Maybe it was the graphic-novel clarity of the images, the perfect geometry of the World Trade Center towers against the flat blue sky, the orange fireballs that blossomed from the puncture wounds. Or perhaps it was the cascading of horrors, a plane striking the seemingly impenetrable Pentagon, another one falling out of the sky into a Pennsylvania field.

Even as it unfolded in real time, 9/11 felt mythic. It had the feeling of an era-divider, a Berlin Wall, a where-were-you moment, separating everything pre- from everything post-. Nothing, everyone kept predicting, would ever seem the same.

And it doesn't. Just not in the way we imagined on 9/11 — or even because of 9/11.

The 10th anniversary of 9/11 arrives in a vastly different world. In the years since that scaldingly memorable day, so much has transpired that 9/11 itself seems to belong to a much more distant past. In many ways, the idea that 10 years has passed prompts not so much the marvel of "Already?" as a disbelieving "Only?"

In the interim, we have gone to war twice — arguably thrice if you count Libya. The economy plunged into a recession that now threatens a second dip. Two presidential elections have come and gone, with the campaign for the next one already under way. Bruising battles over health care and the federal debt continue. A Rip Van Winkle awakening from a 10-year slumber would confront bafflements from the Arab Spring and the tea party to our online friending and tweeting.

As the nation marks this milestone, with memorial services, concerts, museum exhibitions and no end of conflict over what it all means, 9/11 remains that rarity: a shared event.

Televised as it was almost from the start, the terrorist attacks may have happened in the physical spaces of New York, Washington and Shanksville, Pa., but the horror and the sorrow, the disbelief and the outrage, rippled throughout the world.

"This was something experienced by everyone," said Tom Scheinfeldt, a historian and new media specialist who directs a Sept. 11 digital archive at George Mason University.

Scheinfeldt is among the many historians and curators who immediately began trying to bottle that experience. While his archive was collecting more than 150,000 emails, videos and other digital objects, institutions such as the Smithsonian Institution and the National September 11 Memorial and Museum were similarly collecting artifacts and oral histories.

What comes through in even a cursory perusal of these collections is a sense of an event so enormous that it could only be grasped in miniature.

A singed ID card. A battered beeper (Mommy, you imagine a child asking in the not so distant future, what is a beeper?). A bloodied pair of shoes. Dinged and damaged police badges and firefighter helmets.

In a similar vein, reciting the names of the 9/11 dead has become the centerpiece of annual memorials, a sad roll call whose power lies in its sheer length and the world of ethnicities it encompasses.

But if the tragedy of 9/11 can only be understood in the intimate, what has happened both in its name and in its wake sprawls in multiple directions. On the home front, we accepted greater intrusions, in airport security lines and in a Patriot Act that sanctioned a vast and unprecedented government scrutiny.

Much of what 9/11 wrought, though, would occur abroad, first in the war against the Taliban in Afghanistan and then against Saddam Hussein in Iraq, which turned out not to be connected to the terrorist attacks.

To many Americans, this went on so far off-stage from their daily lives as to turn invisible. Everyone supported the troops — some genuinely, some in empty platitudes — but fewer had any sense of what was going on over there, or how great a toll it was taking, in lives lost or interrupted.

Charles Blomquist is heading to his third deployment — this day, as a matter of fact.

"Poetic," he says wryly.

Being both a lieutenant colonel in the National Guard and an assistant state's attorney in Baltimore, Blomquist has shuttled between two very different fields of justice. He has served in Iraq and Afghanistan, and has prosecuted such crimes as the slaying of an off-duty police officer in a Canton parking space dispute.

"You think, 'My God, has it really been 10 years?'" Blomquist said as he prepared to leave for Afghanistan. And he finds his answer in his two sons, who somehow have become teenagers in the interim. "Yeah, it has been."