It is one of the enduring images of the present decade - even though the photograph was taken in 1974. A man steps out into what, from 104 storeys below, appears to be utter nothingness. The man is Philippe Petit, and he is walking an illegal tightrope between the two towers of the World Trade Center. People point at this death-defying feat, police gather on the rooftops, and, finally, after 45 minutes, after making eight journeys backwards and forwards, after running across the rope, kneeling on it and lying on its minuscule width, he is arrested.
Even the "artistic crime of the century" was gradually forgotten about, though, until the days and months after September 11, 2001. Since then there have been Petit's own account, To Reach the Clouds, a children's book, a play, and an Oscar-winning documentary, Man On Wire. The walk has become iconic again; as the author Colum McCann says, an "act of creation that seemed to stand in direct defiance to the act of destruction 27 years later".
Petit's walk is the centrepiece of the Irish writer's sixth book, Let the Great World Spin. And even though it is largely set around the interconnecting lives of the people living in the New York of August 1974, who see or talk about this incredible stunt, it is very much a book that investigates the themes of post-September 11 literature - of bewilderment, of imprecise wars, of bankruptcy (both moral and financial), of the spirit of New York itself - but through a 35-year-old lens.
"Initially I wanted to write about 9/11 and figure it out for myself," McCann says. "Not an answer or a theory or a grand moral, or anything like that. I just wanted to work out my personal reaction about how I felt after what happened, how justice was perverted by the Bush government and what had happened to turn the country around. "I wanted to talk about recovery, how we get out from underneath the rubble. What I soon realised, though, is that I didn't want to write directly about that day, or at least not get tangled up in the awful mechanics of it. I wanted any book I wrote to work on a more poetic, interpretive level, and I remembered Petit's walk and what it signified. So my hope is that there is an allegorical bridge between the two times - with Vietnam for Iraq, and the city going bankrupt. The deeper I discovered the then of New York, the more it seemed to be telling me about the now."
The connection between September 11 and the tightrope walk is only the starting point in a book that is about the power of the human spirit as much as historical events. Indeed, McCann admits that he was so unconcerned about the facts of Petit's walk that he was prepared to have him fall to his death if it meant a better story. "I wanted him to be a grand and obvious metaphor for American and British politics," he says. "Man walks the wire. Man thinks he is king of the hill. Man falls. That sort of thing. But the further along I got, the less interested I became in the tightrope walker and the more interested I became in the people down below. The tightrope walker was just a way for me to talk about them, the other tightrope walkers of life, if you like. I have to admit it, he was a sort of device.
"That's why, even though there is one chapter in 2006, there was no real need to explain in great detail what happened in 2001. Once you mention the words 'World Trade Center' there is only really one thing the memory goes towards. In the end, I'm interested in the small human towers, how the supposedly anonymous people get built back up." By the end of the story, McCann says, the tightrope walker doesn't matter at all. What does matter is the human capacity to love and to nurture through the worst of times. It is why the rescue of two little girls from the roughest part of New York by strangers is, for McCann, the core image of the novel. It is, he says, "the moment when those towers are rebuilt".
It is the people on the ground who really make this a heartbreaking - but ultimately uplifting - novel. This is never more apparent than in the story of one of the book's eight characters, a radical Irish monk called Corrigan, who tests his faith (and his brother's patience) in the projects of the Bronx. He finds a kind of peace, perhaps after seeing Petit's wire-walk, and then a few hours later is involved in a fatal road accident.
Tillie is the imprisoned mother of the woman in the passenger seat when Corrigan loses control of his car. She narrates her life story from a jail cell, talking of her grandchildren, who will later appear fully grown. Let the Great World Spin is full of little connections like this: much like a multi-stranded film such as Crash, part of the joy of the book is the moments when previously unconnected lives suddenly intertwine.
"Tillie was a real discovery for me," McCann says. "It took me six months of writing and researching to find her voice - going out with cops on the streets of NY, going through rap sheets, talking to women in the Bronx, trawling through libraries for oral histories and so on. I mean, I was only nine in 1974. But once I found her I couldn't shake her. I still think she's alive. It's a bit weird, I know, but when I go up to the Bronx I really think I will meet her."
That sense that Tillie is still alive for McCann is the key to the spirit of the book. Prison cells, merciless addiction, death, the shadow of September 11- it is odd to call it an optimistic novel. But despite some desperate lives torn apart - many of the book's connections come from a coffee-morning group of mothers who are grieving for sons killed in Vietnam - there are plenty of moments of beauty in the face of the torment of the everyday. Even the title, taken from a Tennyson poem, is in the end a clarion call to just keep going.
McCann's personal reaction to September 11 is more than just a result of being in New York at the time; his father-in-law was on the 59th floor of Tower One when the planes struck. He escaped what he recalls as the "strange calm" of it all, and was reunited later that day with his family at their New York apartment, where McCann's daughter embraced her grandfather - before saying that the smell of the smoke on his clothes was like he was burning from the inside out. Her grandfather immediately ripped off his clothes and threw them away, appalled at what they might signify. McCann, though, kept the dust-laden shoes as a beacon of hope, a reminder that they carried his wife's father to safety.
But if he writes from the heart, McCann is also an author who takes on huge themes. He has written about the plight and redemption of a Roma girl exiled for betraying her people (Zoli) and the Troubles in Northern Ireland (Everything in this Country Must). So does this best-selling Irishman feel that he is sometimes attempting too much? "Well, I think Zoli, for instance, is a brave failure, but all books are a failure, because they never live up to your desire for what they should have been. I'm like an old record on a skipping scratch that says, 'No matter. Try again. Fail again. Fail better.' I certainly didn't always know what I was doing with Let the Great World Spin, and when Barack Obama got elected I really did think that I needed to push the book towards a point of recovery."
Despite all the years of careful work he had done? "Despite all that. Obama changed my mind, basically. For me, the whole last chapter works as an Obama metaphor, but I shouldn't really say that, because it instructs people on how to read my book, which is a vain and silly thing. Still, I think this is my best novel. I put a lot into it emotionally. I'm still exhausted from it, to be honest. "The question I wanted to pose with this book is: How do we recover? I wanted to see if a nation, like a human being, can recover. What I was looking for, amid all the noise, was a moment of grace and truth. This rescue of beauty even in the face of war, bankruptcy, and so on, is perhaps our duty."
Let the Great World Spin (Bloomsbury) is out now.