The last time I flew to Beijing from the U.S., I had to pass through a full-body scanner at an airport security checkpoint in Louisville, Kentucky. One of the people in front of me was an elderly man in a wheelchair.

When his turn came, two security officers helped him to his feet and guided him into the machine. “Can you stand on your own?” one of the officers asked.

“I think so,” the man said.

He kept his arms raised long enough for the machine to take an image of his body and then, with the help of the security officers, returned to his wheelchair.

I remembered this experience after reading about the bombings at the Boston Marathon. In cities like Washington, London and Moscow, authorities are tightening security at major landmarks, transit hubs and government buildings in response to the attack.
Even cities scheduled to host marathons in the upcoming weeks are reviewing security measures.

Victims of the Sept. 11, 2001 terrorist attack on the Pentagon are loaded into an ambulance.

The way in which the response has reverberated to cities both large and small reminds me of the Sept. 11 attacks. I was in college at the time in Lexington, Kentucky, hundreds of miles from the smoldering ruins of New York City’s World Trade Center. Still, watching the news coverage in the aftermath of the attacks, I came away with the impression that the next terrorist could be lurking anywhere. No suspicious person was to be taken too lightly.

I remember telling friends that as horrible as the Sept. 11 attacks were, a bombing at a mall or an amusement park in small-town America would have a much greater psychological impact because it would make people feel as if no community was safe. Even places like Walmart would need to install metal detectors and employ security guards to pat down customers.

That kind of attack hasn’t happened, but the reaction to the bombings in Boston is a reminder of the realities of living in a post-9/11 world, a place everyone – even old men who can hardly walk – are treated like a threat.