Plug a sensor into a switch, wire up a building full of cameras, or rack a server, and you are using Ethernet. It is the most widely deployed wired networking standard on earth, the quiet backbone under offices, factories, and data centers. And it is named after a scientific idea that turned out to be completely wrong. The name was not an accident or a marketing afterthought. It was a deliberate engineering choice, and the reasoning behind it explains why Ethernet outlived nearly every rival and