On Christmas Eve, 2007, a blond woman in her late 30s arrived at St. Francis Hospital in Hartford, Connecticut, with a crying newborn in her arms. The woman had given birth alone at home and tied off the umbilical cord with a rubber band.

In 1969, the moon landing brought together a nation, millions slack-jawed in the glow of their televisions. In 1986, the explosion of the Challenger became a defining moment for a generation of schoolchildren.

Not long ago, I arrived at an Amtrak station near my home in Southern California and was struck by its pleasant atmosphere: high ceilings, a spare design, a clean and airy waiting room with light streaming in the windows.

AT THE 2010 Shanghai World Expo, audience members strapped themselves into moving seats to watch a 360-degree screen. The scene on display was a quixotic vision of the city in 2030.

Not long ago, while crashing with my parents for a few days, I had the opportunity to sift through a wicker box stuffed with memorabilia from my youth: cards, letters, notes scribbled furtively in class.