To show that lightning was akin to static electricity, Benjamin Franklin originally just wanted to place a sharply pointed metal object - a lightning rod - on the steeple of Christ Church in Philadelphia to draw, as he put it, the "electrical fire" from the sky.

But a kite, of course, could reach higher, so using a large silk handkerchief and two cross-sticks, Franklin built one and mounted a miniature lightning rod on it. At the ground, he tied a large key to the string. With his son William, Franklin went into a field one stormy day to wait for a thunderstorm. When one passed overhead, electrical charges jumped onto the kite and down the wet string to the key. Franklin was unaffected because he was holding a dry silk string which insulated him from the charges, but when he reached to touch the key, he got a small shock, establishing that lightning was indeed a form of electricity, identical in nature to the sparks we experience when we touch a metal object on a dry day.

Following his experiment, "Franklin" rods - that is, lightning rods - showed up on buildings all over colonial America and Europe, providing a safe, grounded path for lightning to follow.