Franklin Proves Lightning is Electricity
In 1752, Benjamin Franklin carried out what is now the most famous experiment in the history of electricity, flying a kite in a thunderstorm near Philadelphia to show that lightning is an electrical phenomenon. The demonstration, along with the lightning rod it helped inspire, made Franklin an international celebrity and became an early symbol of Enlightenment confidence that nature could be understood and put to practical use.
In the 1740s, electricity was a fashionable curiosity. Experimenters in Europe used glass tubes and spinning globes to generate static charge, and the Leyden jar, invented in the mid-1740s, could store it and deliver a startling shock. Franklin, a Philadelphia printer and civic leader, took up these studies around 1746. He proposed that electricity was a single "fluid" that could be present in excess or deficit, introducing the terms positive and negative, and he noticed that pointed metal objects drew off charge more readily than blunt ones. Many had suspected that lightning was a form of electricity, since sparks and thunderclaps seemed like larger versions of laboratory effects, but no one had shown it.
Franklin proposed an experiment using a tall iron rod on a high place to draw electricity from storm clouds. In May 1752, French experimenters, following his published description, successfully did this at Marly, near Paris. Franklin, apparently unaware of their success, is generally said to have tried a kite in June 1752. He attached a metal key or wire to the string and observed sparks and the charging of a Leyden jar. Our main account comes from Franklin's own brief report and a later retelling by his friend Joseph Priestley; Franklin never described it in detail, and some historians doubt exactly how it was done. The popular image of him being struck is a myth, and a direct lightning strike would likely have killed him. Others who later tried similar experiments, including Georg Richmann in Russia in 1753, were killed.
The practical result was the lightning rod, which Franklin described in print in the early 1750s. A pointed metal rod mounted above a building and connected to the ground gave lightning a safe path, protecting wooden houses, church steeples and ships. Rods spread through the American colonies and Europe, though some people argued over whether pointed or blunt tips worked better, a dispute that took on political overtones during the Revolutionary era.
Franklin's work earned him honors from the Royal Society and honorary degrees, and his book on electricity was widely translated. The experiment strengthened the idea that natural events once seen as divine warnings could be explained and managed through observation, and it laid groundwork for later study of electricity.