The National September 11 Memorial & Museum in New York is a profound, beautiful monument to the lives lost in the 1993 and 2001 terror attacks at the World Trade Center. But the iron curtain of security surrounding the site forms its own monument: to our successful adaptation to the realities of a post-9/11 world, and perhaps to choices that speak less well of us.

Advance tickets are required to enter this public, outdoor memorial. To book them, you’re obliged to provide your home address, email address, and phone number, and the full names of everyone in your party. It is “strongly recommended” that you print your tickets at home, which is where you must leave explosives, large bags, hand soap, glass bottles, rope and bubbles. Also, “personal wheeled vehicles” not limited to bicycles, skateboards, and scooters, and anything else deemed inappropriate. Anyone age 13 or older must carry photo ID, to be displayed “when required and/or requested.”

Once at the memorial you must go through a metal detector and your belongings must be X-rayed. Officers will inspect your ticket — that invulnerable document you nearly left on your printer — at least five times. One will draw a blue line on it; 40 yards (and around a dozen security cameras) later, another officer will shout at you if your ticket and its blue line are not visible. Eventually you’ll reach the memorial itself, where there are more officers and no bathrooms. You’re allowed to take photographs anywhere outside the security screening area — in theory if not always in practice.

Eleven years after 9/11 and a year after the memorial opened, it’s time for a freedom-loving people to consider the purpose and impact of such security measures. Let’s ask the experts — and ourselves — three questions. Is enhanced security necessary at the memorial? Are the specific measures in place likely to be effective? And what is their cost to a free society?

At first glance, the need for security at the Sept. 11 memorial seems self-evident. The memorial stands on some of the most sacred ground in America; a third attack there would be an unimaginable blow. But just because an incident would be tragic doesn’t mean it’s a serious possibility. Depending on who’s counting, either 14 or 16 people in America have been killed by Islamic extremists since 9/11 — 13 at Fort Hood, Texas. There have been other plots, of course, disrupted by law enforcement, though a recent study described about half of those as “essentially created or facilitated in a major way by the authorities.” Meanwhile about 15,000 Americans are murdered annually. Tobacco claims the lives of around 440,000 Americans per year. In 2011, lightning killed 26.

Counterterror experts I spoke with differed on the level of security required at the Sept. 11 memorial. But even among those who said they understood the enhanced security, nearly all couched that understanding in terms of the site’s iconic status, not actual risk to the memorial. Richard Barrett, coordinator for the U.N.’s al-Qaida and Taliban monitoring team, described the likelihood of an attack on the memorial as “incredibly small.” Max Abrahms, a counterterrorism fellow at Johns Hopkins University, said that although the memorial’s “extra psychological importance” warrants heightened security, “it’s now clear that sleeper cells are not infesting our country . . . al-Qaida can hardly generate any violence at all.” In policy circles, al-Qaida and the term “strategic defeat” increasingly go together.