To modern observers, lightning is obviously electric. However, the relationship between electricity in the atmosphere and the flashing in the sky was not actually understood until the mid-eighteenth century.
Several experimenters in this period proposed that lightning was the result of electricity in the atmosphere, but no one could explain how or why this occurred. The early attempts at a scientific explanation were dismissed. At the time, since many natural phenomena were still associated with superstitions. In the case of lighting, the general belief was that the dramatic flashes in the sky, so often destructive, were intended as punishments from God.
One of the experimenters who set about to prove otherwise was Benjamin Franklin, recognized in America and Europe as one of the greatest scientists of his era. In 1752, Franklin devised his famous kite-and-key experiment to prove that lightning was caused by electricity in the atmosphere. Although the demonstration seems quaint now, it was a radical –and very dangerous- experiment in 1752.
But Franklin's demonstration worked. Experiments like this one were very effective in diminishing the grip of superstition. In addition, the ability to demonstrate physical mechanisms like lightning encouraged a healthy curiosity about nature and an interest in the developing sciences.