Alessandro Volta

Volta was a physics professor in Como who spent years arguing with Luigi Galvani about a frog. Galvani had made a dead frog’s leg twitch and called the cause "animal electricity", something the animal itself carried. Volta thought the animal was incidental: the electricity came from the two different metals touching it.

To prove it he built a stack with no animal in it at all — discs of zinc and silver, separated by cardboard soaked in brine, one pair on top of another. It produced a steady current, the first source that did not have to be rubbed, sparked or stored in a jar. He described it in a letter to the Royal Society in 1800.

He was right about the metals and wrong to dismiss Galvani entirely; the frog’s nerve really was responding to electricity, and the field Galvani accidentally opened became electrophysiology. Both arguments were worth having.

Every battery since is a pile: two different materials and something wet between them. The one on this board is a 9 V block, which is six small cells stacked in series inside one case — Volta’s pile, in a box.