A kite, a key and a storm cloud proved that lightning is electricity
In June 1752, Benjamin Franklin reportedly flew a kite with a metal key tied near the string during a Philadelphia thunderstorm, and found the key could produce a spark, suggesting the charged cloud had sent electricity down the wet string. Franklin described it only briefly in a letter, and the fullest early account comes secondhand from scientist Joseph Priestley fifteen years later, which is why historians still debate exactly how he performed it, or how much danger he was really in.