He was not the first person to invent a lightbulb—that accolade probably goes to Joseph Swan, a scientist from the north-east of England, though a fair few people had come up with prototypic bulbs even before him. But much as he did for concrete, Edison turned lightbulbs into a mass-market product. He realised that it was not enough to manufacture a lightbulb or clever electrical appliances; he would have to build the electrical infrastructure into which those devices could be plugged as well. And that meant lots and lots of copper: copper for the wires he buried under the streets of New York,
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