We think of 9/11 as part of our modern world—it was, in many ways, the hinge upon which many of the forces of today turn, from Donald Trump’s xenophobia to the instability in the Middle East to the forever war in Afghanistan. In our memories it often seems like September 11, 2001, represents the beginning of the modern world, yet the deeper I got into studying 9/11, the more I felt that it was less the beginning of the 21st century and more the ending of the 20th century—a relic of the analog age rather than the dawn of the digital.

The attacks of September 11 might have been the first global catastrophe experienced in real time by hundreds of millions of people around the world. The first footage came almost immediately, from WNYW-TV Fox 5 on its morning show Good Day New York. CNN had a live feed trained on the Twin Towers at 8:49, barely three minutes after the first plane hit.

As the morning progressed, news permeated almost every TV channel. VH1 and MTV ran CBS’s coverage; ESPN and ESPN2 tapped ABC’s. The TV news crawl—a staple of cable news today—took root that day, a recognition that there was just too much news to talk about. Throughout the day, visuals came first, facts came later—often much later. As night fell in the US, Nielsen estimated that at least 80 million Americans tuned in to watch the evening news, still dominated by three men—Peter Jennings, Dan Rather, and Tom Brokaw, who had been the nation’s stately anchors for a generation.

All told, one estimate by the University of Georgia held that as many as two billion people either watched the attacks in real time or watched the day’s news about it. Timing had something to do with that broad viewership: At 9 am ET, most of the rest of the world was awake as well.

For Europe, it was the middle of the afternoon. For much of eastern Asia, it was mid-evening, catching many just before they went to bed. “I think it was the most photographed event of our time, if not in history,” curator Michael Shulan told David Friend, who wrote a book on the images of 9/11. “It was a photogenic event to an almost unparalleled degree.”

Most of us watched the same thing on that day, united in front of millions of televisions in a way that the nation perhaps hadn’t been since the days of the Kennedy assassination.

Yet part of the reason we all watched the same thing on TV was that, technologically speaking, we were living in a comparative dark age 18 years ago. Apple’s stock was $1.24 on September 10, and according to WIRED, one of the hot new gadgets was the Casio WQV3D-8 wristwatch.

The web was still in its awkward adolescence, AOL the world’s dominant homepage, MSNBC still a partnership between Microsoft and NBC. (Do most viewers today even remember that the “MS” once referred to Microsoft?) News websites slowed to a crawl under the heavy traffic loads, and so the go-to choice was television. As Friend wrote in his book, Watching the World Change, “The city, the nation, and the human race looked on as one unblinking eye.”

I was continually struck in my research by how few alternative sources of information many people had—even those close to the attacks and those seemingly at the epicenter of national leadership. For the entourage traveling with President Bush in Sarasota, Florida, the cutting-edge communication tool that provided the first information about the attacks was a pager.