Alessandro Volta
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The physicist whose 1800 pile - stacked zinc and copper discs separated by brine-soaked cloth - produced the first steady electric current.
Static electricity had been known for centuries and was useless for communication: a discharge is an event, not a signal. The pile gave a current that keeps flowing, and only then is there something to modulate, switch or send. Everything on this timeline after him depends on that one change of kind, from a spark to a supply. His name became the unit, which is a rarer honour than a prize.
Also known as: volta, voltaic pile