Santa Fe, New Mexico, is less than an hour’s drive from Los Alamos, where the atomic bomb was conceived, and only a few hours from Alamogordo, where it burst into life on July 16, 1945. That makes the history of nuclear weapons as much as part of the culture and identity of Santa Fe as the Palace of the Governors, turquoise jewelry, and the scent of piñon on the cool mountain air. This past December, an unusual group of people came together for a few days for an event called the Santa Fe Nuclear Weapons Summit. Their purpose was to consider what remains the fundamental issue of our age: What should we do about nuclear weapons?

One reason that question is so difficult to answer is that, after Hiroshima and Nagasaki, nukes became something of an abstraction, the stuff of nightmares and apocalyptic scenarios, not something that affected our day-to-day lives. And for those born after the Cold War, they’re ancient history, a plot device for TV shows and Hollywood thrillers, not a real and present threat. In his 2012 book “The Partnership: Five Cold Warriors and Their Quest to Ban the Bomb,” the journalist Philip Taubman quoted former Secretary of State George Shultz: “I think to a certain extent after the end of the Cold War the subject went to sleep.”

But out there in the night, the nukes sleep on as well, ever ready to awaken at the slightest nudge, whether through direct intention or miscalculation. And though the Cold War and the Soviet Union have faded into history, the danger has not. In the months since the summit, that hard fact has been made sharply and freshly clear, as President Trump promises vast expansion of the U.S. nuclear arsenal while North Korea conducts new missile tests.

During the first minutes of the summit at Santa Fe’s historic Lensic Theater, Eric Schlosser, author of the book “Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety,” asked former Secretary of Defense William J. Perry: “Right now as we sit here, given your decades of public service in this realm, how great do you think the threat of nuclear weapons is today?”

Perry answered, “I’m sorry to report to you that the likelihood of a nuclear catastrophe today is greater than it was at any time since the Cuban Missile Crisis.”

“I don’t like that answer,” Schlosser responded wryly, to nervous laughter from the audience.

“I don’t like it at all,” Perry said. “But I’m afraid it’s the truth.”

To dead silence from the Lensic audience, Perry went on to recount his own Cold War experiences, from helping to interpret U-2 photography of Russian missile sites during the Cuban crisis to a memorable night as Secretary of Defense: “I was called [at] 3 o’clock in the morning once, telling me that 200 missiles were on their way from the Soviet Union to the United States. I will never forget that moment.”

That turned out to be a computer glitch, one of many that transpired during the Cold War years, as Schlosser details in “Command and Control.” Although in those days, the main threat was military — the nuclear Pearl Harbor that strategists called a “BOOB” (“bolt out of the blue”) attack — the possibility of catastrophic accident or miscalculation also always lurked.

Yet just as that danger receded with the end of the Cold War, another appeared: nuclear terrorism. For decades, the tight control of nuclear weapons and their possession by only a handful of sovereign nations essentially guaranteed that if they were ever used, it would be as an act of national will, not a spasm of ideological violence. That guarantee is gone.

In a stark video, Former Secretary of Defense William J. Perry contemplates the consequences of a nuclear attack by terrorists on Washington, D.C.

Perry showed the Lensic audience a short video dramatizing the consequences of a single terrorist nuke detonating in Washington, D.C. Beyond the immediate catastrophic loss of life, the political, social, and cultural fallout of such a disaster would vastly surpass the physical fallout of the bomb — making the world’s response to 9/11 seem calm and rational by comparison.

Such dangers led Perry to join with George Shultz, Sam Nunn, and Henry Kissinger in publishing a joint editorial in January 2007 in the Wall Street Journal arguing for the total abolition of nuclear weapons. For many world leaders, including then soon-to-be-President Barack Obama, their words transformed the concept of a nuclear-free world from a radical peacenik fantasy to a realistic, achievable goal. Yet the goal remains elusive. While Perry takes justifiable pride in participating in the dismantling of about 8,000 U.S. and Russian nuclear weapons during his career, “the bad news is there’s still 15,000 left,” he notes candidly, adding, “whatever the numbers, it’s the end of civilization” if they’re ever unleashed.

Trained as an engineer and mathematician, Perry still approaches questions of Armageddon with a scientist’s precise clarity of thought, as he did throughout his Washington years. Which raises another issue that was among the many questions addressed by Perry in the Q&A that followed his interview with Schlosser: Given that it was a group of brilliant and gentle scientists who first brought the nuclear demon into the world back in 1945, what can science do now to leash that demon?

In an ideal world, the answer would be obvious: Uninvent the Bomb. Since that’s impossible, politicians and diplomats must find ways to control the nukes, and that’s where science is indispensable. “The treaties are always subject to the issue of, can they be verified, and verification is a very difficult issue,” Perry said. “Scientists in the past have come up with techniques which have given enough confidence in verification that we’ve been able to go ahead with the treaties. So I think at least one thing that scientists can do in this area is work on ways of improving verification.” As an example, Perry cited the global monitoring network of the Comprehensive Test Ban Treaty Organization, which proved sensitive enough to detect the partial fizzle of North Korea’s first failed nuclear test in 2006. “The final estimate was only about a half a kiloton yield, which was a very low-yield nuclear bomb, and yet our seismic network detected it with very high reliability,” Perry said. With North Korea threatening to conduct new underground nuclear tests, such capability is even more vital.

Not only scientists, but students, artists, writers, businesspeople, futurists, and other innovators participated in the summit over the next three days. They traveled to tour Los Alamos National Laboratory, participated in discussions with experts including the former CIA officer Valerie Plame and the former U.S. diplomat Robert Gallucci, and immersed themselves in intensive workshops to develop brief multimedia presentations envisioning the world in 2045 — a century after the Bomb’s debut — and possible futures in a world with and without nuclear weapons.

The summit finale, in which several teams presented imaginative if brief scenarios, raised some intriguing perspectives and led to a spirited discussion with the audience, but offered no final answers — which was not surprising. No one was expecting the most complex existential dilemma of our age to be resolved in a four-day meeting in a picturesque corner of New Mexico.

“My generation was responsible for building up this fearsome nuclear arsenal,” says former Defense Secretary William J. Perry. Visual: Department of Defense

For William Perry, now 89 years old, such activities are more than just a way to kill time in retirement. “I have basically devoted the rest of my life to educating the public on nuclear dangers and what might be done to lessen those dangers,” he told the Lensic audience. As he explained in Philip Taubman’s book, “My generation was responsible for building up this fearsome nuclear arsenal. And my generation has now started the task of dismantling it. But we will not be able to finish this task. So we will have to pass the baton on to your generation.”

It might be easy to dismiss such efforts merely as the forlorn quest of old Cold Warriors for some sense of atonement in the twilight of their lives. And it’s all too easy to feel completely hopeless about the entire issue, and that trying to change it is merely an exercise in futility. As David Kaiser, science historian and physicist at MIT, notes, “I do think that present uncertainties raise the threat level in a way that hasn’t been true for a long time.” He adds that he wasn’t surprised when The Bulletin of the Atomic Scientists decided to move their clock closer to midnight.

Kaiser is referring to the Bulletin’s famous “Doomsday Clock,” which since its inception in 1947 has served as an unofficial cultural indicator of impending Armageddon. “Midnight” on the Clock represents global nuclear war. As the new presidential administration took office in January 2017, the Bulletin moved the hands of the Clock to two and a half minutes to midnight — the closest ever to Doomsday except when it stood at two minutes during the 1950s, after both the U.S. and the USSR acquired the hydrogen bomb.

Other experts are equally uneasy. Peter Galison, professor of history of science and physics at Harvard, notes that the current State Department is in “dire shape,” and that foreign policy has “shifted away from professionals with the linguistic and statecraft skills needed to help guard the peace and toward the White House.” Galison also observes “an increasing and worrisome volatility to Executive Office discussion of increasing nuclear armaments and disparaging accords to build down the current arsenals.” Together, he says, these “present us precisely with a real and worrisome danger.”

Yet it would be a tragic mistake to surrender wholly to fear. The summit demonstrated convincingly that even though the old Cold Warriors such as William Perry must eventually relinquish their crusades, passionate and vigorous people from the generations that follow are more than ready to take up their baton. In the public discussion that closed the summit, several of them summed up the main take-home lesson of the past few days: “Don’t assume [nuclear catastrophe] is inevitable, inescapable, or that you don’t have agency.”

Considering that the new president of the United States is a man who seems to believe that nuclear weapons are nothing more than particularly noisy firecrackers, the cause has never been more timely.

Mark Wolverton, a 2016-17 Knight Science Journalism Fellow at MIT, is a science writer, author, and playwright whose articles have appeared in Wired, Scientific American, Popular Science, Air & Space Smithsonian, and American Heritage, among other publications. His most recent book is “A Life in Twilight: The Final Years of J. Robert Oppenheimer.”