Today we celebrate the birthday of Benjamin Franklin, born on 17 January 1706 in Boston, Massachusetts (USA).
Franklin is celebrated as one of the Founding Fathers of the United States as well as an ambassador, newspaper publisher, postmaster and author of Poor Richard’s Almanack. But he was also a prolific scientist and inventor, famous during his lifetime for his discoveries with electricity.
In a story often told to American school children, Franklin is said to have flown a kite during a thunderstorm in order to prove the connection between lightning and electricity. The kite was able to pick up the electric charge from the storm using a wet hemp string to provide conductivity. A key was attached to the kite and connected a Leyden jar in order to store the electrical charge. For insulation, Franklin used a dry silk string.
During the experiment, Franklin observed the loose threats of the kite string repelling each other. When he moved his hand near the key, he saw an electric spark which proved the electric nature of lightning. Franklin recounted his experiment in a letter to his friend Peter Collison dated October 1752 in which he concluded “thereby the Sameness of the Electric Matter with that of Lightning compleatly demonstrated”.
Not only did Franklin demonstrate the connection between lightning and electricity, but his discovery led to his invention of the lightning rod. As stated by Franklin, with the use of an iron rod with a sharpened point, “The electrical fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike”. This resulted in lightning rods being installed in his hometown of Philadelphia, most notably on the University of Pennsylvania and Independence Hall. Research into lightning protection systems continues to this day and innumerable lives have been saved due to the protection from lightning rods.
Other noteworthy discoveries by Franklin in electricity include his experiments on the non-conduction of ice as well as proving the existence of positive and negative charges and discovering the principle of conservation of charge.