The Long Argument About Lightning

[A] For most of recorded history, lightning was understood as a sign rather than a phenomenon. It belonged to theology, not to physics, and the practical response to it was prayer. [B] By the middle of the eighteenth century, however, a small number of European experimenters had built machines that could store an electric charge and release it as a bright, cracking spark. The resemblance to lightning was obvious to anyone who watched, but resemblance is not proof.

[C] The decisive step was to show that the two were the same substance. Thomas-François Dalibard did so in 1752 by erecting a tall iron rod in a garden near Paris and drawing sparks from its base during a storm. [D] Benjamin Franklin, who had proposed the experiment, is remembered instead for a kite, though the rod came first and was far less dangerous. What followed mattered more than the demonstration itself. If lightning was an electrical discharge seeking the ground, then a metal path to the ground would give it somewhere harmless to go. The lightning rod spread across Europe within twenty years, and it spread despite considerable objection — not from other scientists, but from those who thought it impious to interfere.