-François Dalibard and De Lors) conducted at Marly in France what became known as the Philadelphia Experiment that Franklin had suggested in his book.

Franklin usually gets the credit, as he was the first to suggest this experiment. The Franklin experiment is as follows:

Whilste waiting for completion of the spire, he got the idea of using a flying object, such as a kite, instead. During the next thunderstorm, which was in June 1752, he raised a kite, accompanied by his son as an assistant. On his end of the string he attached a key and tied it to a post with a silk thread. As time passed, Franklin noticed the loose fibers on the string stretching out; he then brought his hand close to the key and a spark jumped the gap. The rain which had fallen during the storm had soaked the line and made it conductive.

However, in his autobiography (written 1771-1788, first published 1790), Franklin clearly states that he performed this experiment after those in France, which occurred weeks before his own experiment, without his prior knowledge as of 1752.

As news of the experiment and its particulars spread, the experiment was met with attempts at replication. However, experiments involving lightning are always risky and frequently fatal. The most well-known death during the spate of Franklin imitators was that of Professor Georg Richmann, of Saint Petersburg, Russia. He had created a set-up similar to Franklin's, and was attending a meeting of the Academy of Sciences when he heard thunder. He ran home with his engraver to capture the event for posterity. While the experiment was under way, ball lightning appeared, collided with Richmann's head and killed him, leaving a red spot. His shoes were blown open, parts of his clothes singed, the engraver knocked out, the doorframe of the room split, and the door itself torn off its hinges.

Modern research

Although experiments from the time of Franklin showed that lightning was a discharge of static electricity, there was little improvement in theoretical understanding of lightning (in particular how it was generated) for more than 150 years. The impetus for new research came from the field of power engineering: as power transmission lines came into service, engineers needed to know much more about lightning in order to adequately protect lines and equipment.

Read more at Wikipedia.org