In 1979, a chain email about science fiction spawned the modern internet.

But the message sent to Cerf’s email wasn’t a technical request. And it hadn’t been sent just to him. Instead, an email with the subject line “SF-LOVERS” had been sent to Cerf and his colleagues scattered across the United States. The message asked all of them to respond with a list of their favorite science fiction authors. Because the message had gone out to the entire network, everybody’s answers could then be seen and responded to by everybody else. Users could also choose to send their replies to just one person or a subgroup, generating scores of smaller discussions that eventually fed back into the whole.

About 40 years later, Cerf still recalls this as the moment he realized that the internet would be something more than every other communications technology before it. “It was clear we had a social medium on our hands,” he said.

From In 1979, a chain email about science fiction spawned the modern internet.